SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES ? NUMBER 24 Catalog of Meteorites from Victoria Land, Antarctica, 1978-1980 Ursula B. Marvin and Brian Mason EDITORS ISSUED JUL291982 SMITHSONIAN PUBLICATIONS SMITHSONIAN INSTITUTION PRESS City of Washington 1982 ABSTRACT Marvin, Ursula B., and Brian Mason, editors. Catalog of Meteorites from Victoria Land, Antarctica, 1978-1980. Smithsonian Contributions to the Earth Sciences, number 24, 97 pages, frontispiece, 41 figures, 13 tables, 1982.?This is the second catalog of meteorite specimens collected on expeditions to Victoria Land led by William A. Cassidy of the University of Pittsburgh. The first {Catalog of Antarctic Meteorites, 1977-1978, U. B. Marvin and B. Mason, editors, 1980) presented the results of the 1976-1977 and 1977-1978 field seasons and described the collection and curation procedures that were adopted under a three-agency agreement between the National Science Foundation, the National Aeronautics and Space Administration, and the Smithsonian Institution for the purpose of protecting the meteorites from terrestrial contamination and allocating them for research. This catalog reports the results of the subsequent two seasons: 309 specimens were collected in 1978-1979, and 73 in 1979-1980. Classifications are given for all specimens weighing more than about 100 grams and also for some smaller pieces from each of the four field seasons. The catalog describes the field camps, the geodetic measurements of ice motion and ablation at the Allan Hills site, and the search for new concentrations. Current information about the character of the collections and new types of meteorites represented in them is outlined in brief articles describing Antarctic achondrites, carbonaceous chondrites and irons, and meteorite weathering and terrestrial residence times on the polar icecap. There is a bibliography of major articles on Antarctic meteorites. An Appendix lists all of the Victoria Land specimens classified as of December 1980, by numerical order for each locality and by meteorite class. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: Aerial view of Ulawan Volcano, New Britain. Library of Congress Cataloging in Publication Data Main entry under title: Catalog of meteorites from Victoria Land, Antarctica, 1978-1980. (Smithsonian contributions to the earth sciences ; no. 24) Bibliography: p. Includes bibliographies. Contents: The field season in Victoria Land, 1978-1979 / by Ursula B. Marvin ? The traverse to Reckling Peak, 1979-1980 / by William A. Cassidy and L. A. Rancitelli ? The Allan Hills Icefield and its relationship to meteorite concentration / by John O. Annexstad ? [etc.] Supt. of Docs, no.: SI 1.26:24 1. Meteorites?Antarctic regions?Catalogs. 2. Meteorites?Antarctic regions?Addresses, essays, lectures. I. Marvin, Ursula B. II. Mason, Brian Harold, 1917- . III. Series. QE1.S227 no. 24. [QB755] 550s [523.5'1'09989] 81-607125 AACR2 Contents Page Editors' Introduction, by Ursula B. Marvin and Brian Mason 1 The Field Season in Victoria Land, 1978-1979, by Ursula B. Marvin. . 3 The Traverse to Reckling Peak, 1979-1980, by W.A. Cassidy and L.A. Rancitelli 9 The Allan Hills Icefield and Its Relationship to Meteorite Concentra- tion, by John O. Annexstad 12 Descriptions of Stony Meteorites, by Roberta Score, Trude V.V. King, Carol M. Schwarz, Arch M. Reid, and Brian Mason 19 Descriptions of Iron Meteorites, by Roy S. Clarke, Jr 49 Overview of Antarctic Irons, by Roy S. Clarke, Jr 57 Overview of Antarctic Achondrites, by Arch M. Reid 59 Overview of Antarctic Carbonaceous Chondrites, by Carleton B. Moore 65 Weathering Effects in Antarctic Meteorites, by Michael E. Lipschutz. . 67 Aluminum-26: Survey of Victoria Land Meteorites, by J.C. Evans, J.H. Reeves, and L.A. Rancitelli 70 Bibliography of Antarctic Meteorites, by Karen Motylewski 75 Appendix: Tables of Victoria Land Meteorites 85 Literature Cited 95 in FRONTISPIECE.?The midnight sun of 6 January 1979 illuminates the Allan Hills campsite, with snow crystals streaming northward before the polar wind. Catalog of Meteorites from Victoria Land, Antarctica 1978-1980 Editors' Introduction Ursula B. Marvin and Brian Mason The United States has sent yearly meteorite collecting expeditions, under the leadership of William A. Cassidy of the University of Pitts- burgh, to Victoria Land, Antarctica, since the austral summer of 1976. This catalog describes those specimens weighing more than 100 grams that were collected during the expeditions of 1978-1979 and 1979-1980. In addition, it de- scribes some of the cherry-sized meteorites col- lected in these and other years. Descriptions of the larger specimens from the 1976-1977 and 1977-1978 expeditions are presented in the Cat- alog of Antarctic Meteorites, 1977-1978 (Marvin and Mason, 1980). That earlier catalog also pro- vides descriptions of field areas, collecting proce- dures, and curation procedures. Current research results show that the Antarc- tic specimens include mineralogical and textural varieties of meteorites that are new to the world collections. In order to make this catalog more informative we include brief reviews of the range of compositions observed among the achondrites, carbonaceous chondrites, and irons, and progress Ursula B. Marvin, Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138. Brian Mason, Department of Mineral Sciences, National Museum of Natural History, Smithson- ian Institution, Washington, D.C. 20560. reports on topics such as geodetic measurements of ice motion and ablation at the Allan Hills site, meteorite weathering under polar conditions, and aluminum-26 determinations of terrestrial resi- dence times. The field parties collected 11 meteorite speci- mens the first year (1976-1977), 300 specimens in 1977-1978, 309 specimens in 1978-1979, and 73 in 1979-1980 ? a season when most of the effort was devoted to measuring ice motion and search- ing for new meteorite concentrations. Table 1 shows the distribution of meteorite types found in the latter two seasons. All of the Victoria Land specimens that were classified as of December 1980 are listed in the three-part appendix. Ap- pendix Table A lists specimens for each locality by consecutive numbers; Appendix Table B lists specimens consecutively by meteorite class; and Appendix Table C lists the paired meteorites that have been identified according to our current, but far from complete, knowledge of them. The final entry in the catalog is a bibliography of the literature on Antarctic meteorites. Articles containing substantive data (analytical informa- tion, petrographic descriptions, comparisons with other meteorites, etc.) for Antarctic meteorites have been included. In general, brief abstracts of 1 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE 1.?Meteorite specimens collected in 1978-1979 and 1979-1980 Type Irons Achondrites Carbonaceous chondrites Chondrites Totals Irons Achondrites Chondrites Totals Allan Hills 2 6 1 253 262 1 52 53 Darwin Glacier 9 34 43 Elephant Moraine 1978-1979 1979-1980 6 4 10 Reckling Peak 4 4 1 9 10 Totals 11 6 1 291 309 1 7 65 73 information published elsewhere in more com- plete form have been excluded. No attempt has been made to survey the literature in Japanese, although some frequently referenced papers are listed. We hope these additions will increase the usefulness of the catalog. During the past three years research on Ant- arctic specimens has burgeoned in laboratories around the world. The procedures for collecting the specimens and maintaining them at below- freezing temperatures until they can be processed at the curatorial facility at the Johnson Space Center in Houston are governed by an intera- gency agreement between the National Science Foundation, the Smithsonian Institution, and the National Aeronautics and Space Administration and are outlined in the previous catalog (Marvin and Mason, 1980). Newly examined and classi- fied specimens are described in the Antarctic Me- teorite Newsletter, published periodically by the Meteorite Working Group, a committee with a rotating membership responsible for monitoring the program and allocating samples. Requests for the Antarctic Meteorite Newsletter or for specimens or thin sections for research should be addressed to the Secretary, Antarctic Meteorite Working Group, Lunar and Planetary Institute, 3303 NASA Road 1, Houston, Texas 77058. Sample requests should detail sample numbers, desired weights, and the type of studies planned. The Antarctic Meteorite Working Group meets twice yearly, usually in April and September. Dates of meetings and deadlines for sample re- quests are published in the newsletter. Sample requests are welcome from all qualified scientists. Requests are considered on the basis of their merit, without regard to whether a scientist is currently funded for meteorite research. The al- location of Antarctic meteorite samples in no way commits any funding agency to support the pro- posed research. Libraries of polished thin sections have been established in Washington, Houston, and Tokyo for the use of visitors who wish to make optical examinations. (Library thin sections are not avail- able for loan.) To obtain meteorite samples from the Japanese collections or to use the thin section library in Tokyo, contact T. Nagata, Director, or K. Yanai, Curator, at the National Institute of Polar Research, 9-10, Kaga 1-chome, Itabushi- ku, Tokyo 173, Japan. Arrangements for using the thin-section library at the Johnson Space Center in Houston may be made by contacting the Secretary of the Antarctic Meteorite Working Group. To use the library at the National Mu- seum of Natural History, Smithsonian Institu- tion, Washington, DC 20560, contact Brian Ma- son, Curator. The Field Season in Victoria Land, 1978-1979 Ursula B. Marvin The 1978-1979 field season had three main objectives: to search new areas near the head of the Darwin Glacier for meteorite concentrations, to lay out a geodetic network to measure ice motion and ablation at the Allan Hills, and to continue systematic collection of specimens in the Allan Hills icefield. This was the third and final year of the coop- erative agreement by which scientists from the United States and Japan, working out of Mc- Murdo Station, collected meteorites together and shared specimens equally. Led by William A. Cassidy, of the University of Pittsburgh, the par- ticipants included John O. Annexstad, NASA Johnson Space Center, Ursula B. Marvin, Smith- sonian Astrophysical Observatory, Dean Clauter, University of Pittsburgh, and Fumihiko Nishio, Kazuyuki Shiraishi, and Minoru Funaki of the National Institute for Polar Research in Tokyo. Annexstad and Nishio set up camp at Allan Hills on December 7 and remained there for 26 days (through more than one 4-day storm that kept them tentbound) installing a 15-km trian- gulation chain across the meteorite concentration field (see Annexstad, this issue). Without making any special effort to search for them, Annexstad and Nishio picked up nearly 100 meteorites along the snowmobile paths from their camp to the network stations. Cassidy and Shiraishi began a careful search by helicopter of the region around the head of the Darwin Glacier (79?50'S, 158?00'E), where the Ursula B. Marvin, Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138. National Science Foundation set up a camp to support a number of field parties during that season (Figure 1). A short time later Cassidy transferred to the Allan Hills camp and Marvin and Clauter joined Shiraishi at the Darwin Camp. The sites examined in that area included the Warren and Boomerang Ranges, Butcher, Finger, and Turnstile Ridges, Haven Mountain, and Westhaven, Bates, and Lonewolf Nunataks. Most of these sites proved barren, but six mete- orites, all moderately weathered and looking sus- piciously like fragments from a single fall, were collected near Bates Nunatak. The three largest, BTNA78001, 78002, and 78004, were later clas- sified as L6, L6, and LL6 chondrites, respectively (see Appendix Table A). Five specimens were found in the upland be- tween the head of the Darwin Glacier and that of the Hatherton Glacier. Twenty-three specimens, most of them small and weathered to a chestnut brown, were collected from ripple identations on a rather steeply sloping, bare ice-surface near the west end of the Darwin Mountains. Their similar appearance and their distribution over an open slope suggested that they represented a relatively recent strewnfield from atmospheric break-up of a single meteorite. In mid-December a group of geologists from the University of Waikato, New Zealand, led by Michael Selby, discovered six iron meteorites on the rocky slopes of Derrick Peak, a conical moun- tain visible on the northern skyline from Darwin Camp (Figure 2). They radioed the news to Cas- sidy at Darwin Camp and he and Shiraishi spent two days searching the slopes with the New Zea- SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES Syowa Base Darwin Camp Purgatory Peak Mt. Baldr 1 Allan Hills Reckling Peak Antarctica KEY: ? Continental Boundary """"? Ice Shelf Border $==* Major Glaciers ? Meteorite Find 180 500 km FIGURE 1.?Location maps of Antarctic meteorite finds: a, outline map of continent; b, areas searched and location of finds in Victoria Land. land team. A short time later, Shiraishi, Marvin, and Clauter spent another day there. In all, nine more specimens were collected, and, later, an- other specimen was donated by Peter King, a New Zealand climber associated with the Darwin Base support group. The Derrick Peak irons range in weight from about 130 grams to 138 kilograms (see Clarke, herein: 54-55). The two largest ones were strik- ingly handsome specimens, very difficult to carry from the steep mountainside to a waiting helicop- ter. All of these irons have a distinctive appear- ance, with large, elongate inclusions standing up in relief on surfaces hollowed by deep regma- glypts or corrosion pits. This unusual textural feature indicates that they belong to a single shower, and the distribution of the specimens high on an ice-free mountain side suggests they fell at that site rather than having been trans- ported. Preliminary metallurgical observations NUMBER 24 Lonewolf Nunatak Bates Nunatak Haven Mt. ^Turnstile Ridge \ ,v-~-Westhaven Nunatak Hatherton Glacier Darwin Camp Tentacle RidgeDarwin Glacier Carlyon Glacier Scott Base KJcMurdo StatioVV Victoria Dry Valley MocKay Glacier Carapace Camp Allan Hills Camp Mawson Glacier / Reckling Peak Elephant Nunatak SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 2.?Meteorite hunter on boulder-strewn slope of Derrick Peak. have confirmed the common parentage of the individual specimens. The raised inclusions are crystals of schreibersite. The Darwin Camp was located on the upper glacier amid superb mountain scenery. All facil- ities?bunkhouse, workroom, gallery, radio shack, repair shop?were housed in demountable James- way huts. A cook served three meals each day and, whenever the generators worked, there were a shower, flush toilets, a washer and dryer for laundry. Field parties came and went all season, but there were always enough people in camp for a volley-ball game at 5 o'clock in the afternoon. The Darwin Camp lay about 320 km from McMurdo Station. Personnel and equipment were carried there by ski-equipped Hercules LC- 130 cargo planes. Three helicopters were kept at Darwin to ferry parties in and out of the field. One fully operational helicopter was always on the ground for possible use in rescue missions. All field parties gathered at Darwin Camp for a festive Christmas dinner featuring roast turkey and cranberry sauce, with a generous array of other dishes. The celebration helped alleviate the sense shared by many polar researchers of being too far from home at holiday time. Shortly before New Year's Day, Shiriashi, Mar- vin, and Clauter left Darwin Camp for Mc- Murdo, and on 2 January they joined Cassidy at Allan Hills. After a long and eventful season, Annexstad and Nishio left Allan Hills on the same helicopter that carried in the newcomers. In contrast to Darwin, the Allan Hills Camp was a traditional Antarctic do-it-yourself operation in which the campers pitched their own Scott tents and were expected to take turns cooking for the party over a Coleman stove. Happily for every- one, after sampling the efforts of others, Shiraishi, who was well supplied with frozen Japanese de- licacies, voluntarily did more than his share of the cooking. Daily trips were made by snowmobile to search for meteorites on the nearby expanse of blue ice, in a moraine at the foot of the Allan Hills ice monocline, or on the polar plateau above it. On the bare ice a fairly high percentage of the rocks present were meteorites. On the plateau, few rocks were sighted but all were meteorites. One iron NUMBER 24 FIGURE 3.?Communications hut and tent city at Darwin Glacier Camp, with Roadend Nunatak in background. meteorite was found part way up the slope to the plateau. In the moraine, meteorites occurred among cobbles and boulders of local ("trash") rocks. The moraines of this area are not similar to the lobate heaps of rubble and clay associated with mountain glaciers; they are collections of rocks, probably derived from a shallow subsurface ridge, scattered over the ice and snow. Keen observation is necessary to detect meteorites and to distinguish some of them from wind-polished dolerites, especially since our sterile collection procedures forbid picking up specimens for close examination. The wind scoops (Figure 4) that form around the base of large boulders proved to be good hunting ground for cherry-sized meter- orites, which are small enough to skitter along the ice until they fall into the hollows. Laboratory studies of cherry-sized stones are revealing a high proportion of unequilibrated chondrites contain- ing newly discovered assemblages of graphite and magnetite (Taylor et al., 1981). Although some meteorites may be covered by snow, only one has been discovered frozen be- neath the surface of the bare ice. That one was small, nearly flat, and had a bronzy luster sugges- tive of either an iron meteorite or a weathered piece of dolerite. Still frozen in a block of ice, the specimen was shipped to Houston where it proved to be a hexahedrite, ALHA78100. The total number of specimens collected at Allan Hills in 1978-1979 was 262. The average size was smaller than that of previous seasons. It appears that, at any one site, the largest and most conspicuous specimens will be collected the first year. Thin drifts of snow may alternately conceal and expose smaller ones. An example of this occurred during an afternoon's search when one member of the party discovered a small ureilite within the moraine and marked the spot by build- ing a cairn topped with a red flag. A short time later, when the whole party came to view the meteorite, no meteorite was seen. Presently the specimen was found under a fresh mound of wind-blown snow; the presence of the cairn had SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 4.?Wind scoop around boulder in a moraine, ideal trap for cherry-sized meteorites that skitter downwind along ice surface. changed wind patterns enough to cover the me- teorite within minutes. Helicopter reconnaissance yielded five speci- mens from a patch of ice about 20 km west, and upstream in the sense of ice motion, from the Allan Hills concentration (Cassidy, 1979). The previous year, 25 specimens, all apparently from a single fall, had been found about midway be- tween the two sites. The ice flowing toward Allan Hills from the west may be carrying many mete- orites, most of them covered with snow. Early in the season, Cassidy flew to the Ell- sworth Mountains to check that area. He con- cluded that the ice was moving too rapidly to form any significant meteorite concentrations there. He also made reconnaissance flights over the Thiel Mountains, where one meteorite was discovered in 1969 and patches of blue ice are visible on satellite photographs. Cassidy feels that area holds sufficient promise to justify future field exploration. During a geological traverse, Philip Kyle of Ohio State University, found five meteorites on a patch of ice a short distance west of Reckling Peak. His discovery led to a snowmobile traverse there in the 1979-1980 season (Cassidy and Ran- citelli, this issue). The meteorite types collected in the 1978-1979 and 1979-1980 field seasons are listed in Table 1. Much more laboratory work will be necessary before it will be possible to estimate the number of falls that are represented among the Victoria Land specimens. The Traverse to Reckling Peak, 1979-1980 W.A. Cassidy and L.A. Rancitelli Reckling Peak is located at 159?15'E, 76?16'S. A blue ice patch extends west from Reckling Peak for about 100 km. The effective limit for routine travel by helicopter from McMurdo Station is reached at Allan Hills, therefore to investigate the Reckling Peak ice patch we travelled north by snowmobile from our Allan Hills put-in site, towing our supplies on Nansen sledges (Figure 5). Other members of the group were J. O. An- nexstad, NASA Johnson Space Center, and Lee Benda, University of Washington. We left Allan Hills on 5 January and made 24 km before camping about 4 km west of Battle- ments Nunatak (Figure 6). On this traverse we skirted families of crevasses resulting from changes in ice flow velocity about the Battlements Nunatak barrier. The next two days were spent at this site due to high winds and consequent low visibility that made travel inadvisable. On 8 Jan- uary the wind died, we broke camp, and made 32 km to a point where increasing size and fre- quency of crevassing made further progress diffi- cult. We were approaching a change in elevation where the ice surface descends fairly steeply to become part of a well-defined convergence area leading to the David Glacier. Crevassing here results from the fact that at the crest of the slope each unit of ice volume at the upper surface is forced to travel a greater distance in the same time than any similar unit below it, i.e., acceler- ation by change of direction. Kyle's party had descended somewhere near W.A. Cassidy, Department of Geology and Planetary Science, Uni- versity of Pittsburgh, Pittsburgh, Pennsylvania 15260. L.A. Ranci- telli, Battelle Memorial Institute, Columbus, Ohio 43201. our location, and Annexstad and Benda soon found several of his trail markers from the pre- vious year. We camped, and the next day de- scended the slope with some care?we had to make a detour at one point when the lead sledge made a hole at the edge of a snow bridge. The lower part of the slope was bare ice, and we used snowmobiles in tandem, one in front pulling and the other behind braking, to transfer each sledge to the bottom. At the bottom, we were on the ice patch within the area where Kyle's party had picked up five meteorites. In a rising wind, we proceeded to a clear, snow-covered spot in an adjacent moraine and set up our camp. We were located about 12 km west of Reckling Peak. During a day and a half spent searching, we recovered 13 meteorites (Figure la). Travelling west along the northern edge of the ice patch on January 12, we were off the bare ice surface so we have no knowledge of whether or not meteorites can be found along its entire length. At a point about 65 km west of Reckling Peak we reached a second large moraine which, by a strange configuration of rock debris and ice sculpting, appears on the aerial photos to have the outline of an elephant. We refer to it as Elephant Moraine. One day's searching around Elephant Moraine netted 12 meteorite specimens (Figure 7 b). On 14 January we recrossed the ice field there, ascended the monocline, and headed south again for a helicopter pickup near Allan Hills. In assessing the results of this part of the 1979? 1980 field effort, several interesting points emerged. The Reckling Peak ice field, 100 km 10 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 5.?Snowmobiles pulling sledges across Reckling Peak icefield during traverse from Allan Hills to Reckling Peak. FIGURE 6.?Route of snowmobile traverse from Allan Hills to Reckling Peak and return via Elephant Moraine. NUMBER 24 11 a 1047 1001 1003 1007 1009 1002 apparent direction of Ice Flow Moraine Camp 500 m 1048 1180 1185 apparent direction I of vlce Flowy Elephant Moraine Camp FIGURE 7.?Positions of majority of specimens at two sites relative to apparent direction of ice flow: a, Moraine Camp; b, Elephant Moraine Camp. long by several km wide, seems to be associated with a bedrock barrier parallel to its long dimen- sion over which ice spills in the same manner as at the Allan Hills and parts of the Yamato Moun- tains. This produces a step-like ice surface config- uration. Aside from Reckling Peak, no rocks crop out along its entire length although morainal deposits, suggesting the presence of bedrock near the surface, are found at two points. Meteorites have been concentrated in at least two locations along this linear ice field. They are associated with moraine deposits on the lower level of the ice step, but apparently are not found in such great numbers at Reckling Peak as at the Allan Hills site. The Allan Hills outcrop pene- trates the ice and forms an absolute barrier to further ice flow downstream from the monocline. There is no such barrier at the Reckling Peak ice field. This may help explain the lower abun- dances of meteorites exposed at the latter site. We may find also that meteorite concentrations have a higher surface density when associated with moraines than they do elsewhere along the length of an ice field, because the bedrock barrier is closer to the surface at those locations and the ice may be flowing more slowly there. Further field reconnaissance is necessary before commenting further on this. Our total recovery on the traverse was 26 spec- imens. An estimate of possible pairings suggests that at most we recovered only 15 individual falls at the two sites we examined. Of these 15, how- ever, at least four (>25%) were relatively rare types (i.e., one iron and three achondrites; one of the achondrites is a shergottite). Inasmuch as the majority of meteorites in any random collection should be ordinary chondrites, one might project higher total numbers in this area than we report here. Alternatively, these two sites could be pre- senting samples that fell during some time frame when the meteorite flux at the earth had a differ- ent average composition. In either case, the Rec- kling Peak icefield appears to be a promising site for further work. ACKNOWLEDGMENTS.?This field work was sup- ported by grant NSF DPP 78100. Louis Ranci- telli's efforts were supported in part under NASA contract NAS-9-11712. John Amrexstad's ex- penses were supported in part by his organization, NASA Johnson Space Center. The Allan Hills Icefield and Its Relationship to Meteorite Concentration John 0. Annexstad The United States Antarctic Search for Mete- orites (ANSMET) has centered on the Allan Hills icefield (76?45'S, 159?40'E) from 1976 through 1979. This area has yielded nearly 700 specimens of varying sizes and types. The main advantage of this icefield for meteorite search is its close proximity to McMurdo Station (230 kilometers) which makes it easily accessible by helicopter. Figure 8 shows the Allan Hills in relation to McMurdo Station on Ross Island. The icefield extends from the west side of the Allan Hills on to the polar plateau. The Allan Hills icefield has been described by Nishio and Annexstad (1979) as a limited icefield that has large concentrations of meteorites. The meteorites appear to be concentrated on the lower limb of an ice monocline (Cassidy, 1978) with other finds scattered throughout the field. In an attempt to understand the mechanisms of meteorite concentration, a triangulation chain was established across the icefield during the 1978-1979 austral summer. This chain is com- posed of 20 stations, two of which are on bedrock, and extends westward from the Allan Hills a distance of 15 kilometers. Figure 9 shows the triangulation chain and its relationship to the meteorite concentrations. Each station is marked by a bamboo or alu- minum pole set into a 50-100 centimeter hole drilled into the ice or firn (Figure 10). Wild T-2 John O. Annexstad, Curator's Office, Johnson Space Center, Houston, Texas 77058. theodolites were used to establish the positions of each station and to measure their evaluations relative to the datum points (Stations 1 and 2). The datum points are located on bedrock at an adopted elevation of 2054 meters (barometric- altimetry) with a base line length of 1546.26 meters. A small strain net of four stations, about 650 meters per side, was installed 1 kilometer north of station 11 during late December 1978. Weather problems precluded an accurate survey of this net at that time, but basic data were obtained for ablation measurements. The triangulation net was resurveyed and the strain net was precisely located during December 1979. Values were measured for the rates of abla- tion, horizontal movement, and vertical emer- gence or submergence of the icefield. It should be noted that the first resurvey was accomplished after only one year because of the availability of personnel. Since the accumulated data are only one year old, they must of necessity be considered preliminary. A final resurvey of the triangulation net is planned for the 1984-1985 austral summer season. FIGURE 8.?Allan Hills in relation to McMurdo Station on Ross Island; icefield with meteorite concentrations extends from the Allan Hills westward onto polar plateau. FIGURE 9.?Triangulation chain extending from Allan Hills, where datum points at Stations 1 and 2 are located on bedrock, westward across exposures of blue ice (dots = meteorite finds). 12 NUMBER 24 13 McMurdo Region, Antarctica Seal* 1:1,000,000 Kilometers Statute Miles ,~ \ Nx SNOW COVERED v \ \\ EXPOSED ,V$> *?? 14 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES b FIGURE 10.?Setting up triangulation network station: a, drilling ice with SIPRE auger; b, implanting bamboo flagpole to measured depth; c, locating survey point by theodolite. NUMBER 24 15 TABLE 2.?Allan Hills triangulation network, preliminary survey data Station number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 A B C D Elevation 2054.00 1909.86 1945.69 1955.71 1952.81 1954.14 1951.79 1946.67 1949.42 1945.19 1944.51 2030.50 2008.37 2014.37 2046.54 2022.05 2075.30 2067.58 2075.06 2070.81 NA NA NA NA Ablation (cm/yr) 0 0 -2.3 -2.3 -1.1 -1.6 -2.5 -3.7 -4.2 -6.5 -5.6 -4.5 -5.6 -7.0 -5.7 -4.2 -5.1 -4.5 -3.1 -1.8 -6.4 -6.2 -6.0 -5.0 Emergence (+) or submergence (?) velocity (cm/yr) 0 0 -0.6 -0.6 -0.8 + 1.9 -1.2 + 1.4 +4.6 +6.7 + 7.1 -1.7 +6.5 +0.8 -2.7 -1.2 -1.0 -1.0 -3.5 -2.5 NA NA NA NA Horizontal velocity (cm/yr) 0 0 7 6 10 20 17 50 30 80 100 123 129 121 140 182 202 237 234 251 NA NA NA NA Type surface Rock Rock Firn Firn Firn Firn Firn Firn Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Firn Firn Ice Ice Ice Ice Table 2 (Annexstad and Nishio, 1980) shows a listing of each station along with its elevation, ablation rate, vertical velocity, horizontal veloc- ity, and type of surface. Because the small 4- station strain net (Stations A,B,C,D) was not precisely located until December 1979, only the rate of ablation for the first year could be in- cluded. The icefield gradually increases in altitude from those stations located near the Allan Hills to the westernmost region at Station 20. Stations I and 2 are located on bedrock with Station 1 on a promontory overlooking the icefield. The field exhibits a steplike topography between Stations I1 and 12 where the altitude increases 85 meters in less than a kilometer. The main area of mete- orite concentration appears to be in the region of those stations (10 and 11) located on the lower part of the step. Using Stations 10 and 11 as a guide in respect to the meteorite concentration mechanism, it can be seen that the rate of ablation is fairly constant at ?6.5 and ?5.6 cm per year respectively. This value compares closely with the rate of ablation measured by Naruse (1978) in the productive meteorite icefield near the Yamato Mountains. If all the stations are considered, (see Figure 11), the rate of ablation ranges from a low of 1.1 cm per year at Station 5 to a high of 7.0 cm per year at Station 14. The average rate of ablation on the ice surface alone is 5.7 cm per year (Figure 12) while that of the firn surface is less: 2.7 cm per year. The higher rate of ablation must be due to the more rapid sublimation of the ice surface once it is exposed. It is interesting to note, however, that the ice or firn is wearing away gradually at all 22 stations. The velocity of emergence (+) or submergence 16 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES JUUL ICE CLIFF ? STATION BARE ICE AREA FIGURE 11.?Rates of ablation measured (cm) after one year at Allan Hills icefield (after Ni- shio and Annexstad, 1980). FIGURE 12.?Ablation lowered surface at Station 14 about 7 cm between 1978 and 1979 field seasons. NUMBER 24 17 (?) is not so clear as the value of ablation. Nishio and Annexstad (1980) report that the relative error in these measurements can be as high as 100% at some stations. The authors note that these errors are the result of small velocity values after only one year that cannot be measured accurately within the tolerances of the instru- ments. It is instructional, however, to look at the values in the vicinity of Stations 10 and 11. In this region of the highest meteorite concentration it appears that the emergent velocity and the ablation rates nearly balance. It is possible that a steady state condition does exist in this part of the Allan Hills icefield. The horizontal velocity gradually increases from a low of 6 cm per year at Station 4 to 251 cm per year at Station 21. Figure 13 shows a schematic representation of the horizontal ice flow by both vector direction and magnitude. The vector direction gradually shifts from NE at the westernmost station to nearly E as the Allan Hills are approached. The change in magnitude as the ice nears the hills indicates that the icefield is slowing down toward stagnation. Although the Allan Hills icefield has yielded over 700 meteorite fragments, it still is a limited area of concentration. The direction of the hori- zontal movement vectors at the westernmost sta- ALLAN HILLS TRIANGULATION NETWORK TRUE NORTH MAGNETIC NORTH HORIZONTAL MOVEMENT IN METERS 0 12 3 4 FIGURE 13.?Vector directions and magnitudes of ice flow across triangulation chain. 5 KM 18 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES tions indicate that the flow of the icecap is gen- erally NE in that vicinity. This implies that most of the ice flows into the large David Glacier (Drewy, 1980) that is north of the Allan Hills. Therefore, the majority of meteorites collected by the icecap are probably deposited by the large outlet glaciers that drain extensive sections of the eastern Antarctic icesheet. This might help to explain why the region around the dry valleys, where the glaciers are small and have corre- spondly small catchment areas, produce few me- teorites. The Allan Hills area appears to be on the fringe of the major flow into the David Glacier with its correspondingly large catchment area. It is predicted that other blue ice fields that inter- cept large flow areas have the potential for pro- ducing many meteorites. Descriptions of Stony Meteorites Roberta Score, Trude V. V. King, Carol M. Schwarz, Arch M. Reid, and Brian Mason This section provides descriptions of the indi- vidual specimens, arranged by class. Within the chondrites, the specimens are grouped according to the Van Schmus-Wood (1967) classification, and the descriptions follow the order of increasing petrographic type. The descriptions are based largely on those published in the Antarctic Me- teorite Newsletter, with additional information as available. The letter-number designation for each meteorite concurs with guidelines recommended by the Committee on Nomenclature of the Me- teoritical Society; it carries the following infor- mation: ALH (Allan Hills); A78 (Expedition A, 1978); XXX (digits indicating the number of the specimen). The original weight of the specimen is given to the nearest gram (nearest 0.1 gram for specimens weighing less than 100 grams). This section comprises material on all charac- terized meteorites collected during the 1978-1979 and 1979-1980 field seasons, together with de- scriptions of some meteorites collected during the 1977-1978 field season and not included in the previous catalog (King et al., 1980). Specimens weighing less than 100 grams are listed without descriptions, unless they show distinctive features. Roberta Score, Trude V. V. King, and Carol M. Schwarz, Northrop- Houston, Johnson Space Center, Houston, Texas 77058. Arch M. Reid, Geology Department, University of Cape Town, Rondebosch, South Africa. Brian Mason, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC. 20560. Chondrites CLASS C2 FIGURE 14 ALHA78261 (5.1 g).?This triangular stone (2.5 X 1.5 X 1.0 cm) is totally covered with thin, dull black, polygonally fractured fusion crust, except along the edges where the fusion crust has abraded away. The matrix revealed in these areas is greenish black and has small (<1 mm), rounded, and irregular white clasts throughout. Small voids, as much as 1 mm in diameter, are present on two surfaces. Chipping the specimen during processing revealed abundant rounded and irregular inclusions in the meteorite. The section shows numerous tiny grains (up to 0.1 mm) and irregular aggregates (up to 0.3 mm) of olivine and polysynthetically twinned clino- pyroxene, and a few small chondrules, in a trans- lucent isotropic olive-brown matrix. The section contains very little troilite as minute scattered grains, and a little nickel-iron as inclusions in the chondrules. Porous fusion crust, up to 2.5 mm thick, rims part of the section. Microprobe anal- yses show that both olivine and pyroxene have variable composition. Olivine ranges from Fao to Faso, with an average of Fa6; it has a notable chromium content, Cr2O3 ranging from 0.3-0.6 weight percent. Pyroxene is generally close to clinoenstatite in composition, ranging from Fsi to Fss, with an average of FS7. This meteorite shows 19 20 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 14.?ALHA78261, C2 chondrite: a, Remnants of fusion crust (lighter gray) present; b, photomicrograph of thin section (area of field is 3 X 2 mm); irregular grains and rare chondrules, mainly of olivine (white to light gray) in translucent to opaque matrix (dark gray to black). a close similarity to ALHA77306, and is tenta- tively paired with it. CLASS H3 FIGURE 15 ALHA78084 (14280 g).?This is a complete stone, covered with splotchy brown and black fusion crust. Several large fractures penetrate the interior. A thin white deposit was evident along some of these cracks after the meteorite was dried. Many light-colored, rounded, and irregular inclu- sions are apparent on the cut faces, some as large as 4 mm in diameter. Metal is visible, though most of the metal grains have oxidation halos around them, giving the cut faces a marbled look of small fresh areas and large oxidized areas. The section shows a close-packed aggregate of chondrules, 0.3-1.2 mm in diameter, and a few angular enclaves (some are chondrule fragments) in a minor amount of fine-grained matrix. A wide variety of chondrules is present, the commonest being porphyritic olivine and olivine-pyroxene with interstitial glass; some of the glass is brown and transparent, but much of it is turbid and partly devitrified. The pyroxene is polysyntheti- cally twinned clinobronzite. The matrix contains a considerable amount of fine-grained nickel-iron and a lesser amount of troilite. Weathering is extensive, with veins and patches of brown limo- nite throughout the section. Microprobe analyses show olivine of rather uniform composition, av- eraging Fais, and pyroxene of variable composi- tion, Fsg-24, average Fsi3. The mean composition of the olivine and the amount of nickel-iron in- dicate H group and the meteorite is tentatively classified as an H3 chondrite. CLASS L3 FIGURES 16, 17 ALHA78038 (363 g).?This angular specimen is approximately 12 X 5 X 5 cm and appears shiny and reddish brown due to weathering and staining by iron oxidation. Several fractures pen- etrate deeply into the sample. One small remnant patch of shiny black fusion crust remains on the B surface. During processing the sample fell apart and revealed no unoxidized material. The section shows a close-packed aggregate of chondrules, 0.3-2.7 mm in diameter, and a few angular enclaves (some are chondrule fragments) in a minor amount of dark fine-grained matrix. A wide variety of chondrule types are present, the NUMBER 24 21 FIGURE 15.?ALHA78084, H3 chondrite: a, fusion crust coats the stone, which shows several penetrating fractures; b, photomicrograph of thin section (area of field is 3 X 2 mm); closely packed aggregate of chondrules and angular enclaves set in minor amount of dark matrix. three commonest being granular olivine and oli- vine-pyroxene, porphyritic olivine, and fine- grained pyroxene. Most of the pyroxene is poly- synthetically twinned. Many of the chondrules have dark rims. Troilite is present in minor amounts in the matrix. Weathering is extensive. The section is rimmed and veined with brown limonite, and little nickel-iron remains. Micro- probe analyses show olivine ranging from Fa4 to Faig, with a mean of Fa22; pyroxene ranges from Fs2 to Fsig, with mean of Fss, and CaO ranging from 0.1 to 1.3 weight percent. The low content of nickel-iron and troilite suggests L group, and the meteorite is tentatively classified as L3 chon- drite. ALHA78188 (0.8 g).?The thin section shows a close-packed aggregate of chondrules, 0.3-1.2 mm across, with a relatively small amount of matrix. Porphyritic olivine chondrules contain intergranular glass, some of which is transparent brown but much is turbid from partial devitrifi- cation. Other chondrules consist of granular oli- vine and polysynthetically twinned low-Ca cli- nopyroxene. Many chondrules have dark rims consisting largely of troilite. A little nickel-iron is present. Weathering is extensive, with veins and patches of brown limonite throughout the section. Microprobe analyses show variable composition for both olivine and pyroxene: olivine, Fai_34, average Fais; pyroxene, FS5-29, average Fsn. ALHA79001 (32.3 g).?The polished thin sec- tion shows a closely packed aggregate of chon- drules, 0.2-2.0 mm in diameter, and irregular crystalline aggregates, set in a small amount of dark, fine-grained matrix that includes minor subequal amounts of nickel-iron and troilite. A considerable variety of chondrules is present, the most common being granular olivine with or without polysynthetically twinned clinopyroxene, porphyritic olivine, and fine-grained pyroxene. Some chondrules have intergranular, transpar- ent, pale brown glass, in others the glass is turbid and partly devitrified. Some weathering is indi- cated by the presence of a moderate amount of brown limonite as veins and patches. Microprobe analyses show a wide range in the composition of olivine (Fa6-39) and pyroxene (FS2-31); the pyrox- ene is a low-calcium clinopyroxene (CaO = 0.2- 1.8%). This range of composition, together with the presence of glass and twinned clinopyroxene, indicates type 3, and the small amount of nickel- iron suggests L group; the meteorite is therefore tentatively classed as an L3 chondrite. ALHA79003 (5.1 g).? The section is texturally identical and the olivine and pyroxene show a 22 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 16.?ALHA78038, L3 chondrite: a, surface bounded by fractures and little or no fusion crust remains; b, photomicrograph of thin section (area of field is 3 X 2 mm); round chondrules and irregular enclaves in dark, fine-grained matrix. FIGURE 17.?Photomicrographs of thin sections of L3 chondrites (area of fields is 3 X 2 mm): a, ALHA79001; b, ALHA79003. (Closely packed aggregates of chondrules and angular enclaves set in minor amount of dark matrix). similar range of composition to these minerals in ALHA79001; hence these two specimens are probably pieces of a single meteorite. ALHA79022 (31.4 g).?This stone (3.5 X 2.5 X 2 cm) is mostly covered with dull black fusion crust. The areas devoid of fusion crust appear to have been spalled off or preferentially plucked off because they occur along ridges. Chipping the stone exposed a relatively fresh, light gray inte- rior, with many inclusions of various colors from black to white. The largest inclusion is white and 7 mm in longest dimension. A narrow (<1 mm) weathering rind is present. The thin section shows well-developed chondri- tic structure, with chondrules ranging up to 1.8 mm in diameter; some have dark rims consisting largely of troilite. The commonest chondrules are granular and porphyritic olivine, with intergran- ular glass; some of the glass is brown and trans- parent, but most is turbid and partly devitrified. The groundmass consists largely of fine-grained olivine and pyroxene, with minor amounts of NUMBER 24 23 nickel-iron and troilite; limonitic staining is pre- sent around the metal grains. Much of the pyrox- ene is polysynthetically twinned. Microprobe analyses show olivine and pyroxene of variable composition: olivine, Fai_28, average Fan; pyrox- ene, FS9-22, average Fsi6. ALHA79045 (115 g).?This specimen (5.5 X 4.5 X 3 cm) has a small patch of weathered fusion crust on one surface; an iridescent, reddish-brown coating on other areas may be remnant fusion crust. The rest of the stone is dull red-brown, but its clastic nature is clearly visible. One clast is 4 mm across and yellow. The thin section shows a close-packed aggregate of chondrules, 0.3-2.1 mm across, and irregular clasts (some of them chon- drule fragments), with a relatively small amount of matrix material. Chondrule types include por- phyritic and granular olivine and olivine-pyrox- ene, barred olivine., and fine-grained pyroxene. Some chondrules have black, troilite-rich rims. Intergranular glass in chondrules may be trans- parent and pale brown, but is usually turbid and partly devitrified. Only a small amount of nickel- iron is present. Most of the pyroxene shows polysynthetic twinning. Brown limonitic staining pervades the section. Microprobe analysis show variable composition for both olivine and pyrox- ene: olivine, Fa2-38, average Fa23; pyroxene FS2-29, average Fss. RKPA79008 (72.9 g).?Black fusion crust cov- ers about half of the stone. Areas devoid of fusion crust are greenish black and show numerous rounded and irregular clasts, up to 2 mm across, and cream to black in color; two larger cream- colored clasts, 7 and 15 mm in largest dimension, are also visible. The stone is extensively fractured. The thin section shows abundant chondrules, 0.3-1.8 mm in diameter; a wide variety of types is present, the three commonest being granular olivine and olivine-pyroxene, barred olivine, and fine-grained pyroxene. The granular chondrules have intergranular glass, sometimes pale brown and transparent, but commonly turbid and partly devitrified. Irregular clasts, some of them chon- drule fragments, are also present. Some of the pyroxene in the chondrules is polysynthetically twinned clinoenstatite or clinobronzite. The ma- trix is fine-grained olivine and pyroxene, with minor subequal amounts of nickel-iron and troil- ite. Remnants of fusion crust, up to 0.3 mm thick, are present along one edge. Minor weathering is indicated by brown limonitic staining in associa- tion with the fusion crust and nickel-iron grains. Microprobe analysis show that most of the olivine has composition Fa23, but a range of composition Fai_29 is present; pyroxene composition is vari- able, FS2-28, average Fsis. CLASS H4 FIGURES 18, 19 ALHA77221 (229 g).?All surfaces of the me- teorite, except the S surface, have remnant patches of thin, dull black fusion crust. The ex- terior surfaces, devoid of fusion crust, are stained by iron oxidation. Several clasts, approximately I mm in diameter, are apparent on the S surface. The specimen is fractured. Chipping revealed no unweathered material in the interior of the sam- ple. ALHA77223 (207 g).?The T surface of this specimen has patches of dull black fusion crust. The remainder of the sample is stained reddish brown by iron oxidation. The surfaces devoid of fusion crust are fracture surfaces. Several cracks penetrate the sample. ALHA77225 (5878 g).?This stone (20 X 19 X I1 cm) has no fusion crust and is uniformly weathered and stained reddish brown; however, some surfaces are more shiny than others. It is extensively fractured. One brassy colored clast, possibly a troilite nodule, is present on the T surface. The B surface has what appear to be slickensides, but because of the severe weathering of the specimen it is impossible to determine this unambiguously. No unweathered material is pre- sent on the exterior of the sample. When the specimen was cleaved it fell into many pieces. No unweathered material was exposed. ALHA77226 (15323 g).?A small patch of dull black fusion crust is present on the S surface. The 24 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 18.?H4 chondrites. (Note snow and ice on ALHA78134, present when specimen was unpacked at Johnson Space Center). W surface is concave and flow bands are present in the T-B direction. The specimen is severely fractured and crumbled into many pieces during processing. Except for a few, small, light gray areas, nearly all the material exposed is exten- sively stained by iron-oxides. ALHA77232 (6494 g).?The stone (20 X 19 X 14 cm) is rounded, and only small patches of remnant fusion crust remain on the exterior sur- face. It is severely weathered, uniformly stained reddish brown, and fractured. When the sample was sawed it crumbled into many pieces. No fresh, unoxidized surfaces were exposed during processing. White deposits developed on some surfaces of the meteorite while it dried in the nitrogen cabinet. ALHA77286 (245 g).?The B surface and por- tions of the N surface are devoid of fusion crust. The remaining surfaces have remnants of a thin black fusion crust. The surfaces lacking fusion crust are rough on a small scale. It appears that many ~l-mm inclusions produce the roughness. Chondrules and lithic clasts are present. No un- weathered material was exposed when the stone was sawed. ALHA78053 (179 g).?This 8.0 X 6.0 X 2.5 cm specimen has a small amount of thin, shiny black fusion crust on the B face. The remainder of the NUMBER 24 25 FIGURE 19.?Photomicrographs of thin sections of H4 chondrites (area of fields is 3 X 2 mm): a, ALHA77221; b, ALHA77223; c, ALHA77232; d, ALHA78134. (Chondritic structure well developed, but some chondrule margins tend to merge with granular matrix.) sample is smooth, weathered, and stained reddish brown by iron oxidation. Fractures are present on the T and B surfaces. No unweathered material was exposed during processing. ALHA78O77 (330 g).?Thin, shiny black fusion crust covers this 6.5 X 6.0 X 5.0 cm stone. In spots the fusion crust is weathered away, revealing a smooth, brownish-red surface. Several deep cracks penetrate the sample. During processing the sample cleaved along one of these fractures, revealing no unoxidized material. ALHA78134 (458 g).?The stone (7.0 X 5.0 X 7.5 cm) has dull black fusion crust on about 40% of the surface. The remaining surfaces are weath- ered and stained by iron oxidation. On the S surface the inclusions in the meteorite have a higher relief then the surrounding matrix, prob- ably as a result of preferential weathering. Inclu- sions (chondrules and lithic fragments) are visible on the other fracture surfaces but have not expe- rienced any preferential weathering. Several large fractures penetrate the meteorite. When it was divided during processing, 60% of the interior was stained reddish brown. The remaining 40% is light gray and contains many clasts 1 mm or less in size. ALHA79030 (108 g).?This 6 X 5 X 2.5 cm stone is totally covered with thin, black fusion 26 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES crust that has a blistery texture on the B surface. The T surface is concave and the B surface is flat. Most of the interior is somewhat weathered, al- though areas of light gray material are present. META78001 (624 g).?This stone (14.5 X 8 X 3 cm) is shaped like a boomerang and is entirely covered with fusion crust. The fusion crust on the B surface has an iridescent sheen, is much thinner than the fusion crust on the remainder of the sample, and has a well-defined area of weathering 1 cm from the edge of the sample. Remaining surfaces have dull, brownish-black fusion crust. Small regmaglypts are apparent on the T and N surfaces and flow bands are present on the B surface at the E and W ends. Small fractures exist on the T and B surfaces, but they do not appear to penetrate the stone. The interior material ranges from being completely weathered and iron-oxide stained to unweathered. The weath- ered portions are massive and are preferentially located in the T half of the sample. The unweath- ered areas are light grayish green and contain unoxidized metal grains. RKPA78OO2 (8483 g).?This tabular-shaped meteorite (17 X 13.5 X 17 cm) has two flat and two semi-rounded surfaces with sharp ridges. Black, polygonally fractured fusion crust, 0.5 mm thick, covers the entire specimen except for areas along the ridges where it has broken off. The areas without fusion crust are greenish brown and contain numerous inclusions. One fraction pene- trates the interior of the meteorite. After drying for several days in the nitrogen cabinet, minute amounts of white deposit appeared along the polygonal fractures. The cut face reveals a weath- ering rind 1-4 mm thick. Abundant metal blebs are obvious, with most of the metal having oxi- dation halos around them. RKPA78004 (166 g).?All but one surface is covered with thin, dull black fusion crust, al- though portions of the fusion crust on another surface appear to have been physically plucked away. The portions devoid of fusion crust are shiny reddish brown. Chipping this small stone was impossible. Sawing revealed an interior with many clasts discernible in the dark gray matrix. Metallic grains are present. On the cut face it appears that the inclusions in the meteorite have a more dense population around the circumfer- ence, from the exterior margin to a depth of approximately 1 cm. H4 chondrites weighing less than 100 g are ALHA78193, 13.3 g; 78196, 11.1 g; 78223, 6.4 g; 79023,68.1 g; 79035, 37.6 g. The thin sections of the H4 chondrites resemble each other closely. They all show well-developed chondritic structure, chondrules 0.2-1.8 mm in diameter. (ALHA77221 has some unusually large chondrules, ranging up to 3 mm in diameter.) A variety of chondrule types is seen, the four com- monest being porphyritic to granular olivine, barred olivine, fine-grained pyroxene, and gran- ular olivine-pyroxene. The chondrules are set in a fine-grained, granular matrix consisting largely of olivine and pyroxene, with minor amounts of nickel-iron and troilite (nickel-iron in greater amount than troilite). Much of the pyroxene is polysynthetically twinned clinobronzite. All these meteorites except META78001 and RKPA78002 are considerably weathered, with brown limonitic staining throughout the sections, and veins and patches of limonite often associated with the nickel-iron grains. The section of META78001 shows areas of blackening that appear to be due to fine-grained troilite, possibly a shock effect. Microprobe analyses (Appendix Table A) show that the olivine in these meteorites has essentially uniform composition (Fai7_ig); pyroxene may have uniform composition (Fsis_i6), but in many of these H4 chondrites shows some variability. CLASS H5 FIGURES 20, 21 ALHA77259 (294 g).?This appears to be a nearly complete stone, with only a small area of the T surface not intact; this area is weathered yellowish brown and shows traces of inclusions. The rest of the surface shows remnant patches of dull black fusion crust over a weathered surface stained reddish brown with iron oxide. Regma- glypts are present on the E/S surface. NUMBER 24 27 FIGURE 20.?H5 chondrites: ALHA781O2, rounded weathered stone with small patches of remnant fusion crust; ALHA78107, angular stone bounded largely by fractures. FIGURE 21.?Photomicrographs of thin sections of H5 chondrites (area of fields is 3 X 2 mm): a, ALHA77259; b, ALHA781O7. (Chondritic structure easily discernible, but many chondrules show partial integration with granular matrix.) ALHA77268 (272 g).?This appears to be a complete specimen with dull black fusion crust on all surfaces. One small area with an iridescent sheen is present on the T surface. A large fracture penetrates the entire stone. No unweathered ma- terial was exposed during processing. ALHA77274 (288 g).?A small patch of black fusion crust remains on the B surface. The other surfaces are devoid of fusion crust and are stained reddish brown with iron oxides. ALHA77287 (230 g).?Small patches of rem- nant fusion crust are preserved on the T and B surfaces. The remaining surfaces are smooth and weathered reddish brown. Small areas of the surface have an iridescent sheen. No unweathered material was exposed during processing. ALHA78075 (280 g).?Thin, shiny fusion crust covers most of this (7X6X3 cm) specimen, with the exception of portions of the T and W faces. Areas devoid of fusion crust are smooth and 28 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES weathered to a shiny, dark reddish brown. Light- colored inclusions and metal grains are apparent in the dark matrix. Several fractures are present. ALHA78085 (219 g).?Except for very thin, black fusion crust on the B surface, this specimen (6.5 X 4.5 X 3.5 cm) is bounded by fracture surfaces that are weathered to a dark reddish brown. A small clast (~2 mm), possibly troilite, is present on the T surface. Processing revealed a brecciated interior with a light-dark structure. The light portion consists of numerous clasts in a wide range of sizes, surrounded by dark material. ALHA78102 (336 g).?Most of the surface of this specimen (9X6X6 cm) is weathered and stained by iron oxidation and spotted with small patches of black fusion crust. The specimen is totally weathered except for the innermost ma- terial, which contains many small (up to 3 mm) dark clasts. ALHA78107 (198 g).?The B, S, and portions of the E surfaces are covered with thin, black, polygonally fractured fusion crust that is slightly stained by iron oxides. Shallow regmaglypts are present on the S surface. Other surfaces are frac- tured and are weathered and stained reddish brown. No unweathered material was seen during processing. ALHA78108 (172 g).?Remnants of fusion crust are present on the T and N surfaces, the specimen (6.0 X 5.5 X 4.0 cm) being elsewhere bounded by weathered, red-brown fracture sur- faces. The specimen appears to be severely shocked and brecciated. Many slickensided sur- faces were exposed during processing. Two black veins (~1 mm wide), with higher relief than the surrounding material, are present in the interior. ALHA7811O (160 g).?The stone (7.0 X 5.0 X 2.5 cm) is covered with thin, patchy black fusion crust except on the B surface, which is stained reddish brown with iron oxides and shows two protruding, chondrules. Small, rounded, and ir- regular inclusions are visible through the fusion crust. The matrix is reddish brown and shows many inclusions and chondrules (up to 2 mm in diameter), as well as metal grains. ALHA78128 (154 g).?Fusion crust is absent, this specimen being weathered and stained a dark reddish brown. The B surface has some small, nearly black spots, and in other areas, where the weathering is less severe, chondrules (maximum diameter 2 mm) can be recognized. The specimen is extensively fractured. ALHA79012 (191 g).?Thin patches of fusion crust are present over all but the B surface of this stone (9.0 X 5.5 X 3.5 cm). Fractures penetrate the interior of the meteorite, which is extensively weathered to a deep reddish brown. Field notes state that this stone was found near ALHA79029, another H5 chondrite. ALHA79025 (1208 g).?Thin, black fusion crust covers the S and B faces of this specimen (10 X 13 X 7 cm). Otherwise it is bounded by fractures that are weathered to a dark reddish brown; remnants of fusion crust are present on the E surface. ALHA79026 (572 g).?This 9 X 6 X 5.5 cm specimen is angular with flat surfaces covered with a very thin, black to brown fusion crust. The fusion crust has been lost from the T and a corner of the N face, exposing a rough, irregular surface, weathered reddish brown. A few small white clasts are visible. The interior is friable and frac- tured. The matrix is gray with oxidation haloes around metal grains. ALHA79029 (505 g).?This 10 X 7 X 4.5 cm stone has a very thin, patchy fusion crust on the T, E, N, and S faces. Where the fusion crust has been worn away, the surfaces are dark reddish brown. Fusion crust and weathered surfaces are smooth and shiny with an iridescent appearance. The stone is extensively fractured. EETA79OO7 (199 g).?When this meteorite was received, it was numbered as two different sam- ples; however, they fit together perfectly and are therefore numbered as a single specimen. The specimen (8 X 4.5 X 3.5 cm) is covered with black fusion crust except for a few spalled areas. The fracture surface between the two pieces has a 5- mm thick weathering rind of reddish-brown color. Many chondrules are visible. An area exposed by chipping is relatively fresh and gray. META78010 (233 g).?Smooth, black fusion NUMBER 24 29 crust covers this specimen (8.5 X 5 X 4.5 cm). Cleaving the stone into two approximately equal parts revealed a light-dark structure. Dark, vein- like areas, which contain small light-colored clasts (1-2 mm), surround large lighter-colored clasts up to 1 cm across. Some areas of the stone are weathered to a dark reddish brown. ,RKPA79004 (370 g).?When the Reckling Peak meteorites were initially processed, it was found that six stones appeared identical. Field notes state that the six stones were found within 49 meters of each other. Examination of thin sections confirm their identity, and they have been combined as RKPA79004. All six stones have brown-black fusion crust on at least one surface. No stone was completely covered with fusion crust, but two stones have fusion crust on a fracture surface, indicating that the meteorite broke up during flight in the upper atmosphere. Fracture surfaces have all weathered to a reddish brown and have uniformly pitted surfaces where chondrules and inclusions have been plucked away. Chondrules, <1 to 3 mm in diameter, are visible on weathered surfaces. H5 CHONDRITES WEIGHING LESS THAN 100 g.?ALHA78209, 12.1 g; 78221, 5.4 g; 78225, 4.5 g; 78227, 2.4 g; 78233, 1.2 g; 79004, 34.9 g; 79006, 40.9 g; 79008, 12.0 g; 79009, 75.6 g; 79010, 25.1 g; 79011, 14.0 g; 79013, 28.3 g; 79014, 10.8 g; 79015, 63.9 g; 79021, 29.4 g; 79031, 2.7 g; 79032, 2.6 g; 79036, 20.2 g; 79038, 49.6 g; 79040, 13.2 g; 79041, 20.1 g; 79042, 11.4 g; 79046, 89.7 g; 79047, 19.3 g; 79048, 36.7 g; 79050, 27.0 g; 79051, 24.0 g; 79053, 86.0 g; 79054, 36.0 g; RKPA79014, 77.7 g- In thin sections all the H5 chondrites show a generally well-developed chondritic structure, with a variety of chondrule types, the four com- monest being barred olivine, granular and por- phyritic olivine and olivine-pyroxene, and fine- grained pyroxene. The groundmass is fine- to medium-grained, and consists largely of olivine and pyroxene, with minor amounts of nickel-iron and troilite; small grains of sodic plagioclase can sometimes be seen. The compositions of the oli- vine (Fai6-i8) and orthopyroxene (FS14-17) are es- sentially uniform within the individual speci- mens. ALHA79004 contains an enclave of gran- ular polysynthetically twinned clinopyroxene that appears to be of a lower petrographic type. ALHA79008 contains a granular olivine-pyrox- ene enclave, 3 mm across, with the same olivine and pyroxene compositions as the main mass of the meteorite. ALHA79026 contains some unusu- ally large chondrules, up to 3 mm across. CLASS L5 FIGURE 22 EETA79009 (140 g).?This stone (6X5X3 cm) was received as two different samples, con- sisting of three pieces. The three pieces fit per- fectly together and are therefore numbered as a single specimen. Dull black fusion crust covers most of the surface. A weathering rind up to 4 mm thick is present. The interior is whitish gray and shows numerous dark gray, fine-grained in- clusions up to 14 mm in maximum dimension. The thin section shows moderately abundant chondrules, many of which are deformed or frag- mented. The matrix consists of fine-grained oli- vine and pyroxene, with minor amounts of nickel- iron and troilite; much of the nickel-iron and troilite is finely dispersed through the silicates, possibly a shock effect. Brown limonitic staining pervades much of the section. Microprobe anal- yses give the following compositions: olivine, Fa24; pyroxene, FS20. RKPA79013 (11.0 g).?This small stone (2.5 X 1 X 1.5 cm) is completely covered with dull brown to black fusion crust. Chipping revealed a weathered interior with two gray, rounded inclu- sions, 2 mm in diameter. The thin section shows well-developed chondritic structure, with chon- drules ranging from 0.3 to 2.2 mm across. Fusion crust, up to 0.5 mm thick, rims most of the section. Brown limonitic staining is concentrated around nickel-iron grains and below the fusion crust. Microprobe analyses give the following compositions: olivine, Fa23; pyroxene, FS20; acces- sory merrillite was identified with the micro- probe. 30 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 22.?Photomicrographs of thin sections of L5 chondrite (area of fields is 3 X 2 mm): a, EETA79009; b, RKPA79O13. (Chondrules discernible, but their margins tend to be poorly defined and to merge with granular matrix.) FIGURE 23.?ALHA78109, LL5 chondrite: a, fusion crust (black) broken away over parts of stone and exposed light gray interior; b, photomicrograph of thin section (area of field is 3 X 2 mm); well-defined chondrules, some broken and deformed, in fine-grained granular matrix. CLASS LL5 FIGURE 23 ALHA78109 (233 g).?Approximately 75% of this stone (7.0 X 5.5 X 3.5 cm) is covered with dull black fusion crust. Areas without fusion crust are light gray and show abundant dark gray chondrules up to 2 mm in diameter. Chondrules are easily removed from the matrix, many falling out on handling. Troilite nodules, 3-10 mm across, and gray clasts are also present. The thin section shows prominent and well-defined chon- drules, some broken and deformed. A variety of types is present, the three commonest being gran- ular olivine, barred olivine, and fine-grained py- roxene. The matrix is dominantly olivine with lesser amounts of pyroxene, and a little nickel- iron and troilite; plagioclase is present as very small grains difficult to recognize. Some limonitic staining occurs in association with the nickel-iron grains. Microprobe analyses gave the following compositions: olivine, Fa2s; orthopyroxene, FS23; plagioclase, Ann. CLASS H6 FIGURES 24, 25 ALHA77183 (288 g).?This is a well-rounded specimen, except for a flat B surface. Fusion crust NUMBER 24 31 FIGURE 24.?H6 chondrites: Fusion crusts coats most of surface of ALHA78076, whereas on ALHA78115 much of fusion crust has been removed by weathering. *'1-. FIGURE 25.?Photomicrographs of thin sections of H6 chondrites (area of fields is 3 X 2 mm): a, META78OO7; chondritic structure barely discernible, chondrules merging with granular matrix; b, ALHA78O76 (reflected light); rounded intergrowth (possibly chondrule) of chromite (white) and plagioclase (light gray) occupies center of field. is absent, and all surfaces are stained a uniform reddish brown. Small inclusions are visible on the T surface. No unweathered material was seen when the stone was cleaved. ALHA78076 (275 g).?Thin, black fusion crust covers most of the stone (8.0 X 5.0 X 4.5 cm). Where the fusion crust is absent, the surface is stained reddish brown with iron oxides and 1-2 mm clasts are visible. Polygonal fractures are present on the T and N surfaces. Cleaved surfaces shows clasts up to 3 mm across, in gray matrix. Minor amounts of iron oxides are present around metal grains. ALHA78115 (847 g).?This is a smooth, rounded stone with scattered fusion crust on the B and E surfaces, and a very small amount on 32 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES the W surface. The fusion crust is black, thin, and pitted. Where fusion crust is absent the surface is weathered reddish brown. Clasts and chondrules, as much as 9 mm across, are present. The interior, exposed during processing, contains metal parti- cles and is moderately weathered. ALHA79002 (222 g).?A small, thin patch of black fusion crust and remnant red-brown fusion crust cover the stone (8 X 5 X 4.5 cm). Several fractures penetrate the interior. No unweathered material was exposed by chipping. ALHA79016 (1146 g).?This stone (13 X 8 X 6.5 cm) is covered with smooth, black fusion crust, except for small patches on the T and E surfaces; these patches are weathered to a reddish brown color. Shallow regmaglypts are present on several faces. The S and B faces appear to have been fracture surfaces that have been covered with fusion crust. The interior has a yellowish color, is friable, and shows metallic particles; no chon- drules are visible. META78006 (409 g).?This specimen is com- pletely covered with fusion crust. Cleaving re- vealed that the interior is considerably stained with iron oxides; unstained areas are light gray; a few darker-colored inclusions are present. META 78007 (174 g.)?Fusion crust, ranging from dull black to iridescent red-brown, totally covers this irregular-shaped meteorite. The inte- rior of the stone is 75% weathered; the unweath- ered part appears to have many clasts, up to 5 mm across. This stone was magnetically oriented in Antarctica and the orientation has been kept throughout processing. RKPA79003 (182 g).? This semi-rounded stone (7 X 4.5 X 3.5 cm) is covered with black fusion crust. Small areas where the crust has been plucked off reveal a reddish-brown interior with many inclusions. H6 chondrites weighing less than 100 g: ALHA78211, 11.4 g; 78213, 9.5 g; 78215, 6.3 g; 78229, 1.9 g; 78231, 1.8 g; 79005, 60.0 g; 79019, 12.1 g; 79020, 4.2g; 79024, 21.6 g; 79028, 16.2 g; 79034, 12.6 g; 79037, 14.8 g; 79049, 54.0 g; 79055, 15.2 g; RKPA79009, 54.6 g; 79012, 12.8 g. In thin sections all the H6 chondrites show very similar petrographic features. Chondrules are sparse and poorly defined, tending to merge with the granular groundmass, which consists mainly of olivine and pyroxene, with minor amounts of nickel-iron, troilite, and sodic plagioclase, and accessory chromite. Compositions of the olivine (Fan-19) and pyroxene (FS15-17) are uniform within the individual specimens. The thin section of ALHA78076 showed a rounded aggregate of closely-packed chromite grains with interstitial plagioclase, possibly a chondrule of unusual com- position. A vein of nickel-iron up to 0.5 thick is present in ALHA79016. CLASS L6 Figures 26, 27 ALHA77180 (190 g).?This stone has remnant fusion crust on three surfaces; other surfaces are fractures and stained reddish brown with iron oxides. Processing revealed a light gray, fine- grained interior and one fine-grained inclusion approximately 10 mm in diameter. ALHA77292 (199 g).?This is an incomplete stone. The T surface is less severely weathered than the other surfaces; the N surface has rem- nants of dull black fusion crust. Surfaces devoid of fusion crust are rough and stained reddish brown with iron oxides. Fractured surfaces show rounded and irregular inclusions. ALHA78039 (299 g).?This specimen (8X4 X 5 cm) is totally covered with black fusion crust except for a 4.0 X 2.5 cm area that shows a light gray interior. Cleaving the stone revealed a light gray matrix with light gray clasts. A well-defined weathering rind penetrates the stone to a depth of 1-10 mm. Scattered areas of partly oxidized metal are present throughout the meteorite. ALHA78042 (214 g).?The T surface of this 5.5 X 4.0 X 5.0 cm specimen has a 4 X 3 cm area of reddish-black fusion crust; the remaining sur- faces are fractures that are weathered reddish brown. The sawed specimen revealed a relatively fresh interior with a light gray matrix and rounded and irregular inclusions up to 1 mm in diameter. ALHA78043 (680 g).?This stone, 10.0 X 8.5 X 6.0 cm, is covered with black fusion crust, ~1 NUMBER 24 33 FIGURE 26.?L6 chondrites. mm thick, that shows some weathering; the W surface appears to be less weathered than the other surfaces. A large chondrule is present on the B surface. The T surface is a fracture with some remnant fusion crust. During processing the stone broke along fractures that were weathered and stained with iron oxides. The matrix is yellowish green and contains some small (<3 mm) clasts. A few metallic flakes are present in the matrix. ALHA78045 (396 g).?This tabular specimen, (8.0 X 5.0 X 5.0 cm) is covered with blackish brown fusion crust except for a 2.5 X 3.5 cm area on the T/E surfaces that is very smooth and highly polished. Three large fractures penetrate the specimen. During processing the specimen broke into two approximately equal pieces along one of the fractures. The matrix is weathered to a reddish yellow. ALHA78048 (190 g).?This specimen is partly covered with brown to black fusion crust. Where fusion crust is absent, a light gray matrix with some iron-oxide staining is seen. Shallow regma- glypts are present on all surfaces. When the stone was cleaved a thin (1-2 mm) weathering rind was exposed. The interior is light gray with darker gray inclusions and shows some unoxidized metal grains. ALHA78050 (1045 g).?This 15 X 8 X 6 cm specimen is an incomplete stone, being bounded by fractures on the N, T, and B surfaces; these surfaces are stained reddish brown with iron ox- ides. Inclusions are apparent on these surfaces, 34 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 27.?Photomicrographs of thin sections of L6 chondrites (area of fields is 3 X 2 mm in a, b, c; 0.9 X 0.7 mm in d): a, ALHA78106; b, BTNA78002; c and d, RKPA78003. (Chondritic structure barely discernible in these sections, chondrules almost completely integrated with granular matrix; ALHA78106 has thick fusion crust (top of section); d, enlargement of c, with shock vein containing ringwoodite and majorite (tentative determinations).) and patches of remnant fusion crust, mottled brown and black, remain on the B surface. Sawed surfaces show metallic grains, some with oxida- tion halos, and small irregular inclusions. ALHA78074 (200 g).?This is an incomplete stone, with shiny fusion crust (1-2 mm thick) on the B, W, and parts of the S, N, and E surfaces; polygonal fractures are present on the B and N surfaces. Fracture surfaces are rough, slightly weathered, and stained with iron oxides. The matrix is light gray, it includes darker gray clasts and chondrules. ALHA78078 (290 g).?This 6.0 X 4.5 X 8.0 cm stone is covered with thin black fusion crust ex- cept at the corners. Processing revealed a light gray matrix speckled with light and dark clasts and metallic grains. ALHA78103 (589 g).?This rounded specimen (11 X 7X4 cm) is weathered and stained with iron oxides, except for a small patch of remnant fusion crust on the E surface. The B surface, which is least weathered, displays several chon- drules, 3-5 mm in diameter. The stone broke along fractures during processing, showing a greenish-gray matrix with some metallic grains and oxidation halos. A weathering rind, ~3 mm NUMBER 24 35 thick, is present on the T surface. ALHA78104 (672 g).?The W surface is partly covered with black fusion crust, but the remain- der of the surface is weathered and stained with iron oxides. A large clast (~7 mm) is exposed on the N surface, and a smaller (~3 mm) possibly metallic clast on the T surface. A number of smaller clasts that appear to be metallic are scat- tered over the surface. Processing revealed a light gray matrix with metallic particles. Weathering rind, ~5 mm thick, is present on some surfaces. ALHA78105 (941 g).?The surface of this stone (11X7X6 cm) is rough and irregular on a mm scale, apparently as a result of the weathering of the fusion crust, of which small patches remain on the B and N surfaces. The interior shows a light to medium gray matrix with chondrules, lithic clasts, and sparse metal grains. ALHA78106 (464 g).? This semi-pyramidal specimen appears to be completely unweathered (a recent fall?). It is covered with a spotted, brown to black, polygonally fractured fusion crust, ~1 mm thick. Shallow regmaglypts are present on all surfaces. The interior shows a light gray matrix with dark and light clasts up to 2 mm across. ALHA78112 (2485 g).?This stone (14 X 13 X 13 cm) is covered with fusion crust, 0.5-1 mm thick, on four surfaces; on one surface the fusion crust has weathered to a brown color, on the other surfaces it is black. The S surface is a fracture, and 80% is weathered and stained with iron oxides. Sawing the specimen revealed light gray matrix with oxidation halos around most of the metal grains; clasts up to 3 mm across are present. ALHA78114 (808 g).?The B surface of this meteorite is planar and has small patches of dull black fusion crust on a shiny reddish-brown back- ground, which may possibly be severely weath- ered fusion crust. All other surfaces are covered with dull black fusion crust except for small areas on the S surface. Small regmaglypts are present on this surface. Many shallow voids are present on the exterior. The stone was cleaved along a large crack, exposing mostly weathered material. Unweathered material is light gray and flecked with light and dark clasts (~1 mm). ALHA78126 (606 g).?Thin black fusion crust, weathering brown in some areas and polygonally fractured on the B surface, covers this specimen (12X8X5 cm) except on the NE corner. Matrix material exposed during processing is greenish gray, with several darker veins penetrating it; small metallic particles were also apparent in this friable specimen. ALHA78127 (194 g).?The stone is covered with very thin shiny fusion crust on the T, B, N, and W surfaces; remnants of fusion crust are present on the S surface, and the E surface is a fracture surface. Where fusion crust is absent, the specimen is reddish brown. Processing showed that nearly all of the specimen is severely weath- ered. ALHA78130 (2733 g).?This meteorite (18 X 9X9 cm) is covered with a thin, dull black fusion crust, except along the edges and a 4 X 4 cm area on the W surface. There is preferential weathering of the fusion crust around clasts. The stone is covered with shallow regmaglypts and is exten- sively fractured. Processing revealed that about 70% of the interior is severely oxidized. The un- weathered portion is light gray and speckled with light and dark clasts, some up to 5 mm across. Small veins of darker material, 20-30 mm long and 3 mm wide, are present in the matrix. ALHA78131 (268 g).?Thin, shiny black fu- sion crust covers the specimen except for most of the T surface and portions of the B and N sur- faces. Shallow regmaglypts are present on the S, W, and T surfaces. Surfaces devoid of fusion crust are weathered and stained with iron oxides; sev- eral light-colored clasts were noted on these sur- faces. Processing exposed only a small amount of unweathered material. ALHA78251 (1312 g).?This specimen (12 X 7.5 X 10 cm) is completely devoid of fusion crust and the surface is rough and irregular. The inte- rior is fine-grained and greenish gray, and shows metal grains surrounded by oxidation halos. Frac- tures are present with iron oxides along their margins. ALHA79007 (142 g).?Dull black fusion crust covers 50% of this stone (6X4X4 cm). Areas devoid of fusion crust range from light gray to 36 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES yellowish brown in color; many clasts are visible, one of which is 6 X 10 mm, greenish yellow, and very fine-grained. The interior is relatively fresh; with a thin weathering rind in some areas and a small amount of oxidation around metal grains in the light gray matrix. ALHA79018 (120 g).?This stone (4.5 X 5 X 3.5 cm) is covered with thin, brown to black, patchy, fusion crust on all but one surface; this surface has a yellow to deep reddish-brown color and shows several inclusions. The interior is mainly weathered but has small areas of fresh material. Several black veins are present (infilled cracks ?), as are rounded inclusions up to 3 mm in diameter. ALHA79027 (133 g).?Dull black fusion crust coats most of this stone (5.5 X 4.5 X 3 cm). A fracture surface has patches of fusion crust, which suggests that the stone broke during passage through the atmosphere. Many inclusions are visible, with the largest being 4 mm in greatest dimension. ALHA79033 (208 g).?All but the T surface of this stone (7.5 X 6.5 X 3.5 cm) is covered with dull brown to black fusion crust. The T surface is a fracture that has weathered reddish brown; a number of mm-sized inclusions were noted. Fresh interior material is light gray with darker gray inclusions; metal grains surrounded by oxidation halos are present. A weathering rind 1-5 mm thick is visible. BTNA78001 (160 g).?The specimen is shaped like a flat plate, 10 X 6 X 1 cm, and is covered with black fusion crust except on the B and portions of the W surface; the B surface is polished and has a mottled, yellowish-red-brown appear- ance. Processing revealed a medium gray matrix with inclusions (~1 mm). The specimen has a prominent (1 mm) weathering rind. BTNA78002 (4301 g).?This specimen consists of two separately collected pieces that fit together. The complete stone (20 X 12 X 14 cm) is almost entirely covered with thin, dull brown fusion crust (apparently weathered) that is dotted with black fusion crust. An approximately 7 X 10 cm area on the S surface appears to have been broken away (this may be BTNA78001, which is petro- logically identical to BTNA78002). Areas devoid of fusion crust are light grayish green except where flecked with iron oxides around metal grains. The T surface shows flow bands in the E- W direction, and regmaglypts are present on the B surfaces. EETA79003 (435 g).?This 7.5 X 6 X 5 cm stone is covered with thin, shiny black fusion crust that is pitted and weathered, leaving a brown surface in some areas. The interior is gray and very friable, with numerous oxidation halos around metal grains. EETA79010 (287 g).?The exterior of this stone (8.5 X 6 X 4 cm) has weathered yellow- brown to red-brown. One small patch of black fusion crust remains. The interior is whitish gray with brown limonitic staining around nickel-iron grains. A thin weathering rind was noted. META78002 (542 g).?Thin, dull black fusion crust is present on three surfaces of this pyramidal specimen; the fusion crust is pitted, apparently the result of preferential weathering of small in- clusions. The T, W, and B surfaces are fractures that are stained reddish brown. Many clasts, up to 3 mm across, can be seen on the T and W surfaces. Processing revealed a greenish-gray ma- trix containing metal grains, some of which have oxidation halos. META78003 (1726 g).?The E, T, and W surfaces of this meteorite (15.0 X 7.5 X 8.0 cm) are covered with thin, dull black fusion crust. The other surfaces are fractures that are weathered to a reddish color; light-colored inclusions are visible on these surfaces. Processing revealed a greenish- gray matrix with oxidation halos around metal grains. META78005 (172 g).?Three surfaces of this stone (6.5 X 5.5 X 4.0 cm) are covered with dull black polygonally fractured fusion crust. Surfaces devoid of fusion crust are fractures, are weathered to a reddish yellow, and contain many inclusions with greater relief than the surrounding matrix. Processing revealed a light gray matrix with small clasts and non-oxidized metallic particles. RKPA78001 (234 g).?Thin dull black fusion crust covers two surfaces of this angular stone (9 X 5 X 4.5 cm). The other surfaces are fractures NUMBER 24 37 that are stained reddish brown by iron oxidation. Processing revealed only a small amount of gray- ish unweathered material. No inclusions were seen. RKPA78003 (1276 g).?This specimen was found as two pieces, which fit together perfectly. Most of it is covered with thin, dull black fusion crust. Surfaces devoid of fusion crust have weath- ered to a deep reddish brown, as have the two surfaces that fit together. The W butt end has a clast, 10 mm across, that appears to be troilite. Chipping revealed surfaces composed of very dark gray and very light gray matrix material, possibly the result of weathering processes. RKPA79001 (3006 g).?Small patches of shiny black fusion are present; the remaining surfaces are fractured, rough, and yellowish brown. Chon- drules can be distinguished; most are small, but the largest one is 6 mm in diameter. Indentations in the surface indicate chondrules may have been plucked out. There is a vein of dark material, 1- 3 mm thick, on one surface, probably indicating weathering along a fracture. A small amount of white powdery deposit is present on the fusion crust. The interior matrix is light gray to yellow, with oxidation halos around metal grains; gray and cream-colored chondrules, ~2 mm in diam- eter, are visible. RKPA79002 (203 g).?Dull black fusion crust partly covers three surfaces of this stone (8.5 X 5.5 X 3.5 cm). The B surface is highly polished in areas of fusion crust. Clasts up to 3 mm are visible on the surface and are identical to those seen in RKPA79001. Surfaces devoid of fusion crust are weathered from brownish yellow to reddish brown. The interior is whitish gray with oxidation halos around metal grains. A small weathering rind was noted. All the RKPA L6 meteorites are petrologically identical, with maskelynite and shock veins con- taining majorite and ringwoodite; it is reasonable to conclude that they are all pieces of a single meteorite. L6 chondrites weighing less than 100 g: ALHA79043, 62.2 g; 79052, 22.6 g. The L6 chondrites are all very similar in their petrographic characters. Polished thin sections show sparse, poorly defined chondrules that tend to merge with the granular groundmass. Principal minerals are olivine and orthopyroxene in sub- equal amounts, together with minor quantities of plagioclase (or maskelynite), nickel-iron, troilite, diopside, and accessory chromite and merrillite. Microprobe analyses (Appendix Table 1) show essentially uniform compositions for the principal minerals: olivine, Fa23-25; orthopyroxene, Fsi9_2i; plagioclase, Anio-12. The following meteorites contain maskelynite: ALHA78039 (in part), 78048 (in part); 79018; 79043; 79052; BTNA78001, 78002; RKPA78001, 78003, 79001, 79002. Ringwoodite and majorite were tenta- tively identified in shock veins in ALHA79018, BTNA78OO1 and 78002, and RKPA78001, 78003, and 79002. CLASS LL6 FIGURE 28 ALHA78153 (151 g).?Thick (1-2 mm), dull, brownish-black fusion crust, with a blistery tex- ture, covers the N, B, and parts of the E surface. A weathering rind, up to 5 mm thick, is present in some areas. Fracture surfaces are dark brown in isolated areas, but the overall color is greenish yellow. It appears that some large clasts have been plucked from the surface. This stone shows an unusual weathering pattern. Dark reddish- brown veins adjoin areas of yellowish material; areas of less severely weathered gray matrix were exposed during processing. In thin section chon- dritic structure is barely discernible, the meteorite showing a rather uniform granular aggregate of olivine and pyroxene, with minor amounts of troilite and plagioclase, a little nickel-iron, and accessory chromite. Limonitic staining is present in association with the metal grains. Microprobe analyses gave the following compositions: olivine, Fa29; orthopyroxene, FS24; plagioclase, Ann. BTNA78004 (1079 g).?This stone (12 X 7 X 7 cm) is covered with thin, dull black fusion crust except on one fracture surface. Regmaglypts are present on the N and S surfaces. The meteorite appears to be composed of angular, light-colored clasts surrounded by greenish-brown to gray in- 38 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 28.?BTNA78004, LL6 chondrite: a, fusion crust (black) coats part of surface; b, fracture surface showing brecciated structure; c, sawn surface showing brecciated structure with light and dark clasts; d, photomicrograph of thin section (area of field is 3 X 2 mm), showing granular clasts bounded and penetrated by black glassy veinlets. terstitial material. The clasts comprise approxi- mately 70% of the surface area and have a wide range in size; some are as much as 2.0 cm across. A thin section shows a granular aggregate con- sisting mainly of olivine and pyroxene (average grain size 0.1-0.2 mm), with minor amounts of plagioclase, nickel-iron, troilite, and accessory chromite. Chondritic structure is barely visible in a few places, and the chondrules are somewhat fragmented. Many of the silicate grains show undulose extinction. The meteorite has a brec- ciated structure, and the breccia fragments are outlined by an anastomosing network of black, glassy veinlets that contain numerous minute troilite globules. A small amount of limonite staining is present around some of the nickel-iron grains. Microprobe analyses show olivine (Fa3o) and orthopyroxene (FS24) of essentially uniform composition; plagioclase is somewhat variable in composition, Ani3-An22, average Ani9. The black glass is quite variable in composition, as follows (range and average, in weight percent): SiO2 31.5-49.9, 40.4; A12O3 0-6.3, 2.8; FeO 17.5-40.9, 23.9; MgO 16.7-31.3, 27.3; CaO 0-3.3, 1.6; Na2O 0-2.4, 1.1; TiO2 0-0.15, 0.09; MnO 0.3-0.5, 0.4. The meteorite shows to a high degree the breccia- tion characteristic of many LL chondrites. Achondrites EUCRITES FIGURES 29, 30 Eucrites and howardites are pyroxene-plagio- clase achondrites, but different authorities have NUMBER 24 39 ALHA78040 FIGURE 29.?Eucrites; black glassy fusion crust coats most of specimens, except EETA79011; note snow and ice still present on ALHA78132 when unpacked at Johnson Space Center. 40 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 30.?Photomicrographs of thin sections of eucrites (area of fields is 3 X 2 mm): a, ALHA78132; b, ALHA78158; c, ALHA78165; d, ALHA79O17; e, EETA79005;/, EETA79011. (Photomicrographs show typical brecciated structure of eucrites, with clasts of plagioclase (white), pyroxene (light gray), and chromite (black) in fine-grained comminuted matrix of these minerals; (c) has area showing ophitic intergrowth of plagioclase (white laths) and pyroxene.) NUMBER 24 41 proposed different criteria for distinguishing be- tween the two classes. Duke and Silver (1967) discussed previous classifications, and adopted the definition of eucrites as monomict breccias and howardites as polymict breccias. Takeda, Miyamoto, Duke, and Ishii (1978:1159), however, described the Yamato-74159 meteorite as a eu- crite that "clearly is polymict in terms of lithic variability but carries no magnesian orthopyrox- ene of the type found in howardites," and the term polymict eucrite has been applied quite widely since. We accept this term and the definition thereof. Howardites are then poly- mict pyroxene-plagioclase achondrites containing magnesian orthopyroxene. Our experience is that these orthopyroxenes have compositions En>70, and some have compositions indicating admix- ture of a diogenitic component, although the range of compositions may be considerably greater than in analysed diogenites. ALHA78040 (211 g).?This is a complete un- weathered specimen (~9.0 X 5.0 X 3.0 cm). Black, shiny fusion crust 0.5 mm thick covers all the surfaces of the stone. The crust has been removed from the edges by spallation and has been pref- erentially weathered away on the surfaces in small circular areas. The B and T surfaces have had the most fusion crust removed, thus revealing light to medium gray matrix material that contains small (<1 mm), elongated, white grains, probably feld- spar. The T and S surfaces each have a 1.0 cm clast present. These clasts have a slightly lighter color than the surrounding fusion crust. On the N surface an oval vug is present. Inside this vug is a weathered yellowish-brown inclusion ~0.5 cm diameter that has a coarser texture than the surrounding matrix material. ALHA78132 (656 g).?This appears to be a complete specimen (11 X 10X8 cm) with vitreous black fusion crust on all sides. The overall shape is pyramidal with the B surface being flat. The fusion crust on the T surface has flow bands, most prominent in the N-S direction and less promi- nent in the W-E direction. The B surface has radial flow lines in a concave area. The fusion crust on the S surface is much duller than on the rest of the stone. The crust has been spalled or chipped in some areas, revealing a medium gray interior material. Small (<1 mm) inclusions, both lighter and darker than the matrix, are apparent. Several holes (voids) that penetrate the fusion crust by as much as ~1 cm were noted over the entire stone. One in particular is ~9 mm in diameter and ~ 1 cm deep and contains a yellow- ish grain (?) ~2 mm long. The cut face shows a light gray matrix dotted with rounded and irreg- ularly shaped grains (?) that are both lighter and darker than the matrix. The largest grain is ~0.5 cm in diameter. The voids on the exterior of this specimen did not appear in the interior. A vein(?) of white grains extends for 6 cm across the cut face in the W-E direction. ALHA78158 (15.1 g).?This is not a complete specimen. Shiny black fusion crust is present on one surface. All other surfaces are fractures that show a medium gray matrix with white flecks. Some clasts (<1 mm) are oxidized to a yellow color. An area ~0.5 cm diameter on the B surface is a darker gray and appears very homogeneous? this appears to be a rounded clast. One fracture goes completely across the sample. Overall di- mensions are 3.0 X 2.5 X 2.0 cm. ALHA78165 (20.9 g).?This is not a complete specimen (~3.5 X 3.0 X 1.5 cm). Shiny black fusion crust covers only one surface. The other surfaces are fracture surfaces that have a medium gray matrix with <1 mm white clasts. A few of these clasts are weathered and yellow. When this stone was cleaved in half, a dark gray clast (~0.5 cm) was exposed. ALHA79017 (310 g).?This meteorite is mostly covered with a shiny black fusion crust with flow bands on all surfaces. The areas devoid of fusion crust are medium gray and speckled with light and dark clasts that are <1 mm in diameter. Some clasts are up to 0.5 cm long. The interior exposed through chipping is lighter gray than the exterior. Several large clasts of up to 1.2 cm are visible on the fresh fractures. Reid and Schwarz (1980:353) have studied the Allan Hills eucrites and give the following de- scription: The basaltic achondrite meteorites collected in the Allan Hills region of Antarctica (76005, 77302, 78040, 78132, 42 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES 78158 and 78165) are all petrographically similar and could even be pieces from a single fall. They are breccias with abundant but small (from fine dust to a maximum diameter of approximately 1 cm) angular clasts of rock and mineral fragments. The lithic clasts are basaltic, consisting of sub- equal amounts of pyroxene and feldspar with a range of igneous textures. The diverse clast types correspond to a range of thermal histories and to a limited range of basaltic compositions. Rock and mineral fragments studied to date correspond in texture and in mineral composition to the known range of eucrites, including both unequilibrated and equilibrated types. The range in pyroxene compositions is wide (\V04En69 to \V013En33) but pyroxenes with the com- positions of those in diogenites are absent or rare. The Allan Hills basaltic achondrites are unlike previously described eucrites and howardites (with the possible excep- tion of Macibini) in that they contain a series of fragments covering a range of eucrite types and are thus polymict but they do not appear to contain a diogenite component as in typical howardites. The name polymict eucrite seems appro- priate. Very similar polymict eucrites are common in the suite of achondrites collected in the Yamato region of Ant- arctica, almost 3000 km from Allan Hills. Petrographic examination of ALHA79O17 has shown that it is a polymict eucrite similar to the previously collected Allan Hills eucrites, and thus possibly another piece of a single fall. Takeda et al. (1980b) have published chemical analyses of ALHA76005 and ALHA78132 that show their near-identity in composition. Delaney et al. (1980) have provided detailed descriptions of eucritic clasts in ALHA78040 and ALHA 77302. EETA79004 (390 g).?This oblong achondrite (11 X 6.5 X 4 cm) is covered with a thin, dull fusion crust on all but two surfaces. The exterior matrix appears medium to dark gray and con- tains numerous clasts as large as 2 cm in diameter. Most of the larger clasts are dark, though light clasts do exist. Vugs occur in this meteorite. Most are concentrated on a surface in an area devoid of fusion crust. These vugs are as deep as 1 cm, as wide as 0.5 cm. The interior matrix is light gray with many inclusions. Many of the clasts in this achondrite will be easily plucked out. Several spots of severe oxidation are visible. The thin section shows a breccia dominantly made up of monomineralic pyroxene and feldspar fragments in a fine-grained matrix. Much of the matrix is dark and may be recrystallized. The clasts are generally angular but some have poorly defined outlines and may have been reheated. Mineral fragments range up to 1.3 mm. They are pyroxene (some showing exsolution), feldspar, and minor opaques. Pyroxene compositions show a range in Ca contents with little variation in Mg/Fe, (\V02En45Fs53 to Wo4oEn36Fs24 with low Ca compositions most abundant, in the few grains analyzed). Feldspars range from OriAbeAn93 to OriAbi4An85. Two major types of lithic clasts are present: (1) angular fragments up to 2.5 mm in size of fine grained eucrites with igneous textures; (2) frag- ments up to 1.6 mm across of dark aphanitic material that appears to consist of extremely fine pyroxene and feldspar in a subparallel growth. The overall texture and nature of the clasts resem- ble those of the Allan Hills polymict eucrites. The small number of pyroxenes analyzed shows essen- tially no variation in Mg/Fe. On this evidence EETA79004 is classified as a monomict equili- brated eucrite rather than a polymict eucrite. EETA79005 (450 g).?One surface of this achondrite (10.5 X 8 X 7 cm) is concave; the rest of the meteorite is convex. Fusion crust is visible only on one surface and it is very shiny and polygonally fractured. The matrix is medium gray in color and is speckled with light and dark clasts up to 3 mm in diameter. Vugs are apparent all over the sample. Chipping a corner off the meteorite revealed one fine-grained, black clast 0.5 cm in diameter. The color of the interior matrix is considerably lighter gray than the ex- terior. EETA79011 (86.4 g).?A patch of dull black fusion crust appears only on one surface. The rest of this achondrite is medium gray. Several types of clasts are visible on the exterior with the largest one being ~0.7 cm in its longest dimension. The interior revealed through chipping is lighter gray in color than the exterior and contains many clasts. Petrographically these two meteorites are so similar that the following descriptions of thin section EETA79011 can serve for both. It shows a fine breccia with highly angular, small, mon- omineralic pyroxene and feldspar clasts predom- NUMBER 24 43 FIGURE 31.?Howardites: a, ALHA78006; black fusion crust coats most of surface; b, EETA79006; fusion crust coats part of surface, but mostly fracture exposing vuggy interior; c, photomicrograph of thin section of ALHA78006 (area of field is 3 X 2 mm) showing brecciated structure and variety of clasts; d, photomicrograph of EETA79006 showing brecciated structure and variety of clasts. inating. Pyroxene grains range up to 2.5 mm, with the large fragments showing evidence of deformation. Some single pyroxene fragments show exsolution textures. Among the small lithic clasts are: (1) fragments of brown, devitrified glass, up to 1.6 mm; (2) fine-grained eucrite clasts with granoblastic texture, up to 0.6 mm; (3) fine- grained eucrite fragments, up to 0.7 mm; and (4) medium-grained eucrite up to 1.6 mm. Pyroxenes have a range of compositions from \V04En66Fs30 to \V02En37Fs6i. The more magnesian pyroxenes all have low Ca contents but the more Fe-rich varieties range from \V02En37Fs6i to \V035En27 Feldspar ranges in composition from to Ori.5Abi9An8o. These two meteorites from Elephant Moraine are classified as polymict eucrites. Their petro- logical similarity and the fact that they were found within 400 m of each other, as shown on the sketch map of Figure 7B (Cassidy and Ran- citelli, this volume), strongly suggest that they are individual pieces of a single fall. HOWARDITES FIGURE 31 ALHA78006 (8.0 g).?This is a nearly com- plete specimen (3.0 X 1.5 X 2.0 cm). Shiny black fusion crust covers all of the stone except portions of the E, W, and S surfaces. Where the sample is 44 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES devoid of fusion crust, light to dark gray interior material is exposed. Cleaving this stone in half revealed an unweathered, brecciated surface. The thin section shows a complex breccia of angular fragments, up to 1 mm long, of pyroxene (orthopyroxene and pigeonite) and plagioclase, with numerous polymineralic enclaves, set in a matrix of comminuted pyroxene and plagioclase. Accessory chromite and ilmenite and trace amounts of troilite and nickel-iron are present. The enclaves are holocrystalline pyroxene-plagio- clase aggregates, and range considerably in tex- ture from coarse-grained gabbroic to fine-grained basaltic types. A slight amount of weathering is indicated by small areas of rusty staining, usually in association with metal grains. Microprobe analyses show a wide range in pyroxene compo- sition: Wo2-i2En3i_72Fs25-6i; a number of grains with uniform composition \V03EnnFs26 suggests the presence of a diogenitic component. Plagio- clase averages Angi. A single grain of iron-rich olivine (Fagi) was analyzed. Takeda, Yanai, and Shiraishi (1980) have pub- lished analyses of orthopyroxene and inverted pigeonite from ALHA78006. EETA79006 (7167 g).?This meteorite (14 X 8.5 X 4.5 cm) is partly covered with dull to shiny black fusion crust. Many vugs are present, some with interior clasts. The medium gray matrix contains a variety of clasts (dark gray, yellow, white), the largest being 1 cm in its longest di- mension. Several rounded spots of oxidation are obvious and several cracks appear to penetrate the sample. The interior of the meteorite is lighter gray than the exterior. Several clasts (~3 mm diameter) were revealed by chipping the speci- men. The thin section shows a fine-grained breccia with angular pyroxene and feldspar fragments and minor opaques. The larger pyroxene frag- ments, up to 1 mm, are commonly deformed and some show exsolution. A variety of clast types include the following: (1) fine grained eucritic fragments, up to 2 mm; (2) polymineralic pyrox- ene-feldspar intergrowths; (3) fragments of brown devitrified glass, up to 1 mm; (4) one fragment, 2 mm, with feldspar :? pyroxene; (5) one frag- ment, 2 mm, with pyroxene >> feldspar; and (6) one 4.5 mm recrystallized eucrite clast with mo- saic texture. Analysis of pyroxenes yields a wide range of compositions from WoiEngoFsig to \V015En28Fs57. SHERGOTTITE FIGURE 32 EETA79001 (7942 g).?All but one surface of this achondrite (22 X 17 X 14 cm) is covered with black fusion crust, but there are areas on all surfaces where the fusion crust has been plucked away. One surface has a deep regmaglypt that is covered with fusion crust. The areas void of fusion crust are white-gray and the matrix appears po- rous. Veins (~0.5 mm wide) of dark material criss-cross each other. Whitish-yellow clasts (~3 mm diameter) are scattered all over this achon- drite. Most of the specimen appears very fine- grained but a small part near the E surface has a different lithology. Sawing exposed a light inte- rior with rounded white clasts, as large as 0.5 cm in diameter. Several large, black, fine-grained clasts, as large as 2.5 cm, are scattered over the cut face. Some of these black clasts contain vugs with glass in their interior. Upon chipping one of these clasts containing a vug, the entire clast popped out easily without adhering matrix. Nu- merous veins of black material criss-cross each other. Most of these veins run through a black clast. The longest vein is ~14 cm long. Near the W end of the cut face are brownish clasts that may be pyroxene. Ninety percent of the cut face is fine-grained. Ten percent (near the E end) of the cut face consists of intergrown pyroxene and feldspar in a basaltic texture. Thin sections were cut from the three different lithologies: (1) the main mass of the meteorite; (2) the material with basaltic texture at one end of the sample; and (3) the dark clasts included in the main mass. The main mass is a shocked but unbrecciated pyroxenite with pyroxene as the major phase but also containing maskelynite, Mg- Al chromite, iron sulfide, and ilmenite(P). The major pyroxene is polysynthetically twinned pi- geonite^) resembling twinned clinobronzite, NUMBER 24 45 FIGURE 32.?EETA79001, shergottite: a, black fusion crust spalled off in some areas, exposing light gray interior; b, sawn surface showing black glassy clasts; c, photomicrograph (area of field is 3 X 2 mm) showing typical shergottite structure with maskelynite (white), pyroxene (gray), and accessory chromite (black); d, photomicrograph (area of field is 3 X 2 mm) showing twinned clinopyroxene (crossed polars). ranging in composition from \Y05En70Fs25 to \V012En50Fs38. Orthopyroxene forms the cores of larger pyroxene grains and ranges in composition from \V01.5En83Fsi6 to Wo3En7sFsi9. The larger pyroxene grains, up to 3.5 mm, comprise un- twinned cores zoned outward to polysynthetically twinned rims. The smaller pyroxenes, 0.3 to 1 mm, are twinned clinopyroxenes and are inter- grown with maskelynite laths. The maskelynite ranges in composition from OriAb3gAn6o to Ori.5Ab44An55. A few large olivines, F077 to F073, range to 2.5 mm. The less abundant lithology closely resembles Shergotty in texture but is finer grained. The major minerals are clinopyroxene and maskelynite; calcium phosphate, S1O2, il- menite(?), and magnetite(?), are also present. Elongate clinopyroxene and laths of maskelynite are about one mm long and generally subparallel; many of the maskelynite grains contain pyroxene inclusions. Analysed pigeonites range from \V010En52Fs38 to Woi8Eni5Fs67- The maskelynite also shows a range in composition from Oro.5Ab38An62 to Or4AbsoAn46. The dark clasts are apparently loci of melting; in many cases they connect with the thin, black, glassy(?) veinlets that traverse much of the meteorite. Thin sections from these dark areas show glass (with relict olivine, pyroxene, and maskelynite inclusions), devitrified glass, areas with mosaic texture, and vesicular areas with quench textures. The dark 46 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES ALHA78OI9 1 cm cube ALHA78262 FIGURE 33.?Ureilites: a, ALHA78019; patchy fusion crust is present; b, ALHA78262; fusion crust coats most of the surface; c, d, photomicrographs (area of fields is 3 X 2 mm) of ALHA78019 (c) and ALHA78262 (d); olivine (white, without cleavage cracks) and pyroxene (light gray, with cleavage cracks), bordered by black material consisting largely of carbon. areas appear to be more common in olivine-bear- ing portions of the main mass. The meteorite is classed as a shergottite because of the close similarities to the shergottites in tex- ture and mineralogy. Both lithologies, however, are distinct from Shergotty and Zagami. UREILITES FIGURE 33 ALHA78019 (30.3 g).?Fusion crust is present on all surfaces but is patchy and does not cover the entire stone. The fusion crust is smooth, dull brownish black, and has polygonal fracture. Where the fusion crust is missing the surface is reddish brown and crystalline. The stone (3.0 X 2.5 X 3.0 cm) was cleaved in half and no un- weathered material was exposed. The sample is reddish brown throughout. The thin section shows an aggregate of rounded to subhedral grains (0.5-3 mm across) of olivine, with minor pyroxene. The grains are rimmed with black carbonaceous material. Trace amounts of troilite and nickel-iron are present, the latter largely altered to translucent brown limonite concentrated along grain boundaries. Microprobe analyses show olivine of uniform composition (Fa22) with notably high CaO (0.4%) and O2O3 (0.7%) contents; the pyroxene is a pigeonite of composition WoioFsi8En72. This me- teorite is a ureilite, with mineral compositions essentially identical to those in the Kenna ureilite NUMBER 24 47 *.** FIGURE 34.?ALHA78113, aubrite: a, dark fusion crust spalled off most of surface, exposing interior consisting largely of white enstatite; b, sawn surface showing brecciated structure of interior; c, photomicrograph of thin section (area of field is 3 X 2 mm) showing brecciated enstatite (white) veined by fine-grained, dark gray material. (Berkley et al., 1976); it appears to be relatively unshocked compared to most ureilites. ALHA 78019 has been described by Takeda and Yanai (1979). ALHA78262 (26.1 g).?This specimen (4.0 X 2.5 X 2.0 cm) is triangular and has thin, dull black fusion crust on three surfaces. The remain- ing surfaces are fracture surfaces that are rough on a small scale, resulting from exposed crystal faces. The overall color is very dark greenish black. The thin section is identical with that of ALHA78019 in all respects, and these two stones are apparently pieces of a single fall. AUBRITE FIGURE 34 ALHA78113 (298 g).?This specimen (8.5 X 6.5 X 3 cm) has a brecciated structure, with abundant large enstatite grains (~2.5 X 2.0 cm) and less numerous dark clasts exposed on the surface; patches of very thin, black fusion crust are present. Half of the B surface has thin, yellow- ish-brown weathering discoloration. Very small spots (< 1 mm) of iron oxidation are present on some surfaces. A cut face shows many large, white enstatite clasts, a few containing isolated rounded blebs of metal, some with oxidation halos. The clasts are surrounded and veined by fine-grained, dark gray material. The thin section consists almost entirely of clasts of orthopyroxene, up to 2 mm long, in a groundmass of comminuted pyroxene. Accessory amounts of sulfides and nickel-iron are present as small grains in the groundmass. The section shows a moderate amount of brown limonitic staining concentrated around the metal grains. Microprobe analyses show that the pyroxene is an iron-free enstatite (FeO 0.1%) with minor and variable amounts of CaO (0.2-0.6, average 0.5%). 48 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 35.?EETA79002, diogenite: a, dull black fusion crust coats stone, except in small areas where spalled off to reveal light gray interior; b, photomicrographs of thin section (area of field 3X2 mm); orthopyroxene clasts (white) in matrix of comminuted orthopyroxene (gray) and a little chromite (black). Watters et al. (1980) have provided a detailed mineralogical and petrographic description of ALHA78113 and compared it with other au- brites. In addition to the minerals mentioned above, they record the presence of accessory amounts of forsterite (Fo 99.99) albite (An 3.39) diopside (Wo 43.89, En 56.09, Fs 0.02), oldham- ite, ferromagnesian alabandite, daubreelite, and schreibersite. DIOGENITE FIGURE 35 EETA79002 (2843 g).?This rounded meteor- ite (15 X 13.5 X 10 cm) is covered with dull fusion crust except on one fracture surface. Fusion crust has been plucked away in places, revealing a medium gray matrix with many light to cream- colored clasts (~0.5 cm diameter). Several areas have been heavily oxidized giving these parts a red-brown color. Many fractures penetrate this meteorite. Chipping revealed an extensive or- ange-brown weathering rind as wide as 1 cm. The interior matrix is blue-gray with many small (< 1 mm) clasts. Two white clasts ~0.5 cm diameter were exposed. No metal was obvious. The thin section shows a breccia with a very cohesive, fine-grained matrix. Clasts are mon- omineralic, angular, and range up to 2 mm. One angular lithic clast is polymineralic but extremely fine-grained. The vast majority of the mineral fragments are low-calcium pyroxenes of near-con- stant composition, Wo2En76Fs22- The only other silicate phase identified is olivine, F075-76. Small areas within the breccia are rich in very fine opaque minerals. The meteorite is a diogenite but is texturally distinct from the common diogenites. Descriptions of Iron Meteorites Roy S. Clarke, Jr. This section provides descriptions of the 19 iron meteorite specimens that have been collected in Victoria Land since 1976. Their textural and chemical properties indicate that five irons from the Allan Hills derive from a single shower as do nine from Derrick Peak (plus six more that were collected from the same site by a New Zealand party). Therefore, the total number of iron me- teorite falls from Victoria Land is now seven. Descriptions of specimens are given below and in Table 3 in the order of their chemical classifica- tion groups. Specimens grouped as members of a single fall are listed by the lowest-numbered spec- imen retained in United States collections. Coarse Octahedrites GROUP IA ALHA76002 Group ALHA76002 (1.51 kg).?This coarse octahed- rite was the first iron meteorite to be recovered from the Allan Hills. It was listed by King et al. (1980:42) in the previous Catalog of Antarctic Meteorites (Marvin and Mason, editors, 1980). It was described and given an ambiguous classifi- cation by Olsen et al. (1978). Clarke et al. (1980) have re-examined ALHA76002 and found it to be indistinguishable from four other Allan Hills specimens that were collected a year later. All five are typical coarse octahedrites of chemical group IA. Roy S. Clarke, Jr., Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington D.C. 20560. (2.19 kg).?This specimen was a photograph by King et al. ALHA77250 (10.5 kg; 26 X 15 X 8 cm). ALHA77263 (1.68 kg).?This specimen was described with a photograph by King et al. (1980:42). ALHA77289 described with (1980:42). ALHA77290 (3.78 kg; 16X13X6 cm). All five specimens have generally similar red- dish-brown iron oxide coatings. Surfaces that were probably initially at least partially regma- glypt-covered have undergone severe weathering. No fusion crust remains. Surfaces of the under side of specimens are more severely weathered than those that were exposed to the atmosphere. An occasional troilite inclusion is visible at the surface. Macroetched surfaces reveal the same basic metallography for all five specimens. They all have surficial patches of an ablation-produced zone of ot2 iron. Kamacite grains are 2-3 mm wide, and their length is generally only a few times their width. Areas of recrystallized kamacite are unevenly distributed. Taenite-plessite areas with comb texture, and grain-boundary taenite are present. Schreibersite occurs at grain bound- aries and as occasional large crystals. There are a few large troilite-carbon inclusions surrounded by schreibersite, and, in some instances, also cohen- ite. The appearance, structure, and chemical data given in Table 3 establish these five specimens as typical coarse octahedrites of Group 1 A. The close similarity in the chemical values makes it highly likely that they are all pieces of the same shower. 49 50 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE 3.?Summary of data on iron meteorites (NMNH = National Museum of Natural History, Smithsonian Institution, Washington, D.C.; NIPR = National Institute of Polar Research, Tokyo; data in 4th to 9th columns from Clarke, Jarosewich, Goldstein, and Baedecker (1980)) Specimen number ALHA76002* 77250 77263* 77289* 77290 PGPA77OO6* ALHA77283 ALHA781OO DRPA78OO1 78002 78003 78004 78005 78006 78007 78008 78009 ALHA78252 ALHA77255* Original wt. (kg) 1.51 10.5 1.68 2.19 3.78 18.9 10.5 0.085 15.2 7.21 0.144 0.134 18.4 0.389 11.9 59.4 138 2.79 0.767 NMNH wt. (kg) 0.307 4.69 0.839 1.08 1.93 7.75 5.68 0.040 7.21 0.134 18.4 0.389 30.1 65.8 1.41 0.387 NIPR wt. (kg) ?** 5.42 0.779 1.01 1.73 8.16 4.34 0.040 15.2 0.144 11.9 26.1 67.6 1.32 0.367 Chemical group IA IA IA IA IA IA IA IIA IIB IIB IVA Anom Structural classification Og Og Og Og Og Og Og H Ogg Ogg Of D %Ni 6.84 6.84 6.84 6.84 6.84 7.27 7.33 9.33 12.23 ppm Ga 92.1 91.5 92.8 92.6 93.7 78.2 69.0 2.5 0.6 ppm Ge 404 455 414 386 407 245 230 <100 <200 ppm Ir 2.9 3.1 3.0 3.0 3.0 2.5 2.2 0.45 12.0 * Specimens listed in Marvin and Mason, editors (1980). ** Specimen material at both the National Institute of Polar Research, Tokyo and the Field Museum of Natural History, Chicago. PGPA77006 (18.9 kg).?This specimen from Purgatory Peak in the Victoria dry valley was described with a photograph by King et al. (1980:42). A macroetched surface revealed kamacite band-width in the 1.5 to 2 mm range, with length- to-width ratios ranging from 4 to 10. Neumann bands are abundant, and along the rim of the specimen kamacite has been converted to ?2 by atmospheric ablation. Taenite and taenite-ples- site areas occupy at least half of the length of kamacite grain boundaries, and a number of areas of comb plessite are present. Schreibersite occurs along grain boundaries, and occasional schreibersites surrounded by cohenite are present. No large inclusions were observed on the small surface available. The structural and chemical data from Table 3 establish that this is a typical coarse octahedrite, a chemical group IA meteor- ite. It is chemically and structurally distinct from both the ALHA76002 group and from ALHA77283. ALHA77283 (10.5 kg; 16.5 X 16 X 12.5 cm).? The specimen has a generally rounded anterior surface that is suggestive of aerodynamic shaping during oriented atmospheric flight and a slightly concave posterior surface. The specimen has been severely weathered, particularly on the posterior surface. Wind erosion while on the ice also ap- pears to have been important. Taenite bands stand out in relief over much of the surface, revealing the internal octahedrite structure of the meteorite. Clarke et al. (1981) have studied this specimen and shown it to contain preterrestrial, impact- produced diamond and lonsdaleite. The meteor- ite is a carbon-rich, coarse octahedrite of chemical group IA (Table 3). It is similar in composition and structure to carbon-rich Canyon Diablo spec- imens and its metallography indicates shock load- NUMBER 24 51 FIGURE 36.?Polished and etched slice of ALHA77283: large inclusion at lower right is troilite- carbon-schreibersite-cohenite; carbonado-like material containing diamond and lonsdaleite found in number of such inclusions, generally at borders between troilite and schreibersite; dark mineral distributed throughout surface and generally at centers of kamacite lamellae is cohenite; kamacite lamellae are arranged in coarse Widmanstatten pattern, with their lengths short compared to their widths; taenite lamellae and taenite-plessite fields present at borders of kamacite lamellae (length of bottom edge of specimen = 9.5 cm). ing to moderate intensity. It contains a number of troilite-carbon-schreibersite-cohenite inclusions that are rich in carbonado-like material contain- ing diamond and lonsdaleite (Figure 36). The presence of an ablation-produced, heat-altered zone indicates an uninterrupted passage through the atmosphere and a non-explosive impact on the earth. This establishes that the diamond and lonsdaleite were produced preterrestrially. Hexahedrite GROUP IIA ALHA78100 (85.0 g; 5 X 4.5 X 0.9 cm).?This specimen, unlike others, was found frozen within the ice. It is a thin, flat, slightly irregular plate that appears to have been oriented during atmos- pheric flight. The anterior surface is rounded at the edges and the posterior surface has been affected more severely. It is covered with an essentially featureless, reddish-brown oxide. The anterior surface contains numerous 1 to 2 mm pockmarks. A microetched median section of the specimen reveals single-crystal kamacite containing Neu- mann bands and inclusions. Schreibersite is abun- dant as rhabdites, and is also present as lamellar schreibersite and as hieroglyphic schreibersite sur- rounding troilite-daubreelite inclusions. Troilite- daubreelite inclusions are present with only small bordering schreibersites. The edge of the anterior surface has an ablation rim averaging about 0.7 mm wide. No OL3000 11 300 309 73 Number of achondrites 0 1 1 28 12 >100 1 4 6 7 59 60 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE 6.?Types of achondrites in the Antarctic meteorite collections Year / Location 1969 Yamato Mts. 1973 Yamato Mts. 1974 Yamato Mts. 1975 Yamato Mts. 1976 Allan Hills 1977 Allan Hills 1978 Allan Hills 1979* Allan Hills, Reckling Peak, Elephant Moraine Totals Diogenite 1 22 7 1 1 32 Howardite 1 1 1 3 Eucrite poly- mict 2 5 1 1 4 2 16 mono- mict 1 1 2 Shergottite 1 1 2 Ureilite Aubrite 3 1 2 1 6 1 * The 1979 Japanese expedition to the Yamato Mountains returned with over 100 achondrites that have not all been classified (Yanai, 1980). Eucrites and howardites are the most common achondrites in the non-Antarctic compilation. The Antarctic samples are distinctive in that howardites and monomict eucrites are not com- mon and that a particular type of eucrite makes up the bulk of the collection. This type is the polymict eucrite, described below, which is rare in non-Antarctic collections. As with the diogen- ites, several of the polymict eucrites are very similar and may be from a single fall. It should be noted, however, that this unusual type of eucrite is common at both the Yamato and Allan Hills sites which are almost 3000 km apart. Aubrites are rather rare in the Antarctic collec- tion and so far none of the very unusual achon- drites such as Nakhla, Chassigny, or Angra dos Reis have been found. It is of great interest to note that two shergottite meteorites, related to, but not identical with, the two previously known members of the shergottite class, have been re- covered. The differences between the Antarctic and non-Antarctic collections are intriguing and while any attempt to understand these differences may be yet premature, we can speculate that: (a) the differences are an artifact produced by inade- quate sampling; (b) there is some factor that results in the achondrite flux in the Antarctic region of the earth being different from elsewhere; or, (c) the distribution of achondrite meteorites reaching the earth has changed with time and the Antarctic collection represents an average over a much longer time increment. Descriptions of the individual meteorites are presented by Score et al., in this volume, and in a variety of other publications. Some of the more interesting characteristics of the collection are briefly summarised below, with particular em- phasis on the aspects of the collection that appear to be unique. ACKNOWLEDGMENTS.?I thank Roberta Score for substantial help. The research reported in this paper was done while the author was a National TABLE 7.?Comparison between Antarctic (excluding those from the 1979-1980 Japanese expedition) and non-Antarctic (Wasson, 1974:292) achondrites Class Diogenites Howardites Eucrites Shergottites Ureilites Aubrites Others Totals Antarctic 32 3 18 2 6 1 0 62 Non-Antarctic 8 19 24 2 6 9 13 81 NUMBER 24 61 Research Council Associate at the Johnson Space Center in Houston, Texas and a Visiting Scientist at the Lunar and Planetary Institute, which is operated by the Universities Space Research As- sociation under Contract No. NASW-3389 with the National Aeronautics and Space Administra- tion. This paper is LPI Contribution number 435. Diogenites TABLE 8 The initial 1969 Japanese collection of 9 me- teorites in the Yamato Mountain regions con- tained one achondrite, originally named Yamato (b), but now renamed Yamato 692. This 138 g TABLE 8.?Data on diogenites in the Antarctic meteorite collections Locality Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Allan Hills Elephant Moraine Specimen number 692 74005 74010 74011 74013 74031 74037 74096 74097 74109 74125 74126 74136 74150 74151 74162 74344 74347 74368 74448 74546 74606 74648 75001 75004 75007 75014 75285 75299 ALHA77256 EETA79OO2 Weight (g) 138.0 3.8 298.5 206.0 2059.5 6.1 591.9 16.1 2193.9 43.5 107.0 14.5 725.0 33.4 49.1 3.9 1.4 7.8 4.1 17.7 7.3 2.9 185.5 4.1 37.0 2.6 3.0 3.1 9.1 676.2 2843.0 diogenite was described by Okada (1975), Okada et al. (1975), and by Takeda et al. (1975). While mineralogically and compositionally similar to the known diogenites, it is texturally unique, having a granoblastic texture rather than the brecciated texture of most diogenites. The recov- ery of 22 diogenites in the 1974 Yamato expedi- tion demonstrated that this texture, indicative of severe recrystallisation, is characteristic of the diogenites from this region of the Antarctic. As noted above many, if not all, of these diogenites may represent a single fall as they are petrograph- ically alike and occur in the same geographic region. The six diogenites in the 1975 Yamato collection also include samples with granoblastic textures. The Yamato diogenites are orthopyroxenites with pyroxenes around En74_72. One sample in the 1975 collection, 75032, is more iron-rich than other diogenites and approaches the more magne- sian eucrites in composition. Yamato 75032 is an unrecrystallised monomict diogenite that has as its dominant phase orthopyroxene (approxi- mately Enes) with exsolved lamellae and blebs of augite. Takeda et al. (1979) conclude that the major primary phase in Yamato 75032 was a low- Ca pigeonite now inverted to orthopyroxene, but that primary orthopyroxene may also be present. The meteorite is transitional between the diogen- ites and the more magnesian eucrites and fills in the "apparent" gap in pyroxene crystallisation trends between diogenites and eucrites. The one diogenite from the Allan Hills region (ALHA77256) weighs 676 g and is described as a normal diogenite. The 2.8 kg diogenite from El- ephant Moraine (EETA79002) has the minerals of a normal diogenite but is a very fine breccia with a few dark, fine-grained, lithic clasts. The Antarctic diogenites thus extend the boundaries of the diogenite class in composition, mineral assemblage, and texture. Eucrites and Howardites TABLE 9 Both eucrites and howardites have been found in the Antarctic but the most abundant samples of this type are the "polymict eucrites." Their 62 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE 9.?Data on eucrites and howardites in the Antarctic meteorite collections Locality Yamato Mountains Elephant Moraine Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Allan Hills Allan Hills Allan Hills Allan Hills Allan Hills Allan Hills Allan Hills Yamato Mountains Allan Hills Elephant Moraine Type/Specimen number EUCRITES 74365 EETA79004 POLYMICT EUCRITES 74159 74450 75011 75015 75295 75296 75305 ALHA76005 ALHA773O2 ALHA 78040 ALHA78132 ALHA78158 ALHA78165 ALHA 79017 HOWARDITES 7308 ALHA78006 EETA 79006 Weight (g) 10.0 390.3 98.2 235.6 121.5 166.6 8.8 8.6 7.9 1425.0 235.5 211.7 656.0 15.1 20.9 310.0 480.0 8.0 716.0 discovery has led to a welcome revision in the nomenclature of basaltic achondrites (see Score et al., this volume). Howardites are polymict pyroxene-plagioclase achondrites containing magnesian pyroxene that probably indicates ad- mixture of a diogenitic component. Polymict eu- crites are polymict pyroxene-plagioclase achon- drites in which magnesian pyroxene, like that in diogenites, is absent or rare. Eucrites can be monomict or polymict and polymict eucrites can contain cumulate and/or non-cumulate eucritic clasts, and fragments of equilibrated or unequi- librated eucrite. The Antarctic collection of eucrites and ho- wardites is dominated by the polymict eucrites, which are rare or absent in other collections. The meteorite Macibini may be the only other known example. The Antarctic polymict eucrites are all fine breccias with no large clasts and with mineral clasts (mostly pyroxene and plagioclase) predom- inating over lithic fragments. The lithic clasts are mostly eucritic, and fragments with fine-grained basaltic textures predominate. In a single sample there is generally a wide range of clast types, including clasts with extremely fine quench tex- tures, clasts with more slowly cooled ophitic tex- tures, clasts with cumulate textures, and eucrites with partly recrystallized and granoblastic tex- tures. Equilibrated and unequilibrated eucrite fragments may be present in the same sample: pyroxene compositions cover a wide range and individual grains may be homogeneous, zoned, or rimmed, and may or may not be exsolved. Tex- tures indicative of rapid, near-surface cooling are most common; more plutonic fragments are rarer, especially in the Allan Hills and Elephant Mo- raine samples. Glass and devitrified glass frag- ments occur in some samples. The meteorites are truly polymict but many of the fragments appear to be derived from a closely related sequence of rocks. The oxygen isotope data, however, suggest that clasts from different oxygen isotope reservoirs may be present in the same sample (Clayton et al., 1979). In addition, preliminary chemical and isotopic studies (Wooden et al., 1981) indicate significant differences between the larger clasts and the bulk meteorites. To date only one of the Antarctic polymict eucrites, ALHA76005, has been described in de- tail (Olsen et al., 1978; Miyamoto et al., 1979; Grossman et al., 1981). The similarities among the 16 known samples are great, however, and it seems certain that they do not all represent indi- vidual falls. Consortia studies of several of the Allan Hills samples, and particularly of separated clasts, are currently underway. Two eucrites in the collections, Yamato 74365 and Elephant Moraine 79004, appear to be nor- mal monomict eucrites. There also are two ho- wardites, Yamato 7308 and Elephant Moraine 79006, that contain a variety of mineral and rock fragments. The presence of magnesian pyroxenes indicates a diogenetic component in these brec- cias. These are howardites but they are very similar in most respects to the polymict eucrites and may only represent a slightly different sam- pling of a diverse source region that runs the NUMBER 24 63 gamut from magnesian diogenite to iron-rich eu- crite. Eucrites and howardites from the Antarctic are breccias of igneous and metamorphic fragments in which eucritic material predominates. Most breccias are polymict but the fragments comprise a series of materials that may be closely related, i.e., that reflect the effects of a range of different thermal histories on compositionally similar ma- terials or that comprise a limited range of rock types related by simple igneous processes. Truly exotic particles appear to be rare but we must await more detailed studies, including isotopic analyses, to test the preliminary petrographic ob- servations. The samples may be representative of regolith material on the basaltic achondrite parent body. The distribution of clast sizes and the relative absence of severe shock effects and melting is consistent with a regolith generated by a very large number of low momentum impacts. Most igneous fragments appear to derive from rapidly cooled surface or near-surface environments. Tex- tures indicative of slow cooling are not common (though they may be more abundant in the Ya- mato polymict eucrites; Takeda, pers. comm.). The apparent scarcity of plutonic materials will also need to be tested in future work as the degree of comminution in these breccias is not conducive to the preservation of coarse-grained polyminer- alic fragments. The regolith sampled by these achondrites is dominantly composed of fragments of eucritic lavas or hypabyssal intrusives and their deriva- tives. Coarser-grained diogenites may have ex- isted at greater depth, as suggested in the layered crust model of Takeda (1979). The differences among the various achondrites may reflect differ- ent sampling of a partly stratified surface region. The nature of the regolith sampled by the Ant- arctic eucrites and howardites is different from the type of material sampled by most non-Ant- arctic basaltic achondrites. If all the eucrites de- rive from a single parent body then the surface of that parent varied with respect to place and/or time. Shergottites The Antarctic program has doubled the num- ber of available samples of the rare meteorite group, the shergottites. This group has been the focus of much recent attention since it represents the third example of extraterrestrial basaltic vol- canism (in addition to the moon and the eucrites). This interest was augmented by the discovery that the shergottites have relatively young crys- tallisation ages (<1.3 b.y., Nyquist et al., 1979), raising the problem of the location of heat sources for basaltic volcanism late in solar system history. Difficulties in interpreting the evolutionary his- tory of the shergottites and in speculating on their possible parent bodies will be eased by the results of studies of two new shergottites, ALHA77OO5 and EETA79001, which are apparently related to, but certainly not identical with, Shergotty and Zagami. Allan Hills 77005 is a 482.5 g achondrite that is heterogeneous, with regions containing cumu- late olivine and chromite poikilitically enclosed by low-Ca and high-Ca magnesian pyroxenes (McSween et al., 1979). Other regions consist of olivine with interstitial maskelynite, chromite, il- menite, troilite, whitlockite, and pyroxene. The meteorite is apparently a heterogeneous cumulate that may have formed from a magma similar to that which gave rise to the shergottites or alter- nately may be representative of the type of source material from which the shergottite parent magma was derived. While credible petrogenetic models can be made linking ALHA77OO5 to the other shergot- tites, the isotopic data (Nyquist et al., 1979) indicate that they cannot be comagmatic. Like the shergottites, ALHA77OO5 appears to have a young crystallisation age and also has undergone shock metamorphism that converted the plagio- clase to maskelynite. The fourth meteorite in this group is a recent discovery from the 1979 U.S. Antarctic collection, EETA79001. The feldspar in this meteorite also has converted to maskelyn- ite, indicative of a shock history. The mineral assemblage is similar to, but not identical with, 64 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES the shergottites, and as yet no information on its age is available. EETA79001 contains two distinct lithologies. The main mass is a pyroxenite with large, com- plexly zoned pyroxenes set in a mostly pigeonite- maskelynite groundmass. In comparison with the other shergottites, the pyroxenes in EETA79001 are more magnesian and less Ca-rich. The other lithology in EETA79001 is texturally and min- eralogically similar to Shergotty but finer-grained and seems on first inspection to lack high-Ca pyroxenes. These two lithologies are in conjunc- tion along what appears to be an undisturbed igneous contact. Obviously the detailed study of EETA79001 will add considerably to our knowl- edge of the shergottites. If the young ages of Shergotty and Zagami and ALHA77OO5 are crys- tallisation ages and indicate melting late in solar system history, then melting could be the result of magmatic or impact events. An increase in the number of related but distinct igneous rocks with young ages argues for magmatic processes rather than impact melting. Ureilites TABLE 10 There are six ureilites recovered from Antarc- tica but only one, ALHA77257, is sizeable, weigh- ing almost 2 kg. These samples extend the range of known variability within the group, as could be expected since there were only eight known ureilites prior to the Antarctic discoveries. Of particular interest is Yamato 74659, which is a low-Fe ureilite carrying the most magnesian pi- geonite recorded from the group. The meteorite also has a higher pyroxene to olivine ratio than the other ureilites. At the other end of the spec- trum Yamato 74130 carries augite rather than TABLE 10.?Data on ureilites in the Antarctic meteorite collections Locality Yamato Mountains Yamato Mountains Yamato Mountains Allan Hills Allan Hills Allan_ Hills Specimen number 74123 74130 74695 ALHA77257 ALHA78019 ALHA78262 Weight (g) 69.9 17.9 18.9 1995.7 30.3 26.2 pigeonite and has an unusually Fe-rich olivine (Fo76). Aubrites The 1978 collection from the Allan Hills area contains a single sample of an aubrite, ALHA78113 (298.6 g). The sample is a breccia with enstatite grains, described as being up to 2.5 X 2.0 cm, which are essentially iron-free, along with minor nickel-iron and troilite. Conclusions The Antarctic meteorite collections have al- ready yielded a substantial number of unique achondrites. Future collections will undoubtedly add to their number and there may be many surprises still to come. With further extension of the search areas we may be able to obtain reason- able statistics on the relative abundances of the various achondrite types. The overall differences between Antarctic and non-Antarctic achondrite abundances may simply be an indication that both data sets are still too small to be represent- ative. The reason for the abundance of polymict eucrites in the Antarctic is not, however, readily apparent. Overview of Antarctic Carbonaceous Chondrites Carleton B. Moore Seven carbonaceous chondrite specimens have been collected from the Yamato Mountains and three from the Allan Hills region of Antarctica. At the Sixth Symposium on Antarctic Meteorites held on 19 February 1981, at the National Insti- tute of Polar Research, Tokyo, it was reported that, of the approximately 3000 meteorites col- lected during the 1979-1980 field season, an ad- ditional 20 uncharacterized, small, carbonaceous, chondrite pieces were recovered. This relatively low yield compared to the large number of ordi- nary chondrites recovered leads to speculation that in Antarctica there are processes that act against the recovery of this interesting meteorite type. The possibility that the recovered carbona- ceous chondrites fell near their recovery sites and have not been transported long distances by mov- ing ice may ultimately be tested by measurements of their terrestrial residence times. The Antarctic carbonaceous chondrites are mostly C2 chondrites. In addition there are three C3 and one C4 chondrite. The precise classifica- tion of several small specimens from the Yamato area has not been reported. The carbonaceous chondrite yield from the Antarctic meteorite ex- peditions is shown in Table 11. The Antarctic carbonaceous chondrites appear to be relatively fresh, unweathered, and uncon- taminated with terrestrial organic molecules. The white precipitates of carbonates and sulfates (re- ported by Marvin and Motylewski, 1980) on one C3 (ALHA773O7) are only minor surface features. Carleton B. Moore, Center for Meteorite Studies, Arizona State University, Tempe, Arizona 85281. Interior and exterior samples of ALHA77306 do not show significant differences in bulk chemical composition (Table 12). The concentrations of amino acids in two large C2 Antarctic meteorites, Yamato 74662 and ALHA77306, have been well established. Analy- ses of interior and exterior splits support the assertion that these meteorite finds are clean, pristine specimens (see also Lipschutz, this issue). Analyses done in different laboratories using dif- ferent techniques give results that do not differ significantly in the abundances of individual amino acids. The C2 chondrite, Yamato 74662, is similar to the Murchison C2 chondrite, while ALHA77306 shows greater similarities to the No- goya C2 chondrite. Petrographic study of ALHA77306 by McSween (1979) establishes its similarity with Nogoya and other matrix-rich C2 chondrites. ALHA773O6 and Nogoya have sig- nificantly lower total amino acid concentrations than Yamato 74662 and Murchison (Cronin et al., 1979; Shimoyama, Ponnamperuma, and Yanai, 1979a,b; Kotra et al., 1979). Holzer and Oro (1979) reported that pyrolysis products de- tected in ALHA773O6 are also lower than those in Murchison. Unpublished work by Cronin (Ar- izona State University laboratory) on ALHA 77307, a C3 chondrite, showed no significant indigeneous or terrestrial amino acids. Magnetic studies of Yamato 74662 and Ya- mato 693 by Nagata (1980) confirm their classi- fication as C2 and C3 chondrites, respectively. Brecher (1980) has studied Yamato 74662 and confirms Nagata's magnetic results. Hyman and Rowe (1979) suggest that the mag- 65 66 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE 11.?Data on carbonaceous chondrites in the Antarctic meteorite collections Locality Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Yamato Mountains Allan Hills Allan Hills Allan Hills Allan Hills Specimen number 693 74641 74642 74662 75003 75260 75293 ALHA77003 ALHA773O6 ALHA773O7 ALHA78261 Type C3 C? C2 C2 C? C2 C? C3 C2 C3V G2 Weight (g) 150 4.5 10.6 151 1.5 4.0 8.1 779 19.9 181 5.1 TABLE 12.?Partial chemical analyses of Antarctic carbonaceous chondrites (Allan Hills analyses by M.-S. Ma and R.H. Schmitt, in litt., June 1980; Yamato analyses by Jochum et al., 1980; carbon and sulfur analyses by Gibson and Andrawes, 1980) Constituent A12O3 FeO MgO CaO Na2O K2O Co Ni C s ALHA77036 Exterior 2.1% 25.4 18.3 1.9 0.52 0.045 0.052 1.1 ? ? Interior 2.1% 25.6 18.5 1.8 0.56 0.038 0.052 1.1 1.32 3.86 ALHA77307 2.7% 30.7 21.0 2.2 0.15 0.029 0.051 1.0 0.83 1.52 Yamato 74662 2.1% 30.1 19.8 1.7 0.22 0.037 0.061 1.4 1.5 3.49 Yamato 693 2.5% 33.2 24.8 2.4 0.43 0.039 0.062 1.3 0.06 1.60 netic properties of ALHA77306 indicate that it contains less than 0.8% magnetite. Clayton, Mayeda, and Onuma (1979) state that Yamato 693 has oxygen isotopic composi- tions virtually identical with Karoonda, classified as a C4 or C5. Matrix phyllosilicates of ALHA77306 have been studied by McKee and Moore (1980) using high-resolution, transmission electron micros- copy. They have been identified as various com- ponents of the serpentine group. ALHA77306 appears to have the most complete assemblage of the various phyllosilicate groups thus far identi- fied in a single meteorite. Available data on the Antarctic carbonaceous chondrites through 1980 are still rather sparse; however, numerous current investigations will make more complete characterization possible in the near future. Weathering Effects in Antarctic Meteorites Michael E. Lipschutz The large number of Antarctic meteorites al- ready recovered includes samples of previously rare and unknown types, and future recoveries will enlarge the sample base even further. Poten- tially, this should permit more complete charac- terization of extraterrestrial parent objects and the genetic and evolutionary processes that formed them; compositional data are essential in this regard. Chemical studies are useful, however, only to the extent that the preterrestrial compo- sition is unaltered by weathering during the me- teorites' terrestrial residence (see accompanying summary by Evans, Reeves, and Rancitelli). I review herein those chemical data bearing upon effects of chemical alteration by weathering of Antarctic stony and stony-iron meteorites. In more temperate regions, weathering effects in meteoritic finds generally involve contamina- tion?usually to such an extent that trace element data of finds are viewed very suspiciously. Con- ditions in Antarctica are sufficiently different that the principal weathering effect in meteoritic finds there is element-loss by leaching; contamination, however, is observed for some elements. Different elements in the same meteorite can respond dif- ferently to weathering; thus, absence of a weath- ering effect for one element need not mean that another will be unaffected. Conceivably, element lability could be affected by host-siting; thus, an element could be unaffected in one type of me- teorite while being very labile in another weath- ered under the same conditions for an identical period. Michael E. Lipschutz, Department of Chemistry, Purdue University, West Lafayette, Indiana 47907. Even in meteoritic falls, indigenous composi- tions vary widely, particularly for elements pre- sent at the ppb-ppt levels. Thus, weathering ef- fects in Antarctic meteorites, all of which are finds, must be established by comparing their compositions with those of similar falls and/or by uncovering systematic compositional variations in exterior versus interior portions. Macroscopically, stony meteorites are classified by degree of weathering and fracturing, increas- ing in severity from class A to C. Minor weath- ering (A) is characterized by traces of rust halos around metal grains and oxide staining along cracks. Moderate weathering (B) produces large rust halos around metal grains and extensive oxide staining along internal cracks. Severely weathered (C) specimens are uniformly stained brown and retain little or no metal. Slightly fractured (A) specimens exhibit few or no cracks and none penetrate the entire specimen. In mod- erate fracturing (B) several cracks may extend across the specimen, which can be readily broken along the fractures. Severely fractured (C) speci- mens exhibit many extensive cracks and readily crumble. Some samples (e.g., seven of ~ 300 collected in 1977-1978) exhibit white surficial deposits that, Marvin and Motylewski (1980) identify as hy- drated magnesium carbonates and sulfates. These authors attribute these deposits to early stages of weathering after the samples' exposure on the ice surface. (The seven specimens include five of weathering type A and one each of types B and C.) Marvin and Motylewski (1980) suggest that the deposits were formed from salts leached from the meteorites by liquid water produced from 67 68 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES snow on sun-warmed meteoritic surfaces. Inorganic carbon-containing compounds (and some organic ones) should be especially sensitive to weathering. Cronin et al. (1979) report that amino acid composition and contents in interior and exterior samples of the weathering type A C2 chondrite ALHA773O6 are similar to those of C2 chondrite falls. Total C contents in this chondrite (and Yamato 74662) are lower than those in other C2 chondrite falls; S contents are not atypical, however (Gibson and Yanai, 1979a,b). Total C and S contents of a ureilite and C4 and E4 chondrites recovered from the Yamato Moun- tains region resemble those of similar meteorites (Gibson and Yanai, 1979a,b) from other regions. Gibson and Andrawes (1980) report that most of the 25 ALH meteorites they studied have C and S contents within ranges reported for similar falls. (This sampling includes ordinary chondrites of petrologic types 3-6, C2 and C3 chondrites, and a ureilite.) Evidence for weathering effects some- times appears. The weathering type B L6 chon- drite ALHA77281 contains 250jiig C/g compared with 160-200jLtg C/g in the possibly related chon- drites 77280 and 77282. Surface samples of the type B chondrites ALHA7 7002(L5) and 77269(L6) contain nearly twice as much C as interior samples of the same stones. Exterior sam- ples are depleted in S by about 10% compared with interior ones. Stepwise pyrolysis of exterior and interior samples of 77002 and an interior sample of another weathering type B L6 chon- drite, ALHA77273, demonstrates CO2 evolution, presumably from secondary cabonates. The C contents of several weathering type C meteorites seem high but S contents seem normal. Trace elements should, in principle, be most informative about weathering processes because even a small absolute change in concentration should be reflected in a large relative change. For example, Patchett and Tatsumoto (1980) studied Lu/Hf isotopic systematics in eucrites and report that data for ALHA773O2 (a weathering type A meteorite) lie slightly off the 176Hf/177Hf vs. 176Lu/177Hf isochron defined by 9 other eucrites. They attribute this to loss of Lu by leaching during weathering, although it is not clear why Lu should be leached preferentially. Unfortu- nately, meteoritic contents of trace elements (par- ticularly the more volatile/mobile ones) are in- trinsically variable since they can be affected by primary nebular condensation, secondary ther- mal processes in parent bodies, or tertiary shock- heating. While weathering effects can be estab- lished at times by comparing data for interior and exterior portions of a sample and by exam- ining data for meteorites of a similar type, it is not always possible to eliminate the possibility that trace element variations pre-date terrestrial residence. Thus far, trace elements studies of Antarctic meteorites have involved mainly those of weath- ering type A. Biswas, Ngo, and Lipschutz (1980) determined Ag, As, Au, Bi, Cd, Co, Cs, Cu, Ga, In, Rb, Sb, Se, Te, Tl, and Zn in exterior and interior portions of ALHA77257 ureilite and 77278 L3 chondrite. They found significant Cs and Rb enrichments in the exterior samples of both meteorites and attributed this to deposition of wind-borne oceanic aerosol. Six elements (As, Au, Co, Cu, Ga, and Zn) seem unaffected by weathering even in surface samples. The eight other elements exhibit contrasting trends in ex- terior/interior parts of the two meteorites. Trace element data for the 16 elements in interior samples of Antarctic meteorites (i.e., those obtained at depths > 1 cm below exterior sur- faces) generally accord well with results for simi- lar meteoritic falls. Thus far, comparisons are available involving the following ALH meteor- ites: 77005 with shergottites (McSween et al., 1979; Biswas, Ngo, and Lipschutz 1980); 77081 with Acapulco and 77307 with C3V chondrites (Biswas et al., unpublished data); 77257 with ureilites, 77278 with L3 chondrites and 77299 with H3 chondrites (Biswas, Ngo, and Lipschutz 1980); 78113 with enstatite achondrites (Biswas, Walsh et al. 1980). The comparison for 77005 also includes K, Th, and U. In each case, concor- dance between data for Antarctic and non-Ant- arctic meteorites is typically as good as that be- tween samples of any two similar meteorite falls. NUMBER 24 69 In summary, Antarctic meteorite compositions reflect contamination. With proper precautions, can be affected by weathering but are unaltered data obtained from Antarctic meteorites are as for interior portions of type A meteorites, at least. reliable as those determined for meteoritic falls. Where weathering effects can be detected, they ACKNOWLEDGMENT.?This research was sup- generally involve elemental loss by leaching. Con- ported in part by NASA grant NGL 15-005-140. tents of a few elements?C and alkali metals? Aluminum-26: Survey of Victoria Land Meteorites J.C. Evans, J.H. Reeves, and L.A. Rancitelli Over the past two years an extensive survey of the 26A1 (ti/2 = 720,000 y) content of Victoria Land meteorites has been carried out by nonde- structive gamma-ray analysis. To date a total of 104 samples from the Victoria Land region has been studied. Most of the samples have been ordinary chondrites from the Allan Hills region. Future studies will, however, increasingly empha- size specimens from other regions, as well as including larger numbers of achondrites. The ultimate goal of this work is to establish terrestrial ages for meteorites recovered from the Antarctic ice sheet. This information can then be used to infer information on long-term movement of the ice sheet, as well as helping to provide an under- standing of the accumulation mechanism for me- teorites at specific sites. Terrestrial residence times can, in principle, be derived from a measurement of the decay of a cosmic ray-produced isotope from its saturation level in space. Shielding and complex exposure history can influence the pro- duction rate in space, making calculation of a terrestrial residence time from a single Al mea- surement rather uncertain for individual mete- orites. The 26A1 measurements are thus most use- ful as a survey to identify interesting cases requir- ing more detailed analysis by other more time- consuming techniques. Such additional measure- ments may include 10Be, 14C, 36C1, 53Mn, noble rare gases, cosmic ray tracks, and thermolumi- nescence. J.C. Evans, J.H. Reeves, and L.A. Rancitelli, Battelle Pacific Northwest Laboratories, P. 0. Box 999, Richland, Washington, 99352. Measurements of 14C are useful for estimating terrestrial ages of less than ~35 X 103 years for setting lower bounds on terrestrial ages. Exposure history is less significant for 14C age estimates than 26A1 age estimates. Ten Allan Hills meteor- ites have been investigated for 14C (Fireman 1979, 1980; Fireman et al., 1981). These are listed in Table 13. One L chondrite, ALHA77OO3, has a positive 14C content, 3.6?1.0 dpm/kg, giv- ing a 14C terrestrial age of (21 ? 4) X 103 years. Cosmogenic x C was observed in the achon- drite ALHA77256 and in the H chondrite ALHA77294, giving them 14C terrestrial ages of (11?1) X 103 years and (30?2) X 103 years, respectively. Only limit values for 14C were ob- tained for the other seven meteorites; their lower limit ages range from 25 X 103 years for ALHA77214 to 32 X 103 years for the others. When combined with 26A1 measurements, the most useful isotopes for determining terrestrial ages in the 0.1 to 1 m.y. range have been 36C1 (ti/2 = 300,000 y) and 53Mn (ti/2 = 3.7 m.y.). Chlorine-36 has been measured in several Ant- arctic meteorites by a La Jolla-Rochester collab- oration using the newly developed Van de Graaff accelerator technique. Manganese-53 was mea- sured on the same samples in La Jolla (Nishiizumi et al., 1978; Nishiizumi et al., 1980) by the now- routine neutron activation procedure. These pub- lished data have been included in Table 13, along with the much larger volume of 26A1 data. For the meteorite studies, by all three methods, it is pos- sible to derive terrestrial ages with some degree of confidence. 70 NUMBER 24 71 TABLE 13.?Cosmogenic isotope content of Victoria Land meteorites (expected saturation values: 26A1 L = 59 ? 9 dpm/kg, H = 55 ? 8 dpm/kg; 36C1 = 25 ? 4 dpm/kg (Fe + Co + Ni + 6 Ca); 53Mn = 450 ? 90 dpm/kg (Fe + 1/3 Ni); 14C = 60 ? 6 dpm/kg Specimen number ALHA76004 ALHA76005 ALHA76006 ALHA76OO7 ALHA76O08 ALHA77OO1 ALHA77OO2 ALHA77OO3 ALHA77OO4 ALHA77OO9 ALHA77O1O ALHA77O11 ALHA77025 ALHA77062 ALHA77O71 ALHA77O81 ALHA77O86 ALHA77118 ALHA77124 ALHA77144 ALHA7715O ALHA77164 ALHA77177 ALHA77182 ALHA77190 ALHA77191 ALHA77192 ALHA77208 ALHA77214 ALHA77215 ALHA77216 ALHA77217 ALHA77224 ALHA77225 ALHA7723O ALHA77232 ALHA77233 ALHA77249 ALHA77256 ALHA77258 ALHA77260 ALHA77261 ALHA77262 ALHA7727O ALHA77272 ALHA77278 Class LL3 Eucrite H6 L6 H6 L6 L5 C3 H4 H4 H4 L3 H5 H5 H5 H H5 H5 H5 H6 L6 L3 H5 H5 H4 H4 H4 H4 L3 L3 L3 L3 H4 H4 L4 H4 H4 L3 Diog. H6 L3 L6 H4 L6 L6 LL3 Weathering category A B C C A B A C C C C C B B B C C C B C C C B C C C C C B B B C C B C C C A B B B B B B A dpm/kg 58 ? 6 89 ?9 51 ? 5 45 ? 4 11 ? 1 52 ? 5 30 ? 3 45 ? 5 52 ?5 32 ? 2 49 ? 3 39 ? 4 54 ? 5 47 ? 5 55 ? 6 42 ? 4 58 ? 6 53 ? 5 70 ? 7 56 ? 6 43 ? 4 44 ? 5 54 ? 3 41 ? 4 51 ? 3 56 ?4 55 ? 6 52 ? 3 56 ?6 36 ?4 40 ? 3 38 ? 3 51 ? 3 51 ? 3 51 ? 3 54 ? 3 47 ? 3 37 ? 2 29 ? 2 37 ? 2 36 ? 4 47 ? 5 40 ? 3 35 ?4 28 ? 3 26Al Terrestrial age (10s y) <3a <3a <5a 0.3b <1.7b >0.3b <1.2b >0.3b <1.7b >0.3b 4.6 ? 1.0f <1.4g >0.3g <3.0f 16.0 ? 1.5f <0.5f 36Cl (dpm/kg Fe + Co + M+6Ca) 9.4 ? 1.0d 20.1 ? 1.2d 4.6 ? l.le 18.4 ? 1.2e 17.0?0.8e 6.6 ? 3.3e 10.9?0.7e S3Mn (dpm/kg Fe+1/3 Ni) 22 ? 2d 422 ? 13d 255 ? 8e 317 ? 13e 151 ?6e 213 ? lle 264 ? lle 72 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE 13.?Continued Specimen number ALHA77282 ALHA77284 ALHA77285 ALHA77294 ALHA77297 ALHA77299 ALHA 7 7300 ALHA77304 ALHA 78001 ALHA78OO3 ALHA 78038 ALHA78039 ALHA 78041 ALHA78043 ALHA78044 ALHA78045 ALHA78046 ALHA78048 ALHA78049 ALHA78050 ALHA 78051 ALHA78O52 ALHA78O76 ALHA78O77 ALHA78102 ALHA 78103 ALHA78104 ALHA78105 ALHA78106 ALHA78109 ALHA78112 ALHA78114 ALHA 78115 ALHA78126 ALHA 78128 ALHA78130 ALHA 78131 ALHA78132 ALHA 78134 ALHA78251 RKPA 78001 RKPA78OO3 RKPA78004 META 78001 META78002 META78003 META78004 META 78005 META78006 Class L6 L6 H6 H5 L6 H3 H5 LL3 L3 L6 L6 L4 L6 L6 L6 H6 H4 H5 L6 L6 L6 L6 LL5 L6 L6 H6 L6 H5 L6 L6 Eucrite H4 L6 L6 L6 H4 H4 L6 L6 L6 H6 Weathering category B B C A B A C B C B B B B/C B B B C C B B B B B B C B B C C C A C B C C A C B B B C dpm/kg 49 ? 3 45 ? 5 38 ? 4 70 ? 7 43 ? 4 54 ? 4 50 ? 3 50 ?4 59 ? 4 36 ?3 42 ? 3 38 ? 3 38 ?3 51 ?4 34 ? 3 46 ? 5 59 ? 5 52 ? 3 44 ? 3 38 ? 3 56 ?4 52 ?4 42 ? 3 35 ? 3 58 ? 3 53 ? 3 61 ? 7 44 ? 4 46 ? 3 42 ? 3 38 ? 2 43 ? 3 45 ? 3 34 ?2 51 ? 4 40 ?3 68 ? 4 61 ? 3 56 ?6 49 ? 3 50 ? 3 39 ?2 53 ? 3 47 ?3 50 ? 3 49 ? 4 44 ? 3 60 ? 4 26Al 14C 36r/ 53 yfut jvin Terrestrial dpm/kg Terrestrial (dpm/kg Fe + (dpm/kg age (l(f y) age (l(f y) Co + M + 6 Ca) Fe + 1/3 Ni) 0.30 ? .02g 1.6?0.3g r, \ Chlo-? ? 0.28 m.y. rine-36 and Mn measurements made subse- quently by Nishiizumi et al. (1979) convincingly demonstrated that this meteorite had experienced a complete bombardment history followed by a relatively short terrestrial residence. A similar situation was also in evidence for one of the Yamato meteorites, Yamato 7301. This clearly demonstrates the hazards of using a single isotopic measurement for an age determination. An alternative approach involves a statistical analysis of the whole body of data. Figure 40 is a histogram of the frequency distribution of 26A1 contents of 87 Antarctic meteorites for which type information was available. A target element cor- rection factor has been included to normalize the data to an L chondrite composition. The dashed line on the figure is the shape of the distribution for contemporary falls and finds obtained by making similar corrections on falls and finds. It is quite clear that the Antarctic meteorites are dis- tributed toward lower 26A1 contents. Figure 41 shows the same type of distribution for H and L chondrites. It appears that most of the low 26A1 values are found amongst the L chondrite population, suggesting a possible shower contribution. There is, nevertheless, a strong suggestion that terrestrial ages somewhat in excess of 500,000 years may be fairly common, while at the same time there is no evidence as yet of any samples having ages in excess of one million years. At present only a fraction of the collection has been surveyed. Future work may yet turn up older cases as the data base continues to expand. 74 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES 36 32 28 tSES uu. O a. LLJ 00 3 Z 24 20 16 12 ALL ANTARCTIC CHONDRITES (87 CASES) WORLD WIDE CHONDRITES (135 CASES) 10 20 40 50 26AI (dpm/kg) 60 70 80 16 12 . ANTARCTIC H CHONDRITES (36 CASES) NORMALIZED TO L COMPOSITION ANTARCTIC L CHONDRITES (51 CASES) 10 20 40 50 6AI (dpm/kg) 70 80 FIGURE 40.?26Al content of Antarctic chondrites normalized to L-type composition. 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Memoirs of the National Institute of Polar Research (Japan), special issue, 8:51-69. 1978. Meteorites from Antarctica. Meteoritics, 13: 673-677. 1978. Yamato-74 Meteorites Collection, Antarctica, from November to December 1974. Memoirs of the National Institute of Polar Research (Japan), special issue, 8:1-37. 1979. Meteorite Search in Victoria Land, Antarctica, in 1977-1978 Austral Summer. Memoirs of the National Institute of Polar Research (Japan), special issue, 12:1-8. 1979. Catalog of Yamato Meteorites in the Collection of National Institute of Polar Research. 188 pages. Tokyo: Na- tional Institute of Polar Research (Japan). Yanai, K., W.A. Cassidy, M. Funaki, and B.P. Glass 1978. Meteorite Recoveries in Antarctica during Field Season 1977-78. In Proceedings of the Ninth Lunar and Planetary Science Conference, pages 977-987. New York: Pergamon Press. 84 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES Yanai, K., and H. Haramura 1978. Yamato-74662 Meteorite: A Carbonaceous Chon- drite Type II. Memoirs of the National Institute of Polar Research (Japan), special issue, 8:264-267. Yanai, K., M. Miyamoto, and H. Takeda 1978. Classification for the Yamato-74 Chondrites Based on the Chemical Compositions of Their C ;vines and Pyroxenes. Memoirs of the National Institute of Polar Research (Japan), special issue, 8:110-120. Yomoerida, K., and T. Matsui 1981. Porosity of Ordinary Chondrites?Is It a Good Measure of a Consolidation State of Composite Materials in Chondrites? In Lunar and Planetary Science XII, pages 1227-1229. Houston: Lunar and Planetary Institute. Yoshida, M., H. Ando, K. Omoto, R. Naruse, and Y. Ageta 1971. Discovery of Meteorites near Yamato Mountains, East Antarctica. Nankyoku Shiryo [Antarctic Rec- ord, Japan], 39:62-65. Yoshida, Y., and S. Mae 1978. Some Information on Topographic Features and the Characteristics of the Sheet Ice around the Yamato Mountains. Memoirs of the National Institute of Polar Research (Japan), special issue 8:93-100. Appendix Tables of Victoria Land Meteorites Terminology Class and type: Au = aubrite; C = carbonaceous chondrite; Di = diogenite; Eu = eucrite; Ho = howardite; H = high-iron chondrite; L = low-iron chondrite; LL = low-iron low-metal chondrite; M ? mesosiderite; Sh = shergottite; Ur = ureilite. Chondrite type is indicated by the digit following the letter. Olivine composition in mole percent Fe2SiC>4 (Fa). Pyroxene (orthopyroxene or low-Ca clinopyroxene) composition in mole percent FeSiC>3 (Fs). Degree of weathering: A = minor; metal flecks have inconspicuous rust halos, oxide stain along cracks is minor. B = moderate; metal flecks show large rust halos, internal cracks show extensive oxide stain. C = severe; specimen is uniformly stained brown, no metal survives. Degree of fracturing: A = slight; specimen has few or no cracks and none penetrate the entire specimen. B = moderate; several cracks extend across the specimen, which can be readily broken along the fractures. C = severe; specimen has many extensive cracks and readily crumbles. Locations: ALH = Allan Hills; BTN = Bates Nunatak; DRP = Derrick Peak; EET = Elephant Moraine; MET = Meteorite Hills; MBR = Mount Baldr; PGP = Purgatory Peak; RKP = Reckling Peak. TABLE A.?Characteristics of meteorites listed by source area, in numerical sequence Specimen number ALHA 76001 76002 76003 76004 76005 76006 76007 76008 76009 77001 77002 77003 77004 77005 77009 77010 77011 Weight (g) 20151 1510 10495 305 1425 1137 410 1150 407000 252 235 779 2230 483 235 295 291 Class and type L6 Iron L6 LL3 Eu H6 L6 H6 L6 L6 L5 C3 H4 Sh H4 H4 L3 %Fa in olivine 25 25 0-34 18 24 19 24 25 25 4-48 17-20 28 18 18 4-36 %Fs in pyroxene 21 21 0-53 37-57 16 21 17 21 21 22 2-25 15-27 23 16 15-18 1-33 Degree of weathering A A A A B A B B B B A C A C C C Specimen number 77012 77014 77015 77021 77025 77033 77061 77062 77064 77071 77074 77081 77086 77088 77102 77118 77119 77124 Weight (g) 180 309 411 16.7 19.4 9.3 12.6 16.7 6.5 10.9 12.1 8.6 19.4 51.2 12.3 7.8 6.4 4.4 Class and type H5 H5 L3 H5 H5 L3 H5 H5 H5 H5 H5 H? H5 H5 H5 H5 H5 H5 %Fa in olivine 18 18 1-21 18 18 8-38 18 18 18 18 18 11 19 19 19 19 18 19 %Fs in pyroxene 16 17 4-24 17 17 8-9 17 17 17 17 17 11 17 17 15 17 17 16 Degree of weathering C cc cc c B B B B B B C C B C C C 85 86 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE A.?Continued Specimen number 77140 77144 77148 77150 77155 77160 77164 77165 77167 77177 77180 77182 77183 77190 77191 77192 77208 77214 77215 77216 77217 77219 77221 77223 77224 77225 77226 77230 77231 77232 77233 77249 77250 77252 77254 77255 77256 77257 77258 77259 77260 77261 77262 77263 77264 77268 77269 77270 77271 Weight (g) 78.6 7.9 13.1 58.3 305 70.4 38.1 30.5 611 368 190 1134 288 387 642 845 1733 2111 820 1470 413 637 229 207 787 5878 15323 2473 9270 6494 4087 504 10555 343 246 765 676 1996 597 294 744 412 862 1669 11.0 272 1045 589 610 Class and type L3 H6 H6 L6 L6 L3 L3 L3 L3 H5 L6 H5 H6 H4 H4 H4 H4 L3 L3 L3 L3 M H4 H4 H4 H4 H4 L4 L6 H4 H4 L3 Iron L3 L5 Iron Di Ur H6 H5 L3 L6 H4 Iron H5 H5 L6 L6 H6 %Fa in olivine 8-44 19 18 25 24 3-46 6-39 8-33 2-41 18 24 19 19 17-19 16-18 16-18 17 1-49 22-26 15-35 17-25 26 15 17 19 17 18 22-25 24 17 14-21 7-35 22-28 23 13 18 18 7-23 24 15-19 19 18 24 24 18 %Fs in pyroxene 2-17 17 16 22 20 6-40 3-41 6-35 3-17 16 20 17 16 15-22 14-16 15-21 14 4-23 9-21. 14-23 9-26 24-28 13-15 15-23 17 16 16 18-29 21 15 15-17 2-25 2-22 20 23 12 16 15 1-28 21 13-16 16 16 22 21 16 Degree of weathering C B C C A/B C C C C C C B C C C C C C B A/B B B C C C C C B A/B C C C B A/B A/B A B/C C C B B A/B C B A/B C Specimen number 77272 77273 77274 77277 77278 77280 77281 77282 77283 77284 77285 77286 77287 77288 77289 77290 77292 77294 77296 77297 77299 77300 77302 77304 77305 77306 77307 78006 78019 78038 78039 78040 78042 78043 78044 78045 78048 78050 78053 78074 78075 78076 78077 78078 78084 78085 78100 78102 Weight (g) 674 492 288 143 313 3226 1231 4127 10510 376 271 245 230 1880 2186 3784 199 1351 963 952 261 235 236 650 6444 19.9 181 8.0 30.3 363 299 211 214 680 164 396 190 1045 179 200 280 275 330 290 14280 219 84.9 336 Class and type L6 L6 H5 L6 LL3 L6 L6 L6 Iron L6 H6 H4 H5 H6 Iron Iron L6 H5 L6 L6 H3 H5 Eu LL3 L6 C2 C3 Ho Ur L3 L6 Eu L6 L6 L4 L6 L6 L6 H4 L6 H5 H6 H4 L6 H3 H5 Iron H5 %Fa in olivine 24 24 18 24 11-29 24 24 24 25 18 17 18 19 24 17 24 24 11-21 18 18-27 24 1-30 22 4-42 24 24 25 23-25 25 24 23 17 24 18 18 19 24 18 18 18 %Fs in pyroxene 20 20 16 20 9-21 21 20 20 21 16 12-16 16 17 20 15 21 20 15-20 16 37-64 13-19 21 1-12 25-61 18 2-19 21 33-52 20 21 19-24 21 21 20 16 21 16 16 15-18 20 8-24 16 17 Degree of weathering B/C B C A/B A B B B A/B C C C B B A A/B A A C A B B/C A A A B/C C B A B B B/C B/C A/B B C B B/C B C A/B B/C B B/C NUMBER 24 87 TABLE A.?Continued Specimen number 78103 78104 78105 78106 78107 78108 78109 78110 78111 78112 78113 78114 78115 78126 78127 78128 78130 78131 78132 78134 78153 78158 78165 78188 78193 78196 78209 78211 78213 78215 78221 78223 78225 78227 78229 78231 78233 78251 78252 78261 78262 79001 79002 79003 79004 79005 79006 79007 79008 Weight (g) 589 672 941 464 198 172 233 160 126 2485 298 808 847 606 194 154 2733 268 656 458 151 15.1 20.9 0.8 13.3 11.1 12.1 11.4 9.5 6.3 5.4 6.4 4.5 2.4 1.9 1.8 1.3 1312 2789 5.1 26.1 32.3 222 5.1 34.9 60.0 40.9 142 12.0 Class and type L6 L6 L6 L6 H5 H5 LL5 H5 H5 L6 Au L6 H6 L6 L6 H5 L6 L6 Eu H4 LL6 Eu Eu L3 H4 H4 H5 H6 H6 H6 H5 H4 H5 H5 H6 H6 H5 L6 Iron C2 Ur L3 H6 L3 H5 H6 H5 L6 H5 %Fa in olivine 24 24 23 24 18 18 28 18 18 25 0 25 18 25 24 19 25 25 18 29 1-34 18 18 18 18 18 18 18 18 18 18 18 18 18 23 0-50 22 6-39 16 10-38 16 18 18 23 17 %Fs in pyroxene 20 20 20 20 17 16 23 16 16 20 0 20 16 21 20 17 21 21 40-68 15-20 24 40-68 37-61 5-29 16 16 15 16 15 16 16 16 16 16 15 16 16 20 1-8 19 2-31 18 5-26 14 16 15 19 15 of weathering B B B A/B C B A/B B/C A B A/B B/C B B B/C C B/C B/C A B/C B/C A A C B/C B/C B/C B/C B/C B/C B B B B/C B B/C B/C B A A C C B B/C B B/C A/B B Specimen number 79009 79010 79011 79012 79013 79014 79015 79016 79017 79018 79019 79020 79021 79022 79023 79024 79025 79026 79027 79028 79029 79031 79032 79033 79034 79035 79036 79037 79038 79039 79040 79041 79042 79043 79045 79046 79047 79048 79049 79050 79051 79052 79053 79054 79055 BTNA 78001 78002 Weight (g) 75.7 25.1 14.0 192 28.3 10.8 64.0 1146 310 120 12.1 4.2 29.4 31.4 68.1 21.6 1208 572 133 16.2 505 2.7 2.6 208 12.6 37.6 20.2 14.8 49.6 108 13.2 20.1 11.4 62.2 115 89.7 19.3 36.7 54.0 27.0 24.0 22.6 86.0 36.0 15.2 160 4301 Class and type H5 H5 H5 H5 H5 H5 H5 H6 Eu L6 H6 H6 H5 L3 H4 H6 H5 H5 L6 H6 H5 H5 H5 L6 H6 H4 H5 H6 H5 H4 H5 H5 H5 L6 L3 H5 H5 H5 H6 H5 H5 L6 H5 H5 H6 L6 L6 %Fa in olivine 18 17 18 17 18 18 17 17 23 17 17 18 1-28 17 17 17 18 24 18 18 16 16 24 18 17 18 18 17 16 18 18 18 23 2-38 18 18 18 18 18 18 23 17 18 18 24 24 %Fs in pyroxene 15 15 16 15 16 16 15 15 28-53 20 15 15 17 9-22 14-17 15 15 16 20 16 16 14 14 20 16 14-18 16 16 15 15 15 16 16 20 2-29 15 15 16 16 15 15 20 15 16 16 21 20 Degree of weathering C B/C B/C C C B B B/C A B/C B B/C B A/B B/C C C B B B C C C B B B B B C B B B B C C B B B C C C B/C B/C B B/C B B 88 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE A.?Continued Specimen number 78004 DRPA 78001 78002 78003 78004 78005 78006 78007 78008 78009 EETA 79001 79002 79003 79004 79005 79006 79007 79009 79010 79011 META 78001 78002 78003 Weight (g) 1079 15200 7188 144 133 18600 389 11800 59400 138100 7942 2843 435 390 450 716 199 140 287 86.4 624 542 1726 Class and type LL6 Iron Iron Iron Iron Iron Iron Iron Iron Iron Sh Di L6 Eu Eu Ho H5 L5 L6 Eu H4 L6 L6 %Fa in olivine 30 23-27 24-25 24 18 24 24 17 23 24 %Fs in pyroxene 24 16-67 22 20 30-61 30-61 19-57 16 20 20 30-61 14-21 20 21 Degree of weathering B A B B B A B B B B B B/C B B Specimen number 78005 78006 78007 78010 78028 MBRA 76001 76002 PGPA 77006 RKPA 78001 78002 78003 78004 79001 79002 79003 79004 79008 79009 79012 79013 79014 79015 Weight (g) 172 409 174 233 20657 4108 13773 19068 234 8483 1276 166 3006 203 182 370 73.0 55.0 12.8 11.0 77.7 10022 Class and type L6 H6 H6 H5 L6 H6 H6 Iron L6 H4 L6 H4 L6 L6 H6 H5 L3 H6 H6 L5 H5 M %Fa in olivine 24 18 19 19 25 18 18 23 18 23 17 24 24 18 18 1-29 18 18 23 18 %Fs in pyroxene 20 15 17 17 21 16 16 20 15 20 14-21 20 20 16 16 2-28 16 16 20 16 24 Degree of weathering B C B/C B B A A C B C A B B B B/C B C B B/C B/C TABLE B.?Meteorites listed by class and source area in numerical sequence Specimen number ALHA77299 ALHA78084 ALHA77004 ALHA77OO9 ALHA77O1O ALHA77190 ALHA77191 ALHA77192 ALHA77208 ALHA77221 ALHA77223 ALHA77224 ALHA77225 ALHA77226 ALHA77232 ALHA77233 ALHA77262 ALHA78286 Weight (g) 260 14280 2230 235 295 387 642 845 1733 229 207 786 5878 15323 6494 4087 861 245 Class and type ORDINARY H3 H3 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 Degree of weathering CHONDRITES A B/C C C C C C C C C C C C cc cB C Degree of fracturing A B C A A C B C C A C C C cc B B B NUMBER 24 89 TABLE B.?Continued Specimen number ALHA78053 ALHA78O77 ALHA78134 META 78001 RKPA78OO2 RKPA78004 ALHA79O23 ALHA79039 ALHA79O35 ALHA78193 ALHA78196 ALHA78223 ALHA77O12 ALHA77014 ALHA77O21 ALHA77O25 ALHA77061 ALHA77062 ALHA77064 ALHA77O71 ALHA77O74 ALHA77086 ALHA77O88 ALHA771O2 ALHA77118 ALHA77119 ALHA77124 ALHA77177 ALHA77182 ALHA77259 ALHA77264 ALHA77268 ALHA77274 ALHA77287 ALHA77294 ALHA773OO ALHA78O75 ALHA78085 ALHA78102 ALHA78107 ALHA78108 ALHA78110 ALHA78128 META 78010 ALHA79004 ALHA79006 ALHA79008 ALHA79009 ALHA79010 ALHA79011 ALHA79O12 ALHA79O13 ALHA79014 ALHA79015 ALHA79O21 ALHA79025 ALHA79026 ALHA79029 ALHA79031 ALHA79036 ALHA79038 Weight (g) 179 330 458 624 8483 166 68.1 108 37.6 13.3 11.1 6.4 180 308 16.6 19.4 12.4 16.7 6.4 10.8 12.0 19.4 51.1 12.2 7.8 6.3 4.4 368 1134 294 10.9 272 288 230 1351 234 280 219 336 198 172 160 154 233 34.9 40.9 12.0 75.7 25.1 14.0 191 28.3 10.8 64.0 29.4 1208 572 505 2.7 20.2 49.6 Class and type H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H4 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 Degree of weathering C C B/C B/C B A B/C B B B/C B/C B C C C C B B B B B C C B C C C C B C A/B C C C A C B/C B B/C C B B/C C B B/C B/C B C B/C B/C C C B B B C B C C B C Degree of fracturing B B B B A A C B B A B B A B A B A B B B B B B B B B A A B B A C A A A B B B B A B B B A B B B A B A B B A B A A B B B B B 90 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE B.?Continued Specimen number ALHA79040 ALHA79041 ALHA79042 ALHA79046 ALHA79047 ALHA79048 ALHA79050 ALHA79051 ALHA79053 ALHA79054 EETA79007 RKPA79004 RKPA79014 ALHA79O32 ALHA78209 ALHA78221 ALHA78225 ALHA78227 ALHA78233 ALHA76006 ALHA76008 MBRA76001 ALHA77144 ALHA77148 ALHA77183 ALHA77258 ALHA77271 ALHA77285 ALHA77288 ALHA78076 ALHA78115 META78006 META78OO7 ALHA79002 ALHA79005 ALHA79016 ALHA79019 ALHA79020 ALHA79024 ALHA79028 ALHA79O37 ALHA79049 ALHA79055 RKPA79003 RKPA79009 RKPA79012 ALHA79034 ALHA78211 ALHA78213 ALHA78215 ALHA78229 ALHA78231 ALHA77081 ALHA77O11 ALHA77O15 ALHA77033 ALHA77140 ALHA7716O ALHA77164 ALHA77165 Weight (g) 13.2 20.1 11.4 89.7 19.3 36.7 27.0 24.0 86.0 36.0 199 370 77.7 2.6 12.1 5.3 4.5 2.4 1.3 271 281 1096 7.8 13.1 288 597 609 271 1880 275 847 409 174 222 60.0 1146 12.1 4.2 21.6 16.2 14.8 54.0 15.2 182 55.0 12.8 12.6 11.4 9.5 6.3 1.9 1.8 8.5 291 411 9.3 78.6 70.4 38.1 30.5 Class and type H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H5 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H6 H? L3 L3 L3 L3 L3 L3 L3 Degree of weathering B B B B B B C C B/C B B B/C B/C C B/C B B B/C B/C C B/C B/C B C C B/C C cB B B C B/C C B B/C B B/C C B B C B/C B C B B B B B/C B B/C B C C C C C C C Degree of fracturing A B A B B B B A B A B B B B B A A B B B B B A B A A A B B B A B B B B B A B B B B B B A B B A B B B B B A A B B B B C C NUMBER 24 91 TABLE B.?Continued Specimen number ALHA77167 ALHA77214 ALHA77215 ALHA77216 ALHA77217 ALHA77249 ALHA77252 ALHA7726O ALHA78038 ALHA79001 ALHA79003 ALHA 79022 ALHA79045 RKPA79008 ALHA 78188 ALHA77230 ALHA77OO2 ALHA77254 EETA79009 RKPA79013 ALHA76OO7 ALHA76009 ALHA77OO1 ALHA7715O ALHA77155 ALHA7718O ALHA77231 ALHA77261 ALHA77269 ALHA7727O ALHA77272 ALHA77273 ALHA77277 ALHA7728O ALHA77281 ALHA77282 ALHA77284 ALHA77292 ALHA77296 ALHA77297 ALHA77305 ALHA 78039 ALHA78042 ALHA78043 ALHA78045 ALHA78048 ALHA 78050 ALHA78O74 ALHA78078 ALHA78103 ALHA78104 ALHA78105 ALHA78106 ALHA78112 ALHA78114 ALHA78126 ALHA78127 ALHA78130 ALHA78131 ALHA78251 Weight (g) 611 2111 819 1470 413 503 343 744 363 32.3 5.1 31.4 115 73.0 0.8 2473 235 245 140 11.0 78.5 3950 252 58.3 305 190 9270 411 1045 588 674 492 142 3226 1231 4127 376 199 963 951 6444 299 214 680 396 190 1045 200 290 589 672 941 464 2485 808 606 194 2733 268 1312 Class and type L3 L3 L3 L3 L3 L3 L3 L3 L3 L3 L3 L3 L3 L3 L3 L4 L5 L5 L5 L5 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 Degree of weathering C cB A/B B C B C C C B A/B C B C B B A/B B B/C B B B C A/B C A/B B B A/B B/C B A/B B B B A/B B A/B A B/C B B B B/C A/B B B A/B B B B A/B B B/C B B/C B/C B/C B Degree of fracturing B C B B B C C C C A B B B B B B A A B B A B B B A A A B A B B B A B B B B A A B B B A B B B B B A B A A A B B B B B A A 92 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE B.?Continued Specimen number BTNA 78001 BTNA78002 META78OO2 META78003 META78005 META78028 RKPA 78001 RKPA78003 ALHA79OO7 ALHA79018 ALHA79027 ALHA 79033 ALHA79043 ALHA79052 EETA79003 EETA79010 RKPA 79001 RKPA79OO2 ALHA76004 ALHA77278 ALHA77304 ALHA78109 ALHA78153 BTNA78004 Subtotals H3 H4 H5 H6 H? L3 L4 L5 L6 LL3 LL5 LL6 Total ALHA77OO3 ALHA77306 ALHA773O7 ALHA 78261 Total ALHA78113 ALHA77256 EETA 79002 ALHA78006 EETA79006 Weight (g) 160 4301 542 1726 172 20657 234 1276 142 120 133 208 62.2 22.6 435 287 3006 203 52.5 312 650 233 151 1079 14,571 50,969 10,550 8,883 8.5 8,536 2,473 632 83,062 1,014 233 1,230 182,161 779 19.9 181.3 5.1 985.3 298 676 2843 8.0 716 Class and type L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 L6 LL3 LL3 LL3 LL5 LL6 LL6 Degree of weathering B B B B B B C C A/B B/C B B C B/C B B B B A A B A/B B/C B CARBONACEOUS CHONDRITES Carbonaceous C3 Carbonaceous C2 Carbonaceous C3 Carbonaceous C2 ACHONDRITES Aubrite Diogenite Diogenite Howardite Howardite A A A A A/B A/B B A B Degree of fracturing B A A B B B B B B A A A B B B C C B A A B A B A A A A A A A B A B NUMBER 24 93 TABLE B.?Continued Specimen number EETA79004 ALHA76005 ALHA773O2 ALHA78040 ALHA78132 ALHA 78158 ALHA 78165 ALHA79017 EETA79005 EETA79011 ALHA77OO5 EETA79OO1 ALHA77257 ALHA78019 ALHA78262 Subtotals Aubrites Diogenites Howardites Monomict Eucrites Polymict Eucrites Shergottites Ureilites Total ALHA 76002 ALHA7725O ALHA77255 ALHA77263 ALHA77283 ALHA77289 ALHA7729O PGPA77OO6 ALHA78252 DRPA 78001 DRPA78002 DRPA78003 DRPA78004 DRPA 78005 DRPA78006 DRPA78OO7 DRPA78008 DRPA78009 ALHA 78100 Total Weight (g) 390 317 235 211 656 15.1 20.9 310 450 86.4 482 7942 1995 30.3 26.1 298 3,519 724 390 2,303 8,424 2,052 17,710 307 10555 765 1669 10510 2186 3784 19068 2789 15200 7188 144 133 18600 389 11800 59400 138100 85.0 302,672 Class and type Monomict Eucrite Polymict Eucrite Polymict Eucrite Polymict Eucrite Polymict Eucrite Polymict Eucrite Polymict Eucrite Polymict Eucrite Polymict Eucrite Polymict Eucrite Shergottite Shergottite Ureilite Ureilite Ureilite IRONS Iron-Group IA or Og Iron-Group I or Og Degree of weathering B A A A A A A A A B A A A B/C A Iron-Group Anom (D) Iron-Group I or Og Iron-Group I or Og Iron-Group I or Og Iron-Group I or Og Iron-Group I or Og Iron-Group IVA Iron-Group IIB Iron-Group IIB Iron-Group IIB Iron-Group IIB Iron-Group IIB Iron-Group IIB Iron-Group IIB Iron-Group IIB Iron-Group IIB Iron-Group IIA Degree of fracturing B A A A A A A A B B A A B C A 94 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES TABLE B.?Continued Specimen number ALHA77219 RKPA79015 Total ALHA78044 ALHA78111 Total Weight (g) 637 10022 10659 164 126 290 Class and type Degree of weathering STONY-IRON Mesosiderite Mesosiderite B UNCLASSIFIED B/C B/C Degree of fracturing B B A TABLE C.?Meteorites tentatively identified as paired specimens Class Eucrite L3 L4 L6 H4 H5 H6 Diogenite Iron, IA/Og Paired specimens ALHA 76005, 77302, 78040, 78132, 78158, 78165, 79017 ALHA 77015, 77033, 77034, 77036, 77043, 77047, 77049, 77050, 77052, 77140, 77162, 77167, 77170, 77178, 77214 ALHA 77160, 77164, 77165, 77249, 77260 ALHA 77033, 77214 ALHA 79001, 79003 ALHA 77215, 77216, 77217 ALHA 77270, 77277, 77284 ALHA 77001, 77296, 77297 ALHA 77001, 77296, 77297 ALHA 77150, 77305 ALHA 77231, 77272, 77273, 77280 BTNA 78002 (2 stones) RKPA 78001, 78003, 79001, 79002 ALHA 77004, 77191, 77192, 77208, 77224, 77233 ALHA 77014, 77264 ALHA 77021, 77061, 77062, 77064, 77071, 77086, 77088, 77102 ALHA 77118, 77119, 77124 RKPA 79004 (6 stones) ALHA 77144, 77148 ALHA 77271, 77288 Yamato 6902 (b), Yamato 74010, 74011, 74037, 74097, 74136, 74648 ALHA 76002, 77250, 77263, 77289, 77290 DRPA 78001, 78002, 78003, 78004, 78005, 78006, 78007, 78008, 78009 Reference Score et al. (this volume) McKinley et al. (1981) Paired with ALHA 77015 group on ev- idence in King et al. (1980:18, 42) Separately paired by King et al. (1980:42) Score et al. (this volume) King et al. (1980) King et al. (1980) Kinget al. (1980) King et al. (1980) King et al. (1980) King et al. (1980) Score et al. (this volume) Score et al. (this volume) King et al. (1980) King et al. (1980) Kinget al. (1980) Kinget al. (1980) Score et al. (this volume) Kinget al. (1980) King et al. (1980) Takeda, Miyamoto, Yanai, Haramura (1978) Clarke (this volume) Clarke (this volume) Literature Cited Annexstad, J.O., and F. Nishio 1980. Glaciological Studies in the Allan Hills, 1979- 1980. Antarctic Journal of the United States, 15(5): 65- 66. Berkley, J.L., H.G. Brown IV, K. Keil, N.L. Carter, J.-C. C. Mercier, and G. Huss 1976. The Kenna Ureilite: An Ultramafic Rock with Evidence for Igneous, Metamorphic, and Shock Origin. Geochimica et Cosmochimica Ada, 40:1429- 1439. Biswas, S., H.T. Ngo, and M.E. 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