SMITHSONIAN CONTRIBUTIONS TO THE
EARTH SCIENCES

NUMBER 2

Paul A. Mohr

Catalog of
Chemical Analyses
of Rocks from the
Intersection of the
African, Gulf of Aden,
and Red Sea
Rift Systems

SMITHSONIAN INSTITUTION PRESS
CITY OF WASHINGTON

1970

ABSTRACT

Paul A. Mohr, Catalog of Chemical Analyses of Rocks from the Intersection of the African, Gulf of Aden, and Red Sea Rift Systems. Smithsonian Contributions to the Earth Sciences, 2, 7+[392] pages, 1970.—A compilation is presented of all published chemical analyses of rocks from the Red Sea, Gulf of Aden, and Ethiopian rift junction area. The chemical analyses are accompanied by further computations, in particular weight-norm and Niggli values, and by brief mineralogical descriptions. A full bibliography and indexes are included.

Official publication date is handstamped in a limited number of initial copies and is recorded in the Institution’s annual report, Smithsonian Year.

UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1970

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $2.75 (paper cover)

Contents

Copyright

Catalog of Chemical Analyses of Rocks from the Intersection of the African, Gulf of Aden, and Red Sea Rift Systems

Introduction

Format

Quality of Analyses

References

Index to Place Names and Rock Types

Rock Analyses

Catalog of Chemical Analyses of Rocks from the Intersection of the African, Gulf of Aden, and Red Sea Rift Systems

Paul A. Mohr

Paul A. Mohr, Smithsonian Astrophysical Observatory, Cambridge, Massachusetts.

Introduction

This compilation lists all rock-analyses known to the author which refer to the PreCambrian Basement and the Tertiary-Quaternary volcanics of Ethiopia, the Somali Republic, Afar and Issa (ex-French Somaliland), Yemen, South Yemen, and the Red Sea islands. The region thus comprises the Arabo-Ethiopian swell and its complexly developed rift systems.

The Ethiopian region is becoming of particular interest to those studying the world ridge-rift system, first because it presents a rift triple-junction (the Red Sea, Gulf of Aden, and African rift systems meet at Afar), and second, because the world’s largest alkaline volcanic province is developed at this triple-junction. For discussions on the spatial, chronological, and chemical distributions and relationships of these lavas, the reader is referred to other papers by the author (1963, 1965, 1968, 1970).

While, with the introduction of rapid, though less precise, chemical techniques, the number of Ethiopian rock analyses is burgeoning, there remains amongst geologists working in Africa a lack of knowledge of previous geochemical work relevant to Ethiopia. This is undoubtedly because many of the earlier published analyses lie in Italian literature not easily accessible. Even where the reader suspects analyses to exist, it can prove a time-consuming task to track down the journal concerned and to obtain a copy of it.

The author, impressed by the usefulness of various rock-analysis compilations published by Dr. Marjorie Hooker of the United States Geological Survey, has therefore endeavored to produce a similar one for the Ethiopian field. This compilation has been made as complete as possible, but omissions and errors are no doubt present and notification of these will be gratefully received, as will lists of new analyses due for publication.

Acknowledgements

Dr. W. G. Melson gave both encouragement and assistance in bringing this work to the publisher. Dr. I. L. Gibson suggested several improvements to the analytical format. The author is most grateful to Mrs. G. Schrauwen for her efficient typing of the text matter.

Format

Each analysis is presented in a fixed format. The top four lines describe as follows:

line 1.   Identification number for this compilation, starting with 101 for Basement rocks and 1001 for volcanic rocks. Identification numbers are in chronological order of publication, and within a given publication are in order of increasing SiO_2 content.

line 2.   Rock-type.

line 3.   Coordinates, in degrees and minutes of arc, of the locality where the specimen was collected (a blank indicates they are not known), followed by a place-name description.

line 4.   Author and year of publication (referces are given in full on pages 3 and 4).

The original rock-names ascribed by the analysts are generally retained, but in some cases, particularly where “lava” units have since been recognised as welded tuffs, a modification has been made. Where it is considered that a rock-name is in need of radical revision, the suggested alternative follows in square brackets after the given name. The Italian term ‘liparite’ is translated as rhyolite.

All specimen localities are specified, where ever possible, by latitude and longitude coordinates taken from the best available maps, but their accuracy cannot always be guaranteed. Some authors give vague descriptions of localities, while others give an unreferenced place-name which cannot be found on any recent map. The unfortunate inadequacy of many locality descriptions, especially in terms of stratigraphical position, derives from the fact that in many cases the analyst and author was not the collector of the rock specimen (see Repossi, 1932, p. 296, for comments on some consequences of this situation).

Following the first four lines of the print-out, the analytical format is presented in two levels. The upper level shows the originally published rock analysis (The value 0.00 signifies “not determined” unless remark is made to the contrary). To the right of the rock analysis is a water-CO_2-free computation of this analysis, summated to 100.0, and farther to the right are atomic proportions in terms of weight and numbers.

The lower level of data shows computed CIPW norms, one based directly on the published analysis and the second with all Fe_2O_3 in the analysis converted to FeO. These weight norms are calculated as far as LC (leucite), any further silica deficiency being printed out explicitly as such; similarly with carbon dioxide in excess of CC (calcite) and phosphorus pentoxide in excess of AP (apatite). Niggli values follow to the right of the norms, and then some three-component percentages for use in plotting triangular diagrams (where F = total iron; M = MgO, C = CaO, N = Na_2O, K = K_2O). D.I. stands for differentiation index (FeO + Fe_2O_3 / MgO + FeO + Fe_2O_3).

The analytical and computed data are accompanied by a paragraph of “remarks” on such factors as quality and possible errors of the published analysis; by a “mineralogy” paragraph containing a very brief summary of the given mineralogy of the rock; and by any pertinent “other information” such as modal percentages and specific gravity.

Quality of Analyses

It is inevitable in producing a compilation of rock-analyses from numerous sources that the quality of analysis will vary considerably. This fact must be borne in mind, considering the equal treatment given to all analyses here. Thus the “Remarks” paragraph must always be scrutinised when examining a particular analysis. Some of the older Ethiopian analyses are of inferior quality; Arsandaux, for example, quotes his values to only one decimal place, and many authors quote “loss on heating” rather than separate determinations of H_2O+, H_2O- and CO_2. Loss-on-heating is listed under H_2O+ in this compilation.

Cases where oxide values have been transposed, or are manifestly incorrect, are noted under “Remarks” for the analysis concerned. Of particular note are the persistently exagerated MnO values in the analyses of Roman, and suspiciously high ferric/ferrous iron ratios in analyses of some early authors. Several instances of incorrect summations are noted; in some it is not known whether the error dies in the summation figure itself, or in one of the oxide values.

References

Abbate, E., P. Facibeni, A. Gregnanin, G. Merla, and M. Sagri

1969.    Basalt Flows and Related Sandstones in the Socota Area (Northern Ethiopia). Bolletino Società Geologica Italica, 88: 499–516.

Aloisi, P.

1927.    Rocce della Somalia, Raccolte dalla seconda Missione Stefanini. Memorie, Società Toscana di Sciènza Naturali di Pisa, 38: 132–152.

1934.    Studio di Alcune Rocce della Migiurtinia. Memorie, Società Toscana di Sciènza Naturali di Pisa, 44: 203–223.

1938.    Geologia della Somalia: Le Rocce Eruttive e gli Scisti Cristallini della Somalia Italiana. Reale Società Geographica Italiana, Bologna, II (I) : 1–63.

Arsandaux, H.

1903a.  Contribution a l’étude des Roches Sodiques de l’Est Africains. Comptes Rendus de l’Académie Scientifique de Paris, 137: 876–879.

1903b.  Contribution a l’étude des Roches Basaltiques de l’Est Africains. Comptes Rendus de l’Académie Scientifique de Paris, 137: 1308–1311.

Augustithis, S. S.

1964.    On the Phenomenology of Phenocrysts (Tecoblasts, Zoned Phenocrysts, Holo-Phenocrystalline Rock Types). Special Bulletin of Petrogenesis, Institute of Petrogenesis and Geochemistry, Athens: 15–31.

1965.    Mineralogical and Geochemical Studies of the Platiniferous Dunite-Birbirite-Pyroxenite Complex of Yubdo/Birbir, W. Ethiopia. Chemie der Erde, 24: 159–196.

Comucci, P.

1928.    Contributo allo Studio della Rocce Effusive della Dancalia. Memorie, Società Toscana di Sciènza Naturali di Pisa, 39: 93–113.

1930.    Sopra Alcune Rocce Vulcaniche della Regione di Sanaa (Arabia). Memorie, Società Toscana di Sciènza Naturali di Pisa, 40: 70–78.

1932.    Alcune Rocce dei Dintorni di Addis Abeba (Abissinia). Processi Verbali Società Toscana di Sciènza Naturali di Pisa, 41: 100–111.

1933a.  Note Petrografiche sulle Rocce Raccolte dalla Spedizione Cerulli nell’Etiopia Occidentale. In: Cerulli, E., Ethiopia Occidentale, Roma, 2: 227–244.

1933b.  Rocce dello Iemen Raccolte dalla Missione de S. E. Gasparini. Periodico di Mineralogia: 4, 89–131.

1948.    Le Rocce della Regione di Jubdo (Africa Orientale). Atti della Accademia Nazionale dei Lincei (Roma), 262 pp.

1950.    Le Vulcaniti del Lago Tana (Africa Orientale). Atti della Accademia Nazionale dei Lincei (Roma), 209 pp.

Dainelli, G., and O. Marinelli

1912.    Risultati Scientifici di un Viaggio nella Colonia Eritrea. Firenze, 601 pp.

De Angelis, M.

1923.    Note di Petrografia Dancala—I. Atti Società Italiana di Sciènza Naturali, 62: 179–200.

1925.    Note de Petrografia Dancala—II. Atti Società Italiana di Sciènza Naturali, 64: 61–84.

De Gennes, A., and A. Bonard

1900.    Les Roches Volcaniques du Protectorate des Somalis. Comptes Rendus de l’Académie Scientifique de Paris, 131: 196–198.

Duparc, L.

1930a.  Sur les Basaltes et les Roches Basaltiques du Plateau Abyssin. Schweizerische Mineralogische und Petrographische Mitteilungen, 10: 1–37.

1930b.  Sur un Trachyte à Anorthose de Gambeila (Abyssinie). Compte Rendus (des Séances) Société de Physique et d’Histoire Naturelle de Genève, 47: 50–53.

Duparc, L., and E. Molly

1927a.  Sur la Roche du Fantalli (Abyssini). Schweizerische Mineralogische und Petrographische Mitteilungen, 7: 412–413.

1927b.  Sur une Augitite d’Abyssinie. Compte Rendus (des Séances) Société de Physique et d’Histoire Naturelle de Genève, 44: 159–160.

1928a.  Sur la Presence de la Kenyite sur le Plateau Abyssin. Compte Rendus (des Séances) Société de Physique et Histoire Naturelle de Genève, 45: 22–23.

1928b.  Sur la Tokeite, une Nouvelle Roche d’Abyssinie. Compte Rendus (des Séances) Société de Physique et d’Histoire Naturelle de Genève, 45: 24–25.

El-Hinnawi, E. E.

1964.    Petrochemical Characters of African Volcanic Rocks. Ethiopia and the Red Sea Region (including Yaman and Aden). Neues Jahrbuch für Mineralogie, Monatshefte, 3: (1), 65–81.

Filjak, R., N. Glumicic, and Z. Zagorac

1959.    Oil Possibilities of the Red Sea Region in Ethiopia. Naftaplin, Zagreb, 104 pp.

Gass, I. G., and D. I. J. Mallick

1968.    Jebel Khariz: An Upper Miocene Strato-Volcano of Comenditic Affinity on the South Arabian Coast. Bulletin Volcanologique, 32: 33–88.

Gaubert, M. P.

1901.    Sur les Échantillons de Roches d’Abyssinie Rapportes par M. Ch. Michel Paris, Musée National d’Histoire Naturelle, Bulletin, 7: 27–28.

Gellatly, D. C., and G. Hornung

1968.    Metasomatic and Nepheline-Bearing Gneisses from Darkainle, Somali Republic. Journal of Geology, 76: 678–691.

Gortani, M., and A. Bianchi

1937.    Osservazioni Geologiche e Petrografiche nella Regione di Harar (Africa Orientale Italiana). Bolletino della Società Geologica Italiana, 56: 499–516.

Hieke Merlin, O.

1941.    Alcune Ossidiane dell’Africa Orientale Italiana. Rendiconti della Società Mineralogica Italiana, 1: 107–120.

1948.    Sulla Presenza di Basalti Limburgitica nell’Africa Orientale. Rendiconti delta Accademia Nazionale dei Lincei, 5: 70–77.

1949.    Facies Ultramafiche nei Basalti dell’Africa Orientale. Rendiconti della Accademia Nazionale dei Lincei, 6: 89–97.

1950a.  Chimismo di Lave Basaltiche della Regione Hararino-Dancala in Africa Orientale. Rendiconti della Società Mineralogica Italiana, 6: 101–118.

1950b.  I Basalti dell’Africa Orientale. Memorie degli Istituti di Geologia e Mineralogia dell’Universita di Padova, 17: 42 pp.

1952.    Ricerce sulla Lave Acide della Regione Hararino-Dancala in Africa Orientale (nota preliminare). Rendiconti della Società Mineralogica Italiana, 8: 124–128.

1953.    Le Vulcaniti Acide dell’Africa Orientale. Memorie degli Istituti di Geologia e Mineralogia dell’Universita di Padova, 18: 45 pp.

Lacroix, A.

1930.    Les Roches Hyperalcalines du Massif du Fantale et du Col de Balla (Abyssinie). Memoires, Société Géologique de France, Paris, 6: 89–102.

LeBas, M. J., and P. A. Mohr

1970.    Tholeiite from the Simien Alkali Basalt Centre, Ethiopia. Geological Magazine (in press).

Macdonald, R., and I. L. Gibson

1969.    Pantelleritic obsidians from the volcano Chabbi (Ethiopia). Contributions to Mineralogy and Petrology, Berlin, 24:239-244.

Manasse, E.

1904.    Rocce della Colonia Eritrea Raccolte a Sud di Arafali. Processi Verbali Società Toscana di Sciènza Naturali di Pisa, 14: 96–109.

1905.    Sopra le Zeoliti di Alcune Rocce Basaltiche della Colonia Eritrea. Processi Verbali Società Toscana di Sciènza Naturali di Pisa, 15: 65–72.

1908.    Rocce Eritree e di Aden della Collezione Issel. Memorie Società Toscana di Sciènza Naturali de Pisa, 24: 153–204.

1909.    Contribuzioni allo Studio Petrografico della Colonia Eritrea. Siena, 169 pp.

1917.    Rocce della Somalia Italiana Raccolte dalla Missione Scientifica Stefanini-Paoli (1913). Memorie, Società Toscana di Sciènza Naturali di Pisa, 31: 3–74.

Merla, G., and E. Minucci

1938.    Missione Geologica nel Tigrai. Reale Accademia Italiana, Roma, 1.

Mohr, P. A.

1963.    The Ethiopian Cainozoic Lavas—a Preliminary Study of some Trends: Spatial, Temporal and Chemical. Bulletin of the Geophysical Observatory, Addis Ababa, 6: 103–144.

1965.    Re-classification of the Ethiopian Cainozoic Volcanic Succession. Nature, 208: 177–178.

1968.    The Cainozoic Volcanic Succession in Ethiopia. Bulletin Volcanologique, 32: 5–14.

1970.    Volcanic Composition in Relation to Tectonics in the Ethiopian Rift System—a Preliminary Investigation. Bulletin Volcanologique (in press).

Muhlen, L. von zur, and J. H. Hellmers

1936.    Die Petrographie der Eruptivegesteine der Dabus-steppe und der Hochlandes von Wollega in West-abessinien. Neues Jahrbuch für Mineralogie, Geologie und Paleontologie, (A) 71: 241–290.

Pagliani, G.

1940.    Pantelleriti e Basalti di Gimma (A.O.I.). Rendiconti, Istituto Lombardi di Sciènza e Lettere, Milan, 123: 33–3.

Pantanelli, D.

1886.    Roccie di Assab. Memoirie, Società Toscana di Sciènza Naturali di Pisa, 7: 29–30.

Prior, G. T.

1900.    On Aegirine and Riebeckite Anorthoclase Rocks Related to the “Grorudite-Tinguaite” Series, from the Neighbourhood of Adowa and Axum, Abyssinia. Mineralogical Magazine, 12: 255–273.

Repossi, E.

1932.    Rocce Eruttive. In: Savoja L. A. (Duke of Abruzzi) La Esplorazione dello Uabi, Uebi Scebeli. Mondadori, Milan: 279–304.

Ricciardi, L.

1886.    Sulla Composizione Chimica delle Rocce Vulcaniche di Assab. Bolletino della Società Geologica Italiana, 5: 57–60.

Rodolico, F., and R. Pieruccini

1942.    Rocce Filoniane del Tigrai. Commentationes, Pontificia Academia Scientiarum, 6: 788–812.

Rohleder, H. P. T. a,nd C. S. Hitchen

1930.    Vulkanologische Beobachtungen Langs der Bahnlinie Adis Abeba-Djibouti (Abessinien). Zeitschrift für Vulkanologie, Berlin, 12: 269–289.

Roman, D.

1926.    Studii Petrografice in Yemen (regiunea Hodeida-Sanaa). Annuarul Institutului Geologic al Romaniei, 11: 207–299.

Scherillo, A.

1938a.  Su Alcune Zeoliti dell’Eritrea. Periodico di Mineralogia, 9: 61–69.

1938b.  La Celadonite delle Rocce Eruttive dell’Altipiano Eritreo. Periodico di Mineralogia, 9: 253–264.

Shukri, N. M., and E. Z. Basta

1955.    Petrography of the Alkaline Volcanic Rocks of Yaman. Bulletin de l’Institut d’égypte 36, 129–164.

1959.    Petrography of the Volcanic Rocks of Aden. Bulletin of the Faculty of Science, Cairo University, 35: 87–107.

Tazieff, H., G. Marinelli, F. Barberi, and J. Varet

1970.    Geologie de l’Afar Septentrional. Bulletin Volcanologique, 33: 1039–1072.

Weber, M.

1906.    Die petrographische ausbeute der expeditionen O. Neumann – v. Erlanger nach Ostafrika und Abessynien 1900–1901. Mitteilung der Geographisch Gesellschaft in Munchen, 1: 637–660.

Index to Place Names and Rock Types

The numbers in this index refer to analysis list number. The precise place-name of each specimen is not given here, where the purpose of the index rather requires an easily recognisable town, province or regional name.

Place Names: Basement Rocks

Eritrea

Adi Kai, 111

Adi Quala, 120

Anseba valley, 106, 107, 112, 115, 118

Asmara, 113, 117, 123

Digsa, 114, 121

Etkokan Mt., 161

Keren, 108, 119

Massawa, 1041

Saganeiti, 105, 109, 110, 116, 122

Socotra Archipelago, 102, 103

Somali, North

Adadle, 101

Darkainle, 162–170

Kandala, 135

Manja Yahan, 134

Somali, South

Bur Akaba, 124, 126, 129, 130

Bur Gulo, 125, 127

Bur Meldak, 128

Malabli, 131

Wollega

Dabus Valley, 136–45

Ghimbi, 148, 149, 155, 156, 158

Sariti (?), 160

Tulu Bottegi (?), 153

Yubdo, 132, 133, 146, 147, 150–152, 154, 157, 159

Place Names: Cainozoic Volcanics

Afar

Alid, 1043, 1045, 1049, 1051–1053

Ayelu, 1218, 1232, 1237

Bio Caboba, 1216, 1230, 1231, 1240

Erta-ali, 1268, 1270, 1271, 1273–1277, 1279–1281, 1284, 1286

Fant-ali, 1018, 1019, 1081, 1104, 1108–1113, 1118, 1120, 1121, 1159, 1160

Gar-uli, 1283, 1285

Lake Assali,. 1269, 1278

Lake Julietti, 1058, 1089, 1272, 1282

Miesso, 1020, 1233, 1236

Sardo, 1229, 1239

Aisha horst, 1223

Arussi

Highlands, 1103, 1133, 1135

Chabbi, 1311–1321

Bali, 1129, 1131, 1132

Beghemder

Addis Zemen, 1189, 1200, 1201, 1205

Gondar, 1179, 1180, 1185, 1195, 1203

Simien, 1187, 1208, 1209, 1322

Danakil horst

Adaylo, 1061, 1062, 1264–1267

Assab-Beilul, 1001–1003, 1084–1087, 1091, 1221

Baharassoli-Dubbi, 1059, 1060, 1083, 1088, 1090, 1092

Eritrea

Adi Kai, 1050

Adi Ugri, 1046, 1047

Asmara, 1042, 1044

Massawa, 1041

Senafi, 1048, 1054, 1055

ex-French Somaliland, 1009–1015, 1023, 1024, 1027, 1029, 1030, 1114–1116

Gojjam

Bahar Dar, 1177, 1181, 1188, 1192

Consela, 1190, 1196, 1207

Danghila-Enjabara, 1182, 1183, 1186, 1193, 1197–1199

Lake Tana, 1178

Hararge

Chercher, 1017, 1025, 1031, 1033, 1105–1107, 1152, 1225

Farso, 1151, 1224

Harar, 1213, 1222, 1226

Jildessa, 1032

Ilubabor, 1102, 1103, 1137, 1175, 1176

Kaffa, 1136, 1154–1157

Red Sea, 1147

Shoa

Adama-Mojjo, 1123, 1134, 1158, 1210, 1234

Addis Ababa, 1117, 1119, 1122, 1124–1128, 1215, 1235

Addis Alem, 1101

Debra Berhan-Debra Sina, 1211, 1217, 1227

Kassam, 1021, 1022, 1026, 1028

Socotra, 1016

Somali, North, 1148

Somali, South, 1056, 1057, 1079, 1080

South Yemen

Aden, 1035–1040, 1262, 1263

J. Khariz, 1287–1308

Tigray

Adua-Axum, 1004–1008

Enda Selassie, 1153

Makalle, 1161–1167

Sokota, 1309, 1310

Wallo

Batie, 1212, 1214, 1220

Borkenna, 1238

Dessie-Lake Hayk, 1219, 1228, 1241

Utchali, 1242

Wollega

Dabus, 1149, 1150

Didessa, 1098, 1099

Ghimbi, 1168, 1173, 1174

Guder, 1082, 1093, 1094, 1100

Lekemti, 1169

Nejjo, 1170, 1171

Yubdo, 1097, 1172

Yemen

San’a-Hodeida, 1063–1078, 1095, 1096, 1138–1146, 1243–1245, 1248–1250, 1253

Ta’iz, 1246, 1247, 1251, 1252, 1254–1261

Rock Types: Basement

Adamellite, 117

Amphibolite, 124, 148, 150

Anorthosite, 138, 149

Aplite, 121, 122, 130, 131, 134, 160

Birbirite, 133

Diorite, 102, 107, 109–114, 125, 126, 130, 137, 141–143, 151, 152, 154

Dunite, 132, 147

Gabbro, 138, 139, 149, 151

Gneiss, 127, 128, 162–166

Granite, 101, 103, 113, 118–121, 129, 135, 144, 145, 156–159

Keratophyre, 123

Kersantite, 105, 108

Malchite, 115, 116

Nepheline Syenite, 167–170

Porphyry, 102, 123, 161

Pyroxenite, 106, 148

Rhyolite, 156

Schist, 136, 140, 146, 155

Syenite, 153

Teschenite, 1041

Xenolith, 137

Rock Types: Cainozoic Volcanics

Andesite, 1266, 1309

Ankaramite, 1014, 1063, 1243, 1244, 1269, 1272

Augitite, 1082

Basalt (not distinguished), 1001–1003, 1034, 1067, 1089, 1130, 1133, 1151, 1168, 1219, 1226

andesine, 1083, 1268, 1270, 1274–1277

ankaramitic, 1063, 1243, 1269, 1272

aphyric, 1025–1027, 1031, 1084, 1088, 1095, 1144, 1152, 1180, 1185, 1193–1195, 1222–1225, 1322

calcitic, 1085, 1086

hyalo, 1177, 1178, 1186, 1188, 1245, 1248

picritic, 1138–1142, 1192

porphyritic,

augite, 1247

augite-olivine, 1056, 1079, 1080, 1094, 1143, 1147, 1148, 1211–1213, 1220

olivine, 1009, 1010, 1042, 1043, 1045, 1086, 1087, 1097, 1098, 1101, 1117, 1125, 1136, 1154, 1162, 1163, 1165, 1166, 1179, 1181, 1184, 1188, 1246, 1246, 1249, 1250, 1264, 1287–1291

plagioclase, 1015, 1028–1030, 1032, 1033, 1035, 1099, 1100, 1182, 1183, 1189–1191, 1196, 1210, 1215–1218, 1221, 1265, 1271, 1273, 1292, 1293, 1310

Bostonite, 1048, 1072, 1172, 1174

quartz-bostonite, 1054, 1055, 1069, 1071

Camptonite, 1044

Comendite, 1023, 1024, 1052, 1060, 1074–1076, 1115, 1128 , 1175, 1234, 1235, 1237–1242, 1259, 1267, 1303, 1306, 1308

riebeckite, 1016

tridymite, 1053

Dacite, 1038, 1051

Dyke, 1044, 1046, 1054, 1055, 1093, 1097, 1137, 1161–1163, 1172, 1174, 1219, 1226, 1306, 1322

Grorudite, 1006, 1007, 1254

Hornblendite, 1187

Kenyite, 1093

Kersantite, 1137

Limburgite, 1214

Microgabbro, 1161, 1164, 1294

Microgranite, 1108, 1110, 1144

Microsyenite, 1017, 1293

Nephelinite, 1129, 1132

Obsidian, 1006, 1011, 1012, 1019, 1021, 1052, 1090, 1092, 1109, 1111, 1113, 1123, 1145, 1160, 1202, 1204, 1206, 1207, 1235, 1237, 1239, 1263, 1311–1321

Paisanite, 1008, 1050

Pantellerite, 1018–1022, 1040, 1059, 1073, 1078, 1109, 1112–1114, 1116, 1120–1124, 1135, 1155–1160, 1233, 1236, 1263, 1282, 1283, 1285, 1311–1321

Phonolite, 1103, 1149, 1150, 1198–1201

Pumice, 1049, 1091

Rhyolite, 1011–1013, 1049, 1077, 1091, 1092, 1145, 1153, 1204–1209, 1260, 1261, 1284, 1286, 1301, 1304, 1305, 1307

Solvsbergite, 1005, 1105–1107

Teschenite, 1041

Tinguaite, 1004, 1046, 1057, 1131, 1132, 1167

Trachyte, 1039, 1047, 1081, 1090, 1096, 1119, 1173, 1202, 1227–1229, 1278–1281, 1297, 1298

analcime, 1062

anorthoclase, 1102, 1126, 1127, 1257, 1258

arfvedsonite, 1058

olivine, 1104

quartz, 1176, 1203, 1232, 1254, 1300, 1302

riebeckite, 1255, 1256

sanidine, 1230, 1231

trachyandesite, 1036, 1037, 1061, 1068, 1070, 1170, 1171, 1295, 1296

trachybasalt, 1065, 1066, 1083, 1129, 1134, 1149, 1169, 1197, 1251–1253, 1262

trachydacite, 1038

tuff and agglomerate, 1047, 1128, 1135, 1298

Rock Analyses

BASEMENT

No. 101

REMARKS: MnO and ZrO traces, H_2O “by difference”; two versions of this analysis are published together, the second containing 0.96% CaO and 1.18-0. 30% FeO.

MINERALOGY: Microgranite. Groundmass: Kaolinised microcline, orthoclase, plagioclase, quartz; accessory biotite, muscovite, chlorite, rutile, magnetite, ilmenite, pyrite, apatite, zircon.

OTHER INFORMATION: Mode: ca. 75% feldspar, 20% quartz.

No. 102

REMARKS: No separate determination of H_2O-.

MINERALOGY: Not given.

No. 103

REMARKS: No separate determination of H_2O-; MnO trace.

MINERALOGY: Not given.

No. 104

REMARKS: Analcime-natrolite teschenite, from Hamassat, Massawa, Eritrea, published in E. Manasse (1909). See analysis 1041; this rock may belong to the Cainozoic volcanics.

No. 105

REMARKS: The analyses of Manasse list “loss on heating,” without separate H_2O determinations. MnO and CO_2 traces.

MINERALOGY: Coarsely porphyritic. Phenocrysts: Kaolinised albite-oligoclase; deeply colored biotite, sometimes chloritised euhedral, strongly pleochroic barkevikite, with linearly arranged inclusions of ilmenite. Groundmass: Abundant pale-green diopside, plagioclase, biotite, accessory apatite, magnetite, ilmenite, pyrite; secondary chlorite, calcite, limonite, leucoxene, yellow epidote, quartz.

No. 106

REMARKS: See under 105.

MINERALOGY: Phenocrysts: Green hornblende, with katophorite inclusions. Groundmass: Coarse-grained abundant Mg-rich diopside, frequently rimmed with hornblende; association of yellow epidote, zoisite and white mica may have been derived from primitive feldspar which occurred in minor amount.

OTHER INFORMATION: This rock-type is a local basic segregation from neighboring quartz-hornblende diorite.

No. 107

REMARKS: See under 105.

MINERALOGY: Medium grained. Groundmass: Fresh or intensely epidotised andesine-labradorite; hornblende, with plagioclase inclusions, in contorted and rotated crystals; uncommon chloritised mica; accessory large apatite, very rare quartz, ilmenite and leucoxene, all showing effects of stress; common epidote.

No. 108

REMARKS: See under 105.

MINERALOGY: Very fine-graind, aphyric. Groundmass: Albite and slightly altered lepidomelane (both with euhedral tendency), common apatite, rare anatase, secondary chlorite, ilmenite, limonite.

OTHER INFORMATION: This rock-type occurs as a sheet intrusion in granite.

No. 109

REMARKS: See under 105.

MINERALOGY: Phenocrysts: Slightly altered An60 with rare diopside inclusions, uralitised pyroxene. Groundmass: Fine-grained andesine-labradorite, colourless diopside associated with secondary(?) blue-green amphibole, fairly common chloritised coloured mica, abundant magnetite, uncommon ilmenite, apatite, rare quartz. No alkali feldspar observed, despite high K_2O content in analysis.

OTHER INFORMATION: Sheet intrusion in quartz-diorite massif.

No. 110

REMARKS: See under 105.

MINERALOGY: Phenocrysts: Large pseudomorphs of zoisite and white mica after feldspar; zoisite forms the centre of the crystals, and is more abundant than white mica forming the periphery, indicating a calcic plagioclase. Groundmass: Fine-grained fresh andesine-labradorite, no alkali feldspar, abundant euhedral Fepoor hornblende, uncommon quartz granules, intensely pleochroic biotite; accessory ilmenite, leucoxene, haematite, apatite, epidote, zoisite; secondary quartz.

OTHER INFORMATION: Occurs as lenses in schists.

No. 111

REMARKS: See under 105. TiO_2 trace.

MINERALOGY: Reported identical with specimen in analysis 114.

OTHER INFORMATION: This rock-type cut by aplites.

No. 112

REMARKS: See under 105. TiO_2 trace.

MINERALOGY: Coarse-grained. Groundmass: Large tabular An30-40, pink-green hornblende, rather uncommon anhedral quartz; accessory apatite, ilmenite, titanite; secondary epidote, zoisite.

No. 113

REMARKS: See under 105. TiO_2 trace.

MINERALOGY: Cataclastic structure. Groundmass: Large fresh An20-25, subordinate microcline (no orthoclase), rather uncommon quartz, equally common biotite and hornblende; accessory titanite, large apatite, rare zircon, epidote, titaniferous magnetite.

OTHER INFORMATION: Basic segregation from granite massif.

No. 114

REMARKS: See under 105. CO_2 trace.

MINERALOGY: Groundmass: Large altered oligoclase-andesine (secondary zoisite, white mica, and rarer epidote and calcite), very subordinate kaolinised alkali feldspar, rather uncommon rounded quartz, hornblende commoner than dark mica, both now chloritised; accessory apatite, ferro-titanite, leucoxene.

No. 115

REMARKS: See under 105. MnO and CO_2 traces.

MINERALOGY: Porphyritic texture, with fluidal groundmass. Phenocrysts: Altered plagioclase (proportions of zoisite-white mica suggest rather calcic). Groundmass: Extremely fine-grained fresh K-feldspar. green hornblende, quartz, apatite very rare ilmenite with leucoxene rims; secondary epidote, calcite, muscovite, chlorite, titanite.

OTHER INFORMATION: Occurs within a hornblende-diorite massif.

No. 116

REMARKS: See under 105. TiO_2, MnO, P_2O_5 traces; rather weathered specimen

MINERALOGY: Phenocrysts: scarce chloritised amphibole and altered oligoclase. Groundmass: Dominantly sodic plagioclase microlites; some quartz, K-feldspar(?); secondary zoisite, calcite, muscovite, magnetite.

No. 117

REMARKS: See under 105. MnO trace.

MINERALOGY: Granophyric texture. Phenocrysts: Rather uncommon orthoclase (cryptoperthite), irregularly distributed quartz grains. Groundmass: Micropegmatitic intergrowth of quartz and orthoclase in equal proportions, some slightly kaolinised albite with accreted orthoclase rims, chlorite laths (after mica?); accessory apatite, zircon; secondary abundant yellow epidote, some calcite, leucoxene.

OTHER INFORMATION: Associated with aplite 121.

No. 118

REMARKS: See under 105.

MINERALOGY: Phenocrysts: Corroded quartz (rare euhedral crystals), less corroded An20-25, coloured mica (with primary chloritisation) in proximity to quartz phenocrysts. Groundmass: Very fine-grained granophyric quartz and kaolinised alkali feldspar; subordinate chloritised mica and magnetite; secondary epidote, muscovite, quartz.

OTHER INFORMATION: Sheet intrusion in Aratu granite.

No. 119

REMARKS: See under 105, except that H_2O is listed as such for 119. TiO_2 trace.

MINERALOGY: Medium grained. Groundmass: Microcline, with very subordinate orthoclase, abundant sub-hedral, zoned albite-oligoclase (fresh, with inclusions apatite, biotite, hornblende, quartz, microcline); quartz, with undulose extinction (inclusions of apatite, zircon); chloritised and epidotised biotite. Accessory fresh muscovite; orthite with mantle of clinozoisite passing out to rim of epidote; titanite, both secondary in biotite and primary; apatite (two generations). Secondary epidote, ilmenite and leucoxene.

No. 120

REMARKS: See under 105. No separate determination of FeO; P_2O_5 trace.

MINERALOGY: Fine-grained leuco-granite. Groundmass: Fresh microcline dominant over zoned(?) albite-oligoclase, subordinate quartz (liquid inclusions), scarce muscovite; accessory altered biotite, titanite, apatite, zircon.

OTHER INFORMATION: Extensive intrusion underlying the Mesozoic sandstones.

No. 121

REMARKS: See under 105. P_2O_5 and CO_2 traces.

MINERALOGY: Very fine-grained. Groundmass: Cryptoperthite and chloritised mica occur separated from quartzitic-textured quartz (rose-coloured); subordinate albite; secondary epidote, titaniferous magnetite, calcite.

OTHER INFORMATION: Associated with adamellite 117, and is the most silicic facies of a huge granodiorite massif.

No. 122

REMARKS: See under 105. No separate determination of FeO; MgO and P_2O_5 traces.

MINERALOGY: Very fine-grained, rose coloured rock. Groundmass: Granophyric aggregate of feldspar and subordinate quartz; altered microcline is dominant over orthoclase and fresher albite; scarce muscovite; accessory apatite, pyrite.

No. 123

REMARKS: See under 105. P_2O_5 trace.

MINERALOGY: Phenocrysts: Large corroded quartz (with undulose extinction, rare liquid inclusions), kaolinised albite. Groundmass: Quartz with fluidal arrangement of albite(?) microlites; accessory white mica, pleochroic chlorite, very minute magnetite; secondary epidote, zoisite, ilmenite, leucoxene, limonite.

OTHER INFORMATION: This rock-type passes into metamorphosed and kaolinised porphyroid rock, which has been incompletely analysed as follows: SiO_2 81.29%, Al_2O_3 11.59%, total Fe_2O_3. 39%, MgO 0. 26% CaO 0.15%, total alkalis 0.28%, loss on heating 5.87% total 99.83%.

No. 124

REMARKS: See under 105. P_2O_5 trace.

MINERALOGY: Groundmass: Large pleochroic hornblende crystals with inclusions of feldspar and quartz; modest aggregates of altered andesine and subordinate quartz; accessory mica, secondary magnetite, rare apatite.

OTHER INFORMATION: The extreme melanocratic facies of a dioritic magma.

No. 125

REMARKS: See under 105.

MINERALOGY: Rather fine-grained. Groundmass: Fresh, zoned labradorite-andesine; occasional crystals bytownite; green-brown hornblende, of earlier generation than clear-green hedenbergite; accessory titanite, epidote, apatite, magnetite; no quartz nor alkali feldspar.

No. 126

REMARKS: See under 105.

MINERALOGY: Panidiomorphic; some lamination developed. Groundmass: Rather large, prismatic amphibole; pleochroism differs from hornblende in being yellow-green – intense green-brown – dark green. Somewhat altered oligoclase-andesine; no alkali feldspar; minor quartz; accessory apatite, magnetite, limonite.

No. 127

REMARKS: See under 105. MnO trace.

MINERALOGY: Cataclastic structure. Groundmass: Albite-oligoclase, commoner than antiperthite (with myrmekite) showing undulose extinction, rare xenoblastic microcline; uncommon quartz, with undulose extinction; common biotite and ferric-poor hornblende, in contorted crystals; accessory ilmenite and leucoxene, titanite, apatite, zircon; secondary muscovite.

No. 128

REMARKS: See under 105. MnO trace.

MINERALOGY: Porphyroblastic cataclasite. Phenocrysts: Fresh microcline. Groundmass: Abundant small albite-oligoclase (slightly kaolinised, with mica and calcite) with zoning out to albite rims; uncommon quartz in irregular grains, with undulose extinction; chloritised biotite; rare muscovite; rare, rather large actinolite associated with biotite; accessory magnetite, ilmenite apatite, zircon, secondary titanite, epidote.

No. 129

REMARKS: See under 105. TiO_2 trace. This analysis is reproduced in Aloisi (1938) with 0. 29% MgO and 0.30% H_2O.

MINERALOGY: Uniformly medium-grained. Groundmass: Abundant microcline, occasionally with perthite or cryptoperthite; rare orthoclase; somewhat sericitised albite-oligoclase, with albite rims; quartz (straight extinction) with numerous inclusions; yellow-black biotite; accessory muscovite, iron-oxides, titanite, apatite, zircon.

No. 130

REMARKS: See under 105. P_2O_5 trace; no separate determination of FeO.

MINERALOGY: Fine-grained, saccharoidal quartz-feldspar rock. Groundmass: Slightly altered, zoned andesine (between labradorite and oligoclase-andesine); no alkali feldspar; quartz, rich in inclusions of tourmaline and less common apatite; accessory hornblende.

No. 131

REMARKS: See under 105. No separate determination of FeO; P_2O_5 trace.

MINERALOGY: Fine-grained, equigranular quartzofeld-spathic rock. Groundmass: Abundant kaolinised micro-cline-microperthite (some cryptoperthite); common altered albite; quartz, with undulose extinction; rare biotite (pleochroism yellow-green brown); accessory zircon, apatite, secondary magnetite; muscovite, orthoclase(?).

No. 132

REMARKS: TiO_2, Al_2O_3 CaO, NiO absent; MnO trace; no separate determination of H_2O-.

MINERALOGY: Groundmass: Serpentinised, round colourless olivine (2V = 88-1/2°); accessory chromite in dispersed form; antigorite; secondary magnetite.

No. 133

REMARKS: Al_2O_3 trace; no separate determination of H_2O-.

MINERALOGY: Groundmass: Quartz, chalcedony limonite.

OTHER INFORMATION: Reddish violet-chocolate coloured rock, with porcelanous appearance, which forms a thick capping to the dunites of the Yubdo region (see Augustithis, 1965).

No. 134

REMARKS: TiO_2 trace, no separate determination of FeO (analyst: P. Comucci).

MINERALOGY: White, very fine-grained rock. Groundmass: Fresh albite, some as micro-phenocrysts; no microcline nor orthoclase; rather rare, small rounded quartz; small laths of irregularly distributed muscovite; accessory iron-oxides, chlorite.

No. 135

REMARKS: MnO trace (analyst: P. Comucci).

MINERALOGY: Medium-grained, hypidiomorphic. Groundmass: Abundant zoned An37 – An20; scarce microcline (with myrmekite); abundant quartz (gently undulose extinction); abundant biotite (fresh or slightly chloritised), intensely coloured and pleochroic; accessory apatite (rather common and large); zircon in pleochroic haloes in biotite.

No. 136

MINERALOGY: Groundmass: Abundant chlorite, kaolinised An30-23, hornblende (more common than in no. 140), accessory iron-oxide and calcite.

OTHER INFORMATION: Specific gravity 3.046, published norm incorrect.

No. 137

REMARKS: Compared with host-rock no. 143: high alkalis (for SiO_2%); higher iron, magnesium, calcium; same aluminium.

MINERALOGY: None given.

OTHER INFORMATION: Specific gravity 3.132.

No. 138

MINERALOGY: Groundmass: Subparallel An58; some olivine with keliphytic hornblende; accessory titanite, magnetite (some in olivine).

OTHER INFORMATION: Specific gravity 2.932; see under no. 139.

No. 139

MINERALOGY: Groundmass: Labradorite, chloritised hornblende, orthoclase, augite, apatite, olivine, biotite, zircon.

OTHER INFORMATION: Specific gravity 2.969. Mt. Karawini is a grabbo-anorthosite massif, with associated hornblende granite and syenitic diorite.

No. 140

REMARKS: CO_2 absent.

MINERALOGY: Groundmass: An25 and chlorite (plagioclase is kaolinised), some magnetite and hornblende(?).

OTHER INFORMATION: Specific gravity 2.790; this rock occurs where the regional foliation is N-NNE.

No. 141

MINERALOGY: Abundant kaolinised microcline. Groundmass: Hornblende (hastingsite with a tendency to barkevikite); augite, hypersthene, some An52-48, magnetite, apatite.

OTHER INFORMATION: Specific gravity 2.878; this rock is associated with syenite and pegmatite, and occurs at the effluence of the Moli into the Dabus.

No. 142

MINERALOGY: Coarse-grained. Groundmass: Hastingsite (3-8 mm grains), fresh An45-43, biotite, orthoclase, magnetite, olivine, apatite, zircon, small augite.

OTHER INFORMATION: Specific gravity 2.878.

No. 143

REMARKS: Analysis of host material to basic inclusions (see no. 137).

MINERALOGY: Fine-grained with schlieren. Groundmass: An60-35, hastingsite, chloritised biotite, augite, large magnetite; some titanite, apatite, zircon.

OTHER INFORMATION: Specific gravity 3.135.

No. 144

MINERALOGY: Phenocrysts: Large bluish quartz, with undulose extinction, and apatite inclusions. Groundmass: Bluish quartz, andesine, dark biotite; accessory orthoclase, muscovite, augite.

OTHER INFORMATION: Specific gravity 2.679; this rock-type forms a 1 × 2 km massif associated with some diorite.

No. 145

MINERALOGY: Groundmass: Dominant microcline, quartz, oligoclase, biotite, augite, apatite.

OTHER INFORMATION: Specific gravity 2.641; this rock-type forms a 9 × 6 km massif.

No. 146

REMARKS: Fe_2O_3 and CaO traces.

MINERALOGY: Phenocrysts: 1-mm magnetite crystals (removed prior to analysis). Groundmass: Yellow-green fibrous chlorite, with some magnetite.

No. 147

REMARKS: No separate determination of H_2O-; P_2O_5 trace.

MINERALOGY: Groundmass: Serpentinised olivine (2V = 90°); abundant large magnetite, and minute second generation associated with lines of serpentinisation; rare bronzite.

No. 148

MINERALOGY: Rather coarse-grained. Groundmass: Actinolite-hornblende (pleochroic: yellow-brown – pale green – blue green) subordinate to non-pleochroic augitic diopside (with iron oxides along cleavages), common magnetite and ilmenite with titanite rims, accessory titanite, and rare zoisite; no olivine.

No. 149

MINERALOGY: Phenocrysts: Fresh An65. Groundmass: Labradorite, colourless fresh olivine with keliphitic rim (radiating fibres of tremolite may occasionally occupy the whole olivine crystal) and associated with magnetite, rare pale-rose hypersthene, tremolite in veins in plagioclase.

No. 150

REMARKS: In Comucci’s end-table SiO_2 is given as 49.43% and the summation as 100.35%.

MINERALOGY: Very fine-grained. Groundmass: Irregularly oriented actinolite fibres (weakly pleochroic); some chlorite; rather rare epidote, altered in part to ferric oxide; accessory titanite, magnetite, plagioclase.

No. 151

MINERALOGY: Medium-fine-grained melanocratic. Groundmass: Zoned An52 – An45, fresh or epidotised; hornblende, with inclusions of iron-oxide and feldspar; small epidote and zoisite; titanite, sometimes as rims to ilmenite.

No. 152

MINERALOGY: Medium-fine grained, melanocratic. Groundmass: Rather uncommon, sericitised An27-25; dominant, large laths of biotite; common hornblende; rather common, irregular grains of titanite; large crystals of apatite, magnetite, ilmenite; accessory quartz (mosaic), calcite, epidote.

No. 153

REMARKS: Occurs near Merech, at the Botteji river and “Tulu Soiaiona.”

MINERALOGY: Variable grain-size, slightly cataclasised. Groundmass: Orthoclase, more abundant than microcline (shows myrmekite with albite); large sub-parallel muscovite (undulose extinction) associated with medium-sized, abundant biotite; rather common epidote; large irregular grains of magnetite; accessory zoisite, orthite, zircon; no quartz.

No. 154

REMARKS: Situated on the “Mora-Gudi-Karavayon” track.

MINERALOGY: Medium-grained, melanocratic. Groundmass: Quartz in mosaic aggregate (straight extinction); abundant biotite in aggregates; large magnetite and ilmenite; accessory apatite, titanite, orthoclase(?).

No. 155

MINERALOGY: Rather fine-grained, not strongly laminated. Groundmass: Abundant biotite, oriented in various-sized grains, of maroon colour; extremely fine-grained quartz-feldspar mosaic; rare yellow garnet, apatite.

No. 156

REMARKS: Summation given as 100.19 in end-table; the SiO_2, value is 68.54%; MnO trace.

MINERALOGY: Phenocrysts: Large corroded orthoclase (but some perthite and some plagioclase twinning – optic angle quoted as “not small”). Groundmass: Microfelsitic; some devitrified glass with abundant magnetite in fluidal arrangement; abundant minute quartz; some muscovite, biotite, epidote.

No. 157

REMARKS: Given as 15 km “east” of Yubdo, from Sotello and Jauri (same as Aleltu-Meti?) streams.

MINERALOGY: Rather coarse-grained, aggregated femics; no lamination. Phenocrysts: Rare quartz, very large with slightly undulose extinction. Groundmass: Kaolinised orthoclase and microcline (perthite and anti-perthite); rather uncommon albite; large biotite, commoner than dark, chloritised amphibole; accessory titanite, magnetite, epidote, apatite, and low-refractive index mineral “sodalite(?).

No. 158

REMARKS: P_2O_5 and C1 traces.

MINERALOGY: Variable grain-size. Groundmass: K-feldspar commoner than plagioclase; microcline commoner than orthoclase; microcline occurs as large crystals with undulose extinction, the orthoclase is sericitised; albite, with muscovite lamellae and anti-perthite; large quartz, with inclusions; abundant biotite (altered to chlorite and epidote) with pleochroic haloes, some associated muscovite; accessory titanite, magnetite, epidote, calcite.

No. 159

REMARKS: TiO_2, and H_2O- traces; specimen collected from 4 km west of Uris River bridge.

MINERALOGY: Medium grained, femics equal mafics in abundance. Groundmass: Microcline (some orthoclase?) with anti-perthite; abundant myrmekite, vermicularitised at contact; abundant An29-22 in rather large plates; large rounded quartz, slightly undulose extinction; pleochroic hornblende, more common than chloritised biotite, both in large crystals; rare large magnetite; rather common apatite; scarce titanite, zircon, epidote.

No. 160

REMARKS: No separate determination of FeO; MnO and P_2O_5 traces; specimen collected from right bank of stream, 1/2 km SE of bridge.

MINERALOGY: Fine-grained, saccharoidal, mafic rock. Groundmass: Small albite-oligoclase, and small quartz (undulose extinction) in mosaic; subordinate muscovite; no orthoclase, no biotite.

No. 161

MINERALOGY: Phenocrysts: Idiomorphic feldspar, corroded quartz. Groundmass: Actinolite (chloritised and epidotised), kaolin, calcite and secondary quartz.

No. 162

REMARKS: SiO_2 determined to two significant figures, Al_2O_3 to three significant figures.

MINERALOGY: Mesocratic non-migmatic (metasomatic) gneiss, medium-coarse grained with granoblastic texture. Groundmass: Abundant fresh anhedral An35-15 often as porphyroblastic clots, olive-brown biotite, feldspathoid (cancrinite or pseudomorphs after cancrinite, or nepheline); less common fresh non-perthitic microcline; accessory calcite, iron-ore, apatite, zircon, very rare sphene, allanite, pyrochlore.

OTHER INFORMATION: Mode:

cancrinite

8.2%

biotite

36.7%

plagioclase

48.0%

calcite

5.4%

microcline

0.2%

apatite

1.5%

No. 163

REMARKS: See under 162. CO_2, present but not determined.

MINERALOGY: Same as 162.

OTHER INFORMATION: Mode:

nepheline

0.2%

biotite

30.7%

cancrinite

14.5%

calcite

1.4%

oligoclase-andesine

42.6%

zircon

0.1%

microcline

10.0%

apatite

0.5%.

No. 164

REMARKS: See under 162.

MINERALOGY: Foliated, medium grained, mesoleucocratic rock with granoblastic texture. Groundmass: Dominant fresh anhedral An35, oriented olive-brown biotite, rather rare fresh poorly-twinned microcline; accessory zircon, sphene, calcite, pyrochlore, and co-existing traces of quartz and nepheline.

OTHER INFORMATION: Mode:

oligoclase-andesine

77.4%

pyrochlore

0.1%

microcline

6.9%

zircon

1.1%

biotite

12.5%

No. 165

REMARKS: See under 162. Published summation is 99.39%.

MINERALOGY: Medium grained, leucocratic, granoblastic rock. Groundmass: Dominant anhedral untwinned An10 and interstitial altered nepheline (pinite); subsidiary potassium feldspar and green biotite; accessory cancrinite, zircon, pyrochlore.

OTHER INFORMATION: Mode:

nepheline

21.7%

microcline

7.7%

cancrinite

4.8%

biotite

8.1%

albite

57.4%

zircon

0.3%

No. 166

REMARKS: See under 162.

MINERALOGY: Similar to 162 and 163.

No. 167

REMARKS: See under 162. Published summation is 99.68%.

MINERALOGY: Coarse-grained, leucocratic, subsolvus type; primary hypidiomorphic-granular texture modified by regional metamorphism to give sutured or irregular grain boundaries. Phenocrysts: Subhedral, slightly altered nepheline. Groundmass: Fresh microcline and microcline-perthite, fresh tabular twinned An5; accessory green biotite or (less commonly) sodic amphibole or aegirine-augite; rarer zircon, apatite, ilmenite, sphene; rare pyrochlore, calcite rimmed with cancrinite.

OTHER INFORMATION: Mode: (Average for Darkainle nepheline syenites.)

nepheline

23.0%

biotite

5.4%

cancrinite

5.0%

calcite

0.4%

albite

37.7%

muscovite

0.2%

microcline

28.0%

natrolite

0.3%

No. 168

REMARKS: See under 162.

MINERALOGY: Same as 167.

No. 169

REMARKS: See under 162.

MINERALOGY: Same as 167.

No. 170

REMARKS: See under 162. Published summation is 99.35%.

MINERALOGY: Same as 167.

VOLCANICS

No. 1001

REMARKS: Loss on heating 6.06%.

MINERALOGY: Comucci (1928) reports the Mt. Ganga basalt as having a groundmass of brown glass with plagioclase microlites, skeletal olivines, chalcedony?.

OTHER INFORMATION: A specimen of olivine basalt from Cape Luma, north of Assab, yielded SiO_2 50.09%. The mineralogy was fresh olivine crystals in a glass and andesine-labradorite groundmass. Manasse (1908) reports four SiO_2 analyses from the Mts. Ganga-Sella basalts: 49.30, 50.32, 49.42, 50.20%. (The last of these is an olivine basalt.) It is difficult to reconcile the SiO_2 values of Ricciardi and Manasse, but Manasse’s values are supported by an analysis of Pantanelli (see 1002).

No. 1002

REMARKS: Loss on heating 3.02%.

MINERALOGY: Comucci (1928) reports the Mt. Sella basalt as phenocrysts of olivine and a groundmass brown glass with andesine microlites.

OTHER INFORMATION: Pantanelli (1886) obtained SiO_2 50.2% from a very fine-grained, scoriaceous black basalt of specific gravity 2.96. He describes phenocrysts of rare olivine set in a groundmass of labradorite, olivine augite, magnetite, and rare apatite.

No. 1003

REMARKS: Loss on heating 2.64%.

MINERALOGY: See 1002.

No. 1004

REMARKS: MnO and MgO traces; loss on heating 1.50%.

MINERALOGY: Phenocrysts: Rare corroded feldspar. Groundmass: Pale yellow-green aegirine, abundant nepheline, some feldspar and epidote. Flow texture sometimes developed.

OTHER INFORMATION: Specific gravity 2.64.

No. 1005

REMARKS: TiO_2 trace; loss on heating 0.83%.

MINERALOGY: Phenocrysts: Anorthoclase. Groundmass: Flow-banded anorthoclase and aegirine.

OTHER INFORMATION: The Axum stellae were carved from this rock-type.

No. 1006

REMARKS: MnO and MgO traces; loss on heating 5.73%.

MINERALOGY: Phenocrysts: Scarce feldspar and augite. Groundmass: Pale-brown perlitic glass with feldspar microlites.

OTHER INFORMATION: Specific gravity 2.376.

No. 1007

REMARKS: No separate determination of FeO; MnO and MgO traces; loss on heating 0.44%.

MINERALOGY: Phenocrysts: Rare anorthoclase. Groundmass: Feldspar, aegirine, quartz, iron-oxides; no flow-texture.

OTHER INFORMATION: Specific gravity 2.58.

No. 1008

REMARKS: No separate determination of FeO; MnO and MgO traces; loss on heating 0.28%.

MINERALOGY: Phenocrysts: Small corroded anorthoclase, quartz, riebeckite phenocrysts die out close to contact with phyllites. Groundmass: Anorthoclase, riebeckite, rare aegirine.

OTHER INFORMATION: Specific gravity 2.58. Prior also gives a partial analysis of a paisanite from Amba Semajata (14.11N 38.58E), east of Adua:

SiO_2

68.96

MnO

tr.

Al_2O

15.17

MgO

tr.

Fe_2O_3

3.10

CaO

0.71

alkalis (by difference from 100.00) 12.06 This rock has a microgranitic appearance, and is composed of anorthoclase, rare quartz and iron-oxide after aegirine(?).

No. 1009

REMARKS: No separate determination of FeO; loss on heating 0.87%.

MINERALOGY: None given.

No. 1010

REMARKS: No separate determination of FeO; loss on heating 0.75%.

MINERALOGY: None given.

No. 1011

REMARKS: No separate determination of FeO; loss on heating 1.38%; published summation is 100.87.

MINERALOGY: Spherulitic vitric rhyolite with arfvedsonite and riebeckite.

No. 1012

REMARKS: No separate determination of FeO; loss on heating 1.20%.

MINERALOGY: Same as 1011.

No. 1013

REMARKS: No separate determination of FeO; loss on heating 2.50%.

MINERALOGY: None given.

No. 1014

REMARKS: In the two source references given it is evident that some oxide values have been transposed; these have been corrected for, following El-Hinnawi (1964).

MINERALOGY: None given.

No. 1015

REMARKS: See under 1014. El-Hinnawi (1964) quotes the SO_3 value as C1.

MINERALOGY: None given.

No. 1016

REMARKS: MnO trace; loss on heating 1.05%.

MINERALOGY: Phenocrysts: Large alkali feldspar, minor plagioclase. Groundmass: Feldspar, riebeckite, quartz, calcite.

OTHER INFORMATION: This is most probably, but not certainly, a PreCambrian Basement rock.

No. 1017

REMARKS: The analyses of Arsandaux (1903a, b) are only quoted to one decimal place; loss on heating is given under H_2O+.

MINERALOGY: Phenocrysts: Anorthoclase crystals with ‘secondary’ albite penetrations. Groundmass: Anorthoclase, aegirine, riebeckite, quartz.

No. 1018

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1019

REMARKS: See under 1017. Loss-on-heating trace.

MINERALOGY: None given.

No. 1020

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1021

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1022

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1023

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1024

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1025

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1026

REMARKS: See under 1017. Published summation 101.6.

MINERALOGY: None given.

No. 1027

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1028

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1029

REMARKS: See under 1017. Published summation 101.0.

MINERALOGY: None given.

No. 1030

REMARKS: See under 1017.

MINERALOGY: Phenocrysts: Large anorthites.

No. 1031

REMARKS: See under 1017.

MINERALOGY: None given.

No. 1032

REMARKS: See under 1017.

MINERALOGY: Phenocrysts: Labradorite.

No. 1033

REMARKS: See under 1017.

MINERALOGY: Phenocrysts: Labradorite.

No. 1034

REMARKS: See under 1017.

MINERALOGY: None given.

OTHER INFORMATION: Location uncertain.

No. 1035

REMARKS: CO_2 and SO_3 traces. The analyses of Manasse (1908, 1909, 1917) tend to have high summations; loss on heating is given under H_2O plus; otherwise these analyses appear to be of good quality.

MINERALOGY: Phenocrysts: Zoned bytownite, with margins of andesine-labradorite; rare titanaugite and very rare iron-rich olivine. Groundmass: Labradorite, green pyroxene, altered Fe-rich olivine, magnetite, ilmenite, apatite and glass. Fluidal texture.

No. 1036

REMARKS: See under 1035. SO_3 trace.

MINERALOGY: Phenocrysts: Very rare oligoclase. Groundmass: Oligoclase, sanidine, accessory diopside-augite, acmite, magnetite, limonite.

No. 1037

REMARKS: See under 1035. CO_2 trace.

MINERALOGY: Phenocrysts: Very rare oligoclase. Groundmass: Oligoclase, sanidine (“not nepheline”), green non-pleochroic augite-diopside; accessory glass, magnetite, apatite, calcite, acmite(?).

No. 1038

REMARKS: See under 1035. SO_3 trace.

MINERALOGY: Phenocrysts: Zoned bytownite-oligoclase, chiefly andesine-labradorite; rare augite-diopside. Groundmass: Yellow-grey crystallite base composed of green non-pleochroic pyroxene, glass, apatite, rare tridymite, altered olivine, feldspar.

OTHER INFORMATION: Another specimen with SiO_2, 6319% contains chalcedony, tridymite, labradorite-bytownite.

No. 1039

REMARKS: See under 1035.

MINERALOGY: Fresh, very fine-grained rock with a trachytic texture. Groundmass: Aegirine-augite, aegirine, alkali feldspar, katophorite and/or acmite, cossyrite, rare tridymite; no feldspathoids.

No. 1040

REMARKS: See under 1035.

MINERALOGY: Phenocrysts: Anorthoclase, rare sanidine and aegirine-augite. Groundmass: Dark brown glass (n = 1.512-1.520); spherulites of feldspar microlites; green pyroxene, cossyrite, rare magnetite and apatite.

OTHER INFORMATION: This rock contains schlieren, the mineralogy of which is identical with the host. Two specimens gave SiO_2 contents of 69.42% and 71.66%, the latter bearing some chalcedony.

No. 1041

REMARKS: See under 1035.

MINERALOGY: Groundmass: Chloritised andesine, titan-augite, rare barkevikite and biotite?; abundant magnetite, leucoxene (from ilmenite); common apatite; rare pyrite; analcime and natrolite.

OTHER INFORMATION: The analcime may be derived from nepheline, and has the composition:

SiO_2

56.24

Na_2O

13.30

Al_2O

21.68

K_2O

0.42

Fe_2O_3

tr.

H_2O

8.40

MgO

tr.

total

100.37

CaO

0.33

n = 1.4837

Dainelli and Marinelli (1912), who collected the Eritrean specimens analysed by Manasse, state that this teschenite was taken from a lithological lens in the PreCambrian basement. There remains some doubt about this; however, see Comucci (1948).

No. 1042

REMARKS: See under 1035.

MINERALOGY: Aphyric. Groundmass: Labradorite, titanaugite, altered olivine, magnetite, ilmenite, rare apatite.

OTHER INFORMATION: Doleritic olivine basalts from Shicket (15.10N, 38.51E) contain amygdale zeolites which have been analysed:

(1)

(2)

(3)

SiO_2

46.69

52.84

41.30

Al_2O_3

20.27

tr.

29.49

CaO

9.72

24.46

11.61

Na_2O

0.96

tr.

5.11

k_2O

tr.

5.42

tr.

H_2O

22.80

16.48

13.32

Total

100.44

99.20

100.83

(1) chabazite (2) apophyllite (3) thomsonite.

No. 1043

REMARKS: See under 1035.

MINERALOGY: Scoriaceous rock. Phenocrysts: Augite, corroded olivine. Groundmass: Glass, labradorite, pyroxene, olivine?, ilmenite and magnetite, calcite, apatite.

No. 1044

REMARKS: See under 1035. Published summation 101.49% can be accounted for by adding CO_2 content to “loss on heating.”

MINERALOGY: Groundmass: Labradorite-bytownite, abundant titanaugite, barkevikite, magnetite, ilmenite, accessory apatite, calcite, serpentinite.

OTHER INFORMATION: Manasse also describes an augitic camptonite from Suru in the Comayli Valley, due west of Arafali.

No. 1045

REMARKS: See under 1035. MnO trace.

MINERALOGY: Calcitic scoria. Phenocrysts: Zoned bytownite-labradorite. Groundmass: Abundant brown glass with minute iron-oxide crystals; An60-65, olivine, pyroxene, magnetite, ilmenite.

OTHER INFORMATION: Some associated tuffs bear 43.06% SiO_2. Extra basalt SiO_2 determinations from Manasse (1904, 1908, 1909). See also under 1001.

Porphyritic olivine basalt:

Hyalobasalt:

Mt. Surrisan

48.78%

Mt. Daggaro

49.25%

Mt. Darcot

48.31%

50.68%

Mt. Carallumto

49.24%

51.52%

Mt. Coma Chari

47.36%

SE flank Mt. Alid

50. 79%

No. 1046

REMARKS: See under 1035. C1 trace.

MINERALOGY: Groundmass: Dominant alkali feldspar microlites; very small nephelines; wöhlerite (rather than lavenite); non-titaniferous magnetite; scarce apatite, sodalite.

OTHER INFORMATION: For comments on the occurrence of wöhlerite, see Rodolico & Pieruccini (1942, p. 800-801).

No. 1047

REMARKS: See under 1035. MgO and P_2O_5 traces.

MINERALOGY: White porcellanous rock. Groundmass: Pale yellow glass, sanidine, anorthoclase, magnetite, zircon.

OTHER INFORMATION: Occurs intercalated in doleritic basalts. Silicic tuff from between the Mesozoic sand-stone and the basalts at Adi Quala yielded SiO_2 71.10%.

No. 1048

REMARKS: See under 1035. No separate determination of FeO; MgO trace.

MINERALOGY: Very fine grained. Groundmass: Very abundant Na-feldspar, scarce quartz, no femics, no nepheline.

No. 1049

REMARKS: See under 1035. MnO, P_2O_5, SO_3, C1 traces.

MINERALOGY: Filamented, very porous pumice. Phenocrysts: Large zoned anorthoclase, with inclusions of glass, apatite, magnetite, green pyroxene, cossyrite. Groundmass: Glass (n 1.4958), no microlites.

OTHER INFORMATION: Other SiO_2 determinations on pumices: Alid, 67.45%; Deri, 72.50%.

No. 1050

REMARKS: See under 1035. MnO and P_2O_5 traces.

MINERALOGY: Medium-grained (dyke?). Phenocrysts: Micro-phenocrysts of Na-sanidine, riebeckite, scarce aegirine. Groundmass: Alkali feldspar, quartz.

No. 1051

REMARKS: See under 1035. MnO, P_2O_5, SO_3 traces.

MINERALOGY: Schlieren contain alkali feldspar and brown amphibole. Phenocrysts: Micro-phenocrysts of andesine-oligoclase. Groundmass: Micro-feldsitic, with tridymite cavities; also, glass, magnetite, apatite, fresh mica, brown amphibole rimmed with iron-oxide and diopside.

OTHER INFORMATION: Other SiO_2 determinations:

South rim of Alid caldera, hornblende felsodacite 71.60%,

hornblende hyalodacite 68.28%;

Hewchew, SW of Deggherto, hyalodacite 67.36%.

No. 1052

REMARKS: See under 1035. MgO trace.

MINERALOGY: Groundmass: Colourless glass (n 1.49); spherulites with microlites of alkali feldspar and augite.

OTHER INFORMATION: Other SiO_2 determinations on obsidians: West flanks Alid, 71.19%; Agoghito, SE of Alid, 73.65%.

No. 1053

REMARKS: See under 1035. MnO trace.

MINERALOGY: Mariolitic cavities with tridymite (n 1.474). Groundmass: Microfelsitic and spherulitic, with schlieren; alkali feldspar; kataphorite, magnetite, calcite.

No. 1054

REMARKS: See under 1035. No separate determination of FeO; P_2O_5 trace.

MINERALOGY: Phenocrysts: Albite, sanidine, quartz. Groundmass: Quartz, albite, K-feldspar, magnetite, kataphorite?.

No. 1055

REMARKS: See under 1035. MnO trace.

MINERALOGY: Phenocrysts: Na-feldspar. Groundmass: Fluidal tecture; sanidine more abundant than quartz; scarce magnetite, kataphorite(?).

No. 1056

REMARKS: See under 1035.

MINERALOGY: Black, compact, very fine-grained rock. Phenocrysts: Extremely rare labradorite. Groundmass: Fresh labradorite, with apatite inclusions; pale-green augite, small rounded and altered olivines; common magnetite, ilmenite; some devitrified glass.

No. 1057

REMARKS: See under 1035. TiO_2 and P_2O_5 traces.

MINERALOGY: Holocrystalline, very fine-grained. Phenocrysts: Sanidine, nepheline, rare pale-green augite. Groundmass: Dominant sanidine; subordinate fresh nepheline; rare sodalite (analysis suggests 5-6% in mode); aegirine, in minute aggregates, is commoner than cossyrite; accessory apatite.

OTHER INFORMATION: This rock-type forms numerous small hills on the Degder plain.

No. 1058

MINERALOGY: Phenocrysts: Anorthoclase, quartz. Groundmass: Fluidal texture; quartz, alkali feldspar, glass, arfvedsonite-riebeckite, rare sodic pyroxene.

No. 1059

REMARKS: P_2O_5 trace.

MINERALOGY: Trachytic texture. Phenocrysts: Abundant small anorthoclase; zoned aegirine-augite (aegirine margins); rare sodalite?, arfvedsonite, cossyrite. Groundmass: Alkali feldspar, arfvedsonite, Fe-rich olivine, quartz, apatite.

OTHER INFORMATION: Pantellerite from Nomenta-ali (see 1058) contains riebeckite-arfvedsonite and zircon.

No. 1060

MINERALOGY: Phenocrysts: Abundant corroded quartz, anorthoclase?. Groundmass: Very fine-grained quartz and alkali feldspar, sometimes as spherulites; rare iron-oxide, brown amphibole.

OTHER INFORMATION: Comendite from Nomenta-ali (see 1058) is similar to the above, plus containing some rare aegirine.

No. 1061

REMARKS: CO_2 figure derived from “calcining.”

MINERALOGY: A slightly weathered rock. Phenocrysts: Zoned andesine-labradorite, rare augite, analcime?. Groundmass: Fluidal texture; oligoclase-andesine, green pyroxene, hornblende (with rim reactions), apatite, magnetite; nodules of brown basic material contain chlorite-rimmed epidote, and augite and hornblende.

No. 1062

MINERALOGY: Phenocrysts: Zoned An15-20 (ca. 2 cm long), augite and zoned aegirine-augite, rare brown hornblende. Groundmass: Trachytic groundmass; Trachytic groundmass; feldspar (orthoclase?), aegirine-augite and associated analcime, apatite, magnetite. Norm suggests analcime could be secondary after nepheline.

OTHER INFORMATION: Analysis (%) of the oligoclase phenocrysts (contaminated with some analcime):

SiO_2

61.79

CaO

3.12

Al_2O_3

22.61

Na_2O

9.65

Fe_2O_3

0.34

K_2O

1.15

MgO

0.11

Total

99.99

Other specimens from Adaylo and Assacoma contained large oligoclase-andesine and brown hornblende phenocrysts.

No. 1063

REMARKS: MnO values in the analyses of Roman (1926) are distinctly too high; the value of these analyses is further reduced by the evident transposition of some of the mineralogical descriptions from their related analyses (eg. see 1076!). H_2O+ values refer to loss on heating.

MINERALOGY: Phenocrysts: Serpentinised zoned augite-diopside. Groundmass: An45-55, pyroxene, magnetite, apatite.

OTHER INFORMATION: Specific gravity 3.158.

No. 1064

REMARKS: See under 1063.

MINERALOGY: Refers to a rock other than the analysed specimen? Groundmass: Trachytic texture. An20-25, quartz, chlorite, calcite, often as spherulites.

No. 1065

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: An60-70, diallage-diopside. Groundmass: Plagioclase, pyroxene, magnetite, orthoclase; veins of chlorite, quartz, calcite.

OTHER INFORMATION: Specific gravity 2.893.

No. 1066

REMARKS: See under 1063. MnO ridiculously high.

MINERALOGY: Phenocrysts: An60, “isometric sanidine” (nepheline?). Groundmass: An40, Mg-rich diopside, chlorite, “sanidine.”

No. 1067

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: An60-70. Groundmass: An50-55; augite, partly “altered” to green hornblende; chlorite, magnetite.

No. 1068

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: An36. Groundmass: An20; magnetite; rare quartz, calcite, white mica.

OTHER INFORMATION: Specific gravity 2.672.

No. 1069

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: An5-7 (3 mm length) with inclusions of magnetite, apatite, mica. Groundmass: Microlites of orthoclase (albite rims), green biotite, magnetite, apatite, quartz.

OTHER INFORMATION: Specific gravity 2.657. Sheet intrusion.

No. 1070

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: Zoned An50-70. Groundmass: An15 in trachytic texture; geodes containing chlorite, calcite, chalcedony.

No. 1071

REMARKS: See under 1063.

MINERALOGY: Groundmass: Trachytic texture; orthoclase with albitic rims; quartz, green biotite, ilmenite, magnetite.

OTHER INFORMATION: Specific gravity 2.740. Sheet intrusion.

No. 1072

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: An5. Groundmass: Fluidal, trachytic texture; anorthoclase?; some magnetite, apatite, white mica, rare quartz.

OTHER INFORMATION: Specific gravity 2.531.

No. 1073

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: Anorthoclase rhombs with inclusions of magnetite and muscovite. Groundmass: Saccharoidal quartz and feldspar, some An10.

OTHER INFORMATION: Specific gravity 2.538. Sheet intrusion in comendite lavas.

No. 1074

REMARKS: See under 1063.

MINERALOGY: Groundmass: Devitrified to microfelsite with some quartz.

No. 1075

REMARKS: See under 1063. This rock may be the host to 1073.

MINERALOGY: Phenocrysts: Corroded quartz with apatite inclusions, microperthitic orthoclase, An5. Groundmass: Microfelsitic, rare iron-oxide.

OTHER INFORMATION: Specific gravity 2.585.

No. 1076

REMARKS: See under 1063.

MINERALOGY: Evidently transposed from another specimen. Phenocrysts: An70-55. Groundmass: Corroded K-feldspar crystals, quartz, chlorite, magnetite, calcite, epidote.

OTHER INFORMATION: Specific gravity 2.500.

No. 1077

REMARKS: See under 1063.

MINERALOGY: Phenocrysts: Anorthoclase (sericitised). Groundmass: Devitrified, felsitic; some femics, no quartz?.

OTHER INFORMATION: Specific gravity 2.570.

No. 1078

REMARKS: See under 1063. Sub-aluminous.

MINERALOGY: Groundmass: Brown glass; microlites quartz, An5-8, cośsyrite(?).

No. 1079

MINERALOGY: Groundmass: Labradorite, titanaugite, uncommon olivine, magnetite, some glass.

OTHER INFORMATION: Specific gravity 2.97.

No. 1080

MINERALOGY: Groundmass: Brown glass, An60, fresh Fe-rich olivine; no augite.

OTHER INFORMATION: Specific gravity 2.95.

No. 1081

REMARKS: Loss on heating 1.34%. The work of Lacroix (1930) suggests that in this analysis the values for Na_2O and K_2O have been transposed. The low summation suggests an incomplete analysis or an error in one of the oxide values.

MINERALOGY: Phenocrysts: Abundant, flow-aligned alkali feldspar (2V = 43°); rare grey augite; crocidolite?. Groundmass: Glass with microlite trains, crocidolite with quartz rims.

OTHER INFORMATION: Specimen from large flow reaching nearly to railway. Grey scoriaceous surface to flow.

No. 1082

REMARKS: Loss on heating 2.40%.

MINERALOGY: Dark basaltic rock. Phenocrysts: Zoned titanaugite, magnetite octahedra. Groundmass: Brown glass with microlites of augite, magnetite, plagioclase.

No. 1083

REMARKS: No separate determination of H_2O-.

MINERALOGY: Flow-texture. Phenocrysts: Andesine, rare olivine with reaction rims. Groundmass: Feldspar, augite, magnetite, ilmenite, rare glass.

No. 1084

REMARKS: No separate determination of H_2O-.

MINERALOGY: Groundmass: An57-60, red-brown titanaugite, rare altered olivine, rare glass, abundant magnetite.

No. 1085

REMARKS: Decarbonated with acetic acid prior to analysis; the exceptionally high CaO in the remaining rock suggests that contamination from the dissolved calcite has occurred (see Hieke-Merlin, 1950). No separate determination of H_2O-.

MINERALOGY: Groundmass: Labradorite, augite, altered Fe-rich olivine, dark glass; calcite-filled vesicles up to 1 cm diameter; no zeolites.

OTHER INFORMATION: Calcitic scoria also occur on the Asbol plain, 20 km from Assab. Manasse (1908) also mentions the presence of calcitic rocks from this region.

No. 1086

REMARKS: See important note under 1085.

MINERALOGY: Phenocrysts: Large fresh olivine. Groundmass: Abundant glass with labradorite microlites.

OTHER INFORMATION: Weathers with iron-rich surface. Other specimens less rich in calcite vesicles contain labradorite phenocrysts, with decomposed olivine, rare augite and glass, and magnetite in the groundmass.

No. 1087

REMARKS: See under 1085.

MINERALOGY: Very fresh rock. Phenocrysts: Yellow-green olivine. Groundmass: Flow-texture; glass, labradorite, magnetite, calcite (primary?); no pyroxene.

OTHER INFORMATION: See under 1001.

No. 1088

REMARKS: No separate determination of H_2O-.

MINERALOGY: Groundmass: Andesine-labradorite, augite, magnetite-ilmenite more abundant than in 1083, rare glass.

No. 1089

REMARKS: No separate determination of H_20-.

MINERALOGY: Phenocrysts: Labradorite-bytownite. Groundmass: Pale-brown glass, abundant magnetite and ilmenite?; rather uncommon plagioclase microlites, brown augite, scarce altered olivine.

OTHER INFORMATION: Olivine-andesine trachybasalt from Dadda-ho contains ca. 61% SiO_2; vetrose olivine basalts reported from Foroddu (with calcite scoria), Ela, Ulului, Doctummo (with calcite scoria); olivine basalts reported from Dubbi, Addula, Dioita.

No. 1090

REMARKS: No separate determination of H_2O-; notably rich in manganese and potassium.

MINERALOGY: Groundmass: Brown glass with plagioclase and rare augite microlites.

No. 1091

REMARKS: No separate determination of FeO or H_2O-.

MINERALOGY: Groundmass: Glass with elongated vesicles; signs of incipient crystallisation.

No. 1092

REMARKS: No separate determinations of FeO or H_2O; too many terminal zeros in analysis, and summation is low.

MINERALOGY: Groundmass: Glass with rare microlites.

OTHER INFORMATION: An alkaline rhyolite scoria from SW of Dubbi contained ca. 70% SiO_2 and was composed of glass with corroded sanidine and aegirine-augite.

No. 1093

REMARKS: MnO trace. Loss on heating, 3.67%; published summation of 100.02%.

MINERALOGY: Phenocrysts: Very corroded anorthoclase, up to 2 cm length. Groundmass: Glass with anorthoclase and femic microlites; rare apatite, magnetite, hornblende, no nepheline(?).

OTHER INFORMATION: Occurs as large dyke.

No. 1094

REMARKS: Loss on heating, 1.96%.

MINERALOGY: Phenocrysts: Very abundant; large titanaugite; olivine, magnetite octahedra, scarce plagioclase which is younger than the other phenocrysts. Groundmass: Augite, magnetite, rare biotite, An56, no glass.

No. 1095

MINERALOGY: Compact dark rock. Groundmass: Fresh brown glass, andesine-labradorite microlites, some decomposed femics?.

No. 1096

MINERALOGY: Phenocrysts: Corroded anorthoclase. Groundmass: Anorthoclase, possible orthocalse, rare plagioclase, aegirine-augite, brown glass, no quartz or cossyrite.

OTHER INFORMATION: Specific gravity 2. 577. Also from the San’a Valley: vitric sanidine rhyolite contains 77.32% SiO_2, Na-plagioclase and augite rock contains 58.90% SiO_2.

No. 1097

REMARKS: In Duparc (1930a, b) there are no separate water determinations, only loss on heating.

MINERALOGY: Phenocrysts: Olivine, rare augite. Groundmass: Labradorite, magnetite, augite, scarce olivine, common glass.

OTHER INFORMATION: Dyke cuts birbirite near Yubdo.

No. 1098

REMARKS: See under 1097.

MINERALOGY: Phenocrysts: Olivine, magnetite, rare augite. Groundmass: Gray augite, magnetite, microlites of labradorite, rare olivine.

No. 1099

REMARKS: See under 1097.

MINERALOGY: Very fine-grained rock. Phenocrysts: Small augite, rare olivine. Groundmass: Flow-texture; labradorite microlites in glass, abundant magnetite, titanaugite.

No. 1100

REMARKS: See under 1097.

MINERALOGY: Phenocrysts: Abundant, small corroded olivines. Groundmass: An72-78, titanaugite, olivine,magnetite, no glass.

No. 1101

REMARKS: See under 1097.

MINERALOGY: Phenocrysts: Olivine, magnetite, small plagioclase. Groundmass: Labradorite microlites in glass, magnetite, augite, rare olivine.

OTHER INFORMATION: A basalt from this region examined by Comucci (1933a) contains large andesine phenocrysts which are zoned from An32 at the center to An50 at the crystal boundary. A similar feature has been observed in the Simien basalts. See also Augustithis (1964).

No. 1102

REMARKS: See under 1097; P_2O_5 trace; no separate determination of FeO.

MINERALOGY: Aphyric with flow-texture. Groundmass: Very abundant anorthoclase, magnetite, rare zircon, brown amphibole, aegirine(?), cossyrite(?), no glass.

OTHER INFORMATION: This rock forms numerous small domes between the Baro River and the plateau.

No. 1103

MINERALOGY: No description by the author. Groundmass: Gaubert (1901) describes an assemblage of nepheline, green pyroxene, apatite, magnetite and rare olivine.

No. 1104

MINERALOGY: Phenocrysts: Anorthoclase with glassy inclusions, some Fe-rich olivine with pyroxene borders, pale-green diopside with aegirine-augite borders. Groundmass: Orthoclase microlites, diopside, olivine, magnetite, rare quartz.

OTHER INFORMATION: This rock-type occurs between green pantellerite (below) and obsidian (above).

No. 1105

MINERALOGY: Phenocrysts: Large anorthoclase, rare albite. Groundmass: Anorthoclase, albite, rare quartz.

No. 1106

MINERALOGY: Phenocrysts: Anorthoclase, rare albite, amphibole (laneite) and later aegirine. Groundmass: Same as phenocrysts plus rare nepheline.

No. 1107

REMARKS: TiO_2 trace.

MINERALOGY: Very fine-grained. Groundmass: Anorthoclase, scarce aegirine and quartz.

No. 1108

MINERALOGY: Resembles solvsbergites 1105-7. Phenocrysts: Anorthoclase, hedenbergite. Groundmass: Anorthoclase, aegirine(?), quartz, cossyrite, glass, Fe-rich olivine in some specimens.

No. 1109

REMARKS: No separate determination of H_2O-; sub-aluminous.

MINERALOGY: Groundmass: Glass, cossyrite, hedenbergite, magnetite.

No. 1110

MINERALOGY: Resembles Karsa solvsbergites 1105-7. Phenocrysts: Anorthoclase, Hedenbergite. Groundmass: Anorthoclase, green pyroxene (aegirine?), quartz cossyrite, glass, Fe-rich olivine in some specimens.

No. 1111

MINERALOGY: Phenocrysts: Alkali feldspar, corroded quartz, brown amphibole, cossyrite, magnetite. Groundmass: Glass, feldspar, pyroxene, and magnetite microlites; bears fragments of porphyritic basalt, and corroded isolated An30 xenocrysts.

No. 1112

MINERALOGY: Flow-texture. Phenocrysts: Abundant aegirine-hedenbergite; cossyrite, anorthoclase, Fe-rich olivine rimmed with hedenbergite. Groundmass: Glass, with microlites of feldspar and green femics.

No. 1113

MINERALOGY: Phenocrysts: Hedenbergite-aegirine, cossyrite, corroded quartz, sodic orthoclase. Groundmass: Yellow glass, with pyroxene microlites.

OTHER INFORMATION: Occurs above rock 1104.

No. 1114

REMARKS: P_2O_5 trace.

MINERALOGY: None given.

No. 1115

MINERALOGY: Poor in femics, so not designated a pantellerite.

No. 1116

REMARKS: MnO and CaO traces.

MINERALOGY: None given.

No. 1117

MINERALOGY: Phenocrysts: Serpentinised olivine. Groundmass: Plagioclase, augite, magnetite, olivine(?).

No. 1118

REMARKS: No separate determination of FeO. The nature of this rock is puzzling, and the presence of native carbon suggests contamination.

MINERALOGY: Not given.

No. 1119

MINERALOGY: None given.

No. 1120

MINERALOGY: Flow-texture. Phenocrysts: Anorthoclase, quartz, aegirine-augite, cossyrite, riebeckite. Groundmass: Glass.

No. 1121

MINERALOGY: Flow-texture. Phenocrysts: Anorthoclase, quartz, aegirine-augite, cossyrite, riebeckite. Groundmass: Glass.

No. 1122

MINERALOGY: None given.

No. 1123

REMARKS: No separate determination of H_2O-.

MINERALOGY: None given.

No. 1124

REMARKS: No separate determination of H_2O-.

MINERALOGY: None given.

No. 1125

REMARKS: High-alumina basalt.

MINERALOGY: Dark, dense rock. Phenocrysts: Rare An50, olivine. Groundmass: An50, olivine, augite, rare magnetite and glass.

No. 1126

REMARKS: FeO trace.

MINERALOGY: Flow-texture. Groundmass: Brown glass; abundant anorthoclase/sanidine, sometimes as corroded micro-phenocrysts; magnetite, ilmenite(?); very rare plagioclase; no femics, no quartz.

OTHER INFORMATION: A yellow-brown rock of localised occurrence.

No. 1127

REMARKS: High water-content due to weathered nature of rock.

MINERALOGY: Flow-texture. Phenocrysts: Anorthoclase, rare quartz. Groundmass: Glass, anorthoclase; rare brown hornblende, altered augite; fragments of basalt, glass; cavities filled with yellow earthy material.

OTHER INFORMATION: Used in building construction in Addis Ababa.

No. 1128

REMARKS: MgO trace.

MINERALOGY: Flow texture. Phenocrysts: Sanidine. Groundmass: Glass, abundant sanidine, rare quartz, no femics.

OTHER INFORMATION: A similar rock from km 5 along the railway is richer in quartz.

No. 1129

REMARKS: C1 trace.

MINERALOGY: Phenocrysts: Corroded aegirine-augite, less common brown hornblende. Groundmass: Microlites of pyroxene, feldspar/nepheline, and of sodalite(?), common magnetite; rare vesicles contain natrolite and calcite.

OTHER INFORMATION: A similar rock from between Guri and Mio contains pyroxene phenocrysts zoned from titanaugite to aegirine-augite; also serpentinised olivine phenocrysts.

No. 1130

MINERALOGY: Groundmass: Abundant zoned labradorite, common serpentinised olivine (occasionally as phenocrysts), abundant magnetite, rare ilmenite, rare brown hornblende and biotite.

OTHER INFORMATION: An identical rock occurs in the Wosho Valley north of Bokoji. Basalt from the Katar headwaters, north of the Sella di Karra, contains abundant iddingsitised olivine phenocrysts in a glassy groundmass.

No. 1131

REMARKS: Weathering shows in water and carbon dioxide contents C1 trace.

MINERALOGY: Phenocrysts: Uncommon small altered nepheline, abundant zoned pyroxene (augite out to aegirine), barkevikite with rims of aegirine-augite. Groundmass: Nepheline, aegirine-augite, apatite, titanite rare biotite, sodalite(?); vesicles contain natrolite-scolecite, calcite.

No. 1132

REMARKS: High water content.

MINERALOGY: Phenocrysts: Abundant nepheline, with altered margins (hydrated and carbonated); scarce corroded biotite, apatite. Groundmass: Phonolitic texture; nepheline, aegirine-augite, no sodalite, no iron-oxides.

No. 1133

REMARKS: Repossi gives a summation of 100.48, but the actual summation of his figures (op. cit. p. 286) is 108.78. Examination of the Niggli values calculated by Repossi from this analysis reveals that the error lies in the Al_2O_3 figure. To obtain the published summation, 8. 30% has been subtracted from the published Al_2O_3 21.15% to obtain 12.85% as given here.

MINERALOGY: Phenocrysts: Labradorite, with ilmenite inclusions scarce pale-green augite, rare rounded olivines. Groundmass: Plagioclase, pyroxene, rare olivine and glass; accessory ilmenite, magnetite, apatite.

OTHER INFORMATION: Repossi discusses basalts from the Mt. Chilalo and Gasara (Bali) regions under one heading. This rock is usually cited by later authors as from Gasara -- see Comucci (1948) and Hieke-Merlin (1950) -- but a careful reading of Repossi (p. 286) reveals that Mt. Chilalo is the locality.

No. 1134

REMARKS: SiO_2 seems high for the given mineralogy.

MINERALOGY: Phenocrysts: None. Groundmass: Labradorite, augite, olivine, common magnetite, scarce glass.

No. 1135

MINERALOGY: Green, flow-textured rock. Phenocrysts: Anorthoclase, scarce quartz. Groundmass: Brown glass (n 1.510), magnetite and aegirine-augite microlites, fragments of basalt.

OTHER INFORMATION: Repossi notes the uncertainty of this locality, and a more likely source for such a rock-type is either eastern Ghedeb, further south, or Adama, further north.

No. 1136

MINERALOGY: Phenocrysts: An65, rare serpentinised olivine. Groundmass: Plagioclase, Fe-rich olivine, magnetite, altered rose-coloured material; no augite, no glass.

OTHER INFORMATION: Basalts from:

Abalti: Large augite phenocrysts rimmed with magnetite, large olivines, small An50, in groundmass plagioclase, magnetite, glass. Jimma: Zoned phenocrysts, An50 (center) to An70 (rim). Agaro: Zoned phenocrysts, An70 (center) to An55 (rim), in groundmass of plagioclase, olivine, augite, magnetite, very rare glass.

No. 1137

REMARKS: High Fe_2O_3 due to weathering(?).

MINERALOGY: Phenocrysts: Sodic labradorite. Groundmass: Plagioclase, brown hornblende, biotite(?).

No. 1138

MINERALOGY: Phenocrysts: Large titanaugite, large colourless Mg-rich olivine. Groundmass: Brown glass; magnetite; microlites of augite and olivine; rare plagioclase.

No. 1139

MINERALOGY: Phenocrysts: Common large augite, less common, smaller Mg-rich olivine. Groundmass: Clear brown glass (more abundant than in 1138), microlites augite and olivine(?).

No. 1140

MINERALOGY: Phenocrysts: Not abundant, large yellow augite, iddingsitised olivine. Groundmass: Ca-rich plagioclase, augite; no glass.

No. 1141

MINERALOGY: Phenocrysts: Large colourless augite; equally abundant olivine, serpentinised or occasionally iddingsitised. Groundmass: Flow-texture; plagioclase, augite, magnetite; no glass or olivine.

No. 1142

MINERALOGY: Phenocrysts: Augite, uncommon, small Mg-rich olivine (serpentinised and iddingsitised). Groundmass: Abundant augite; plagioclase, magnetite; no glass.

No. 1143

MINERALOGY: Vesicular rock. Phenocrysts: Zoned brown-red augite, serpentinised olivine. Groundmass: Labradorite-andesine, augite, abundant magnetite.

No. 1144

MINERALOGY: Phenocrysts: Rare labradorite. Groundmass: Chiefly glass with common magnetite, augite microlites, rectangular “feldspar” crystals replaced with chalcedony fibres.

OTHER INFORMATION: Collected from 630 m above Hajela river.

No. 1145

REMARKS: No separate determinations of FeO, H_2O-; TiO_2 included in Al_2O_3; MgO trace.

MINERALOGY: Phenocrysts: Rare small, altered anorthoclase. Groundmass: Flow-texture; grey glass with patches of green glass.

OTHER INFORMATION: From Hajela, sanidine hyalorhyolite, SiO_2 75.06%. From Mt. Nekum, San’a, obsidian, SiO_2 59%.

No. 1146

REMARKS: No separate determinations of FeO, H_2O-; TiO_2 included in Al_2O_3; MgO trace.

MINERALOGY: Groundmass: Rather fine-grained, uniform grain size, quartz and sericitised K-feldspar.

OTHER INFORMATION: From 3 km east of Manaka, yellow-green rock with iron-stained concentric zoning; too fine-grained for microscopic resolution; possibly a glassy alkali rhyolite(?): SiO_2 77.94%, R_2O_3 12.74% (low in iron), H_2O 1.92%, a little CaO, no CO_2.

No. 1147

REMARKS: H_2O- trace.

MINERALOGY: Phenocrysts: Zoned An60 (center) to An30 (rim) large brown-red augite, altered olivine. Groundmass: Flow-texture; labradorite, augite, fresh olivine; uncommon black glass with magnetite-ilmenite.

No. 1148

REMARKS: Analyst P. Comucci.

MINERALOGY: Phenocrysts: Olivine. Groundmass: Ophitic, holocrystalline; zoned An70-50; titanaugite, olivine, scarce magnetite, calcite.

OTHER INFORMATION: From Moga, on the Hafun Peninsula, North Somali: an erratic boulder of olivine basalt on the shoreline (note: the nearest land-exposure of basalt is 250 km to the WNW on the Gulf of Aden coast. This erratic is presumably derived from the Indian Ocean floor). Niggli values (the original analysis is not given): si 92.9, ti 2.6, al 17.3, fm 47, c 30, alk 5.7, mg. 0.56, k 0. 18. Mineralogy: Fresh olivine phenocrysts in a medium-grained groundmass of zoned An70-50, olivine, ophitic titanaugite, uncommon magnetite.

No. 1149

MINERALOGY: Phenocrysts: Andesine-labradorite, augite, magnetite. Groundmass: Feldspar, hornblende, nepheline.

OTHER INFORMATION: Specific gravity 2. 564, published norm inaccurate.

No. 1150

REMARKS: Strongly potassic.

MINERALOGY: Phenocrysts: Plagioclase, nepheline, some hauyne. Groundmass: Flow-texture; glass, with andesine and nepheline; rare biotite, magnetite, hornblende, augite, olivine.

OTHER INFORMATION: Specific gravity 2.501.

No. 1151

REMARKS: Republished by Hieke-Merlin (1950) (see this list no. 1224). Hieke-Merlin has taken 2.00% from FeO and added it to Fe_2O_3; has interchanged H_2O+ with CO_2, and H_2O- with total H_2O

MINERALOGY: Recent scoriaceous lava. No mineralogy given by Gortani and Bianchi. For Hieke-Merlin see 1224.

No. 1152

REMARKS: Analysis republished by Hieke-Merlin (1950), but allocated to a different locality, (see this list no. 1225). No separate H_2O- determination.

MINERALOGY: See 1225.

No. 1153

REMARKS: Published summation of 100.32.

No. 1154

MINERALOGY: Phenocrysts: An50 (not zoned), fresh olivine (1/2-mm diameter), rather uncommon. Groundmass: Labradorite, titanaugite, olivine, magnetite (some large crystals), apatite; no glass.

OTHER INFORMATION: Comucci (1933a) refers to a specimen from this vicinity which contained zoned An60 phenocrysts.

No. 1155

REMARKS: MnO trace.

MINERALOGY: Phenocrysts: Anorthoclase (could be sanidine) cossyrite. Groundmass: Glass (n = 1.510), quartzo-feldspathic aggregates, accessory riebeckite, more common than aegirine.

No. 1156

REMARKS: TiO_2 trace.

MINERALOGY: Phenocrysts: Rounded anorthoclases. Groundmass: Quartz-anorthoclase, common riebeckite (no aegirine); accessory biotite, magnetite; no cossyrite.

No. 1157

REMARKS: TiO_2, trace.

MINERALOGY: Anorthoclase. Groundmass: Quartz-anorthoclase, no femics, extremely fine-grained yellowish background material.

No. 1158

REMARKS: TiO_2 and MnO traces; no separate H_2O- determination.

MINERALOGY: Very similar to Jimma pantellerites (1155-7). Phenocrysts: Anorthoclase. Groundmass: Quartz-anorthoclase, minute aegirine, rare cossyrite; calcite-lined vesicles.

No. 1159

REMARKS: P_2O_5 absent.

MINERALOGY: Phenocrysts: Anorthoclase, zoned aegirine-augite, cossyrite. Groundmass: Spherulitic and fluidal glass, rare magnetite, fragments of trachy-andesite (bearing augite with arfvedsonite rims) and trachyrhyolite.

No. 1160

REMARKS: P_2O_5 trace.

MINERALOGY: Phenocrysts: Micro-phenocrysts of anorthoclase and aegirine-augite. Groundmass: Finely vesicular glass, feldspathic microlites, cossyrite.

OTHER INFORMATION: Occurs as schlieren in 1159.

No. 1161

MINERALOGY: Ophitic texture: zoned labradorite and titanaugite, both in large crystals. Common limonitised magnetite.

OTHER INFORMATION: Occurs in a laccolith, where this rock-type grades into orthoclase gabbro (see 1164).

No. 1162

MINERALOGY: Ophitic diabasic texture. Groundmass: Zoned An70 (center) to An45 (rim); abundant titanaugite; abundant magnetite, also as inclusions in plagioclase; talc-chlorite after olivine.

No. 1163

REMARKS: Published summation is 100.96.

MINERALOGY: Aphanitic, semi-ophitic texture. Groundmass: An65, titanaugite, fresh olivine (large negative optic angle) all in equal abundance; much magnetite, minute apatite.

No. 1164

REMARKS: CO_2 trace. Highly potassic rock.

MINERALOGY: Medium-grained, ophitic texture. Groundmass: Fresh An65-70, Sericitised orthoclase, abundant augite; rare biotite, apatite, magnetite, ilmenite, pyrite; cavities with quartz and calcite.

OTHER INFORMATION: Occurs in laccolith, where it grades into rock-type 1161.

No. 1165

MINERALOGY: Black, fine-grained, ophitic rock. Groundmass: Poorly zoned An58-55 (very rarely phenocrysts), abundant large augite, small green olivines, common large magnetite, rare limonite and apatite.

OTHER INFORMATION: Occurs at margin of large laccolith.

No. 1166

MINERALOGY: Fine-grained. Phenocrysts: Micro-phenocrysts of zoned An70 (center) - An35 (rim). Groundmass: Labradorite; fresh olivine (large negative optic angle) with incipient alteration, diopside-augite as common as olivine; rare biotite associated with magnetite (coarse-grained); rare apatite.

No. 1167

REMARKS: Published summation is 100.33. C1 trace.

MINERALOGY: Very fine-grained, aphanitic, grey rock. Groundmass: Flow-texture; orthoclase (also some phenocrysts) and slightly subordinate nepheline, rather uncommon aegirine-augite with aegirine rims, rare muscovite (katapleite?); no observed sodalite, lavenite, or wöhlerite.

OTHER INFORMATION: Specific gravity 2.57. This rock-unit has flowed out on the Antalo Limestone.

No. 1168

MINERALOGY: Holocrystalline. Groundmass: An42, titanaugite, fresh olivine, magnetite.

No. 1169

REMARKS: P_2O_5 trace. A potassic rock.

MINERALOGY: Vetrose base. Phenocrysts: An60-65. Groundmass: Plagioclase, iddingsitised olivine, rare brown augite.

No. 1170

MINERALOGY: Flow-texture. Groundmass: Sanidine, aegirine-augite, magnetite, calcite.

OTHER INFORMATION: Possibly a welded tuff.

No. 1171

MINERALOGY: Flow-texture. Groundmass: Sanidine (An40?), aegirine-augite, large magnetite octahedra, rare calcite.

OTHER INFORMATION: Possibly a welded tuff.

No. 1172

MINERALOGY: Groundmass: K-feldspar, nepheline, aegirine, rare magnetite.

No. 1173

MINERALOGY: Vetrose base. Phenocrysts: Sanidine. Groundmass: Glass with some feldspar, aegirine, magnetite.

No. 1174

MINERALOGY: Holocrystalline, flow-textured. Groundmass: Very dominant K-feldspar; nepheline, aegirine, magnetite, chlorite.

No. 1175

REMARKS: P_2O_5 trace.

MINERALOGY: Phenocrysts: Sanidine. Groundmass: Dominant alkali feldspar; some sodic plagioclase, arfvedsonite; rare quartz, muscovite, epidote, barkevikite(?).

OTHER INFORMATION: Imprecise locality.

No. 1176

REMARKS: Published summation is 100.41.

MINERALOGY: Abundant glass shows in H_2O content. Phenocrysts: Sanidine. Groundmass: Sanidine, sodic plagioclase, green pyroxene, magnetite, all set in glass; no quartz; spherulites bear calcite.

OTHER INFORMATION: Locality not identified.

No. 1177

MINERALOGY: Groundmass: Dark brown glass, possible femic microlites, bands of fine vesicles.

OTHER INFORMATION: Locality not identified.

No. 1178

MINERALOGY: Highly scoriaceous rock. Groundmass: Dark-brown glass, corroded Mg-rich olivine and augite (augite crystallised after olivine), feldspar microlites.

OTHER INFORMATION: Young lava of Aden Series.

No. 1179

MINERALOGY: Phenocrysts: Olivine, rare brown augite. Groundmass: Basic plagioclase, abundant femics (olivine and augite(?), magnetite.

No. 1180

REMARKS: Very high water content.

MINERALOGY: Phenocrysts: Large An70, rare augite. Groundmass: Medium grained, rare large vesicles; An70(?), abundant augite; serpentinised olivine, glass; magnetite.

No. 1181

REMARKS: Titaniferous, sub-aluminous.

MINERALOGY: Phenocrysts: Olivine showing resorbtion, rare titanaugite. Groundmass: Feldspar, augite, magnetite.

OTHER INFORMATION: Locality not identifiable.

No. 1182

MINERALOGY: Phenocrysts: Abundant fresh Mg-rich olivine. Groundmass: Olivine, titanaugite, subordinate plagioclase An55, glass, magnetite.

OTHER INFORMATION: Recent lava; locality not identifiable. Analysis of scolecite from north of Danqual hot springs (locality not identifiable): SiO_2 45.40%, Al_2O_3 26.26%, total iron as Fe_2O_3 0.16%, MgO 13.76%, Na_2O 0.72%, K_2O 0.18%, total H_2O 13.75%, summation 100. 23.

No. 1183

REMARKS: High water content.

MINERALOGY: Groundmass: Yellow-brown glass with rare magnetite and rare vesicles, serpentinised olivine, augite, An70.

OTHER INFORMATION: Locality not identified.

No. 1184

MINERALOGY: Phenocrysts: Somewhat altered olivine. Groundmass: Plagioclase, augite, olivine, magnetite.

OTHER INFORMATION: Locality not identified.

No. 1185

REMARKS: Sub-calcic-magnesic.

MINERALOGY: Extemely fine-grained rock. Groundmass: Abundant plagioclase, glass, augite, idding-sitised olivine (occasional phenocrysts), magnetite.

No. 1186

MINERALOGY: Groundmass: Preponderant brown glass, augite, corroded olivine, magnetite, rare plagioclase.

OTHER INFORMATION: Finely scoriaceous, young lava of Aden Series.

No. 1187

MINERALOGY: Groundmass: Fine-grained actinolite and altered plagioclase, nodules of serpentinite(?) and magnetite.

OTHER INFORMATION: Precise nature of this rock is uncertain. From 100 m below the summit of Selki: altered quartz-gabbro, composed of abundant zoned An67, actinolite, epidote, chlorite, common magnetite, brown titanite, rare quartz.

No. 1188

MINERALOGY: Coarsely scoriaceous rock. Phenocrysts: An70-75, olivine, augite. Groundmass: Plagioclase, magnetite, glass, femics(?), no zeolites.

OTHER INFORMATION: Locality not identified.

No. 1189

MINERALOGY: Phenocrysts: Small plagioclase, titanaugite, olivine, Groundmass: Plagioclase, magnetite, augite.

No. 1190

MINERALOGY: Abundant An65, augite, iddingsitised olivine. Groundmass: Plagioclase, abundant magnetite, altered olivine.

No. 1191

MINERALOGY: Very fine-grained, minutely vesicular rock. Phenocrysts: Zoned An70 (center) to An73 (rim), small serpentinised olivines. Groundmass: Plagioclase, abundant magnetite, augite.

OTHER INFORMATION: Locality not identified.

No. 1192

MINERALOGY: Aphyric, with rare vesicles. Groundmass: Abundant brown augite, uncommon An50, rather altered olivine, scarce magnetite, some brown glass.

OTHER INFORMATION: Young lava of Aden Series.

No. 1193

MINERALOGY: Groundmass: Abundant An60-55, common augite, fresh Mg-rich olivine, black glass, rare magnetite.

OTHER INFORMATION: Locality not identified.

No. 1194

REMARKS: H_2O+ and CO_2 together equal 1. 39%; high alumina, high alkalis.

MINERALOGY: Extremely fine-grained. Groundmass: An52, magnetite, olivine(?), calcite (signs of alteration).

OTHER INFORMATION: Locality not identified.

No. 1195

MINERALOGY: Medium-grained. Groundmass: Rather large anhedral augite, An70, scarce altered olivine, magnetite, glass(?).

OTHER INFORMATION: Locality not identified.

No. 1196

MINERALOGY: Phenocrysts: An70 (center) to An60 (rim). Groundmass: An50, rather rare augite, iddingsitised olivine, no glass.

OTHER INFORMATION: Another specimen from this locality had plagioclase about 10% An more calcic in both phenocrysts and groundmass.

No. 1197

MINERALOGY: Phenocrysts: An50, anorthoclase, very large titanaugite, uncommon aegirine-augite, brown hornblende with rim of augite and magnetite. Groundmass: Plagioclase, augite, magnetite, no olivine.

No. 1198

MINERALOGY: Fine-grained, aphyric. Groundmass: Minute sanidine, common nepheline, green hornblende, rather large barkevikite, pale-pink cancrinite, very rare colourless pyroxene, red-brown iron-oxide (cossyrite?).

No. 1199

MINERALOGY: Fine-grained, aphyric. Groundmass: Minute sanidine (anorthoclase?) common nepheline, green hornblende, rather large barkevikite, very rare colourless pyroxene, red-brown iron-oxide (cossyrite?).

No. 1200

MINERALOGY: Very fine-grained, aphyric. Groundmass: Sodic plagioclase(?), K-feldspar, pale yellow nepheline, rare aegirine or aegirine-augite, magnetite, glass.

No. 1201

MINERALOGY: Very fine-grained, aphyric. Groundmass: Sodic plagioclase(?), K-feldspar, pale yellow nepheline, rare aegirine or aegirine-augite, magnetite, glass.

OTHER INFORMATION: Termed “nepheline trachyte” by Comucci (also 1200).

No. 1202

MINERALOGY: Groundmass: Yellow-brown glass, some aegirines; microlites anorthoclase, magnetite, and femics.

OTHER INFORMATION: Locality not identified.

No. 1203

REMARKS: Potassic quartz-trachyte.

MINERALOGY: Phenocrysts: Corroded anorthoclase, rare aegirine. Groundmass: K-feldspar, augite, magnetite, quartz(?), plagioclase(?), limonite(?).

OTHER INFORMATION: Locality not identified.

No. 1204

MINERALOGY: Finely scoriaceous rock. Groundmass: Yellow glass, sanidine, magnetite, mica(?), zeolite(?).

OTHER INFORMATION: Locality not identified.

No. 1205

REMARKS: Potassic rock.

MINERALOGY: Phenocrysts: K-feldspar. Groundmass: Holocrystalline quartz, slightly altered K-feldspar, some anorthoclase(?), epidote, iron-oxide.

OTHER INFORMATION: Locality not identified.

No. 1206

MINERALOGY: Groundmass: Yellow-brown (partly devitrified), corroded anorthoclase.

OTHER INFORMATION: Locality not identified.

No. 1207

REMARKS: Potassic rock.

MINERALOGY: Groundmass: Abundant red-brown glass (with spherulites), sanidine, corroded anorthoclase(?), common quartz, phlogopite, magnetite.

No. 1208

REMARKS: Potassic rock.

MINERALOGY: Phenocrysts: Very rare quartz and sanidine. Groundmass: Holocrystalline quartz and K-feldspar spherulites, aegirine-augite.

OTHER INFORMATION: Imprecise locality.

No. 1209

MINERALOGY: Fine-medium grained. Groundmass: Holocrystalline, spherulites, abundant limonite, quartz, anorthoclase, no femics.

No. 1210

REMARKS: Published summation is 99.69; the error would appear to lie in either SiO_2 or Al_2O_3.

MINERALOGY: Phenocrysts: Zoned An72 (center) to An57 (rim). Groundmass: Mostly glass; rare feldspar, pyroxene, fresh olivine, magnetite, ilmenite.

No. 1211

REMARKS: P_2O_5 trace.

MINERALOGY: Penocrysts: Titanaugite, zoned olivine (Fa16 center; Fa28 periphery). Groundmass: Labradorite-bytownite, abundant magnetite, rare glass, apatite.

OTHER INFORMATION: Mode: 26% pyroxene phenocrysts, 18% olivine phenocrysts, 56% groundmass.

No. 1212

MINERALOGY: Phenocrysts: Titanaugite, serpentinised (net pattern) olivine Fa25 An70. Groundmass: Pyroxene, altered olivine, plagioclase, magnetite, rare biotite, very rare brown hornblende; tiny calcite veins cut this rock.

OTHER INFORMATION: Mode: 25% pyroxene phenocrysts, 10% olivine phenocrysts, 5% plagioclase phenocrysts, 50% groundmass, 10% serpentine, talc (from olivine).

No. 1213

REMARKS: Published summation is 99.86.

MINERALOGY: Phenocrysts: Titanaugite, fresh olivine (2V = 84°). Groundmass: An65, titanaugite, olivine, magnetite, ilmenite.

No. 1214

MINERALOGY: Phenocrysts: Microphenocrysts: augite, olivine Fa26, almost wholly iddingsitised with serpentine borders. Groundmass: Labradorite, pyroxene, olivine, abundant yellow-ochre glass, common magnetite, octahedra.

OTHER INFORMATION: Mode: 21% augite microphenocrysts, 3% olivine microphenocrysts, 35% pyroxene, olivine, magnetite, 26% glass, 6% plagioclase, 9% serpentine (from olivine).

No. 1215

REMARKS: Published summation 100.28.

MINERALOGY: Phenocrysts: Zoned An83 (center) to An54 (rim). Groundmass: Extremely fine-grained An70, augite, olivine, iron-oxides.

OTHER INFORMATION: The locality of this specimen is suspect, as the Entotto Range is entirely formed of alkali rhyolite and trachyte lavas and tuffs (eg., see 1235).

No. 1216

MINERALOGY: Phenocrysts: An64, not zoned with the exception of a few individual crystals (all in the bytownite-labradorite range); zoned olivine (Fa40 center to Fa30 rim), with iddingsitised margins. Groundmass: An64, completely iddingsitised olivine, augite, common iron-oxides, rare apatite.

No. 1217

REMARKS: CO_2 trace.

MINERALOGY: Phenocrysts: Large (1 cm), zoned An63 (center) to An58 (rim). Groundmass: Minute plagioclase crystals, altered femics, abundant minute magnetites.

No. 1218

MINERALOGY: Scoriaceous grey lava. Penocrysts: Zoned An70 (center) to An58 (rim), augite, altered olivine (2V - 86°). Groundmass: Plagioclase, augite, altered olivine, magnetite, ilmenite.

No. 1219

MINERALOGY: Fine-grained, flow textured. Phenocrysts: Rare An86 (center) to An57 (rim), very rare serpentinised olivine. Groundmass: An61, pyroxene, olivine, magnetite, yellow glass.

No. 1220

MINERALOGY: Flow-texture. Phenocrysts: Augite, altered olivine. Groundmass: An70, augite, magnetite, green nodules (chalcedony?).

No. 1221

MINERALOGY: Phenocrysts: Abundant zoned An68 (center) to An34 (rim), rare olivine with iddingsitised borders. Groundmass: Plagioclase, pyroxene, olivine, common magnetite, some ilmenite, rather common apatite, secondary calcite.

No. 1222

REMARKS: Hieke-Merlin (1950) gives for this analysis two summations: 99-46% on p. 16 and 99.94% on p. 26; neither agrees with the total of oxide values.

MINERALOGY: Groundmass: Zoned An62 (center) to An54 (rim), augite, very abundant magnetite, partly devitrified brown glass, some ilmenite, calcite in cavities.

No. 1223

REMARKS: Published summation is 99.87; CO_2, trace.

MINERALOGY: Groundmass: Zoned An68 (center) to An56 (rim), Fe-rich augite, scarce altered olivine, magnetite, ilmenite, some calcite-filled vesicles.

No. 1224

REMARKS: Republication of analysis 1151 (see remarks under 1151 for manner of re-adjusting some oxide values).

MINERALOGY: Extremely fine-grained. Phenocrysts: Very rare An61-59. Groundmass: Plagioclase, pyroxene, magnetite, green glass, very rare olivine.

No. 1225

REMARKS: Republication of analysis 1152, but under different locality; three types of basalt from this region are discussed, but the analysed one is not distinguished. No separate determination of H_2O-.

MINERALOGY: Very fine-grained. Groundmass: Labradorite-bytownite, augite, rare altered olivine, yellow glass, magnetite, ilmenite.

No. 1226

MINERALOGY: Fine-grained, flow-textured. Groundmass: An60-58, pyroxene, rarer olivine, magnetite, apatite; geodes bearing pyroxene, biotite, brown hornblende (2V = 80°).

No. 1227

MINERALOGY: Phenocrysts: Anorthoclase (corroded crystals with secondgeneration anorthoclase and glass on rims), rare sanidine, aegirine-augite. Groundmass: K-feldspar, plagioclase, aegirine-augite, common magnetite, some apatite.

No. 1228

MINERALOGY: Cryptocrystalline. Groundmass: Glass with An45 and magnetite, scarce apatite, calcite, altered pyroxene(?).

No. 1229

MINERALOGY: Phenocrysts: Microphenocrysts of An38, aegirine-augite, and Fe-oxide. Groundmass: Feldspar, glass, magnetite, aegirine-augite.

No. 1230

REMARKS: Potassic rock.

MINERALOGY: Welded tuff(?). Phenocrysts: Sanidine. Groundmass: Fluidal glass, with sanidine and Fe-oxides.

No. 1231

REMARKS: MnO trace; potassic rock.

MINERALOGY: Phenocrysts: K-feldspar (sanidine?). Groundmass: Trachytic texture, sanidine, plagioclase, quartz, haematite, limonite.

No. 1232

MINERALOGY: Phenocrysts: Rare sanidine/anorthoclase. Groundmass: Fluidal glass, quartz, feldspar, aegirine-augite, rare magnetite, limonite, calcite.

OTHER INFORMATION: Derived from the Ayelu volcanic center (see also 1237).

No. 1233

REMARKS: Originally published by O. Hieke (1941). Potassic rock.

MINERALOGY: Vitric crystal tuff with lenses and layers of obsidian schlieren. Phenocrysts: Corroded quartz, anorthoclase (2V 38 = 40°), brown hornblende. Groundmass: Yellow-brown glass, cossyrite, magnetite, microlites of arfvedsonite-riebeckite(?).

No. 1234

REMARKS: Potassic rock.

MINERALOGY: Aphyric. Groundmass: Sanidine, quartz, plagioclase, aegirine, limonite, cossyrite(?).

No. 1235

REMARKS: Originally published by O. Hieke (1941).

MINERALOGY: Wholly glassy with rare signs of devitrification.

OTHER INFORMATION: This obsidian occurs in flow-banded vitric trachyrhyolite.

No. 1236

REMARKS: Potassic rock.

MINERALOGY: Porphyritic, with some micropegmatitic texture. Phenocrysts: Sanidine, barkevikite-riebeckite more common than aegirine-augite, both rimmed with aegirine. Groundmass: sanidine, quartz, riebeckite, aegirine, cossyrite (with aegirine rims), iddingsitised Fa88 (with aegirine rims), limonite; no glass, no plagioclase.

No. 1237

MINERALOGY: Groundmass: Glass with abundant crystallites of anorthoclase; magnetite, uncommon aegirine-augite; no quartz(?).

No. 1238

MINERALOGY: Spherulitic texture. Phenocrysts: Strongly resorbed K-feldspar phenocrysts, composed of anorthoclase (2V=50°) accreted on orthoclase (2V=61°). Groundmass: Spherulites composed of orthoclase(?) and chalcedony; haematite, magnetite, zircon; zeolites in cavities.

No. 1239

REMARKS: Originally published by O. Hieke (1941).

MINERALOGY: Groundmass: Fluidal glass; crystallites of feldspar, apatite, zircon, green pyroxene.

OTHER INFORMATION: This rock forms characteristic cupolas, presumably formed by trapped gases.

No. 1240

REMARKS: TiO_2, MnO, P_2O_5, CO_2 traces; strongly potassic rock.

MINERALOGY: Microspherulitic texture. Groundmass: Spherules of orthoclase (sanidine?) and chalcedony; quartzo-feldspathic mosaic between spherules; some haematite, limonite, calcite.

No. 1241

MINERALOGY: Phenocrysts: Anhedral quartz, euhedral sanidine. Groundmass: Quartz, sanidine titaniferous sodic hornblende, magnetite, limonite, apatite, glass.

No. 1242

REMARKS: P_2O_5 trace.

MINERALOGY: Phenocrysts: Corroded quartz, sanidine (2V=41°). Groundmass: Quartz, sanidine, albite, aegirine-augite, barkevikite.

No. 1243

REMARKS: No separate determination of H_2O-.

MINERALOGY: Phenocrysts: Diopside-augite and titanaugite, fresh olivine Fa 11, with bowlingite rims. Groundmass: Augite, olivine, labradorite microlites, magnetite.

OTHER INFORMATION: Mode: 23% labradorite, 49.5% augite, 1 3.5% olivine, 14% magnetite.

No. 1244

MINERALOGY: Phenocrysts: Large diopside (or diopside-augite) and younger zoned titanaugite, olivine. Groundmass: Augite, olivine, magnetite, labradorite microlites.

OTHER INFORMATION: Mode: 14% labradorite, 62% pyroxene, 7.5% magnetite, 16.5% serpentine (mostly after olivine).

No. 1245

REMARKS: CO_2 trace.

MINERALOGY: Groundmass: Pyroxene more abundant than olivine, magnetite, labradorite with intersertial glass.

OTHER INFORMATION: Mode: 31% labradorite, 28% pyroxene, 6% glass, 15.5% olivine, 19.5% magnetite.

No. 1246

REMARKS: No separate determination of H_2O-.

MINERALOGY: Phenocrysts: Labradorite, titanaugite, olivine Fa18. Groundmass: Same minerals as phenocrysts, plus Fe-oxides.

OTHER INFORMATION: Mode: 62.2% labradorite, 13.5% pyroxene, 8.1% olivine, 5.4% serpentine and chlorite, 10.8% magnetite and ilmenite.

No. 1247

REMARKS: No separate determination of E_2O-.

MINERALOGY: Phenocrysts: An58, and titanaugite together make up about 30% of rock. Groundmass: An50 microlites, titanaugite, magnetite, rare glass, chlorite, calcite, epidote.

OTHER INFORMATION: Mode: 50% labradorite, 12% augite, 22% magnetite (and ilmenite), 8% chlorite, 8% calcite and epidote.

No. 1248

REMARKS: CO_2 trace.

MINERALOGY: Groundmass: Vesicular black glass, with minute magnetite(?), few laths labradorite, some olivines, rare titanaugite.

OTHER INFORMATION: Mode: 11.8% labradorite, 17.6% olivine, 70.6% glass and iron-ores.

No. 1249

MINERALOGY: Phenocrysts: Olivine (slightly iddingsitised). Groundmass: Labradorite laths, titanaugite, magnetite; no glass.

OTHER INFORMATION: Mode: 44.2% labradorite, 26.4% olivine, 23.5% pyroxene, 5.8% magnetite.

No. 1250

REMARKS: CO_2 trace; published summation is 100.913.

MINERALOGY: Groundmass: Predominant glass, with labradorite, pyroxene, magnetite.

No. 1251

REMARKS: No separate determination of H_2O-.

MINERALOGY: Phenocrysts: Large labradorite (forms 62% of whole rock). Groundmass: Andesine-labradorite, magnetite, chlorite, calcite, vesicles with epidote.

No. 1252

MINERALOGY: Phenocrysts: Large labradorite, rare green hornblende. Groundmass: Andesine-labradorite, magnetite; amygdales with chlorite, epidote, calcite, orthoclase, quartz.

No. 1253

REMARKS: CO_2 trace.

MINERALOGY: Aphyric texture. Groundmass: Andesine-oligoclase laths, olivine Fa42, scarce diopside-augite, magnetite, orthoclase(?) microlites.

OTHER INFORMATION: Mode: ca. 50% plagioclase, ca. 20% olivine.

No. 1254

REMARKS: No separate determination of H_2O-; this rock would have been termed “grorudite” by some Ethiopian authors.

MINERALOGY: Phenocrysts: Anorthoclase, scarce albite. Groundmass: Trachytic texture; anorthoclase, quartz, magnetite and haematite (after riebeckite).

OTHER INFORMATION: Mode: 64.5% anorthoclase and albite, 8.5% quartz, 27% iron oxides.

No. 1255

REMARKS: Same rock as 1266.

MINERALOGY: Phenocrysts: Euhedral Na-sanidine, less common and larger anorthoclase. Groundmass: Trachytic texture; sanidine, riebeckite, aegirine, iron-oxides.

OTHER INFORMATION: Mode: 77.5% sanidine, 10% anorthoclase, 9.5% riebeckite, 3% magnetite and haematite.

No. 1256

REMARKS: Same rock as 1255; no separate determination of E_2O-,.

MINERALOGY: See under 1255.

No. 1257

REMARKS: Same rock as 1258.

MINERALOGY: Phenocrysts: Anorthoclase, scarce An8, scarce dark-brown biotite. Groundmass: Trachytic texture; anorthoclase, rare aegirine-augite, katophorite, magnetite-haematite, quartz.

OTHER INFORMATION: Mode: 74.2% anorthoclase, 4% quartz, 5.1% albite, 15.5% iron-oxides (altered femics), 1.2% biotite and chlorite.

No. 1258

REMARKS: Same rock as 1257; no separate determination of H_2O-.

MINERALOGY: See under 1257.

No. 1259

REMARKS: No separate determination of H_2O-.

MINERALOGY: Phenocrysts: Na-sanidine. Groundmass: Quartz-feldspar microspherulites, riebeckite.

OTHER INFORMATION: Mode: 36.5% quartz, 50.5% Na-sanidine, 13% riebeckite. Aegirine-katophorite pantellerites occur at Hais, Wessil, Hadjellah, Manaka.

No. 1260

REMARKS: Same rock as 1261; no separate determination of H_2O-.

MINERALOGY: See under 1261.

No. 1261

REMARKS: Published summation is 99.90; same rock as 1260.

MINERALOGY: Phenocrysts: Corroded quartz, Na-sanidine. Groundmass: Up to 80% spherulitic quartz-feldspar intergrowth, also micrographic texture with myrmekite, some haematite and magnetite, no femics.

OTHER INFORMATION: Mode: 35.9% quartz, 61.7% Na-sanidine, 2.3% iron-oxides. Also, a comendite from El-Barh (between Ta’iz and Mokha) contains 77.24% SiO_2, 4.14% Na_2O, 3.77% K_2O, and is composed of quartz and Na-Sanidine phenocrysts, in a fluidal, microspherulitic ground mass with aegirine.

No. 1262

MINERALOGY: Phenocrysts: Oligoclase-andesine, orthoclase, small, sometimes euhedral olivine ca. Fa70, pale-green diopside (euhedral). Groundmass: An30 microlites (trachytic texture), magnetite, orthoclase, pyroxene, olivine, apatite, rare glass.

OTHER INFORMATION: Mode: 56.7% oligoclase-andesine, 10.0% orthoclase, 7.2% olivine, 5.3% diopside-augite, 19.6% magnetite and haematite, 1.2% apatite.

No. 1263

REMARKS: MnO absent; no separate determination of H_2O-.

MINERALOGY: Phenocrysts: Anorthoclase/Na-sanidine, aegirine-augite, rare albite. Groundmass: Pale-grey perlitic glass, aegirine-augite microlites.

OTHER INFORMATION: Mode: 31.5% Na-sanidine, 3.3% aegirine-augite, 63.2% glass.

No. 1264

MINERALOGY: Incomplete description. Phenocrysts: Olivine. Groundmass: An70, scarce magnetite, some calcite.

OTHER INFORMATION: Occurs intercalated in the Lower Dogali Beds.

No. 1265

MINERALOGY: Incomplete description. Groundmass: An70, abundant magnetite.

OTHER INFORMATION: Occurs intercalated in the Lower Dogali Beds. Manasse (1908) notes the occurrence of a porphyritic uralite basic rock from Desset (where Neogene sediments outcrop).

No. 1266

REMARKS: Published summation is 100.08.

MINERALOGY: Phenocrysts: Abundant An23, somewhat altered and with inclusions of apatite, augite. Groundmass: Plagioclase, green pleochroic augite rimmed and fissured with chlorite and magnetite, strongly corroded hornblende.

No. 1267

REMARKS: Published summation is 99.96; TiO_2 and MnO traces; potassic rock.

MINERALOGY: Phenocrysts: Corroded sanidine, uncommon euhedral quartz. Groundmass: Spherulitic, devitrified cristobalite grains, tridymite aggregates, intense-green, pyroxene (non-pleochroic) — aegirine-augite(?).

No. 1268

REMARKS: Also for 1270, 1274, 1275, 1276, 1277.

MINERALOGY: General description for the above numbered specimens. Phenocrysts: Zoned An50-40 (not always present). Groundmass: Microlites An40-28, glass with small crystals olivine (Fa20-30, occasionally Fa50), and later titanaugite, iron-oxides, no ortho-pyroxene, no pigeonite.

OTHER INFORMATION: This is the most abundant rock-type of the Erta-ali volcanic chain. The basalts have a high TiO_2 content and high Na/K. The norms are frequency quartz-bearing.

No. 1269

MINERALOGY: Phenocrysts: Abundant small olivines (Fa15-20), An70, titanaugite. Groundmass: An60-55, titanaugite, olivine, scarce black glass with iron-oxides, late-stage alkali feldspar.

No. 1270

REMARKS: See under 1268.

No. 1271

MINERALOGY: As for 1269, except plagioclase phenocrysts much more abundant than olivine.

No. 1272

REMARKS: See under 1269.

No. 1273

REMARKS: See under 1271.

No. 1274

REMARKS: See under 1268.

No. 1275

REMARKS: See under 1268.

No. 1276

REMARKS: See under 1268.

No. 1277

REMARKS: See under 1268.

No. 1278

MINERALOGY: Aphyric; dark rocks extremely finegrained. Groundmass: Abundant glass with magnetite, abundant sodic plagioclase (ca. 50% mode), some pale-coloured clinopyroxene.

OTHER INFORMATION: Forms flows at the northern end of the Erta-ali chain, and also an end-phase posterior to the alkali rhyolites of the chain volcanoes.

No. 1279

REMARKS: See under 1278.

No. 1280

REMARKS: No separate determination of H_2O-.

MINERALOGY: Phenocrysts: Scarce An28, colourless pyroxene, fayalite. Groundmass: Glass, with very finegrained anorthoclase and tridymite (determined by X-rays).

OTHER INFORMATION: Forms dark blocky lava in flows 30-50 m thick.

No. 1281

REMARKS: See under 1280.

No. 1282

REMARKS: See under 1284.

No. 1283

REMARKS: See under 1284.

No. 1284

REMARKS: Also for 1282, 1283, 1285, 1286. No separate determination of H_2O-; H_2O+ is loss on heating; high Na/K ratio in rhyolites (less marked in pantellerites despite higher total alkalis).

MINERALOGY: Phenocrysts: An18, occasional corroded An38-40, rather uncommon pyroxene and fayalitic olivine. Groundmass: Predominantly glassy.

No. 1285

REMARKS: See under 1284.

No. 1286

REMARKS: See under 1284.

No. 1287

MINERALOGY: Phenocrysts: An79, olivine Fa14, clinopyroxene. Groundmass: Plagioclase, olivine, clinopyroxene, magnetite; zeolites.

No. 1288

MINERALOGY: Phenocrysts: An80-71, olivine Fa16. Groundmass: An59, Fa24, clinopyroxene, magnetite, haematite, serpentine, calcite.

No. 1289

MINERALOGY: Phenocrysts: Olivine Fa14. Groundmass: An70-60, olivine, clinopyroxene, magnetite, biotite, calcite.

No. 1290

MINERALOGY: Not given.

No. 1291

MINERALOGY: Phenocrysts: An66-53, olivine Fa32, clinopyroxene, magnetite. Groundmass: Plagioclase, clinopyroxene, magnetite.

No. 1292

MINERALOGY: (General description for the Jebel Umm Birka trachy-basalts). Phenocrysts: Subhedral plagioclase forming up to 25% of rock (zoned labradorite-andesine), small pale-brown clinopyroxene, sometimes subhedral magnetite, Fa16-40. Groundmass: Plagioclase laths (An61-48) with zoning out to more sodic composition; interstitial magnetite, clinopyroxene, olivine (or iddingsite); sometimes brown glass, alkali feldspar, apatite, zeolite.

No. 1293

MINERALOGY: See under 1292.

No. 1294

MINERALOGY: Phenocrysts: Large subhedral plagioclase, zoned both progressively and oscillatory between An63-18, often with albitic rims. Groundmass: Colourless pyroxene, serpentinised olivine, magnetite, accessory albite, alkali feldspar-quartz intergrowths.

No. 1295

MINERALOGY: See under 1296.

No. 1296

MINERALOGY: Sub-trachytic texture. Phenocrysts: An38-29, clinopyroxene, magnetite. Groundmass: Plagioclase, clinopyroxene, magnetite, alkali feldspar (interstitial), apatite.

No. 1297

MINERALOGY: Phenocrysts: Oligoclase-andesine, magnetite, pale-green augite. Groundmass: Trachytic texture; albite-oligoclase; scarce magnetite, serpentine (after olivine), apatite.

No. 1298

MINERALOGY: Medium-grained, equigranular. Groundmass: Mode: 70% alkali feldspar (anorthoclase); 5% oligoclase (An27); 10% quartz; 15% green clinopyroxene, sodic amphibole, magnetite. Femic minerals may be complexly zoned, with pyroxene and amphibole occurring in the same crystal, and showing end-stage alkali enrichment.

No. 1299

MINERALOGY: Not given.

No. 1300

MINERALOGY: Phenocrysts: Anorthoclase, olivine Fa94, sodic ferro-hedenbergite, magnetite. Groundmass: Same minerals as phenocrysts, plus quartz.

No. 1301

MINERALOGY: Phenocrysts: Euhedral anorthoclase, bright-green sodic ferro-hedenbergite. Groundmass: Very fine-grained quartz, alkali feldspar, small needles green clinopyroxene, accessory haematite, sodic amphibole (cossyrite?).

No. 1302

MINERALOGY: See under 1300.

No. 1303

MINERALOGY: Phenocrysts: Common anorthoclase, rare sodic ferro-hedenbergite, rare fayalitic olivine, magnetite. Groundmass: Quartz, feldspar, sodic pyroxene, magnetite, sodic amphibole (riebeckite); accessory fluorite, zircon, devitrified glass.

No. 1304

MINERALOGY: See under 1301. Phenocrysts: Additional cossyrite.

No. 1305

MINERALOGY: See under 1301.

No. 1306

MINERALOGY: Similar to 1303.

No. 1307

MINERALOGY: See under 1301.

No. 1308

MINERALOGY: Similar to 1303.

No. 1309

REMARKS: Analysis made on powder dried at 110°C.

MINERALOGY: Weakly porphyritic. Phenocrysts: Zoned An45 (center) - An60 (rim), augite (2V = +50°), hypersthene (En68). Groundmass: Hyalopilitic structure with sparse microlites of An64-67, rare pyroxene, common magnetite.

No. 1310

REMARKS: See under 1309.

MINERALOGY: Weakly porphyritic. Phenocrysts: Zoned An58 (center) - An62 (rim), augite (2V = +50°). Groundmass: Interstitial An62 microlites, augite, skeletal magnetite, rare ilmenite, brown glass; some euhedral serpentinised Fa20.

No. 1311

REMARKS: SiO_2 determined to three significant figures. Sample dried at 105°C prior to analysis. P_2O_5 less than 0.05%. Published summation is 99.90%.

MINERALOGY: Aphyric glass.

No. 1312

REMARKS: See under 1311. SiO_2 quoted as “by difference” (this would seem to apply more appropriately to 1311 with its 100.00 summation and its identical SiO_2 content).

MINERALOGY: Same as 1311.

No. 1313

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1314

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1315

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1316

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1317

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1318

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1319

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1320

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1321

REMARKS: See under 1311.

MINERALOGY: Same as 1311.

No. 1322

MINERALOGY: Fine-grained rock. Phenocrysts: Occasional clusters of large, oscillatory-zoned labradorite laths intergrown with colourless augite; numerous microphenocrysts of serpentinised olivine. Groundmass: Fresh labradorite (sometimes zoned to oligoclase), intergranular colourless augite and iron-ore, interstitial pale-brown glassy mesostasis.

OTHER INFORMATION: 1-1/2 - 2 m wide dyke cutting alkali olivine basalt lavas of the early Miocene Simien center.