Alkaline Rocks and Carbonatites of the World

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Ali Sabieh (Aysha)

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Occurrence number: 
045-00-005
Country: 
Djibouti
Location: 
Longitude: 42.78, Latitude: 11.17

The Ali Sabieh-Aysha horst extends southwards into Ethiopia and along its northwestern and eastern margins are rhyolitic rocks which are correlated with the Mablas rhyolites of the North Tadjura area (No. 2) (Varet, 1978). The more easterly group are referred to as the Ali Adde rhyolites and these are older than the northwestern group of rhyolites. The rhyolites are peralkaline and the brief petrographic details given for the North Tadjoura area apply also to Ali Sabieh (Gadalia and Varet, 1983). Major and trace elements, including REE and Sr, Nd and Pb isotopic data, are given for rocks by Deniel et al. (1994).

Age: 
K-Ar age determinations on the Ali Adde rhyolites gave 25-19 Ma and on the Mablas rhyolites 15-10 Ma (Chessex et al., 1975; Gadalia and Varet, 1983).
References: 
CHESSEX, R., DELALOYE, M., MULLER, J. and WEIDMANN, M. 1975. Evolution of the volcanic region of Ali Sabieh (T.F.A.I.), in the light of K-Ar age determinations. In A. Pilger and A. Rosler (eds), Afar Depression of Ethiopia. 221-7. Inter-Union Commission on Geodynamics, Scientific Report 14. E. Schweizerbart'sche Verlagsbuchhandlung (Nagele u. Obermiller). Stuttgart. DENIEL, C., VIDAL, P., COULON, C., VELLUTINI, P.-J. and PIGUET, P. 1994. Temporal evolution of mantle sources during continental rifting: the volcanism of Djibouti (Afar). Journal of Geophysical Research, 99, B2: 2853-69.GADALIA, A. and VARET, J. 1983. Les rhyolites Miocènes de l'est de l'Afar. Bulletin de la Société Géologique de France, Serie 7. 25: 139-53.
Location: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith