Alkaline Rocks and Carbonatites of the World

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Olsirwa And Loolmalasin


Occurrence number: 
Longitude: 35.8, Latitude: -3.05

The overlapping Olsirwa and Loolmalasin volcanoes are built predominantly of basalt lavas, but some phonolite and trachyte occur on the summit ridge of Loolmalasin and basanite within Olsirwa. The small cone of Oldoinyo Wass several kilometres west of Olsirwa is of tephrite. Three analyses of basalt and trachyte, including trace element and Sr, Nd and Pb isotope data, are in Paslick et al. (1995).

PASLICK, C., HALLIDAY, A.N., JAMES, D. and DAWSON, J.B. 1995. Enrichment of the continental lithosphere by OIB melts: isotopic evidence from the volcanic province of northern Tanzania. Earth and Planetary Science Letters, 130: 109-26.PICKERING, R. 1965. Ngorongoro. Geological Survey of Tanzania, Quarter Degree Sheet, 53.
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