Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Chilwa Province
Longitude: 35.7, Latitude: -15.8

Michese is an almost perfectly circular intrusion 8 km in diameter that forms a spectacular, shear conical peak rising to some 1700 m above the plain. It lies 3 km north of the Mlanje intrusion from which it is separated by the Fort Lister Gap. The outer contact is close to vertical. Quartz syenite is the principal rock type but along the western and southern margins is a zone up to 800 m wide of granite which appears to be younger than the syenite (Garson and Walshaw, 1969). The quartz syenite consists of perthite, quartz, aegirine, which is extensively replaced by arfvedsonite or riebeckite, and in some rocks a brown-green amphibole and biotite. Accessory aenigmatite, olivine and pyrochlore may be present. The granites are also peralkaline consisting of quartz, perthite, riebeckite, aegirine replaced by riebeckite, and a little aenigmatite. In the rocks of one area altered brown olivine is mantled by aegirine. Accessories include pyrochlore and fluorite.

GARSON, M.S. and WALSHAW, R.D. 1969. The geology of the Mlanje area. Bulletin, Geological Survey of Malawi, 21: 1-157.
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