Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: 8.87, Latitude: 13.68

The 35x20 km Zinder occurrence is partly masked by Cretaceous sediments. It consists of biotite, riebeckite and arfvedsonite granites, microgranites and rhyolites with a small isolated intrusion of alkaline syenite lying 6 km to the east. Coarse granites, with microcline perthite crystals 5-10 mm in diameter, are the most abundant rocks. They contain either riebeckite or arfvedsonite with aegirine occurring sporadically. The biotite granite, which is less extensive, contains riebeckite as well as biotite. Both sodic amphiboles and biotite are found in the microgranites.

Rb-Sr gave 330(6 Ma (Bowden et al., 1976).
BESSOLES, B. and TROMPETTE, R. 1980. Geologie de l'Afrique. La chaine panafricaine “zone mobile d’Afrique centrale (parie sud) et zone mobile soudanaise”. Mémoire du Bureau de Recherches Géologiques et Minières, 92: 1-397.BOWDEN, P., VAN BREEMEN, O., HUTCHINSON, J. and TURNER, D.C. 1976. Palaeozoic and Mesozoic age trends for some ring complexes in Niger and Nigeria. Nature, London, 259: 297-9.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith