Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: 10.03, Latitude: 11.1

This is a large, somewhat elongate complex which, being difficult of access, has not been studied in detail. The area is about 285 km2 but the central and northern parts are of low relief with only scattered exposures. The most southwesterly section of the complex is apparently composed of volcanic rocks including crystal-poor and spherulitic varieties but little else is known about these rocks. The rest of the complex is dominated by arfvedsonite granite which is a coarse-grained, equigranular rock in which the arfvedsonite often encloses small crystals of astrophyllite; aegirine is scarce and there is occasional biotite. A distinct area of biotite granite has also been recognised within the arfvedsonite granite and is also to be found in the volcanic area to the southwest; the rock contains accessory topaz and fluorite.

Rb-Sr determinations on three fractions of a biotite granite gave 191(3 Ma (Rahaman et al., 1984).
BENNETT, J.N., TURNER, D.C., IKE, E.C. and BOWDEN, P. 1984. The geology of some northern Nigerian anorogenic ring complexes. Overseas Geology and Mineral Resources, 61: 1-65.RAHAMAN, M.A., VAN BREEMEN, O., BOWDEN, P. and BENNETT, J.N. 1984. Age migrations of anorogenic ring complexes in northern Nigeria. Journal of Geology, 92: 173-84.
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