Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: 9.2, Latitude: 10.15

Emplaced within Archaean gneisses the Kwandonkaya complex covers 190 km2 and is formed wholly of granites with some granite porphyry dykes. There are no associated volcanic rocks. Alkaline rocks are absent from the complex, pyroxenes being hedenbergite and amphiboles ferrohastingsites, and chemical analyses confirm the absence of normative ac (Imeokparia, 1984a). Although part of an essentially alkaline province, and therefore covered briefly here, only the least alkaline magma types are represented in this occurrence. Early quartz-feldspar porphyry dykes were followed by emplacement of hornblende-fayalite granite, hornblende-biotite granite and then four phases of granite and microgranite (Buchanan et al., 1971). Some 26 rock analyses together with analyses of amphibole and biotite are available (Imeokparia, 1984a).

BUCHANAN, M.S., MACLEOD, W.N., TURNER, D.C., BERRIDGE, N.G. and BLACK, R. 1971. The geology of the Jos Plateau. Volume 2, Younger granite complexes. Bulletin, Geological Survey of Nigeria, 32: 1-159.IMEOKPARIA, E.G. 1984a. Geochemistry of the granitic rocks from the Kwandonkaya complex, northern Nigeria. Lithos, 17: 103-15.
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