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Geochemical features of a strongly fractionated alkali igneous suite

1965; Elsevier BV; Volume: 29; Issue: 2 Linguagem: Inglês

10.1016/0016-7037(65)90120-1

1872-9533

G. Siedner,

Geochemistry and Elemental Analysis

Geochemical data for 37 igneous rocks from the Paresis volcanic complex, South West Africa, are presented and discussed. Unusual abundances of certain minor constituents and variation trends of element-ratios support the view that the central rhyolites and syenitic dykes are products of a strongly differentiated magma—probably originating by palingenesis of the basement granite. Granitophile elements are strongly enriched in the rhyolite sequence but their variation in the holocrystalline dykes is more subdued. Differences in trace element distribution between rhyolites and syenitic dykes are attributed largely to the relative prominence of the forces governing diadochy. The abundances and distribution of V, Cr, Ni, Co, Sr, Ba, Ga, Zr, Pb, La, Li, Rb. and Cs are discussed in terms of their relationships to the major rock-forming constituents.