Application of Biotite Composition in Determination of Petrogenesis of Diorites from Toro and Dass, North Central, Nigeria

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Author(s) Dada, O.A | Ashano, E.C
Pages 164-169
Volume 1
Issue 4
Date April, 2012
Keywords Biotite composition, petrogenesis, diorites, Toro and Dass, North-central Nigeria.

The compositional systematics of biotites from diorites of Toro and Dass, north Central Nigeria have been examined for the purpose of describing the nature of the granitic magma. Based on chemistry of biotites, Toro and Dass diorites are formed from the transition between peraluminous and calc-alkaline magmas. This type of magma is typically produced in subduction environments. It means that the diorites could have formed in an orogenic suit from calc-alkaline magma derived from melting in a subduction zone slab. There is little evidence of either magma mixing or large-scale crustal contamination. The petrographic studies of the representative samples of diorite from Toro show biotite replacing pyroxenes, which necessarily produce a biotite-pyroxene-plagioclase paragenesis from pre-existing assemblage. The Dass diorite samples show biotite overgrowing amphiboles and also replacement of biotite by chlorite.

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