Experimental studies concerning the genesis of the Nigerian younger granites |
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| Authors: | Dr G C Brown P Bowden |
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| Institution: | (1) Department of Geology, University of Manchester, Manchester;(2) Department of Geology, University of St. Andrews, Fife, Scotland;(3) Present address: Sub-Department of Geophysics, Oliver Lodge Laboratory, University of Liverpool, L69 3BX Liverpool |
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| Abstract: | Partial melting experiments on Nigerian charnockitic monzonite associated with migmatised gneisses provide consanguineous liquids from which the metaluminous and peraluminous younger granites may be derived. After 40–60% melting at 750–800° C the liquids are metaluminous with hastingsite-fayalite granite affinities. On cooling towards the granite system minimum these liquids can evolve into metaluminous hastingsite-biotite granite and peraluminous biotite granite compositions. These experiments show that partial melting of charnockitic monzonites cannot yield peralkaline liquids at the specified conditions (750–850° C).Syenitic rocks of this province may either reflect the action of late stage albitising fluids on residual charnockitic material after partial melt extraction or the collection of feldspar floated from a hastingsite-fayalite granite liquid. |
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