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Authors
Affiliations
1 North Eastern Region, Shillong - 793 003, IN
2 Northern Region, Lucknow-226 024, IN
3 Bangalore-560 078
4 Eastern Region, Kolkata -700 091, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 1 (2007), Pagination: 53-58
Abstract
Early mafic differentiate of quartz diorite to quartz monzodiorite composition related to Mid-ProterozoIc, late to post-tectonic calc-alkaline (diorite-granodiorite) plutons in Meghalaya occur in three different modes, viz. (l)dykes in country rock gneisses along tectonic locales, (2) endogenous inclusions in the diorite-granodionte intrusive plutons, as early differentiated product through fractional crystallization or liquid immiscibility, and (3) xenohths in Upper Proterozoic-Early Palaeozoic granite plutons (Nonpoh granite). These appear to be basic precursors of thc granitoids. The mafic inclusions were subjected to metasomatism by granitoids over an extended period starting with the formation of the granitic differentiates of calc-alkaline intrusions and ending with the placement of the later granitic plutons. Petrology and chemistry of the mafic rocks suggest a possible basic parentage.
Keywords
Calc-Alkaline plutons, Mafic differentiates, Petrology, Meghalaya.
