PETROGENESIS OF KUMRAT GRANITE, UPPER DIR, KHYBER PAKHTUNKHWA, PAKISTAN

Abstract

The granitic rocks in Kumrat Valley, Upper Dir, Khyber Pakhtunkhwa, Pakistan are studied in terms of their petrographic and geochemical characteristics. Field relationship and petrographic studies display coarse-grained to porphyritic texture and classify it as a twomica granite. Alkali feldspar, quartz, plagioclase and biotite make the essential minerals whereas muscovite apatite, zircon, titanite and chlorite are the accessory contributors. The modal mineralogy and colour index plots depict calc-alkaline and leucocratic character of the studied rocks. The Harker plots of major element reveal early fractionation of feldspars and biotite from the system. The CaO/(FeO+MgO+TiO2) versus CaO+FeO+MgO+TiO2 and Al2O3/TiO2 versus CaO/Na2O plots show per-aluminous nature and pelitic to psamtic source for this granite. The tectonic discrimination plots predict collisional island arc type of tectonic environment during the formation and emplacement of Kumrat granite.