PETROLOGY OF ROCKS IN THE SINGAL GAH AREA, DISTRICT GHIZER, GILGIT – BALTISTAN, PAKISTAN

Abstract

This thesis presents the petrographic and geochemical study of rocks in the Singal Gah area, Gilgit. Singal Gah area lies within the northern part of Kohistan Island arc terrane. The study area is occupied by the Chalt volcanic group (CVG) of Cretaceous age intruded by the Kohistan batholith (KB). Generally, Chalt volcanic group comprises of tuffs and metavolcanics. Stage I gabbro and stage II diorite and granodiorite present in the area belongs to the Kohistan batholith, forming an intrusive contact with the Chalt volcanic group. Petrographic study conducted on the rocks reveal gabbro, diorite, granodiorite, quartz mica schist, amphibolite and microgranite. These rocks are partially altered. Sericite, epidote and chlorite are the common alteration minerals after plagioclase and hornblende. Deformation of rocks is indicated by kinking and bending in minerals. Geochemical study supports the mafic to intermediate and felsic composition of rocks in Singal Gah area. The geochemical signature of the rocks indicates the calc-alkaline affinity of the rocks with some tholeiitic input in the source of Ghizer Formation and Kohistan batholith due to the partial melting of the subducting slab and metasomatized mantle, supporting the island arc type settings. Major element chemistry shows a common primary melt for the rocks of the study area.