Abstract:
This study deals with petrology and economic mineral investigation in Kar Gah
Valley, Gilgit. The thesis area was situated approximately five kilometers towards west of
Gilgit city and bounded by latitude ~ 35⁰ 45‟ to 36°00‟ longitude ~ 74°00 to 74°15‟ E. The
rocks exposed in the Kar Gah Valley represent igneous and metamorphic rocks belonging
to Kohistan island arc. Igneous rocks such as diorites, granodiorites, granites (Kohistan
Batholith), basalts, dolerite dykes and metamorphites (paragneisses, slates, marble and
green schist) were the lithological constituents of the Kar Gah Valley. The metamorphic
rocks were grouped as the Jaglot group comprising the Thelichi and Gilgit formations and
Gashu-Confluence volcanics in between them. The Kohistan Batholith intrudes the Jaglot
group. Sulphide mineralization is noticed in a zone that extends from Shingai Gah and
terminates at Chelili Gah within the Thelichi formation, which comprises basalts, basaltic
dykes, dolerites, slates, siliceous schist and marble metamorphosed into greenschist
metamorphic facies. Heavy metal analysis in altered rocks of the studied area reveal
concentrations of gold, silver, copper, cobalt, lead, zinc, manganese, nickel, chromium and
cadmium out of which gold, silver and copper have relatively enriched. Petrographic
studies reveal hydrothermal alteration in the rocks. The minerals include amphibole,
plagioclase, as primary minerals and chlorite, epidote, biotite, muscovite, sericite, calcite,
clayey material as secondary minerals formed after the alteration of volcanic rocks. Quartz
occurs as primary and secondary mineral in all the rock types. Opaque includes oxides and
sulphides. XRD analysis also confirms the petrographic study. Based on field and
laboratory study, the mineralization seems to be polymetallic vein type and fracture
controlled. It is suggested that polymetallic mineralization in the area is due to postcollisional granitoid intrusions within the Thelichi formation and the Kohistan Batholith
after the ceasing of subduction processes.
