Petrology of a Part of Western Limb of the Nangaparbat-Haramosh Loop, Northern Pakistan
Abstract
A part of the western limb of the Nanga Parbat-Haramosh loop has been studied in terms of petrography and geochemistry of the constituent rocks. In this area a recent fault, the Raikot Fault, separates the tectono-stratigraphic zones of the Kohistan Island arc in the west from the Nanga Parbat massif (which forms the basement of the Indian plate) in the east. Major rock types, west of the fault, include a sequence of inter-layered amphibolite-gneiss and gabbro/gabbronorites. Chemical constants of these rocks are indicative of their derivation from an igneous parent, in an inland arc-type environment. East of the fault, the rocks are schists and gneisses of the Nanga Parbat-Haramosh Group. These rocks, on the basis of major-oxide geochemistry, are shown to be formed from a Proterozoic granitic protolith of I-type origin and are geochemically distinct porn the S-type Mansehra and equivalent granites in the Indian plate.
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