Trondhjemites in the southeastern part of the Kohistan island-arc terrane, Pakistan: A product of partial melting
Abstract
The Kohistan terrane in N. Pakistan is sandwiched between the Shyok suture in the north and Indus suture in the south. The SE base of the terrane is occupied by the stratiform Sapat mafic-ultramafic complex., which overrides the crust of the Indian plate along the Indus suture. The complex intruded into the base of a thick pile of meta volcanics (now amphibolites) of different environments (the Kamila belt), The Kamila belt is intruded by various rocks including gabbros, diorites, tonalities, granodiorites, granites and trondhjemites. The trondhjemites occur .as thin veins and dykes, mostly in the northern part of the Kamila amphibolite belt. Here, the belt is in contact with the Chilas Complex along the Jal shear zone. The tondhjemites contain feldspar, quartz and amphibole with minor epidote, muscovite, biotite, sphene, garnet and ore, and display parallel alignment of mineral grains in one major direction. They show very spiked pattern for mantel normalized incompatible trace elements and are depleted in all High Field Strength Elements (HFSE) particularly Strongly in n, P and Mb relative to the other granitoids of the studied area. The trondhjemites are probably a product of partial melting of Kamila amphibolites, and a direct role of subduction is not observed.
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