Abstract

In the Karakorum Range there is a structurally complicated Cretaceous are comprising the Kohistan sequence. On its northern side the Northern Suture consists of a mega-mélange and is bounded to the S by tightly folded pillow-bearing volcanics and sediments. To the S the Kohistan Plutonic Belt consists of (southwards): (a) early foliated and late post-tectonic tonalites and diorites, (b) aplites and pegmatites (up to 30% of rock volume), (c) basic dykes up to 10 m thick, (d) the Chilas Complex, a stratiform cumulate body over 300 km long and 8 km thick (chromite-layered dunites, gabbros and norites) with a low pressure granulite-facies mineral fabric of tectonic origin, (e) an amphibolite belt with a complex mixture of other rocks, and (f) the Jijal Complex, a 200 km2 tectonic wedge of high pressure granulites and chromite-layered dunites. Cumulate graded units in the Chilas Complex show that it is folded by an isoclinal anticline (F1). The mid-upper crust of the are is folded by a 50 km half-wavelength F2, syncline. The whole Kohistan sequence with its two phases of isoclinal folds was tilted during Himalayan collision so that the structures are now subvertical. The Southern Suture (Main Mantle Thrust) has a wedge of glaucophane schists. The Indian plate contains a basement of psammites and schists intruded by Cambrian granites and overlain by isoclinally folded and metamorphosed carbonates and shales.

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