Rupal - Chhichi Shear Zone

From the northwest side of Rupal Valley at Rupal village, extending for 5km across strike into most of the length of the western wall of Chhichi Nullah [valley], we have found a major ductile shear zone developed in a granitic protolith. The S/C mylonites of this shear zone show a clear and consistent shear sense of thrusting from the NW, along with a subordinate dextral strike-slip component. The thrust component has accommodated the rise of the core of the Nanga Parbat massif, including the area of the summit of Nanga Parbat, relative to the metasedimentary rocks of Indian cover provenance that occur to the south east of this shear zone. The rocks of the shear zone show qualitatively moderate strains [Photo5; Photo 6], but these are maintained across a 5km-wide zone dipping from 40ºNW to subvertical, so we think that the overall displacement is likely to be significant. While it is possible that this zone may have been rotated from an intially SE-dipping attitude [which would have had a normal-sense, down to SE shear], we think it more likely that the present attitude and thrust shear sense are original. [See the adjacent panel on tectonic denudation for reasons]. We interpret this shear zone to connect with an east-directed thrust zone/pinched syncline located between two large antiforms in the Astor River valley section [ Photos 2, and 3], and beyond to the previously known mylonites at Shengus on the Indus Gorge section, which also separates two regional antiforms [Geological Map - Fig. 2.]

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