Inter-relationships of deformation and metamorphism across the western hinterland zone, NW Pakistan.

Abstract

Microscopic to mesoscopic structural investigations and foliation intersection axes (FIAs) preserved in porphyroblasts reveal a very complex history of deformation and tectonism within the southwestern part of the western hinterland zone along the northern margin of the Indian plate, NW Pakistan. D1, D2, and D3 related structures in the southwestern part resemble the F1/F2, F3, and F4 related structures in the northeastern part of the western hinterland zone. These structures developed at the same time through the same changes in the direction of bulk shortening in southwestern and northeastern parts of the western hinterland zone. FIA set 1 indicates NW-SE shortening. The D2 fabrics, mineral lineations and fold axes indicate E-W shortening. FIA set 2, D3 fold axes and mineral lineations indicate NNE-SSW shortening. D3 deformation event is equivalent to the F4 deformation event in the northeastern part of the western hinterland zone. D4 fold axes, mineral stretching lineations and axial plane foliation suggest ENE-WSW shortening. The D4 NNW-SSE fabrics, which formed in the region after the formation of the MMT (main mantle thrust), Khairabad-Panjal thrust fault, Hissartang thrust fault and MBT (main boundary thrust), likely resulted from ENE-WSW bulk shortening related to development of the Hazara-Kashmir syntaxis. KEY WORDS: FIA, western hinterland zone, microstructure, mesostructure, metamorphism, tectonics, NW Pakistan.