Rock deformation processes in the Karakoram fault zone, Eastern Karakoram, Ladakh, NW India

Abstract

The Karakoram fault shows a full range of fault rocks from ductile (deformation by intracrystalline plasticity) mylonites to low temperature brittle fault rocks along the trace of the fault in the Eastern Karakoram, Ladakh, NW India. The Karakoram fault is a prominent feature on satellite images and has estimated long-term average slip rates between 3 and 11 mm/year, based on U-Pb geochronology of mapped offset markers, notably mid-Miocene leucogranites. Mylonitic marbles, superimposed by cataclastic deformation and clay-bearing fault gouges and late fracturing were found on a presently active strand of the fault, and testify to progressive deformation from plastic through brittle deformation during unroofing and cooling. From microstructural analysis we confirmed the right-lateral strike slip character of the fault, estimated peak differential stresses of ca. 200 MPa at the transition from plastic to brittle deformation, and found microstructural features to be consistent with inferences from the extrapolation of deformation behaviour from experimental rock deformation studies. Implied long-term averaged slip rates from microstructural constraints were found to be broadly consistent with estimates from geochronologic and geodetic studies.