The Greater Himalayan Sequence (GHS) is one of the major tectonic units of the Himalaya running for more than 2400 km along-strike. It has been considered as a coherent tectonic unit bound by the South Tibetan Detachment (STD) and the Main Central Thrust (MCT). However, thrusts within it have been recognized in several places and have been mainly interpreted as out-of-sequence thrusts being active after the main phase of exhumation of the crystalline unit after the MCT activated. Recent integrated studies allow the recognition of several ductile shear zones in the core of the GHS, with top-to-the-SW-sense of shear (Higher Himalayan Discontinuity (HHD)). U–Th–Pb in situ monazite ages provide ages older than the MCT. Data on pressure and temperature evolution testify that these shear zones affected the tectonometamorphic evolution of the belt and different pressure and temperature conditions were recorded in the hanging wall and footwall of the HHD. The correlation of the WNW–ESE-trending HHD with other discontinuities recognized in the GHS led to the proposal that it is a tectonic feature running for several hundred kilometres, documented at the regional scale dividing the GHS in two different portions.
Tectonometamorphic discontinuities in the Greater Himalayan Sequence: a local or a regional feature?
MONTOMOLI, CHIARA;IACCARINO, SALVATORE
2015-01-01
Abstract
The Greater Himalayan Sequence (GHS) is one of the major tectonic units of the Himalaya running for more than 2400 km along-strike. It has been considered as a coherent tectonic unit bound by the South Tibetan Detachment (STD) and the Main Central Thrust (MCT). However, thrusts within it have been recognized in several places and have been mainly interpreted as out-of-sequence thrusts being active after the main phase of exhumation of the crystalline unit after the MCT activated. Recent integrated studies allow the recognition of several ductile shear zones in the core of the GHS, with top-to-the-SW-sense of shear (Higher Himalayan Discontinuity (HHD)). U–Th–Pb in situ monazite ages provide ages older than the MCT. Data on pressure and temperature evolution testify that these shear zones affected the tectonometamorphic evolution of the belt and different pressure and temperature conditions were recorded in the hanging wall and footwall of the HHD. The correlation of the WNW–ESE-trending HHD with other discontinuities recognized in the GHS led to the proposal that it is a tectonic feature running for several hundred kilometres, documented at the regional scale dividing the GHS in two different portions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
