P-T-T-D PATHS OF HAIMANTA GROUP METAPELITIC ROCKS THAT MANTLE THE LEO PARGIL DOME, NW INDIA

The metasedimentary rocks of the Haimanta Group in the upper Sutlej Valley, NW India, record an extensive history of Himalayan deformation and metamorphism. Situated in the hanging wall of the South Tibetan detachment system (STDS), these poly-deformed rocks record Eocene–Oligocene Barrovian metamorphism, crustal thickening, and shortening. Decompression and mid-crustal melting in the early Miocene is recorded within rocks of the Leo Pargil Dome (LPD), which was exhumed through the Haimanta Group along orogen-perpendicular shear zones. Staurolite and kyanite porphyroblasts consistently overgrow fabrics in the Haimanta Group, suggesting that Barrovian metamorphism outlasted the majority of crustal shortening. In the NE portion of Sutlej Valley near the LPD, low-pressure assemblages (cordierite + sillimanite + quartz) overgrow Barrovian porphyroblasts. Detailed petrography on pelitic samples collected near the dome indicates a gradient in the intensity of the low-pressure overprint in the Haimanta Group that increases with proximity to the LPD, supporting models in which exhumation of this portion of the Haimanta Group was coupled with exhumation of the dome. We present new P-T-t-d paths for Haimanta Group rocks and in-situ U-Th-Pb monazite geochronology results that place further age constraints on porphyroblast growth and fabric development in the Haimanta Group. The ­P-T-t-d­ analyses of the Haimanta Group schist may yield implications for orogen-parallel dome exhumation and the evolution of the hanging wall rocks of the STDS in this portion of the Himalaya.