Cenozoic deep crust in the Pamir

Multiple high-grade crystalline domes across the Pamir contain Barrovian facies-series metapelites with peak metamorphic assemblages of garnet + kyanite +/- staurolite + biotite + oligoclase +/- K-white mica. Thermobarometry yields pressures of 6.5-8.2 kbar and temperatures of 600-650 degrees C for the Kurgovat dome in the northwestern Pamir, 9.4 kbar and 588 degrees C for the west-central Yazgulom dome, 9.1-11.7 kbar and 700-800 degrees C for the east-central Muskol dome, and 6.5-14.6 kbar and 700-800 degrees C for the giant Shakhdara dome in the southwestern Pamir. These new data indicate exhumation of the Pamir crystalline domes from crustal depths of similar to 30-40 km. New titanite, monazite and zircon geochronology, in conjunction with published ages, illustrate that this metamorphism is Oligocene-Miocene in all but the Kurgovat dome (where it is Triassic). If the Pamir had a pre-collisional crustal thickness less than 30 km and if the India-Asia convergence within the Pamir is less than 600 km, the current 70 km-thick crust could have been created by plane strain with no net gain or loss of material. Alternatively, if the pre-collisional crustal thickness was greater than 30 km or India-Asia convergence within the Pamir is more than 600 km, significant loss of continental crust must have occurred by subhorizontal extrusion, erosion, or recycling into the mantle. Crustal recycling is the most likely, based on deep seismicity and Miocene deep crustal xenoliths. (C) 2011 Elsevier B.V. All rights reserved.