Earth and Planetary Science
EPS Near-Surface Geochemistry and Geobiology

Berkeley Geochronologist Examines Crustal Stacking, Extensional Collapse and Lateral Extrusion in Central Asia

Monday, March 6, 2017

Daniel Rutte is first author of “Building the Pamir-Tibet Plateau—Crustal stacking, Extensional Collapse, and Lateral Extrusion in the Central Pamir: 2. Timing and Rates.” The article was accepted on 11 January 2017 in the journal Tectonics.

Geo-thermochronologic data outline the temperature-deformation-time evolution of the Muskol and Shatput gneiss domes and their hanging walls in the Central Pamir. Prograde metamorphism started before ~35 Ma and peaked at ~23–20 Ma, reflecting top-to- ~ N thrust-sheet and fold-nappe emplacement that tripled the thickness of the upper ~7–10 km of the Asian crust. Multimethod thermochronology traces cooling through ~700–100 °C between ~22–12 Ma due to exhumation along dome-bounding normal-sense shear zones. Syn-kinematic minerals date normal sense shear-zone deformation at ~22–17 Ma. Age-versus-elevation relationships and paleoisotherm spacing imply exhumation at ≥3 km/Myr. South of the domes, Mesozoic granitoids record slow cooling and/or constant temperature throughout the Paleogene, and enhanced cooling (7–31 °C/Myr) starting between ~23–12 Ma and continuing today. Integrating the Central Pamir data with those of the East (Chinese) Pamir Kongur Shan and Muztaghata domes, and with the South Pamir Shakhdara dome implies i) regionally distributed, Paleogene crustal thickening; ii) Pamir-wide gravitational collapse of thickened crust starting at ~23–21 Ma during ongoing India-Asia convergence; and iii) termination of doming and resumption of shortening following northward-propagating underthrusting of the Indian cratonic lithosphere at ≥12 Ma. Westward lateral extrusion of Pamir Plateau crust into the Hindu Kush and the Tajik depression accompanied all stages. Deep-seated processes, e.g., slab breakoff, crustal foundering, and underthrusting of buoyant lithosphere, governed transitional phases in the Pamir, and likely the Tibet crust.

Daniel Rutte is a postdoctoral researcher in the Berkeley Earth and Planetary Science Department and the Berkeley Geochronology Center.

For the full-length article please click here.