Abstract
The exhumation history of pelitic migmatite samples from the High Himalayan Crystalline Complex (HHC) near the South Tibetian Detachment System in the Sikkim-Darjeeling section has been determined on the basis of thermobarometric analyses, retrograde breakdown reactions and compositional zoning of garnet. The peak metamorphic condition is estimated to be Ο10.4 kbar, 800°C from thermo-barometric and phase equilibrium constraints. The observed retrograde breakdown of garnet to spinel and cordierite requires near isothermal and, hence, extremely rapid (15 mm/yr) exhumation up to the depth of Ο15 km. Numerical modeling suggests that the initial rapid exhumation must have been followed by a much slower process, 2 mm/yr, up to at least 5 km depth, to lead to the development of the observed compositional zoning of garnet. The dramatic change of the exhumation velocity (Vz) might reflect a process of tectonic thinning followed by erosion and/or horizontal flow at shallow depth. Assuming that the Vz did not change significantly below 5 km depth, these results suggest that the HHC samples studied in this work exhumed from a depth of 34 km within 8 Ma.
Original language | English (US) |
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Pages (from-to) | 471-486 |
Number of pages | 16 |
Journal | Earth and Planetary Science Letters |
Volume | 183 |
Issue number | 3-4 |
DOIs | |
State | Published - 2000 |
Keywords
- Crystal zoning
- Exhumation
- Himalayas
- P-T conditions
- Sikim India
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science