RECONSTRUCTING REGIONAL METAMORPHISM USING PAIRED ROCK RECORDS
Seminars
Semester 1
Metamorphic rocks preserve a record of the pressures and temperatures crustal materials experience during mountain building, offering a window into how orogens evolve. This study examines pelitic and metabasic rocks from the Suru Valley, NW India, which together preserve a remarkably complete record of Barrovian metamorphism spanning the early collision and subsequent exhumation of the Himalayan orogen.
By combining detailed petrography with phase equilibrium modelling across rocks of varying structural level and metamorphic grade, we reconstruct pressure-temperature paths that trace the tectonometamorphic record.
The results show that deformation and metamorphism swept southwestward through the crust as collision progressed, with the highest-grade rocks recording an extended period of near-isobaric heating consistent with rapid, substantial crustal thickening.
This was followed by decompression facilitated by erosion- and exhumation along the South Tibetan Detachment system rather than melt-assisted processes. We also find evidence for regionally reduced water activity, likely due to CO2- or salt-rich fluids sourced from adjacent carbonate- and graphite-bearing rocks, which appears to have suppressed melting and shaped the rheological behaviour of the orogenic crust.
For additional information, please contact Dr. Ian Cawood, ipcawood@hku.hk