HR: 16:00h
AN: T24A-01    [Abstracts]
TI: Subduction and Exhumation Processes Associated with UHP-HP Metamorphism in pre-, syn- and post-collisional Settings: Examples from Oman, Himalaya and Hindu Kush
AU: * Searle, M
EM: mikes@earth.ox.ac.uk
AF: Oxford University, Dept. Earth Sciences Oxford University Parks Road, Oxford, Oxford, OX1 3PR United Kingdom
AU: Parrish, R
EM: rrp@nigl.nerc.uk
AF: NERC Isotope Geoscience center, NERC Isotope Geoscience center Keyworth Nottingham NG12 5GG, Nottinghan, NG12 5GG United Kingdom
AU: Gough, S
EM: simon.gough@earth.ox.ac.uk
AF: Oxford University, Dept. Earth Sciences Oxford University Parks Road, Oxford, Oxford, OX1 3PR United Kingdom
AU: Warren, C
EM: clare.warren@earth.ox.ac.uk
AF: Oxford University, Dept. Earth Sciences Oxford University Parks Road, Oxford, Oxford, OX1 3PR United Kingdom
AU: Waters, D
EM: Dave.Waters@earth.ox.ac.uk
AF: Oxford University, Dept. Earth Sciences Oxford University Parks Road, Oxford, Oxford, OX1 3PR United Kingdom
AB: High-pressure and Ultrahigh pressure eclogites occur along continental plate margins associated with ophiolite obduction (Oman), arc-continent collision (Kaghan and Tso Morari, Ladakh Himalaya) and along continent-continent collision zones (western Alps, Western gneiss region Norway, Dabie Shan-Sulu massif, China, Kokchetav massif, Kazakhstan). Both the Oman and western Himalayan eclogites are metamorphosed Permian basalts that were originally part of the thinned passive margin of the Arabian and Indian plates. The thinned margin was stretched and sheared during rapid subduction to ca 20 kbar (during ophiolite emplacement) and 27 kbar (during Kohistan arc obduction) respectively. Old oceanic crust originally attached to the thinned continental crust was eclogitised, and provided the dense anchor to pull the slab down. When this anchor broke off, buoyancy forces rapidly forced the thin UHP-HP slab back to the surface by return channel flow. Fabrics within and above the HP rocks are extensional and related to rapid exhumation of footwall eclogites back up the same subduction zone. U-Pb dating of zircon, allanite, titanite and rutile from Oman and Pakistan shows that exhumation rates were approximately 1 cm/yr. The Hindu Kush seismic zone along the NW frontier of the Himalaya provides a modern-day analogue for deep subduction of thinned continental crust in a continental collision setting.
DE: 8100 TECTONOPHYSICS
DE: 8102 Continental contractional orogenic belts
DE: 3600 MINERALOGY AND PETROLOGY (replaces
DE: 3660 Metamorphic petrology
DE: 1035 Geochronology
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting