HR: 0800h
AN: T31D-0667    [Abstracts]
TI: Petrology of the Leo Pargil gneiss dome, northwest Himalaya
AU: * Cornell, M
EM: cornell.molly@gmail.com
AF: San Francisco State University, Department of Geosciences, 1600 Holloway Avenue, San Francisco, CA 94132, United States
AU: Leech, M L
EM: leech@sfsu.edu
AF: San Francisco State University, Department of Geosciences, 1600 Holloway Avenue, San Francisco, CA 94132, United States
AB: The Leo Pargil gneiss dome is comprised of intermediate-grade paragneiss, migmatite, calc-silicate rocks, and granitoid dikes and small plutons, including two-mica granite, tourmaline granite, and leucogranite. Petrologic and thermometry data from the Leo Pargil dome constrain the metamorphic thermal history and mineral compositions for tourmaline-rich paragneisses. The gneiss underwent multiple deformation events, evidenced by the alignment of biotite within the foliation plane and shear bands that obliquely cross-cut the biotite. Deformation includes microboudinage, mylonitic layers, and mica fish indicate a top to the northwest sense of shear. The host gneiss contains the assemblage qtz + bt + ms + pl (Ab95-78 An4-21) + tur + weakly-zoned grt (Alm62-70 Pyr10-14 Grs2-11 Sps1-18) ± ky/sil ± st + rt + ap + zrn. Phase equilibria, using the KFMASH system, indicate intermediate pressure conditions of approximately 6-12 kbar and temperatures of approximately 400- 700°C in the garnet amphibolite-facies field. Verification of this phase equilibria estimate was possible with electron microprobe mineral chemistry data and biotite Fe-Mg exchange thermometry, yielding temperatures of 450-660°°C.
DE: 1042 Mineral and crystal chemistry (3620)
DE: 3612 Reactions and phase equilibria (1012, 8412)
DE: 3625 Petrography, microstructures, and textures
DE: 3651 Thermobarometry
DE: 3660 Metamorphic petrology
SC: Tectonophysics [T]
MN: 2007 Fall Meeting