The Proterozoic P-T-t Evolution of the Kemp Land Coast, East Antarctica; Constraints from Si-saturated and Si-undersaturated Metapelites

6555 26 archive 266 disk0/00/00/65/55 2008-05-26 02:37:43 2008-07-18 11:00:05 2008-07-16 17:26:45 article show jahalpin@utas.edu.au Halpin JA jahalpin@utas.edu.au White RW rwhite@uni-mainz.de Clarke GL geoffc@mail.usyd.edu.au Kelsey DE david.kelsey@adelaide.edu.au The Proterozoic P-T-t Evolution of the Kemp Land Coast, East Antarctica; Constraints from Si-saturated and Si-undersaturated Metapelites pub 260100 restricted electron microprobe monazite dating; granulite facies; Rayner Complex; sapphirine; THERMOCALC The definitive publisher-authenticated version is available online at: www.oxfordjournals.org Integrated metamorphic and geochronological data place new constraints on the metamorphic evolution of a Neoproterozoic orogen in east Antarctica. Granulite-facies rocks from a 150 km stretch of the Kemp Land coast reflect peak conditions involving T~870-990 ºC at P~7.4-10 kbar, with pressure increasing westward towards an Archaean craton. Electron microprobe-derived (Th+U)-Pb monazite ages from metapelitic assemblages indicate that the major mineral textures in these rocks developed during the c. 940 Ma Rayner Orogeny. Complex compositional zoning in monazite suggests high-T recrystallization over c. 25 Myr. Diversity in metapelitic reaction textures reflects silica and ferromagnesian content: Si-saturated Fe-rich metapelites contain garnet that is partially pseudomorphed by biotite and sillimanite, whereas Si-saturated Mg-rich metapelites and Siundersaturated metapelitic pods have reaction microstructures involving cordierite enclosing orthopyroxene, garnet and/or sapphirine, cordierite+sapphirine symplectites around sillimanite and coarse-grained orthopyroxene+corundum separated by sapphirine coronae. Interpretations based on P-T pseudosections provide integrated bulk-rock constraints and indicate a clockwise P-T-t path characterized by a post-peak P-T trajectory with dP/dT~15-20 bar/ºC. This moderately sloped decompressive-cooling P-T path is in contrast to near-isothermal decompression P-T paths commonly cited for this region of the Rayner Complex, with implications for the post-collisional tectonic response of the mid- to lower crust within this orogenic belt. 2007-07 submitted Journal of Petrology 48 7 1321-1349 10.1093/petrology/egm020 TRUE http://petrology.oxfordjournals.org/cgi/content/full/48/7/1321 5396 5 6555 1 application/pdf en staffonly cc_utas

Halpin_et_al_2007.pdf

Halpin_et_al_2007.pdf 2256403 http://eprints.utas.edu.au/6555/1/Halpin_et_al_2007.pdf