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

Citation

Halpin, JA and White, RW and Clarke, GL and Kelsey, DE, The Proterozoic P-T-t Evolution of the Kemp Land Coast, East Antarctica; Constraints from Si-saturated and Si-undersaturated Metapelites, Journal of Petrology, 48, (7) pp. 1321-1349. ISSN 0022-3530 (2007) [Refereed Article]


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Copyright Statement

Copyright 2007 Oxford University Press

DOI: doi:10.1093/petrology/egm020

Abstract

Integrated metamorphic and geochronological data place new constraints on the metamorphic evolution of a Neoproterozoic orogen in east Antarctica. Granulite-facies rocks from a 150km stretch of the Kemp Land coast reflect peak conditions involving T ≈ 870-990°C at P ≈ 74-10 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. 940Ma Rayner Orogeny. Complex compositional zoning in monazite suggests high-T recrystallization over c 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 Si-undersaturated 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/°C. 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. © The Author 2007. Published by Oxford University Press. All rights reserved.

Item Details

Item Type:Refereed Article
Keywords:electron microprobe monazite dating; granulite facies; Rayner Complex; sapphirine;THERMOCALC
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Halpin, JA (Dr Jacqueline Halpin)
ID Code:75907
Year Published:2007
Web of Science® Times Cited:30
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2012-02-20
Last Modified:2012-06-27
Downloads:0

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