High-grade Paleoproterozoic reworking in the southeastern Gawler Craton, South Australia
Date
2008
Authors
Dutch, R.
Hand, M.
Kinny, P.
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Journal article
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Australian Journal of Earth Sciences, 2008; 55(8):1063-1081
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R. Dutch, M. Hand, P. D. Kinny
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Abstract
SHRIMP U-Pb geochronology and monazite EPMA chemical dating from the southeast Gawler Craton has constrained the timing of high-grade reworking of the Early Paleoproterozoic (ca 2450 Ma) Sleaford Complex during the Paleoproterozoic Kimban Orogeny. SHRIMP monazite geochronology from mylonitic and migmatitic high-strain zones that deform the ca 2450 Ma peraluminous granites indicates that they formed at 1725 ± 2 and 1721 ± 3 Ma. These are within error of EPMA monazite chemical ages of the same high-strain zones which range between 1736 and 1691 Ma. SHRIMP dating of titanite from peak metamorphic (1000 MPa at 730°C) mafic assemblages gives ages of 1712 ± 8 and 1708 ± 12 Ma. The post-peak evolution is constrained by partial to complete replacement of garnet-clinopyroxene-bearing mafic assemblages by hornblende-plagioclase symplectites, which record conditions of ∼ 600 MPa at 700°C, implying a steeply decompressional exhumation path. The timing of Paleoproterozoic reworking corresponds to widespread deformation along the eastern margin of the Gawler Craton and the development of the Kalinjala Shear Zone.
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© 2008 Geological Society of Australia