Fluid-rock interaction during low-pressure polymetamorphism of the Reynolds Range Group, central Australia

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Authors:Buick, Ian S.; Cartwright, Ian
Author Affiliations:Primary:
La Trobe University, School of Earth Sciences, Bundoora, Victoria, Australia
Monash University, Australia
Volume Title:Journal of Petrology
Source:Journal of Petrology, 37(5), p.1097-1124. Publisher: Clarendon Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:1996
Note:In English. 57 refs.; illus., incl. 11 tables, geol. sketch maps
Summary:Marbles and metapelites from the Reynolds Range group were regionally metamorphosed at low P during a second metamorphic episode at ∼ 1600 m.y. This metamorphism ranged from greenschist to granulite facies along the length of the Reynolds Range and overprinted ∼ 1780 m.y. granites and their contact aureoles in the Reynolds Range metasediments. At all grades the marbles and metapelites have highly variable oxygen isotope ratios (marbles Δ^>18Ocarb ∼ 14-200/00, metapelites Δ^>18O ∼ 6-140/00. Similarly, ∼ 1780 m.y. granites have highly variable Δ^>18O values of ∼ 5-130/00, with the lowest values occurring at the granite margins. In all rock types, the lowest oxygen isotope values are consistent with the infiltration of channelled magmatic and/or meteoric fluids. The variable lowering of Δ^>18O values resulted from the earlier contact metamorphism and fluid-rock interaction around the ∼ 1780 m.y. granites. In contrast, mineral assemblages in the marbles define a trend of increasing XCO2 with increasing grade from <<<[dollar]I> 0.05 for the greenschist facies to ∼ 0.7-1.0 for the granulite facies. This, together with the lack of regionally systematic resetting of oxygen isotope ratios, implies that there was little fluid-rock interaction during prograde regional metamorphism. [R.A.H.]
Subjects:Aureoles; Contact metamorphism; Geochemistry; Isotope ratios; Isotopes; Lithogeochemistry; Low pressure; Marbles; Mesoproterozoic; Metamorphic rocks; Metamorphism; Metapelite; Metasedimentary rocks; O-18/O-16; Oxygen; Polymetamorphism; Precambrian; Pressure; Prograde metamorphism; Proterozoic; Stable isotopes; Upper Precambrian; Water-rock interaction; Australasia; Australia; Mount Lofty Ranges; South Australia; Reynolds Range Group
Abstract Numbers:97M/2249
Record ID:1997026226
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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