Fluid--Rock Interaction during Low-Pressure Polymetamorphism of the Reynolds Range Group, Central Australia |
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| Authors: | BUICK IAN S; CARTWRIGHT IAN |
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| Institution: | 1SCHOOL OF EARTH SCIENCES AND VICTORIAN INSTITUTE OF EARTH AND PLANETARY SCIENCES (VIEPS), LA TROBE UNIVERSITY BUNDOORA, VIC. 3083, AUSTRALIA
2DEPARTMENT OF EARTH SCIENCES AND VIEPS, MONASH UNIVERSITY CLAYTON, VIC. 3168, AUSTRALIA |
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| Abstract: | Marbles and metapelites from the Reynolds Range Group (centralAustralia) were regionally metamorphosed at low pressure duringM2 at  1.6 Ga, M2 ranged in grade from greenschist to granulitefacies along the length of the Reynolds Range, and overprinted1.78 Ga granites and their contact aureoles in the ReynoldsRange Group metasediments. At all M2 grades the marbles andmetapelites have highly variable oxygen isotope ratios marbles: 18O(carb) 14–20% ; metapelites: 18O 6–14%). Similarly, 1.78 Ga granites have highly variable oxygen isotope ratios(18O 5–13%), with the lowest values occurring at thegranite margins. In all rock types, the lowest oxygen isotopevalues are consistent with the infiltration of channelled magmaticand/or meteoric fluids. The variable lowering of oxygen isotopevalues resulted from pre-M2 contact metamorphism and fluid—rockinteraction around the 1.78 Ga granites. In contrast, mineralassemblages in the marbles define a trend of increasing XCO2with increasing grade from <0.05 (greenschist facies) to0.7–1.0 (granulite facies). This, together with the lackof regionally systematic resetting of oxygen isotope ratios,implies that there was little fluid—rock interaction duringprograde regional metamorphism. KEY WORDS: low pressure; polymetamorphism; fluids; stable isotopes; petrology
*Corresponding author Fax: 61–3–94791272. e-mail: geoisb{at}lure.latrobe.edu.au |
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