Volume 38: January - December 1997

Issue 7: July 1997

Abstract

High-temperature retrogression of granulite-facies marbles form the Reynolds Range group, Central Australia: phase equilibria, isotopic resetting and fluid fluxes

  • High-temperature retrogression of granulite-facies marbles form the Reynolds Range group, Central Australia: phase equilibria, isotopic resetting and fluid fluxes

    • IS. Buick, I. Cartwright2 and IS. Williams3

    1School of Earth Sciences and Victorian Institute of Earth and Planetary Sciences, (VIEPS), La Trobe University, Bundoora, Victoria 3083, Australia and 2Department of Earth Sciences and VIEPS, Monash University, Clayton, Victoria 3168, Australia3Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, AustraliaCorresponding author email: I.Buick@latrobe.edu.au

    ABSTRACT

    Reynolds Range Group rocks underwent granulite-facies metamorphism (M2) at @1.6 Ga ( 5 kbar, 750-800oC) and were subsequently retrogressed in narrow strike-parallel zones at 1.59-1.57 Ga. Within these zones, metacarbonates that initially equilibrated at XCO2 >0.8 during M2 were mineralogically reset by the infiltration of water-rich fluids (XCO2 <= 0.02-0.3) at 650-700oC and 3-4 kbar. &dgr18O(Carb) values of the retrogressed metacarbonates were variably reset during fluid infiltration, with the lowest values (10-13%o) suggesting that the fluids that caused retrogression were exsolved from segregated partial melts, themselves derived from the underlying granulite-facies metapelites. Mineralogical and isotopic resetting were locally accompanied by silica metasomatism. The mineralogically reset marbles record time-integrated fluid fluxes of typically 101-104m3/m2. For upward flow of high-temperature fluids through the marbles over a distance of 200 m in 18 Ma, the observed mineralogical and isotopic resetting, and metasomatism require intrinsic permeabilities between 10-22 and 10-19 m2 that vary across strike on a centimetre to metre scale, indicating that fluid flow was strongly channelled.

    Keywords: granulites; marbles; retrogression; petrology; fluid mixes

    Pages: 877 - 910

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