Polyphase metamorphic fluid flow in the Lower Calcsilicate Unit, Reynolds Range, central Australia

Ian Cartwright, Ian S. Buick, Julie K. Vry

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19 Citations (Scopus)


Lower Calcsilicate Unit metasediments and Napperby Gneiss metagranites at Conical Hill in the Reynolds Range, central Australia, underwent at least two periods of fluid flow. The ingress of surface-derived fluids (δ 18O < 6‰; δ 2H < -80‰) during 1780 Ma contact metamorphism produced wholesale lowering of δ 18O values in both the Lower Calcsilicate Unit and the Napperby Gneiss. Fluid flow during cooling from the peak of 1600 Ma regional metamorphism formed quartz + garnet veins and caused epidotisation of the Lower Calcsilicate Unit. The fluids in this later event were water-rich (XCO2 < 0.1), saline, and were probably exsolved from crystallising partial melts within the Napperby Gneiss. Quartz-epidote oxygen isotope fractionations suggest that epidotisation occurred at 575-625°C. The scale of fluid flow during epidotisation was probably smaller than that during contact metamorphism and represents a local redistribution of mass. The Reynolds Range as a whole shows a long history of fluid-rock interaction and the final isotopic and petrological character of the terrain is the product of several fluid-flow events.

Original languageEnglish
Pages (from-to)211-229
Number of pages19
JournalPrecambrian Research
Issue number3-4
Publication statusPublished - 1 Jan 1996

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