Reynolds Range Group rocks underwent granulite-facies metamorphism (M2) at ∼1·6 Ga (∼5 kbar, 750-800°C) 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 650-700°C and 3-4 kbar. δ18O(Carb) values of the retrogressed metacarbonates were variably reset during fluid infiltration, with the lowest values (10-13‰) 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 ∼101-102 m3/m2 and metasomatic rocks record time-integrated fluid fluxes as high as ∼103-104 m3/ 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.
|Number of pages||34|
|Journal||Journal of Petrology|
|Publication status||Published - 1 Jan 1997|
- Fluid fluxes