PATTERNS OF FLUID-FLOW IN PROTEROZOIC CALC-SILICATES - FLUID CHANNELING AND VARIATIONS IN FLUID FLUXES AND INTRINSIC PERMEABILITIES

Gale-silicates in three Proterozoic terrains (Mt Isa, the Reynolds Ran ge and the Grenville of Canada) record the influx of water-rich fluids through the resetting of mineral assemblages, stable-isotope ratios a nd major elements. In all cases time-integrated fluid fluxes are infer red to have varied by over an order of magnitude on the millimetre to metre scale, and fluids were often channelled across strike. These res ults indicate that intrinsic permeabilities during metamorphism varied considerably over a small scale. It is suggested that fluid flow was within microfractures, and that the variations in intrinsic permeabili ty reflect variable microfracture densities.