HEAT REFRACTION AND LOW-PRESSURE METAMORPHISM IN THE NORTHERN FLINDERS RANGES, SOUTH AUSTRALIA

Unusually high lateral temperature gradients associated with metamorphism of the lower sedimentary sequences of the Adelaide Fold Belt near the basal unconformity with Proterozoic gneisses of the Mt Painter Inlier in the northern Flinders Ranges raise the possibility that heat refraction can give rise to a unique type of regionally extensive, unconformity-related, contact metamorphism. Numerical models are used to explore the possibility that the metamorphism may reflect lateral variations in thermal conductivity and heat production using simple geometries appropriate to the deformed basement-cover interface at Mt Painter. The thermal models provided here show that with typical values of thermal conductivity and heat production, heat refraction can account, at most, for about 1/3 to 1/2 of the observed metamorphic signature, Additional advective heat transfer such as high-temperature fluid flow focused by the heat-refraction mechanism may have contributed to the lateral temperature gradients surrounding the basement-cover contact.