Palaeozoic Intraplate Crustal Anatexis in the Mount Painter Province, South Australia: Timing, Thermal Budgets and the Role of Crustal Heat Production     

McLAREN  SANDRA; SANDIFORD  MIKE; POWELL  ROGER; NEUMANN  NARELLE; WOODHEAD  JON 《Journal of Petrology》2006,47(12):2281-2302

The effect of radiogenic heat production within the crust onthermal processes such as crustal anatexis is generally disregardedas bulk geochemical models suggest that crustal heat generationrates are too low to effect significant heating. However, theMount Painter Province in northern South Australia is characterizedby a total crustal contribution to surface heat flow of morethan twice the global average. The province is composed dominantlyof Proterozoic granites and granite gneisses with an area averageheat production of 16·1 µW/m³; individual lithologieshave heat production >60 µW/m³. These Proterozoic rocksare intruded by the British Empire Granite, a younger intrusivewhose origin has remained enigmatic. Isotope geochemistry suggestscrustal sources for the melt and it has a crystallization ageof 440–450 Ma, which places the setting >750 km inboardof the nearest active plate boundary zone at this time. Phaseequilibria calculations suggest that temperatures of at least720–750°C are required to produce the granite butthe intensity of crustal thickening during Palaeozoic deformation(12%) cannot account for these conditions. Here we describea model for the generation of the British Empire Granite inwhich the primary thermal perturbation for mid-crustal anatexiswas provided by the burial of the high heat-producing MountPainter basement rocks beneath the known thickness of Neoproterozoiccover sediments. The high heat-producing rocks at Mount Painterimply that the natural range and variability of crustal heatproduction is much greater than previously believed, with importantconsequences for our understanding of temperature-dependentcrustal processes including the exploitation of geothermal energyresources. KEY WORDS: geothermal energy; low-pressure anatexis; thermal conductivity; thermal regime  相似文献