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Abstract
LA-ICP-MS U–Pb geochronological data from metamorphic monazite in granulite-facies metapelites in the Barossa Complex, southern Australia, yield ages in the range 1580–1550 Ma. Metapelitic rocks from the Myponga and Houghton Inliers contain early biotite–sillimanite-bearing assemblages that underwent partial melting to produce peak metamorphic garnet–sillimanite-bearing anatectic assemblages. Phase equilibrium modelling suggests a clockwise P–T evolution with peak temperatures between 800 and 870°C and peak pressures of 8–9 kbar, followed by decompression to pressures of ∼6 kbar. In combination with existing age data, the monazite U–Pb ages indicate that the early Mesoproterozoic evolution of the Barossa Complex is contemporaneous with other high geothermal gradient metamorphic terranes in eastern Proterozoic Australia. The areal extent of early Mesoproterozoic metamorphism in eastern Australia suggests that any proposed continental reconstructions involving eastern Proterozoic Australia should share a similar tectonothermal history.
澳大利亚南部Barossa复合体中的麻粒岩相变质泥质岩内的变质独居石中所得LA- ICP-MS U-Pb同位素年代学数据表明其年龄范围为1580至1550Ma。Myponga和Houghton内露层中的变泥质岩含有早期含黑云母-矽线石组合，该组合经历过部分熔融而产生高度变质榴矽线石深熔组合。相平衡模型指示顺时向的P-T演变，其峰值温度在800和870℃之间，峰值压力为8-9千巴，之后解压到〜 6千巴。将现有的年龄数据和独居石U-Pb年龄结合起来，可以表明，Barossa复合体的中元古代早期演变与元古代澳大利亚东部其它高地温梯度变质地体是同时的。澳大利亚东部地区的元古代早期变质区域范围表明，涉及元古宙澳大利亚东部的任何大陆再造模式应该有着相似的构造地热历史。
ACKNOWLEDGEMENTS
Anthony Reid is thanked for his comments on a previous version of this manuscript. David Kelsey is thanked for helpful discussions regarding THERMOCALC. Steve Boger and Mike Rubenach are thanked for detailed and constructive reviews that significantly improved the manuscript. This work was funded by an Australian Research Council (ARC) Discovery Project (DP1095456). LJM is supported by an Australian Postgraduate Award. This manuscript forms TRaX record no. 281.