东南极格罗夫山镁铁质麻粒岩的变质作用

Metamorphism of mafic granulites in the Grove Mountains, East Antarctica

东南极内陆 -格罗夫山存在一套经历了麻粒岩相变质作用的镁铁质麻粒岩和斜长角闪岩。变质反应结构显示该区多为单一的区域性麻粒岩相变质作用。但是 ,对含石榴石的镁铁质麻粒岩的详细工作则显示了包括 3个阶段的近等温降压(ITD)的顺时针 PT演化轨迹 ,M1:0 .93 GPa,>80 0℃ ;M2 :0 .65GPa,73 3～ 850℃ ;M3:0 .46～ 0 .61GPa,并有着与拉斯曼丘陵相似的演化历史。根据矿物组合和成分、变质反应结构及温压计算结果 。

Mafic granulites and amphibolites crop out in the Grove Mountains (GMs), 450km south of Zhongshan Station on the coast of Prydz Bay, East Antarctica. Most metamorphic reaction textures suggest that the high-grade metamorphic rocks were formed by a single-granulite facies event. But, the garnet-bearing mafic granulites exhibit corona of Opx + Pl + minor Hbl on garnet, formed after peak metamorphic conditions (M-1), The corona was originated during a second metamorphic event (M-2) via the reaction Grt + Cpx + SiO2 = Opx + Pl. The mafic granulite shows a near-isothermal decompression (ITD) P-T history from 0.93 GPa and >800degreesC (M-1) based on the assemblage of garnet core with Cpx-Pl-Qtz occurred as inclusion within. the garnet to 0.65GPa and 733 similar to 850degreesC (M-2), followed by 0.46 similar to 0.61 GPa (M-3). Conventionally, this clockwise P-T path can be explained in a model involving extensional collapse and exhumation of thickened crust, which can be compared with that of Larsemann Hills East Antarctica. Based on metamorphic temperatures and pressures estimated by geothermometer - geobarometer, we proposed that the mafic granulite from Grove Mountains, East Antarctica, might be the high-pressure granulite.