东南极普里兹带高级变质作用演化

东南极普里兹带是经历泛非期高级变质和强烈变形的造山带,其内发现有经历格林维尔期高级变质事件的残块。格林维尔期变质矿物组合局部见于姐妹岛和赖于尔群岛,其高峰变质条件达到>950℃和>0.95GPa。泛非期高级变质作用是区域性的,其高峰变质并不像前人想象的那样只发生在中低压麻粒岩相条件下,而是高达850~950℃和0.90~0.95GPa。这些岩石随后经历了近等温减压过程,在760~860℃和0.55~0.70GPa的条件下达到了重新平衡,并进一步减压或近等压冷却至450~750℃和0.30~0.50GPa。同造山的紫苏花岗岩在减压伸展阶段侵位于格罗夫山地区的变质杂岩中,而晚-后造山的A型花岗岩、伟晶岩和花岗岩脉则遍布于整个普里兹带,从而构成一个完整的造山演化序列。由此可见,现有研究资料支持普里兹带是一条冈瓦纳超大陆在泛非期拼合的碰撞造山带的认识。

Evolution of high-grade metamorphism in the Prydz Belt, East Antarctica

The Prydz Belt is a Pan-African orogen with the Grenvillian high-grade metamorphic relics. The Grenvillian mineral assemblage was only observed on the Sstrene and Rauer Islands. Their metamorphic peak reaches >950 ℃ and >0.95 GPa. The Pan-African metamorphism is widespread in the Prydz Belt. The metamorphic peak of the Pan-African rocks is not under low-to medium-pressure granulite facies conditions, as previously thought, but reaches as high as 850-950 ℃ and 0.90-0.95 GPa. The subsequent decompression of the rocks is from 760-860 ℃ and 0.55-0.70 GPa to 450-750 ℃ and 0.30-0.50 GPa. Syn-orogenic charnockites intruded the metamorphic rocks in the Grove Mountains during crustal extension, whereas late-to post-orogenic A-type granites, pegmatites and granitic dikes emplaced everywhere. Therefore, a whole process of orogenic evolution was revealed in the Prydz Belt. This supports the inference that the Prydz Belt is a continental collision zone associated with the Gondwana assembly during the Pan-African event.