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西天山高压-超高压变质带沿中天山南缘缝合带近东西向展布约200 km,南北最宽达30 km,构成一增生楔[1,2]。在对该高压-超高压变质带进行研究,不断发现新的榴辉岩体和蓝片岩体[3]。超高压变质岩原岩的构造环境判别,对于经历深俯冲折返的变质岩具有重要限制意义。通过对西南天山榴辉岩、蓝片岩样品进行岩石学、主微量元素检测和构造投图分析。研究表明榴辉岩和蓝片岩有着不同的原岩性质:榴辉岩原岩为E-MORB和N-MORB两类,而蓝片岩原岩介于E-MORB与OIB。西南天山的高压-超高压岩石形成于近岛弧的海洋环境中。
The west Tianshan high pressure-ultrahigh-pressure metamorphic belt distributes about 200 km along the south-eastern edge of the middle Tianshan Mountains and extends up to 30 km north-south, forming an accretionary wedge [1,2]. In the study of the HP-UHP metamorphic belt, new eclogite bodies and blueschipped rock bodies were discovered continuously [3]. The discrimination of tectonic environment of the original UHP metamorphic rock has important restriction significance for metamorphic rocks experiencing deep subduction. Based on the petrological, main and trace elements detection and tectonic projection analysis of the eclogite and blue schist samples in the southwestern Tianshan Mountains, The study shows that the eclogite and the blue schist have different protolith characteristics: the eclogite protoliths are E-MORB and N-MORB, while the lithofacies protoliths are between E-MORB and OIB. Southwest Tianshan high pressure - high pressure rock formed in the near island arc marine environment.