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变质岩石学、同位素年代学和地球化学研究表明,北大别罗田榴辉岩在俯冲和折返过程中经历了超高压变质作用以及多阶段的高温变质过程,并导致了一系列矿物以及元素和同位素组成的变化.从超高压榴辉岩相到高压麻粒岩相,经历了多阶段>900℃的近等温减压变质过程.通过锆石U-Pb定年及矿物包体和微量元素分析,限定了超高压榴辉岩相、高压榴辉岩相和麻粒岩相变质时代分别为226±2,214±2和207±4 Ma,并确定了两期角闪岩相变质和燕山期热事件影响与部分熔融的时代.根据元素和同位素地球化学研究,证明罗田榴辉岩是由新元古代镁铁质下地壳岩石在三叠纪发生超高压变质形成的,其原岩是由幔源岩浆在新元古代侵位过程中不同程度地混染古老地壳物质形成的辉长岩和少量玄武岩,并且在超高压岩石折返过程中受到了部分熔融和流体活动的影响与改造,造成了元素和同位素组成的不同变化.在此基础之上,获得了折返初期发生部分熔融的同位素年代学和地球化学证据.
Metamorphic petrology, isotopic geochronology and geochemical studies have shown that the Ertanluota eclogites have undergone ultrahigh-pressure metamorphism and multi-stage high-temperature metamorphism during subduction and reentry and have resulted in a series of mineral and elemental and isotopic compositions Changes from ultrahigh-pressure eclogite facies to high-pressure granulitic facies underwent near-isothermal destructive metamorphism at multi-stage> 900 ℃ .According to U-Pb zircon dating and mineralogical inclusions and trace elements analysis, The high-pressure eclogite facies, high-pressure eclogite facies and granulite facies metamorphism were 226 ± 2,214 ± 2 and 207 ± 4 Ma, respectively, and the influence of phase amphibolite facies and Yanshanian thermal events and partial melting Based on the elemental and isotopic geochemical studies, it is proved that the Luotian eclogite is formed by the Neoproterozoic mafic lower crustal rocks occurring during the Triassic epithermal metamorphism, and the original rocks were formed by the mantle-derived magmas in the Neoproterozoic In the course of the process, the gabbro and a few basalts formed by the ancient crustal materials are mixed to different extents, and are affected and transformed by the partial melting and fluid activities during the reentry of the ultra-high pressure rock, Different variations and isotopic composition. On this basis, access to isotope geochronology and geochemical evidence of the occurrence of partial melting of the initial exhumation.