首页> 外文期刊>Proceedings of the Indian Academy of Sciences. Earth and Planetary Sciences >Contrasting metamorphism across Cauvery Shear Zone, south India
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Contrasting metamorphism across Cauvery Shear Zone, south India

机译:印度南部Cauvery剪切带的对比变质作用

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The Palghat Cauvery Shear Zone (CSZ) is a major shear zone that possibly extends into different fragments of Gondwanaland. In the present study mafic granulites occurring on either side of the CSZ in Namakkal area, southern India are examined. Textural features recorded in the mafic granulites are crucial in elucidating the metamorphic history of the southern granulite terrane (SGT). In the mafic granulites occurring to the south of CSZ, evidence of garnet breaking down during near isothermal decompression (ITD) is indicated by the development of orthopyroxene + plagio-clase moats in between quartz and garnet. The presence of comparatively small elongated second generation garnet embedded in pyroxenes from the mafic granulites occurring to the north of CSZ is indicative of the garnet formation via reaction between pyroxenes and plagioclase. which occurred during isobaric cooling (IBC). Rocks occurring to the south of CSZ have recorded comparatively higher temperature and pressure (849? and 9.6 kbar) than those occurring to the north of the CSZ (731℃ and 8.6 kbar) using conventional geothermobarometry. The rocks occurring to the north of CSZ have suffered more complex metamorphic histories in comparison to the southern part. Integrating the results of the present field and metamorphic studies with the earlier investigations and available geochronologi-cal data we suggest that the CSZ could represent a suture zone between two different continental blocks that underwent distinct metamorphic evolution.
机译:帕尔加特农作物剪切带(CSZ)是一个主要的剪切带,可能延伸到冈瓦纳兰的不同片段。在本研究中,研究了印度南部那马卡尔地区CSZ两侧出现的镁铁质粒岩。镁铁质花岗石中记录的质地特征对于阐明南部花岗石地层(SGT)的变质历史至关重要。在CSZ南部出现的镁铁质花岗石中,石榴石在接近等温减压(ITD)期间破裂的迹象由石英和石榴石之间的邻苯二茂铁和斜长石沟形成。在CSZ北部出现的镁铁矿粒中,埋在辉石中的较小的细长第二代石榴石的存在表明石榴石是通过辉石与斜长石之间的反应形成的。发生在等压冷却(IBC)期间。使用常规的地热大气压法,在CSZ南部出现的岩石的温度和压力(849?和9.6 kbar)要比在CSZ北部出现的岩石(731℃和8.6 kbar)要高。与南部相比,CSZ北部的岩石经历了更复杂的变质历史。将当前领域和变质研究的结果与较早的调查结果和可用的年代学数据相结合,我们建议CSZ可以代表经历了明显的变质演化的两个不同大陆块之间的缝合带。

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