Metamorphic P-T evolution of garnet-clinopyroxene rocks from the Gondwana collisional orogen in southern India
Metamorphic P-T evolution of garnet-clinopyroxene rocks from the Gondwana collisional orogen in southern India
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印度南部冈瓦纳碰撞造山带石榴石-单斜辉石岩石的变质 P-T 演化
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发表时间：
2015
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通讯作者：
M. Santosh
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作者：
Minami Yano;T. Tsunogae;M. Iinuma;M. Santosh
包括马达加斯加、南印度、斯里兰卡、东南极地区在内的东非南极造山带，被认为是新元古代冈瓦纳超大陆拼合作用的产物，经历了复杂的俯冲-增生-碰撞构造事件。印度南部的Palghat-Cauvery缝合带是莫桑比克洋闭合过程中形成的主要缝合带。530-550 Ma。缝合带的主要岩性为长英质至中间正片麻岩、变质沉积岩和镁铁质-超镁铁质岩套。特别是，镁铁质-超镁铁质岩套（蛇绿岩或层状侵入体）的出现是缝合带与周围麻粒岩块和岩块相比的独特特征。在这里，我们报告了新的岩石学数据变辉长岩石榴石单斜辉石岩石从印度南部，并讨论其岩石学意义。岩石的矿物组合为石榴子石+单斜辉石+钛铁矿+斜长石+石英，具退变质角闪石。类似的岩石和结构已经在南印度的Palghat-Cauvery缝合带报道过（Nishimiya等人，2008; Saitoh等人，2011），斯里兰卡高地综合体（Osanai et al.，2006; Takamura等人，2014），以及东南极洲的Lutzow-Holm复合体（Saitoh et al.，2012年）。然而，根据地质温压法推断的变质辉长岩的温度和压力条件为680- 710 ℃和1.99 kbar，这明显低于以前的研究结果（>12 kbar，> 800 ℃）。变质辉长岩可能是一个外来的块体，在Palghat-Cauvery缝合带形成过程中被捕获了离散的P-T演化。
The East African Antarctic Orogenic Belt, which includes Madagascar Southern India Sri Lanka East Antarctica regions, is regarded to have been formed by complex subduction-accretion-collision tectonic events related to the amalgamation of Gondwana Supercontinent during Neoproterozoic. The Palghat-Cauvery Suture Zone in southern India is known as a major suture zone that formed during the closure of Mozambique Ocean at ca. 530-550 Ma. The dominant lithologies of the suture zone are felsic to intermediate orthogneiss, metasediments, and mafic-ultramafic suites. Particularly, the occurrence of mafic-ultramafic suites (ophiolite or layered intrusion) is a unique character of the suture zone compared to surrounding granulite blocks and cratons. Here, we report new petrological data of metagabbroic garnet-clinopyroxene rocks from southern India and discuss its petrological implications. Mineral assemblages of the rocks are garnet + clinopyroxene + ilmenite + plagioclase + quartz with retrograde hornblende. Similar rocks and textures have been reported from the Palghat-Cauvery Suture Zone in South India (Nishimiya et al., 2008; Saitoh et al., 2011), Highland Complex in Sri Lanka (Osanai et al., 2006; Takamura et al., 2014), and Lutzow-Holm Complex in East Antarctica (Saitoh et al., 2012). However, temperature and pressure conditions inferred for the metagabbro based on geothermobarometry are 680-710C and ̃9 kbar, which is significantly lower than the results of previous studies ( >12 kbar,>800C). The metagabbro could be an exotic block with discrete P-T evolution trapped during the formation of the Palghat-Cauvery Suture Zone.