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首页> 外文期刊>Journal of Asian earth sciences >Proterozoic orogens in southern Peninsular India: Contiguities and complexities
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Proterozoic orogens in southern Peninsular India: Contiguities and complexities

机译：印度半岛南部的元古代造山带：连续性和复杂性

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The Precambrian terranes of southern Peninsular India have been central to discussions on the history of formation and breakup of supercontinents. Of particular interest are the Proterozoic high grade metamor-phic orogens at the southern and eastern margins of the Indian shield, skirting the 3.4 Ga Dharwar craton which not only preserve important records of lower crustal processes and lithospheric geodynamics, but also carry imprints of the tectonic framework related to the assembly of the major Neoproterozoic super-continents - Rodinia and Gondwana. These Proterozoic orogens are described as Southern Granulite Ter rane (SGT) in the southern tip and the Eastern Ghats Mobile Belt (EGMB) in the eastern domains of the peninsula. The contiguity of these orogens is broken for a distance of ～400 km and disappears in the Bay of Bengal. These orogens expose windows of middle to lower crust with well-preserved rock records displaying multiple tectonothermal events and multiphase exhumation paths. Recent studies in these orogens have led to the recognition of discrete crustal blocks or terranes separated by major shear zone systems, some of which represent collisional sutures. The SGT and EGMB carry several important features such as fold-thrust tectonics, regional granulite facies metamorphism of up to ultrahigh-temperature conditions in some cases, multiple P-T paths, development of lithospheric shear zones, emplacement of ophiolites, presence of alkaline and anorthositic complexes, development of crustal-scale "flower structures", transpressional strains, and reactivation tectonics. A heterogeneous distribution of different metamorphic and magmatic assemblages with distinct spatial and temporal strain variations in shaping the fabric elements in different blocks is identified. Both EGMB and SGT share a common transpressional deformation history during the latest Neoproterozoic characterized by the steepening of the initial low angle crustal scale structures leading to a subvertical grain conducive to reactivation tectonics. Our synthesis of the spatial distribution, geometry, kinematics and the transpressional strain of the shear zone systems provides insights into the tectono-metamorphic history of the Proterozoic orogens of southern India and their contiguity and complexities. Recent understanding of subduction, accretion and collisional history along these zones together with a long lived transpressional tectonic regime imply that these orogens witnessed identical tectonic regimes at different times in Earth history, although the major and common structural architecture was built during the final assembly of the Gondwana supercontinent.
机译：印度半岛南部的前寒武纪地层一直是关于超大陆形成和分裂历史的讨论的中心。特别令人感兴趣的是印度盾构南缘和东缘的元古代高级变质造山带，绕过3.4 Ga Dharwar克拉通，不仅保留了下地壳过程和岩石圈地球动力学的重要记录，而且还具有构造的印记与主要新元古代超级大陆-Rodinia和Gondwana的组装有关的框架。这些元古代造山带在半岛的南端被描述为南部花岗石地（SGT），在半岛的东部被称为东高止山脉活动带（EGMB）。这些造山带的连续性在〜400 km的距离内破裂，并在孟加拉湾消失。这些造山带暴露出中下地壳的窗口，保存完好的岩石记录显示了多个构造热事件和多相掘出路径。这些造山带的最新研究导致人们认识到被主要剪切带系统隔开的离散的地壳块或地层，其中一些代表了碰撞缝合线。 SGT和EGMB具有几个重要特征，如褶皱冲断构造，在某些情况下直至超高温条件下的区域花岗石相变质，多条PT路径，岩石圈剪切带的发育，蛇绿岩的位置，碱性和钙硅铁杂化物的存在，地壳尺度的“花朵结构”，超压变应变和再活化构造的发展。确定了不同变质和岩浆组合的异质分布，在对不同块体中的织物元素进行整形时具有明显的时空应变变化。在最新的新元古代，EGMB和SGT都具有相同的压变变形历史，其特征是初始的低角度地壳尺度结构变陡，导致亚垂向晶粒，有利于重新构造。我们对剪切带系统的空间分布，几何学，运动学和超压应变的综合研究，为深入了解印度南部元古代造山带的构造变质历史及其连续性和复杂性提供了见识。对沿这些带的俯冲，增生和碰撞历史以及长寿的压变构造政权的最新了解表明，这些造山带在地球历史的不同时期见证了相同的构造政权，尽管主要的和共同的结构构造是在该构造的最终组装期间建立的。冈瓦纳超大陆。

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