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Petrological and Geochronological Constraints on the Evolution of Charnockitic Rocks in the Massifs of Cauvery Shear Zone, Southern Granulite Terrain, India
Journal of the Geological Society of India ( IF 1.2 ) Pub Date : 2020-05-01 , DOI: 10.1007/s12594-020-1472-6
R. Kar , S. Bhattacharya , M. Basei , A. K. Chaudhary

Cauvery shear zone of the southern granulite terrane, India, is sandwiched between the amphibolite to granulite transition zone in the north and the Neoproterozoic granulite belt in the south. Two massifs of this shear zone consist of charnockitic rocks of tonalitic to granodioritic composition and include hornblende-mafic granulite enclaves. Petrology and geochemistry clearly indicate dehydration partial melting of mafic rocks as the mode of origin of the charnockitic rocks. However, high MgO, Ni and Cr contents and negative Nb anomalies suggest some interaction with the mantle in a subduction zone environment. U-Pb and Lu-Hf isotopic data of zircons in mafic granulite enclave and charnockite-enderbite host rocks indicate ca. 2.5 Ga granulite-cum-anatectic event. Juvenile mafic magmatism at ca. 2.7 Ga could represent the precursor of the mafic granulites. With the chemical and isotopic evidence of subduction zone environment, the Cauvery shear zone could be appropriately described as a suture along which Archaean-Paleoproterozoic granulite terrain and Neoproterozoic granulite terrain had collided.

中文翻译:

印度南部花岗岩地块 Cauvery 剪切带地块中 Charnockitic 岩石演化的岩石学和地质年代学约束

印度南部麻粒岩地体的高维剪切带夹在北部角闪岩向麻粒岩过渡带和南部新元古代麻粒岩带之间。该剪切带的两个地块由斜长岩至花岗闪长岩组成的炭质岩组成,并包括角闪石-镁铁质麻粒岩飞地。岩石学和地球化学清楚地表明,基性岩的脱水部分熔融是卡诺克岩的成因模式。然而,高 MgO、Ni 和 Cr 含量以及负的 Nb 异常表明在俯冲带环境中与地幔存在一些相互作用。U-Pb 和 Lu-Hf 同位素数据显示在镁铁质麻粒岩飞地和炭黑-尾矿主岩中的锆石。2.5 Ga麻粒岩兼深熔事件。幼年基性岩浆作用在大约。2. 7 Ga 可以代表镁铁质麻粒岩的前体。凭借俯冲带环境的化学和同位素证据,可将高维剪切带恰当地描述为太古宙-古元古代麻粒岩地貌与新元古代麻粒岩地貌相碰撞的缝合线。
更新日期:2020-05-01
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