Mesoproterozoic P–T–t–d history in the Vinjamuru domain, Nellore schist belt (SE India), and implications for SE India–East Antarctica correlation
Mesoproterozoic P–T–t–d history in the Vinjamuru domain, Nellore schist belt (SE India), and implications for SE India–East Antarctica correlation
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DOI：
10.1016/j.precamres.2019.04.002
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发表时间：
2019-07
影响因子：
3.8
通讯作者：
H. Hrushikesh;N. Prabhakar;A. Bhattacharya
中科院分区：
文献类型：
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作者：
H. Hrushikesh;N. Prabhakar;A. Bhattacharya
Vinjamuru域是Nellore片岩带（NSB）的重要地壳段，其构造变质演化为印度东南部元古宙造山作用提供了重要信息，也与古元古代晚期和中元古代中期的印-南对比有关。含石榴子石-十字石-蓝晶石的变质岩具有三个变质阶段，即Saidapuram-Sangam地区（S区）的M1S、M2S和M3S，Vinjamuru-Malakonda地区（N区）的M1N、M2N和M3N。在这两个扇区中，变细岩表现出较早的褶皱（S1）的浅叶理（S2）轴向平面至平卧褶皱（F2），并叠加有平缓倾伏的直立F3褶皱，轴向平面组构（S3）在S扇区中向北，在N扇区中向北北东。Syn-D3S石榴石+十字石+蓝晶石+白云母+黑云母+石英+钛铁矿±斜长石和石榴石（晚-D2N-早-D3N）+蓝晶石+白云母+黑云母+石英+钛铁矿+斜长石±十字石组合是S区变质峰期的特征（M3S，P = 8.8 - 9.2 kbar，T = 630 - 650 ° C）和扇区N（M3N，P = 6.5 - 7.5 kbar，T = 620 - 640 ° C）。变岩中的P-T峰值条件（M3S/M3N）与S扇区中的陡倾S3N和N扇区中的浅倾S2N大致同时存在。独居石全Pb测年结果表明，独居石的年龄分别为1.65 - 1.55Ga、1.50 - 1.40Ga、1.38 - 1.25Ga和0.84 - 0.76Ga。最古老的年龄人口（1.65 - 1.55 Ga）可能对应于大规模改造的预先存在的地壳在Vinjamuru域。随后，在1.50和1.40 Ga之间，该区域经历了逆冲变质（M1S/M1N-M2S/M2N），这可能归因于NSB内的中地壳缩短。1.38 - 1.25 Ga年龄对应于上角闪岩相变质作用（M3S/M3N），并与NSB中广泛存在的长英质深成作用相吻合。新元古代的年龄（0.84 - 0.76 Ga）可以说是一个蚀变事件，影响NSB在Rodinia超大陆解体。中元古代变质作用和长期造山事件（1.65 - 0.76 Ga）在Vinjamuru域是类似的记录在东南极洲的基底岩石，建议一个可能的构造联系沿着增生边缘。
The Vinjamuru Domain is an important crustal segment in the Nellore schist belt (NSB) and the tectono-metamorphic evolution of the belt provides insights into Proterozoic orogenesis in southeastern India, and is also relevant to an Indo-Antarctic correlation in the Late Paleoproterozoic and Middle Mesoproterozoic. Garnet-staurolite-kyanite bearing metapelites in this domain exhibit three metamorphic stages, e.g. M1S, M2Sand M3Sin the Saidapuram–Sangam area (sector-S) and M1N, M2Nand M3Nin the Vinjamuru–Malakonda area (sector-N). In both sectors, the metapelites exhibit shallow foliation (S2) axial planar to recumbent folds (F2) of an earlier schistosity (S1), and overprinted by gently-plunging upright F3folds, with axial planar fabric (S3) trending north in sector-S, and NNE in sector-N. Syn-D3Sgarnet + staurolite + kyanite + muscovite + biotite + quartz + ilmenite ± plagioclase and garnet (late-D2Nto early-D3N) + kyanite + muscovite + biotite + quartz + ilmenite + plagioclase ± staurolite assemblages characterize the peak metamorphic episodes in the sector-S (M3S, P = 8.8–9.2 kbar, T = 630–650 °C) and sector-N (M3N, P = 6.5–7.5 kbar, T = 620–640 °C) respectively. The peakP–Tconditions in the metapelites (M3S/M3N) are broadly contemporaneous with the steep-dipping S3Sin sector-S and shallow-dipping S2Nin sector-N. Total-Pb monazite dating in the chemically distinct monazite domains yields age populations at 1.65–1.55 Ga, 1.50–1.40 Ga, 1.38–1.25 Ga and 0.84–0.76 Ga. The oldest age population (1.65–1.55 Ga) possibly corresponds to large-scale reworking of the pre-existing crust in the Vinjamuru domain. Subsequently, the domain experienced prograde metamorphism (M1S/M1N–M2S/M2N) between 1.50 and 1.40 Ga, which may be attributed to a mid-crustal shortening within the NSB. The 1.38–1.25 Ga ages correspond to upper amphibolite facies metamorphism (M3S/M3N) and coincides with widespread felsic plutonism in the NSB. The Neoproterozoic ages (0.84–0.76 Ga) arguably represent an alteration event that affected the NSB during Rodinia supercontinent breakup. The Mesoproterozoic metamorphism and the long-lived orogenic events (1.65–0.76 Ga) in the Vinjamuru domain are similar to those recorded in the basement rocks of East Antarctica, suggesting a possible tectonic linkage along accretionary margins.