| Summary: | The southernmost portion of the Indian subcontinent, the Southern Granulite Terrane of India, holds a pivotal role in the reconstructions of the Ediacaran-Cambrian supercontinent Gondwana. Bound to the west by Madagascar and the East African continental fragments and to the east by Sri Lanka and Antarctica, this terrane offers a breadth of information regarding across terrane correlations and palaeotectonic settings, Arguably, within the Southern Granulite Tenane, the most debated issue of all is the existence of a late Neoproterozoic (ca. 550 - 500 Ma) suture zone between the Salem and Madurai Blocks, termed the Palghat Cauvery ShearZone (or alternatively, the Cauvery Shear Zone). The U-Pb zircon geochronology of the orthopyroxene-bearing orthogneisses (charnockites) in the northern part of Madurai Block yielded Neoarchaean and Cryogenian (ca.2.7 - 2.5 Ga and 795 ± 17 Ma) crystallization ages with metamorphic overprinting at ca. 535 Ma. Their Nd and Sr isotopic ratios (εNd₍τ₎ = -16.9 and +4.55, ⁸⁷Sr/⁸⁶Sr = 0.7017 - 0.7567) suggest they were generated by variable mixing of mantle-derived magmas with the older Archaean crust. The charnockites and garnet-biotite bearing granitoids in the southern part of the Madurai Block yielded much younger crystallization (1007 ± 23 Ma and 784 ± 18Ma) and Nd depleted mantle model ages ranging between 1.69 Ga and 1.38 Ga with low initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7054 - 0.7084, suggesting that the Madurai Block is not a uniform crustal domain, The age of metamorphism in this southern part of the Madurai Block is similar to that further north and indicates isotopic disturbance and zircon growth during the Ediacaran-Cambrian metamorphism. The coupled U-Pb and Lu-Hf isotopic study of the metasedimentary rock packages from the Salem Block mainly yielded late Archaean to early Palaeoproterozoic (ca. 2.7 - 2.45 Ga) detrital zircon ages with εHf values between +0.3 and +8.8, suggesting derivation from largely juvenile sources. ln contrast, the metasedimentary rocks from the Madurai Block ...
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