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The Nagercoil block, which is situated at the southernmost part of the Southern Granulite Terrane of south India, is dominantly comprised of garnet-bearing I-type massive charnockites. These charnockites preserve imprints of two major thermal events timed at Palaeoproterozoic (∼2.0–1.9 Ga) and Neoproterozoic (∼550 Ma). However, there is a lack of understanding on correlating the growth and stabilization of garnets within these charnockites, corresponding to these events. In the present study, rare earth element-based partition modeling between garnet and age-constrained accessory phases such as zircon and monazite is carried out to identify the exact timing of garnet formation in a representative sample from the area. U-Pb dating of zircon cores constrains the timing of protolith emplacement at ∼2.0 Ga and metamorphism at ∼550 Ma from zircon rims and monazites. REE modeling of zircon and monazite from these age domains suggests an equilibrium relation between the Neoproterozoic zircon rims and monazites, while the Palaeoproterozoic zircon cores are not in equilibrium with garnet. These results suggest that the formation of garnets in the Nagercoil charnockites is in response to the Neoproterozoic metamorphism recorded in the terrane associated with the final stage of the Gondwana supercontinent assembly. [ABSTRACT FROM AUTHOR]

Much of the geological record of the northern Indian passive continental margin has been lost due to erosion or obscured due to tectonic burial associated with the India-Eurasia collision. Consequently, tectonic models of India's breakup from East Gondwana incorporate limited data from the northern margin of Greater India. We present evidence of the Late Jurassic clastic dykes crosscutting contemporaneous sedimentary sequences in the Tethys Himalaya. We propose that the original orientation of the clastic dykes provides kinematic information about Greater India's breakup from East Gondwana. The clastic dykes are meters to hundreds of meters long and centimeters to meters wide. They taper downwards and crosscut country rocks at high angles. The clastic dykes and their host strata are quartzose sandstones and share similar textures and detrital zircon age populations (dominantly 600–500 Ma and 1000–800 Ma zircon grains). These similarities indicate the clastic dykes and their host rocks share a common source as well as comparable transport and deposition dynamics. Notably, the clastic dykes lack distinct signs of ptygmatic folds, shale/mudrock clasts, surface orientated structures, or bifurcations on dyke margins. Decompaction and structural restoration of the sequences show that the sandstone dykes/fractures and en échelon dyke arrays can be classified into three distinct orientation groups NW (349° − 295°), SW (∼210°) and NE (∼40°). There is no apparent difference in the age or provenance of the clastic material within the different orientation groups. We propose that the clastic dykes signify passively infilled tensile fractures formed within a NW-SE dextral strike-slip megashear system during the Late Jurassic. This system likely developed in a transform zone within Greater India prior to the separation of the Indian Plate from East Gondwana. [Display omitted] • Quartz clastic dykes found in Late Jurassic sequences of Tethys Himalaya. • Restored dyke orientations indicate main NE and SE palaeostress orientations. • Passive infilling clastic dykes formed within a strike-slip megashear system. • A transform zone developed in Greater India during East Gondwana breakup. [ABSTRACT FROM AUTHOR]

• Two diamictites units are recognized on the western margin of Cathaysia Block, and correlate with the global Sturtian and Marinoan glaciations. • Late Tonian, middle Cryogenian and early Ediacaran siliciclastic rocks overlying the Cathaysia Block were derived from sources external to South China. • The Cathaysia Block was linked to North India before 720 Ma. Neoproterozoic paleogeography of the Cathaysia Block of South China is directly linked to the formation of Rodinia, its break-up, and the subsequent amalgamation of Gondwana. Two diamictite units occur in the Neoproterozoic sedimentary successions on the western margin of Cathaysia Block. In combination with our detrital zircon U-Pb dating results and corrected chemical weathering index data (CIA corr), these units coincide with the global Sturtian and Marinoan glaciations. Late Tonian to early Ediacaran sedimentary rocks from western Cathaysia contain abundant late Mesoproterozoic to early Neoproterozoic (1150–870 Ma) and some mid-Neoproterozoic (800–720) detrital zircons. Paleocurrent data indicate sediment transport to the northwest. The timing and character of the ages of detrital zircons match the records of North India and East Antarctica, indicating that the Cathaysia Block received detritus from Gondwana. Thus, South China lay adjacent to northern Gondwana since at least 720 Ma, and possibly considerably earlier. [ABSTRACT FROM AUTHOR]