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The Chotanagpur Gneissic Complex (CGC) is characterized by the Makrohar Granulite Belt (MGB) at its north‐western margin parallel to Son‐Narmada lineaments. The MGB exhibits a typical association of mantle‐derived mafic tholeiitic and alkaline rocks along with the felsic units. The zircon U–Pb data on the intrusive granite gneiss from this association define a crystallization age of 1,498 ± 38 Ma, representing a widespread Mesoproterozoic within‐plate magmatic event in CGC synchronous with the breakup of the Columbia Supercontinent. These granite gneisses have an alkaline affinity and are metaluminous in character. They exhibit many of the geochemical characteristics of anorogenic (A‐type) magmas, including enrichment of incompatible trace elements, like Zr, Hf, Nb, Y, Ga, and rare earth elements (REE), but low in Ba and Sr as well as high FeOt/(FeOt + MgO) (~0.98) values and Ga/Al (~3.92) ratios. They show less fractionated REE patterns, characterized by relatively enriched LREE and flat HREE with negative Eu anomaly, and have high Zr‐saturation temperatures (~955°C). Considering their field characteristics and all the geochemical and isotopic features, we conclude that they were derived from melting the lower crust metasomatized by mantle‐derived alkali‐rich fluids due to asthenospheric upwelling. [ABSTRACT FROM AUTHOR]

The depositional history of the Himalayas has been overprinted by the tectonic activities during the Himalayan Orogeny. A detailed investigation of the sedimentary units can provide crucial information regarding their depositional history and provenance. This study aims at constraining the weathering history, tectonic setting, and provenance of meta‐sediments from the Shimla and Chail Groups of Outer Lesser Himalaya. With similar major element chemistry, these meta‐sediments comprise a low‐silica group (avg. SiO2/Al2O3 <3.29). Weathering intensity parameters chemical index of alteration (CIA), plagioclase index of alteration (PIA) and index of chemical variability (ICV) range from 62 to 78 (avg. = 69.41), 70 to 96 (avg. = 85.34), and 0.45 to 1.45 (avg. = 1.01), respectively indicating moderate to severe degrees of weathering. Transition element ratios [Cr/V (1.68–5.18), Ni/Co (1.47–30.99), and V/Ni (0.87–4.61)], and trace element bivariate plots suggest a recycled, felsic to intermediate provenance that has primarily been derived from Post‐Archean sources with minor inputs from Archean units. A passive margin depositional setting with arc‐derived sources is suggested for the Chail and Shimla meta‐sediments. Rare‐earth element patterns reveal similarities between the studied metasediments with TTG gneisses and sanukitoids from the Aravalli and Bundelkhand Cratons, as well as Chaur and Jutogh granitoids. Therefore, Neoproterozoic Himalayan granitoids and Archean Aravalli‐Bundelkhand granitoids (TTGs and high‐K granitoids) could be potential sources of these meta‐sediments, as also suggested by the detrital zircon age distribution from the Beas‐Satluj‐Pabbar valleys and Shimla Group. [ABSTRACT FROM AUTHOR]

A precise age for the collision of the Kohistan-Ladakh block with Eurasia along the Shyok suture zone (SSZ) is one key to understanding the accretionary history of Tibet and the tectonics of Eurasia during the India-Eurasia collision. Knowing the age of the SSZ also allows the suture to be used as a piercing line for calculating total offset along the Karakoram Fault, which effectively represents the SE border of the Tibetan Plateau and has played a major role in plateau evolution. We present a combined structural, geochemical, and geochronologic study of the SSZ as it is exposed in the Nubra region of India to test two competing hypotheses: that the SSZ is of Late Cretaceous or, alternatively, of Eocene age. Coarse-continental strata of the Saltoro Molasse, mapped in this area, contain detrital zircon populations suggestive of derivation from Eurasia despite the fact that the molasse itself is deposited unconformably onto Kohistan-Ladakh rocks, indicating that the molasse is postcollisional. The youngest population of detrital zircons in these rocks (approximately 92 Ma) and a U/Pb zircon date for a dike that cuts basal molasse outcrops (approximately 85 Ma) imply that deposition of the succession began in the Late Cretaceous. This establishes a minimum age for the SSZ and rules out the possibility of an Eocene collision between Kohistan-Ladakh and Eurasia. Our results support correlation of the SSZ with the Bangong suture zone in Tibet, which implies a total offset across the Karakoram Fault of approximately 130-190 km. [ABSTRACT FROM AUTHOR]

The Sakoli Mobile Belt comprises bimodal volcanic rocks that include metabasalt, rhyolite, tuffs, and epiclastic rocks with metapelites, quartzite, arkose, conglomerate, and banded iron formation (BIF). Mafic volcanic rocks are tholeiitic to quartz-tholeiitic with normative quartz and hypersthene. SiO2 shows a large compositional gap between the basic and acidic volcanics, depicting their bimodal nature. Both the volcanics have distinct geochemical trends but display some similarity in terms of enriched light rare earth element–large ion lithophile element characteristics with positive anomalies for U, Pb, and Th and distinct negative anomalies for Nb, P, and Ti. These characteristics are typical of continental rift volcanism. Both the volcanic rocks show strong negative Sr and Eu anomalies indicating fractionation of plagioclases and K-feldspars, respectively. The high Fe/Mg ratios for the basic rocks indicate their evolved nature. Whole rock Sm–Nd isochrons for the acidic volcanic rocks indicate an age of crystallization for these volcanic rocks at about 1675 ± 180 Ma (initial 143Nd/144Nd = 0.51017 ± 0.00017, mean square weighted deviate [MSWD] = 1.6). The εNdt ( t = 2000 Ma) varies between −0.19 and +2.22 for the basic volcanic rock and between −2.85 and −4.29 for the acidic volcanic rocks. Depleted mantle model ages vary from 2000 to 2275 Ma for the basic and from 2426 to 2777 Ma for the acidic volcanic rocks, respectively. These model ages indicate that protoliths for the acidic volcanic rocks probably had a much longer crustal residence time. Predominantly basaltic magma erupted during the deposition of the Dhabetekri Formation and part of it pooled at crustal or shallower subcrustal levels that probably triggered partial melting to generate the acidic magma. The influence of basic magma on the genesis of acidic magma is indicated by the higher Ni and Cr abundance at the observed silica levels of the acidic magma. A subsequent pulse of basic magma, which became crustally contaminated, erupted as minor component along with the dominantly acidic volcanics during the deposition of the Bhiwapur Formation. [ABSTRACT FROM AUTHOR]

Callovian (late Middle Jurassic) ammonoids Macrocephalites and Jeanneticeras were recovered from the Shyok suture zone, northeast of Chang La Pass, Ladakh, northwest India. They are the first reliable Jurassic fossils and the oldest chronologic data from the Shyok suture zone. The ammonoid-bearing Jurassic strata, newly defined as the Tsoltak Formation, consist largely of terrigenous mudstone with thin sandstone beds and were probably a part of the continental basement to the Cretaceous Ladakh Arc. [ABSTRACT FROM AUTHOR]

Examines the Archaen to Paleo-Protezoic Bundelkhand massif basement of the central Indian shield dissected by mafic dykes on the Proterozoic age. Composition of the dykes; Influence of subduction process on the development of enriched mantle or lithospheric sources; Representation of subduction related juvenile crust by the Bundelkhand massif basement.