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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]

The Leo Pargil dome (LPD) in northwest India exposes an interconnected network of pre-, syn-, and post-kinematic leucogranite dikes and sills that pervasively intrude amphibolite-facies metapelites of the mid-crustal Greater Himalayan sequence. Leucogranite bodies range from thin (5-cm-wide) locally derived sills to thick (2-m-wide) crosscutting dikes extending at least 100 m. Three-dimensional exposures elucidate crosscutting relations between different phases of melt injection and crystallization. Combined laser ablation inductively coupled plasma mass spectrometry U-Th/Pb geochronology and trace element analysis on well-characterized monazite grains from nineteen representative leucogranites yields a large, internally consistent data set of approximately 700 U-Th/Pb and 400 trace element analyses. Grain-scale variations in age correlate with trace element distributions and indicate semi-continuous crystallization of monazite from 30 to 18 Ma. The youngest U-Th/Pb ages in a given sample are consistent with the outcrop-scale crosscutting relations, whereas older ages within individual samples record inheritance from partially crystallized melt and source metapelites. U-Th/Pb isotopic and trace element data are incorporated into a model of melting within the LPD that involves (1) steady-state equilibrium batch melting of compositionally homogeneous metapelitic sources; (2) pulses of increased melt mobility lasting 1-2 m.y. resulting in segregation of melt from its source and amalgamation into mixed magmas; and (3) rapid emplacement and final crystallization of leucogranite bodies. Melt systems in the LPD evolved from locally derived, in situ melt in migmatitic source rocks into a vast network of dikes and sills in the overlying non-migmatitic host rocks. [ABSTRACT FROM AUTHOR]

Field, petrological and mineral chemistry for meta-volcanic rocks from the Aravalli sequence (Aravalli Craton, India) are presented. Field evidence such as volcanic flows and suspect pillow lava structures, dominant Fe-tholeiite lava flows intercalated with quartzites and argillaceous sediments, indicate rift tectonic environment. Primary mineralogy was obliterated during post-magmatic processes such as metamorphism corresponding to the greenschist to lower amphibolite facies conditions. The rock's mineral composition was overprinted by plagioclase–chlorite–amphibole–epidote assemblage. The relicts of clinopyroxene were observed. The P-T estimation indicates a temperature of 550–600 °C for the pressure ranging from 3.0 to 7.0 kbar for the majority of amphiboles and 8.0–10.7 kbar for the minority. Geochemically, these rocks are komatiitic (picritic) and high-Fe tholeiitic basalts with 45.06−59.2 wt.% SiO2 and MgO content from 5 to 22.4 wt.% and Mg# of 17 to 71. They show large-ion lithophile elements (LILE) and light rare-earth elements (LREE) enrichment. Chondrite normalized rare-earth elements (REE) patterns for the Aravalli lava are moderately enriched with (La/Sm)N = 1.1−3.85, (La/Yb)N from 1.49 (komatiites) to 14.91 (komatiitic basalts). The trace element systematics with the negative Nb, P and Zr anomalies reflect their derivation from enriched sub-continental lithospheric sources, although minor crustal contamination cannot be ruled out. Aravalli rocks are considered to represent the transition from continental rift magmatism to shallow submarine eruption. [ABSTRACT FROM AUTHOR]

• A-type granites are identified in the Mahakoshal Supracrustal Belt, India. • These granites are 1645–1796 Ma old. • They were derived by reworking of the Archean basement of Bundelkhand Craton. • They were originated during extension in post-collisional tectonic setting. There are several A-type granitic plutons in the central and western parts of the Mahakoshal Supracrustal Belt (MSB), India. We report new whole-rock elemental and Nd isotope data along with zircon U-Pb ages on these granites. The ID-TIMS zircon U-Pb ages of these granites are 1645 ± 25 Ma, 1695 ± 9 Ma, and 1796 ± 17 Ma. These granites are metaluminous to weakly peraluminous, alkali-calcic to calc-alkalic and ferroan in composition. They are characterized by enrichment in REEs (except Eu) and HFSEs (Zr, Y), and depletion in LILEs (Ba, Sr). They have high Ga/Al (2.6–5.4) ratios and elevated magmatic temperatures (≥900 °C). Elemental ratios such as Y/Nb, Nb/Ta, Th/Nb, La/Nb and Ce/Pb coupled with negative Nb, Sr, Eu, and Ti anomalies suggest their derivation from crustal sources. They have very low ε Nd (t) values (−11.4 to −5.6) and older Nd model ages (T DM : 2481–3225 Ma) confirming their crustal derivation. We propose that partial melting of the Archean tonalitic-granodioritic crust of basement Bundelkhand Craton in low-pressure high-temperature conditions generated the parental magma of these granites. Their A 2 -type affinity (Y/Nb ˃ 1.2) further suggests their emplacement in an extensional environment related to post-collisional tectonic setting. [ABSTRACT FROM AUTHOR]