Santosh Kumar
@kunainital.ac.in
Professor, Department of Geology, Faculty of Science
Kumaun University
RESEARCH, TEACHING, or OTHER INTERESTS
Geology, Geochemistry and Petrology
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Chandni Chaurasia, Satyajeet S. Thakur, Suresh C. Patel, Amiya Kumar Samal, Santosh Kumar, and Nainika Gour
Elsevier BV
Chinmay Sethi, Bodhisatwa Hazra, Mehdi Ostadhassan, Hem Bahadur Motra, Arpan Dutta, J.K. Pandey, and Santosh Kumar
Elsevier BV
Raj Vardhan Sharma, Santosh Kumar, Ashis K Adak, and Sudip Maity
Elsevier BV
Akshay Kumar Singh Choudhary, Santosh Kumar, and Sudip Maity
Elsevier BV
Santosh Kumar, Talat Ahmad, and Shailendra Pundir
Springer Science and Business Media LLC
Akshay Kumar Singh Choudhary, Santosh Kumar, Raj Vardhan Sharma, Manavalan Satyanarayanan, and Sudip Maity
Informa UK Limited
Ranjit Nayak, Debasis Pal, Sakthi Saravanan Chinnasamy, Manavalan Satyanarayanan, Santosh Kumar, Jitendra Dash, Pratap Chandra Sethy, and Akhin Mohan
Elsevier BV
Santosh Kumar, Akshay K Singh Choudhary, A Keshav Krishna, and Sudip Maity
Springer Science and Business Media LLC
Ch. Narshimha and Santosh Kumar
Springer Science and Business Media LLC
Santosh Kumar
Springer Science and Business Media LLC
Diezeneino Meyase, Vikoleno Rino, Santosh Kumar, and Rokozono Nagi
Wiley
Shailendra Pundir, Vikas Adlakha, Santosh Kumar, Saurabh Singhal, and Satyabrata Das
Frontiers Media SA
The Karakoram Terrane (KT) represents the southern margin of the Eurasian Plate, mainly consisting of Late Jurassic-Early Cretaceous subduction-related granites and post-collisional Miocene leucogranites, which intrude the Late Neo-Proterozoic basement. We report for the first time the existence of the Cryogenian KT basement as recorded from the geochemistry and geochronology of tonalite gneiss (ca. 806 Ma) in the southeastern Karakoram terrane, NW India. Geochemically, the studied tonalite gneiss is slightly peraluminous (Molar Al2O3/CaO+Na2O+K2O=1.1), calc-alkaline volcanic-arc granitoid, strongly fractionated REE (LaN/YbN=33.99), and high Sr/Y =19.75, more akin to its affinity with Tonalite–trondhjemite–granodiorite (TTG)/adakite. The whole-rock elemental data suggest that tonalite gneiss is more likely sourced from ancient mafic lower crust where garnet remained in the residue. The petrogenetic modeling of REE suggests that the melt similar to the observed tonalite gneiss can be generated through ∼50% partial melting of a mafic lower crust with garnet, clinopyroxene, and amphibole assemblage. The synthesis and comparison of present and published Proterozoic magmatic records on the rocks from KT strongly dictate that the produced partial melt similar to observed tonalite gneiss most likely served as the parental melt for the development of TTGs in the Southern Pamir and more evolved granitoid in the Central Tibetan terrane. We propose that the studied tonalite gneiss from the southeast Karakoram is a product of Neoproterozoic Andean-type orogeny formed on the northwestern margin of the Rodinia supercontinent. Thus, our study favors the first time, the position of KT within the Cimmerian belt along with other East Asian continental blocks.
Shubham Choudhary, Koushik Sen, Shruti Rana, and Santosh Kumar
Springer Science and Business Media LLC
AbstractThe Sung Valley ultramafic–alkaline–carbonatite complex (UACC) of Meghalaya, NE, India, is a result of magmatic activity related to the Kerguelen mantle plume spanning from 101 to 115 Ma. In the present study, an integrated crystal size distribution (CSD), mineral chemistry, and melt inclusion analysis are carried out on the ijolites present within this UACC. The CSD analysis shows that these ijolites were formed in multiple stages through changes in the crystallization environment, such as cooling and nucleation rates. Raman spectroscopy of mineral inclusions of rutile, aphthitalite, apatite, carbonate–silicate melt inclusions, and disordered graphite within clinopyroxene and titanite, respectively, indicates a heterogeneous composition of the parental magma. These mineral and melt inclusion phases further suggest localized changes in oxygen fugacity (fO2) due to redox reactions in the lower crust. SEM–EDX analysis of the exposed melt inclusions reveals the presence of alkali-bearing diopside, phlogopite, and andradite, along with an unidentified carbonated silicate daughter phase. The studied melt inclusions are dominated by carbonate, whereas silicates are subordinate. The presence of this fully crystallized carbonate–silicate melt as calcite, diopside, phlogopite, magnetite, apatite, and andradite suggests the presence of “nano-calciocarbonatites” in these ijolites. Our study provides insights into different mechanisms of the loss of alkalies from initially entrapped alkaline carbonate melt in clinopyroxenes. The predominant occurrence of calcite as the only carbonate phase in the studied melt inclusions is a result of silicate–carbonate melt immiscibility, calcite-normative system in these inclusions, dealkalization of the alkaline carbonates in the presence of external fluid, and/or redistribution of the alkalies to the daughter alkali-bearing silicates.
Santosh Kumar and Jean-François Moyen
Springer Science and Business Media LLC
Akshay K Singh Choudhary, Santosh Kumar, and Sudip Maity
Springer Science and Business Media LLC
Kapil Singh Panwar and Santosh Kumar
Springer Science and Business Media LLC
Sudip Maity, Akshay K. Singh Choudhary, Santosh Kumar, and Pavan K. Gupta
Springer Science and Business Media LLC
Santosh Kumar, Shailendra Pundir, Vikoleno Rino, Sita Bora, Manjari Pathak, Anettsungla, Hansa Joshi, Manohar Singh Rawat, Thepfuvilie Pieru, and Kh. Mohan Singh
Wiley
The Meghalaya Plateau including the Mikir Hills represents the northeastern extension of the Precambrian Indian Shield and mainly comprises the Proterozoic basement granite gneisses, granites (sensu lato), granulites, metasediments, Cambrian granites, and Mesozoic‐Tertiary lithounits. A new whole‐ rock geochemical dataset of Proterozoic and Cambrian granites is presented and investigated to decipher the petrogenesis of these granites with its implications on understanding the crustal growth history of Meghalaya Plateau. Cambrian granites commonly intrude the Proterozoic basement granite gneisses and Shillong Group of rocks. Both the Proterozoic and Cambrian granites exhibit similar mineral assemblages (Bt ± Amp‐Pl‐Kf‐Qz‐Zrn‐Mag‐Ttn‐Ap ± Ilm), but they are texturally distinct. Microgranular enclaves are ubiquitous in Cambrian plutons but are devoid or rare in the Proterozoic granites. Cambrian granites are medium‐ to coarse‐grained, inequigranular, hypidiomorphic, frequently porphyritic, and undeformed to mildly deformed, whereas Proterozoic granites are medium‐ to coarse‐grained, less frequent porphyritic, and mildly to strongly deformed. Geochemically, the Proterozoic (molar Al2O3/CaO + Na2O + K2O (A/CNK) = 0.86–1.15; FeOt/FeOt + MgO = 0.60–0.93) and Cambrian (A/CNK = 0.77–1.20; FeOt/FeOt + MgO = 0.56–0.90) granites are nearly identical showing strongly metaluminous to moderate peraluminous, magnesian to ferroan, and alkali‐calcic to calc‐alkaline and transitional character between I‐type and A‐type oxidized granites formed in a post‐collision tectonic environment. Comparison of studied granites with experimental melt compositions derived from various protoliths suggests that they are sourced from metabasics to tonalites. Harker bivariate plots demonstrate fractional differentiation as a dominant process in the evolution of these granites. However, occurrence of hybrid microgranular enclaves and geochemical features manifest that the mixing and fractionation of coeval mafic and felsic magmas have also played a key role in the evolution of some Cambrian plutons. A slightly higher zircon saturation temperatures for Cambrian (700–950°C) than the Proterozoic (675–900°C) granites characterize a relatively higher‐T melting regime for the generation of Cambrian than the Proterozoic granites. Petrogenetic modelling constrains that the parental magma to the Proterozoic granites can be generated by about 25.5% melting of heterogeneous lower crustal sources with low maficity, which subsequently had undergone fractional crystallization involving bt‐amp‐pl‐Kf‐qz assemblage. However, parental to Cambrian granites can be produced by about 32% melting of the amphibolitic lower crust that subsequently evolved through synchronous fractional crystallization and mixing with a mantle‐derived mafic melt. The chronological records and the present petrogenetic findings on Proterozoic granites propound a viable geodynamic model that the assembly and growth (thickening) of the Columbia Supercontinent during ca. 1,800–1,600 Ma caused a high‐temperature regime that induced the melting of the lower crust and formed the Proterozoic granites. On the other hand, the delamination‐induced decompression melting of lower (amphibolite) crust during the break‐up (ca. 550–500 Ma) of Pan‐African‐Brasiliano orogeny‐related Gondwana Supercontinent led to the generation of felsic magmas in batches that interacted, at least in some cases, with lithospheric mantle‐derived mafic magma and formed the Cambrian plutons of Meghalaya Plateau.
Shubham Choudhary, Koushik Sen, and Santosh Kumar
Geological Society of London
Abstract Sulfides play a crucial role in the distribution of chalcophile elements in the Earth's mantle. In this work, combined petrography and mineral chemistry of sulfide and diopside in a pyroxenite from an ultramafic–alkaline–carbonatite complex of NE India, related to the Kerguelen plume, was carried out and a considerably high sulfur concentration in the parental melt of the pyroxenite was obtained. Two types of sulfide, with similar compositions, were detected in pyroxenite: Type A are multifaceted polygons, elliptical and spherical in shape, occurring as poikilitic inclusions in diopside; and Type B are intergranular sulfides of irregular shapes in silicate grains. These sulfides are often partially replaced by magnetite. Mineral chemistry suggests that both types of sulfide are products of re-equilibration of high-temperature monosulfide solid solution and represent a low-temperature (c. 400°C) mineral phase of the Cu–Fe–S system. Petrographical features suggest that the sulfides were separated as immiscible melt droplets at the time of sulfur saturation and fractionation of diopside in the coexisting silicate magma. Our study implicates that both high- and low-temperature sulfides can form in the plume-associated ultramafic rocks.
Shruti Rana, Rajesh Sharma, and Santosh Kumar
Springer Science and Business Media LLC
Saurabh Gupta and Santosh Kumar
Springer Science and Business Media LLC
Deepa Arya, Saurabh Gupta, Santosh Kumar, and Xisheng Xu
Elsevier BV