U-Pb (Zircon) Chronology of Late Paleo/Late Mesoproterozoic and Late Cambrian Tectonism in the West Garo Hills, NE India: Tracing the Eastward Continuation of a Proposed Circum-Global Rodinia-Age Collision Zone Abhijit Bhattacharya, Pritom Borah, Nathan Cogné, Anwesa Banerjee, Amulya Chandra Mazumdar, Mridul Rabha, Nicole Sequeira Tectonics, 2025 The Assam‐Meghalaya Gneiss Complex (AMGC), NE India is located at the junction of a proposed present‐day E‐striking circum‐global Rodinia‐age (1.03–0.93 Ga) collision zone in the Central Indian Tectonic Zone (CITZ) and a NNE‐striking Pan African collision belt. The chronology of tectonic events in AMGC is poorly constrained, and impedes global scale correlation of crustal domains. We integrate mesoscale structures and U‐Pb zircon ages to reconstruct the tectonic evolution of the West Garo Hills crustal domain in west‐AMGC bordering Bangladesh. In this domain, late Paleoproterozoic (1.68–1.62 Ga) basement gneisses and ∼1.62 Ga with steeply dipping N/NE‐striking S1a‐S1b tectonic fabrics are intruded by post‐S1b, pre‐S2 ∼1.47 and ∼1.13 Ga granitoids. A hitherto undocumented post‐S2 phase of recumbent folding tentatively associated with extensional tectonism was overprinted by local E‐striking steeply dipping S4 shear zones. The 0.50–0.48 Ga post‐tectonic granitoids mark the last phase of plutonism in this domain. The pre‐S2 1.68–1.62 Ga anatexis in the basement gneisses is prevalent throughout the CITZ, and in the charnockite‐granitoids in drill cores in northern Bangladesh. The 1.13 Ga AMGC granitoids pre‐date the 1.03–0.93 Ga syn‐collisional granitoids in the CITZ. We infer the CITZ extends across north‐Bangladesh into AMGC, but the Pan African tectonism does not extend west of AMGC. In the West Garo Hills, 1.77–1.75 Ga granitoids are similar in age with those in northern Bangladesh and flanking the CITZ in east‐central India. However, these granitoids did not experience the 1.68–1.62 Ga anatexis in the associated basement gneisses. This suggests the CITZ comprises tectonically interleaved disparately evolved crustal blocks.
Petrography, mineral chemistry, metamorphism and Raman spectroscopic studies of Mahadevpur fall meteorite, India Amulya Chandra Mazumdar, Jayanta Kumar Pati, Anuj Kumar Singh, Balen Bhagabaty, Sarat Phukan, Pritom Borah Geological Journal, 2023 The Mahadevpur (27°39′48″ N, 95°51′32″ E; Arunachal Pradesh, India) meteorite is a fall‐type, coarse‐grained rock consisting of a heterogeneous mixture of chondrules of varying types occurring in a matrix comprising mostly chondrule fragments. It was earlier classified as poorly shocked (S1, unshocked) ordinary chondrite (H4/5). The minerals observed in the Mahadevpur meteorite include olivine, orthopyroxene, clinopyroxene, albitic‐plagioclase, Fe‐Ni alloy and troilite with minor amounts of chromite and phosphate. Olivine and orthopyroxene are almost equilibrated. The textures and compositional features of minerals and chondrule margins indicate a limited degree of recrystallization. The equilibration temperature (700–800°C) for the Mahadevpur chondrite is consistent with the computed temperature (752–902°C) derived from the coexisting orthopyroxene‐clinopyroxene pairs. In the light of new evidences observed during the present study, such as olivine exhibiting undulose extinction and planar to sub‐planar fractures, olivine and orthopyroxene showing strong mosaicism, the shock‐melted plagioclase glasses, the presence of high‐pressure mineral phases and silicate darkening, the earlier proposed shock stage pronouncement has been modified to S4–S5 with supporting petrographic, sub‐microscopic and Raman spectroscopic data. This is the first comprehensive account of the Mahadevpur chondrite with an upgraded shock stage classification.
Geochemical characteristics of Tukureswari and Barbhita granitoid in Goalpara district, Assam B. Bhagabaty, M. K. Mazumdar, A. C. Mazumdar, P. Borah Journal of the Geological Society of India, 2017 ABSTRACT Late intrusive Tukureswari granitoids (TKG) and the Barbhita granitoids (BBG) of Goalpara district in western Assam constitute an important component of the continental crust of the Shillong Plateau. Thus, the geochemical study of these two granitoids involving their origin, classification and petrogenetic significance would be a contribution towards a better understanding of the evolution of continental crust of the Shillong Plateau. The major oxide and trace element geochemistry reveals several genetic issues on these two granitoids. The I-type affinity of the TKG is indicated from the geochemical features such as high TiO2, P2O5 and K2O contents, low normative corundum (< 1%), high Na2O/K2O ratios, and low concentrations of Ni, Co and Cr. Further, enriched LREE-LILE and HFSE depletion, as well as the normal calc-alkaline nature of arc affinity (e.g., enhanced LILE abundance and low HFSE/LILE ratios) of the TKG indicate subduction-related magmatism. The TKG are also categorized as a deep-level pluton, being enriched in LREE and depleted in total REE and HFSE (Y, Nb, Ta, Zr, Hf). The high La/Nb ratio (1.9 – 8.6), negative Nb and Ti anomalies also suggest orogenic related magmatism. On the other hand, the geochemistry of the BBG reveal a high Niggli Si and Mg values, slightly high normative corundum values (2.16 – 3.41), high Th/Ta, Y/Nb, La/Nb, K2O/Na2O, and Rb/Sr ratios. It also shows ASI, K, Rb, and U contents, prominent depletion of Nb, Sr and Ti on the primitive mantle-normalized multi-element spider diagrams and a low concentrations of Cu, Cr, V and Na2O (> 3.2%). All these geochemical characteristics provide strong evidences in support of a sedimentary parentage for Barbhita granitoids (BBG) and are dominantly of S-type.
RECENT SCHOLAR PUBLICATIONS
Geochemistry and geochronology of high-K metaluminous (I-type) Cambrian Guwahati granites from Shillong plateau, Northeast India: Insight into petrogenesis involving peritectic … D Doley, G Sarma, B Bhagabaty, S Kumar, P Borah Geochemistry, 126325 , 2025 2025 Citations: 1
Fluid-induced alteration and associated rare-earth elements (REEs) distribution in accessory minerals in Mayong granite, Shillong Plateau, northeast India D Doley, B Bhagabaty, P Borah International Journal of Earth Sciences 114 (5), 841-854 , 2025 2025 Citations: 1
U‐Pb (zircon) chronology of late Paleo/late Mesoproterozoic and late Cambrian tectonism in the West Garo Hills, NE India: Tracing the eastward continuation of a proposed circum … A Bhattacharya, P Borah, N Cogné, A Banerjee, AC Mazumdar, M Rabha, ... Tectonics 44 (4), e2023TC008024 , 2025 2025 Citations: 4
Petrography, mineral chemistry, metamorphism and Raman spectroscopic studies of Mahadevpur fall meteorite, India AC Mazumdar, JK Pati, AK Singh, B Bhagabaty, S Phukan, P Borah Geological Journal 58 (10), 3630-3645 , 2023 2023 Citations: 1
Modelling B-release and isotopic fractionation during metamorphic dehydration of basalt and pelite: Implications for the source of mineralizing fluid in greenstone-hosted … P Hazarika, D Upadhyay, B Mishra, P Borah, K Abhinay Geochimica et Cosmochimica Acta 304, 83-100 , 2021 2021 Citations: 19
Charnockites and associated rocks in the Shillong Plateau: Petrological implications in the evolution of high grade terrain in Northeast India P Borah Gauhati University , 2020 2020
Monazite and xenotime U–Th–Pbtotal ages from basement rocks of the (central) Shillong–Meghalaya Gneissic Complex, Northeast India P Borah, P Hazarika, AC Mazumdar, M Rabha Journal of Earth System Science 128 (3), 68 , 2019 2019 Citations: 20
Geochemical characteristics of Tukureswari and Barbhita granitoid in Goalpara district, Assam B Bhagabaty, MK Mazumdar, AC Mazumdar, P Borah Journal of the Geological Society of India 89 (5), 532-540 , 2017 2017 Citations: 9
MOST CITED SCHOLAR PUBLICATIONS
Monazite and xenotime U–Th–Pbtotal ages from basement rocks of the (central) Shillong–Meghalaya Gneissic Complex, Northeast India P Borah, P Hazarika, AC Mazumdar, M Rabha Journal of Earth System Science 128 (3), 68 , 2019 2019 Citations: 20
Modelling B-release and isotopic fractionation during metamorphic dehydration of basalt and pelite: Implications for the source of mineralizing fluid in greenstone-hosted … P Hazarika, D Upadhyay, B Mishra, P Borah, K Abhinay Geochimica et Cosmochimica Acta 304, 83-100 , 2021 2021 Citations: 19
Geochemical characteristics of Tukureswari and Barbhita granitoid in Goalpara district, Assam B Bhagabaty, MK Mazumdar, AC Mazumdar, P Borah Journal of the Geological Society of India 89 (5), 532-540 , 2017 2017 Citations: 9
U‐Pb (zircon) chronology of late Paleo/late Mesoproterozoic and late Cambrian tectonism in the West Garo Hills, NE India: Tracing the eastward continuation of a proposed circum … A Bhattacharya, P Borah, N Cogné, A Banerjee, AC Mazumdar, M Rabha, ... Tectonics 44 (4), e2023TC008024 , 2025 2025 Citations: 4
Geochemistry and geochronology of high-K metaluminous (I-type) Cambrian Guwahati granites from Shillong plateau, Northeast India: Insight into petrogenesis involving peritectic … D Doley, G Sarma, B Bhagabaty, S Kumar, P Borah Geochemistry, 126325 , 2025 2025 Citations: 1
Fluid-induced alteration and associated rare-earth elements (REEs) distribution in accessory minerals in Mayong granite, Shillong Plateau, northeast India D Doley, B Bhagabaty, P Borah International Journal of Earth Sciences 114 (5), 841-854 , 2025 2025 Citations: 1
Petrography, mineral chemistry, metamorphism and Raman spectroscopic studies of Mahadevpur fall meteorite, India AC Mazumdar, JK Pati, AK Singh, B Bhagabaty, S Phukan, P Borah Geological Journal 58 (10), 3630-3645 , 2023 2023 Citations: 1
Charnockites and associated rocks in the Shillong Plateau: Petrological implications in the evolution of high grade terrain in Northeast India P Borah Gauhati University , 2020 2020
