Browsing by Author "Sun-Lin Chung"

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Age and isotope geochemistry of magmatic rocks of the lohit plutonic complex, eastern himalaya: Implications for the evolution of transhimalayan arc magmatism
(Geological Society of London, 2019) R.K. Bikramaditya; Sun-Lin Chung; A. Krishnakanta Singh; Hao-Yang Lee; Te-Hsien Lin; Yoshiyuki Iizuka
We present integrated in situ zircon U–Pb and Hf isotope data, along with whole-rock Sr–Nd isotope and geochemical data for plutonic rocks of the Lohit Plutonic Complex of eastern Himalaya to understand the age distribution and petrogenetic–tectonic evolution of the Transhimalayan batholiths in the eastern Himalaya. The plutonic rocks are gabbro, diorite and quartz-diorite in composition, have calc-alkaline signatures with metaluminous character and have an affinity with Gangdese I-type granitoids of southern Tibet. The enrichment of large ion lithophile elements with highly depleted negative Nb anomalies is consistent with their origin in a subduction-related environment. Our laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb ages suggest that two major stages of magmatic emplacement took place at c. 145 Ma (Early Cretaceous) for gabbro and c. 100–90 Ma (early Late Cretaceous) for diorite and quartz-diorite. The zircon Hf isotopes in both the gabbro and diorite samples show high positive εHf (t) values between +11 and +20, suggesting crystallization from juvenile crust or depleted mantle derived melts, as also constrained by the low initial87 Sr/86 Sr ratios (0.7038–0.7045) and high positive εNd (t) values (+2.9 to +5.9). Results of REE modelling indicate that the source of these rocks is garnet lherzolite. Field observations and mineralogical and geochemical characteristics in conjunction with the isotopic database suggest that the Transhimalayan magmatic rocks in eastern Himalaya were generated by partial melting of the lithospheric mantle wedge and emplaced into the lower crust (c. 25–30 km) during at least two major magmatic events that took place in the Cretaceous period. © 2019 The Author(s).
Magmatism in the Siang window of the Eastern Himalayan Syntaxis, NE India: a vestige of Kerguelen mantle plume activity
(Geological Society of London, 2022) Athokpam Krishnakanta Singh; Govind Oinam; Sun-Lin Chung; R.K. Bikramaditya; Hao-Yang Lee; Mallickarjun Joshi
We report new U–Pb zircon ages for mafic plutonic (gabbro) and volcanic (andesite) rocks, along with the whole-rock chemistry of a mafic–felsic suite of volcanic rocks from the Siang window of the Eastern Himalayan Syntaxis, NE India. Field relationships, and mineralogical and geochemical characteristics, of the studied mafic–intermediate–felsic rocks suggest their co-magmatic linkage that was generated in an extensional tectonic environment. Incompatible trace elements and low concentrations of large ion lithophile elements (LILEs) and REE behaviour reflect both the enriched nature of the mafic rocks and the limited influence of crustal contamination in their genesis. Partial melting and fractional crystallization processes have played a major role during the genesis of these felsic volcanics from the parental mafic magma. The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb ages suggest that the mafic plutonic rock was emplaced at c. 121.18 + 1 Ma and intermediate volcanic rock was emplaced at c. 135.48 + 0.50 Ma during the Early Cretaceous period. The new ages are consistent with earlier reported zircon U–Pb ages (133.0 + 1.9–130.7 + 1.8 Ma) of felsic volcanic rocks from the present study area. Our new field observations, and mineralogical and geochemical characteristics, in conjunction with the U–Pb isotopic database suggest that the major magmatic event in the core of the Siang window of the Eastern Himalaya is coeval with the Raj-mahal–Sylhet–Mikir–Shillong flood basalts of eastern and northeastern India, and the Comei–Bunbury Large Igneous Province of southeastern Tibet and SW Australia. These events are related to the break-up of eastern Gondwana and outbreak of the Kerguelen plume. © 2021 The Author(s).
Tectonic evolution of the neoproterozoic tusham ring complex, Northwestern India: Constraints from geochemistry and zircon U–Pb geochronology, and implications for Rodinia supercontinent history
(Elsevier B.V., 2023) A. Krishnakanta Singh; Naveen Kumar; Sun-Lin Chung; Hao-Yang Lee; M. Santosh; Radhika Sharma; Naresh Kumar; R.K. Bikramaditya; Govind Oinam; Nongmaithem Lakhan
Neoproterozoic felsic magmatic suites are important proxies to investigate the breakup history of the Rodinia supercontinent which likely coincided with the emplacement of voluminous Silicic Large Igneous Provinces (SLIPs). Here we report new zircon U–Pb ages with comprehensive whole-rock and mineral chemistry data on the felsic volcano-plutonic rocks from the Tusham Ring Complex (TRC) that forms part of the anorogenic Malani Igneous Suite (MIS) (∼780–750 Ma) in NW India. The plutonic rocks (granites) and contemporaneous volcanic rocks (rhyolites) show affinity to A-type granitoids, hypersolvus to subsolvus, and metaluminous to peraluminous. The granitoids investigated in this study are enriched in SiO2, Na2O + K2O, Fe/Mg, Ga/Al, U, Th, REE (except Eu), and depleted in MgO, CaO, Cr, Ni, P, Ti, Sr, and Eu contents. The zircon U–Pb dating for felsic volcanic rocks (four rhyolite samples) yielded Neoproterozoic ages ranging from 827 to 764 Ma whereas zircon in five felsic plutonic rocks (granite) shows ages ranging from 830 to 787 Ma, indicating coeval nature of the intrusive and extrusive rocks. The zircon grains have mostly negative εHf(t) values up to −3.62 and yield crustal Hf model ages from 1.6 Ga to 1.9 Ga, suggesting that the magmatic event involved melting of a Paleoproterozoic source. Based on geochemical features, we propose that the partial melting of crustal protoliths, fractional crystallization, and crustal contamination played a significant role in the magmatic evolution of these rocks. We also infer that the felsic anorogenic magmatism in the TRC occurred in an extensional tectonic regime, possibly associated with a mantle plume event. Our results, in conjunction with previous studies, support the model of anorogenic magmatism linked with the disruption of the Neoproterozoic Rodinia supercontinent. © 2023 Elsevier B.V.
Zircon U–Pb ages and Hf isotopes of I-type granite from western Arunachal Himalaya, NE India: Implications for the continental arc magmatism in the Palaeoproterozoic supercontinent Columbia
(John Wiley and Sons Ltd, 2022) R.K. Bikramaditya; Sun-Lin Chung; Athokpam Krishnakanta Singh; Hao-Yang Lee; Leiphrakpam Lemba
We present integrated in situ zircon U–Pb and Hf isotope data, along with whole-rock and mineral chemistry data for the Salari granite of western Arunachal Himalaya to constrain its emplacement age, origin, and geodynamic evolution. The investigated Salari granites are high Fe2O3, CaO, and Nb, and low SiO2 and Rb/Sr ratio with fractionated rare earth element patterns ((Ce/Yb)N = 9.90–20.24) and minor negative Eu anomaly (Eu/Eu* = 0.69–0.94). They are metaluminous (molar A/CNK = 0.93–1.07) and have relatively similar FeOt/MgO ratio in biotite (1.58–1.60) to Mg-biotite, indicating their affinity with I-type granites. The enrichment of large-ion lithophile elements with highly depleted negative Nb anomalies is consistent with their origin in a subduction-related environment. Our zircon U–Pb ages suggest that the magmatic emplacement of the Salari granite took place between 1,791 and 1,768 Ma. The zircon grains have mostly negative εHf(t) values up to −5.5 and yield crustal Hf model ages from 2.4 to 2.8 Ga, suggesting the occurrence of a major crustal growth event in the Neoarchean and re-melting of the crust during the Palaeoproterozoic. Our new results, that is, zircon U–Pb age and Hf isotope data, in conjunction with the field observations and petro-mineralogical and geochemical characteristics, suggest that the Salari granite of eastern Himalaya was produced by partial melting of older metabasaltic/metatonalitic rocks in a continental arc setting of the supercontinent Columbia during the Palaeoproterozoic. © 2021 John Wiley & Sons Ltd.
Zircon u–pb ages and lu–hf isotopes of metagranitoids from the subansiri region, eastern himalaya: Implications for crustal evolution along the northern indian passive margin in the early paleozoic
(Geological Society of London, 2019) R.K. Bikramaditya; A. Krishnakanta Singh; Sun-Lin Chung; Rajesh Sharma; Hao-Yang Lee
We studied the zircon U–Pb ages, Hf isotopes, and whole-rock and mineral chemistry of metagranitoids from the Subansiri region of the Eastern Himalaya to constrain their emplacement age, origin and geodynamic evolution. The investigated metagranitoids have high SiO2, Na2 O + K2 O, Rb, Zr and low Fe2 O3, Nb, Ga/Al ratios with fractionated rare earth element patterns [(Ce/Yb)N = 6.46–42.15] and strong negative Eu anomalies (Eu/Eu* = 0.16–0.44). They are peraluminous (molar A/CNK = 1.04–1.27) and calc-alkaline in nature, with normative corundum (1.04–3.61) and relatively high FeOt /MgO ratios in biotite (c. 3.38), indicating their affinity with S-type granites. The time of emplacement of the Subansiri metagranitoids is constrained by zircon U–Pb ages between 516 and 486 Ma. The zircon grains have negative εHf(t) values ranging from −1.4 to −12.7 and yield crustal Hf model ages from 1.5 to 2.2 Ga, suggesting the occurrence of a major crustal growth event in the Proterozoic and re-melting of the crust during the early Paleozoic. The geochemical data in conjunction with the U–Pb ages and Hf isotope data suggest that the Subansiri metagranitoids were produced by partial melting of older metasedimentary rocks in the Indian passive margin. © 2019 The Author(s). Published by The Geological Society of London. All rights reserved.
Zircon U–Pb geochronology, Hf isotopic compositions, and petrogenetic study of Abor volcanic rocks of Eastern Himalayan Syntaxis, Northeast India: Implications for eruption during breakup of Eastern Gondwana
(John Wiley and Sons Ltd, 2020) Athokpam Krishnakanta Singh; Sun-Lin Chung; Rajkumar Bikramaditya; Hao-Yang Lee; Shoraisam Khogenkumar
This paper reports new zircon U–Pb ages and Hf isotopic compositions of felsic units of the Abor volcanic rocks (AVR) of Eastern Himalayan Syntaxis (EHS), Northeast India, and discusses their relationship to the Kerguelen plume activity. The AVR are bimodal and predominantly constituted by mafic rocks with minor felsic units. Mafic volcanics are identified as basalt and basaltic andesite with light rare earth elements (LREE) enriched and slightly depleted heavy rare earth elements (HREE) pattern without Eu anomalies. Low concentrations of LILE, high contents of Fe2O3, and other incompatible trace elements ratios reflect enriched nature of these mafic volcanics. Felsic volcanic rocks are dacitic to rhyolitic in composition, which have high REE content, high LREE/HREE, and pronounced negative Eu anomalies. Enriched LREE, high Th/Nb, Ce/Nb ratios, and variations in Rb/Zr, K/Rb, La/Sm ratios with negative anomalies of Ba, Nb, Sr, P, Ti in felsic rocks suggest substantial contribution of crustal contamination at the time of eruption. Zircons from felsic units yield an average U–Pb age of ~132 Ma and unradiogenic (ƐHf(t) < 0) Hf isotope values of −7.0 to −13.3 with model ages between 1.5 and 2.1 Ga, suggesting old crustal assimilation in their genesis. The AVR were emplaced in the continental rift tectonic setting, and depth of the magma source is confirmed as near spinel stability zone. The AVR are positively comparable with other flood basalts that were formed due to the Kerguelen plume activity. Therefore, our combined new geochemical and geochronological data show that the AVR were emplaced at early stage (~132 Ma) of eastern Gondwana breakup due to outbreak of the Kerguelen plume. This study thus supports the idea of the Kerguelen plume affecting a large area of Eastern India, Western Australia, and Antarctica during early stage of Gondwana breakup. © 2019 John Wiley & Sons, Ltd.