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Mineralogy and geochemistry of trachytic rocks from the Lichi Volcanics, eastern Himalaya: insights into the Kerguelen mantle plume activity in the eastern Himalayan Region

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Acta Geochimica 2024年第1期43卷 180-197页

作者： Pallabi Basumatary Deepshikha Borah Hiredya Chauhan Tribujjal Prakash Bibhuti Gogoi Department of Geology Cotton UniversityGuwahatiAssam 781001India Wadia Institute of Himalayan Geology DehradunUttarakhand 248001India

The Lichi volcanics are a suite of mafic-intermediate-felsic rocks and are considered coeval with the Abor volcanics(~132 Ma) of the Siang window in the eastern Himalaya. Here, we present the first report of trachytic rocks from the Lichi volcanics, which are exposed in the Ranga valley, along the Kimin-Yazali road section in the eastern Himalayan Region, Northeast India. The trachytes occur in close association with sandstones of the gondwana Group of rocks and are characterised based on field, petrographical, and geochemical investigations.These fine-grained trachytes are composed of alkali feldspar, biotite, plagioclase, sodic-amphibole, apatite, illmenite, and titanite. The REE profiles of the evolved trachytic rocks(higher SiO_(2)content) display fractionated trends. The fractionation of accessory mineral phases, like apatite and titanite, was possibly responsible for the strongly fractionated REE patterns of the evolved samples.The trachytic rocks demonstrate high apatite saturation temperatures of 988 ± 14 ℃(1σ, n = 8). The Aluminium Saturation Index(eastern gondwana due to the onset of Kerguelen plume activity further led to underplating of basic magma in lower crustal levels. These parental basaltic magmas underwent fractionation processes forming differentiated trachyandesites and trachytes.Taking into consideration the similarities recorded between the Lichi volcanics and Abor volcanics, this study supports the idea that Kerguelen plume activities resulted in the emplacement of these vo

关键词： Peralkaline trachytes Trachyandesites A-type granitoids Apatite saturation temperature Abor volcanics eastern gondwana

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Petrology, Geochemistry and Zircon U-Pb Geochronology of the Xiangshan Group in the eastern Hexi Corridor Belt: Implications for Provenance and Tectonic Evolution

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Acta Geologica Sinica(English Edition) 2017年第5期91卷 1680-1703页

作者： ZHAO Xiaochen LIU Chiyang WANG Jianqiang DUAN Liang ZHAO Yan ZHANG Qihang LUO Wei College of Geology and Environment Xi'an University of Science and Technology State Key Laboratory of Continental Dynamics Department of GeologyNorthwest University

The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provenance, and even the age of the sedimentary strata in the eastern HCB during the Early Paleozoic remain controversial. This study analyzes the provenance of the poorly studied Xiangshan Group, discusses its age of development and tectonic setting in the eastern HCB using a combination of petrological, geochemical and LA-ICP-MS U-Pb zircon dating methods. Based on the youngest age peaks and the fossil evidence, we suggest that the Xiangshan Group is Middle Cambrian to Late Ordovician in age. The complexity of the geochemical characteristics and associated diagrams suggests that the early stage of the Xiangshan Group developed in a passive continental margin environment, late in the backarc basin of the eastern HCB. Based on the sandstone detrital composition, whole-rock geochemistry and detrital zircon ages, we conclude that the Xiangshan Group had an early provenance that was mainly from the Qilian Block and a late provenance from the Qilian Block and the western Alxa Block. The eastern HCB and its northern and southern blocks have similar palaeontology, lithology and basement age characteristics to the South China Block. This indicates that the eastern HCB might not have formed in the intra-continental aulacogen of the North China Block during the Early Paleozoic but has a close affinity to eastern gondwana.

关键词： Detrital zircon Xiangshan Group Early Paleozoic eastern Hexi Corridor eastern gondwana

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First record of stable isotopes(δ^(13)C, δ^(18)O) and element ratios(Mg/Ca, Sr/Ca) of Middle to Late Jurassic belemnites from the Indian Himalayas and their potential for palaeoenvironmental reconstructions

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Journal of Palaeogeography 2021年第3期10卷 416-437页

作者： Matthias Alberti Franz T.Fursich Dhirendra K.Pandey Nils Andersen Dieter Garbe-Schonberg Suraj Bhosale Ketan Chaskar Jorg M.Habermann State Key Laboratory for Mineral Deposits Research School of Earth Sciences and EngineeringCenter for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material CyclingNanjing UniversityNanjing 210023Jiangsu ProvinceChina GeoZentrum Nordbayern Friedrich-Alexander-Universität Erlangen-NürnbergLoewenichstraße 2891054 ErlangenGermany Department of Geology School of EarthBiological and Environmental ScienceCentral University of South Bihar SH 7Gaya-Panchanpur RoadVillage KarharaPost FatehpurGaya 824236(Bihar)India Department of Earth and Environmental Science KSKV Kachchh UniversityBhujIndia Leibniz Laboratory for Radiometric Dating and Stable Isotope Research Christian-Albrechts-Universität zu KielMax-Eyth-Straße 1124118 KielGermany Institut für Geowissenschaften Christian-Albrechts-Universität zu KielLudewig-Meyn-Straße 1024118 KielGermany

Middle to Late Jurassic belemnites from the Spiti and Zanskar valleys in the Indian Himalayas were used for stable isotope(δ^(13)C, δ^(18)O) and element(Mg/Ca, Sr/Ca) analyses. Although the Himalayan orogeny deformed and altered a large portion of the collected fossils, cathodoluminescence and scanning electron microscopy in combination with analyses of iron and manganese contents allowed the identification of belemnites believed to still retain their original chemical composition. Results indicate a long-term temperature decrease from the Middle Callovian–Oxfordian to the Tithonian, which is proposed to have been caused by a concomitant drift of eastern gondwana into higher palaeolatitudes. Reconstructed absolute temperatures depend on the used equation and assumed δ^(18)O value of seawater, but most likely varied between 17.6 ℃ to 27.6℃ in the Kimmeridgian and Tithonian with average values between 22 ℃ to 24 ℃. This way, temperatures were similar to slightly warmer than today at comparable latitudes. The reconstruction of absolute temperatures for the Middle Callovian–Oxfordian was hindered by a larger number of poorly preserved belemnites representing this time interval.

关键词： Jurassic Palaeoclimate Water temperature Spiti Zanskar India Tethyan Himalaya eastern gondwana

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Fingerprints of the Kerguelen Mantle Plume in Southern Tibet: Evidence from Early Cretaceous Magmatism in the Tethyan Himalaya

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Acta Geologica Sinica(English Edition) 2020年第S1期94卷 29-29页

作者： LIAN Dongyang YANG Jingsui LIU Fei WU Weiwei XU Zhiqin School of Earth Sciences and Engineering Nanjing UniversityNanjing 210023China Center for Advanced Research on Mantle(CARMA) Chinese Academy of Geological SciencesBeijing 100037China College of Marine Science and Technology China University of GeosciencesWuhan 430074China

Early Cretaceous magmatism suggested to be related with the Kerguelen mantle plume has been reported in both the eastern and western Tethyan Himalayan terrane.Coeval magmatism(133-138 Ma)recorded by hypabyssal intrusive rocks have been recently discovered in the central Tethyan Himalaya(TH).The hypabyssal intrusions are dominated by OIB-like basaltic rocks intruded by later porphyritic/ophitic intermediate rocks and are characterized by strongly light rare earth element enrichment and prominent Na-Ta depletion and Pb enrichment.The basaltic rocks have low 143Nd/144Nd ratios ranging from 0.512365 to 0.512476 but relatively high 87Sr/86Sr ratios ranging from 0.708185 to 0.708966.TheεNd(t)ratios of the basaltic rocks are between-4.33 and-2.20 and initial 87Sr/86Sr ratios are 0.707807 to 0.708557.Geochemical data demonstrate that these rocks have experienced combined crustal assimilation and fractional crystallization processes.Magmatic zircons from the hypabyssal rocks exclusively have negativeεHf(t)values ranging from-0.7 to-12.7,suggestive of assimilation of crustal material.Zircons from these hypabyssal rocks have UPb ages ranging from 130 to 147 Ma.Inherited zircons have UPb ages from 397 to 2495 Ma.All the zircons are characterized by negativeεHf(t)values.The Jiding ocean island basalt(OIB)-like magmatism is geochemically and geochronologically comparable with that in the western and eastern Tethyan Himalaya,indicating widespread OIB-like magmatism in the northern margin of Greater India during the Cretaceous.Collectively,these rocks can be correlated with other early Cretaceous magmatism in western Australia and northern Antarctica.Considering the similarities,we suggest that the Jiding hypabyssal rocks are also genetically related to Kerguelen plume.Within the Yarlung Zangbo Suture Zone(YZSZ),there are also numerous occurrences of OIB-like rocks derived from mantle sources different from those of N-MORB-like magmas.The OIB-like magmatism in the YZSZ is nearly coeval with that in the TH,and the two are geochem

关键词： Tethyan Himalaya greater India Kerguelen plume ocean island basalt Yarlung-Zangbo Suture Zone eastern gondwana

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