Late Triassic rifting and volcanism on the northeastern Indian margin: A new phase of Neo-Tethyan seafloor spreading and its paleogeographic implications

https://doi.org/10.1016/j.palaeo.2021.110367Get rights and content

Highlights

  • Late Triassic (229–223 Ma) bimodal volcanism was identified on northern Indian margin.

  • Alkalic signature of mafic rock fragments indicates within-plate extensional setting.

  • Late Triassic rifting developed all along the northern margin of eastern Gondwana.

  • The Langjiexue deposystem was formed because of the rifting and volcanic event.

Abstract

The stratigraphic record of the northern Indian margin documents tectonic extension and magmatic activity during the Late Triassic. The geodynamic process and the paleogeographic implications of this event remain, however, incompletely understood. This study presents new stratigraphic, petrographic, geochronologic and geochemical data from a mixed carbonate-clastic Upper Triassic succession of the Tethys Himalaya in southern Tibet (Tela Formation). The new finding of volcanic detritus with bimodal mafic/felsic composition in the Tela Formation indicates nearby volcanic activity constrained by detrital zircon Usingle bondPb dating as latest Carnian to early Norian in age (229–223 Ma). The alkalic signature of mafic volcanic rock fragments, showing LREE enrichment and HREE depletion, indicates a within-plate extensional setting. The igneous activity in northeastern India compares with coeval volcanism in northwestern Australia, suggesting that a rift-related volcanic belt developed along the northern margin of eastern Gondwana in the Late Triassic. This volcanic belt controlled the accumulation of thick turbidites of the Langjiexue Group in northeastern India and induced accelerated tectonic subsidence and increased sedimentation rates all along the Tethys Himalayan zone as far west as the Zanskar-Spiti Synclinorium. This major rifting phase is suggested to have initiated a new phase of sea-floor spreading in the Neo-Tethys Ocean that torn off the Lhasa Block from eastern Gondwana.

Introduction

The Tethys Himalaya zone preserves Paleozoic to Eocene sedimentary successions deposited on the northern margin of the Indian subcontinent facing the Neo-Tethys Ocean in the north (Gansser, 1964). Understanding the paleogeographic configuration of the Tethys Himalaya is therefore important for reconstructing the tectono-sedimentary history of the northern Indian margin and the evolution of Neo-Tethys.

Paleogeographic studies on the Late Triassic of the Tethys Himalaya had suffered from notable uncertainties. One major issue is represented by the presence in southern Tibet of the huge Langjiexue Group submarine fan deposystem deposited in continental-slope to rise environments (Li et al., 2003a, Li et al., 2003b; Li et al., 2004; Zhang et al., 2014; Zhang et al., 2015; Zhang et al., 2017; Wang et al., 2016a; Wang et al., 2016b). As provenance features of detritus from the Langjiexue Group differ significantly from those of most Tethys Himalayan terrigenous rocks, their provenance and depositional mechanism has been strongly disputed (Dai et al., 2008; Li et al., 2011; Li et al., 2014; Li et al., 2016a; Li et al., 2016b; Cai et al., 2016; Wang et al., 2016a; Wang et al., 2016b; Cao et al., 2018; Fang et al., 2018; Liu et al., 2020). A similar unit is represented by the Lamayuru complex and associated volcanic rocks, exposed in the Ladakh region of the northwestern Himalaya (Thakur, 1981; Robertson and Degnan, 1993; Robertson and Sharp, 1998; Robertson, 2007). The Lamayuru unit was deposited onto the distal Indian passive continental margin south of a Permian-Triassic Neo-Tethyan spreading axis (Robertson, 1998). In the more proximal shelfal environments of the Tethys Himalayan zone, accelerated tectonic subsidence, terrigenous influx, increased sedimentation rates, and transgression-regression cycles are well documented from southern Tibet (Jadoul et al., 1998; Meng et al., 2019) to Nepal (Garzanti et al., 1992, Garzanti et al., 1994a; Garzanti et al., 1994b) and the Spiti-Zanskar Synclinorium in the northwestern Himalaya (Garzanti et al., 1995).

The depositional pattern of the Upper Triassic Tethys Himalaya succession points to regional extension all along the northern Indian margin (Gaetani and Garzanti, 1991; Garzanti, 1993). The paleogeographic and tectonic significance of this extensional event, and its associated intraplate magmatism, however, are still incompletely understood and have been variably interpreted as the result of drifting of the Lhasa Block away from Gondwana (Metcalfe, 2002, Metcalfe, 2009) or as tectonic rejuvenation of the northern Gondwana margin (Sciunnach and Garzanti, 2012).

This paper presents data from the Upper Triassic mixed carbonate-terrigenous succession exposed in the Nanggarze area of southern Tibet and provides evidence of abundant bimodal mafic/felsic volcanic detritus indicating penecontemporaneous magmatic activity. Our aim is to discuss the geodynamic process that triggered such a magmatism and to shed new light on the paleogeographic implications of compositional and facies changes recorded by the sedimentary succession deposited onto the passive continental margin of northern India at Late Triassic time.

Section snippets

Geological background

The Neo-Tethys was a roughly E-W oriented paleo-ocean developed during Late Paleozoic to the earliest Cenozoic time and between the Laurasia landmass to the north and the Gondwana megacontinent to the south (Şengör, 1984). It was formed as a result of rifting along the north margin of Gondwana, and was closed due to the collision between Indian and Eurasian continents (The Indian subcontinent is a part of Gondwana and was broken away from the later in the Early Cretaceous; Hu et al., 2010).

Methods

The Tela Formation exposed near the Tela village was studied in detail and mapped in the field. Distribution of exposures, attitude of strata, rock type, and sedimentary structures were investigated and marked on a contour topographic base map (Fig. 2). The stratigraphic column was logged meter by meter, and samples were collected for laboratory study. Sedimentary facies were interpreted based on sedimentary structures and carbonate microfacies. Provenance analysis was carried out by

Stratigraphy and sedimentary facies

The Tela Formation was first defined by Wang et al. (1983) and described as exotic blocks within the Yamdrok mélange. During the 1:250000 regional geological mapping, the unit was subsequently revealed to represent a thrust slice covering an area > 20 km2. Our field investigation indicated that the Tela Formation is a tectonic unit juxtaposed with the Zongzhuo mélange in the north (Yamdrok mélange of Liu and Aitchison, 2002) and with Tethys Himalayan Jurassic–Cretaceous strata in the south (

Petrography of terrigenous clastics

The Tela Formation includes two different lithologies containing terrigenous detritus with different composition and zircon-age spectra. Sandy limestones found through the upper part of the Lower Member and the lower part of the Upper Member (Fig. 2) contain exclusively volcanic-derived mafic to felsic rock fragments and plagioclase accounting for 2–37% of framework grains, the rest being represented by bioclasts, ooids, and peloids (Figs. 6a–g, and 7). Angular to subrounded volcanic rock

Late Triassic rifting and volcanism along the northern margin of eastern Gondwana

Plagioclase, mafic and felsic volcanic rock fragments in sandy limestones of the Tela Formation and Usingle bondPb detrital-zircon ages of ~229–223 Ma indicate penecontemporaneous bimodal magmatic activity (Fig. 8a-e). The lack of quartz and recycled sedimentary and metamorphic detritus suggests that the volcanic source was isolated from the main continent, and that was transported from nearby volcanic centers to shallow marine environments as airfall tuffs or by wave- and storm-induced currents. The

Conclusions

Integrated stratigraphic, petrographic, geochronologic and geochemical data from the Upper Triassic Tela Formation of the eastern Tethys Himalaya in southern Tibet shed new light on the paleogeographic and paleogeodynamic evolution of eastern Gondwana. Volcanic detritus in the Tela Formation indicates penecontemporaneous bimodal magmatism along the northeastern Indian margin. Usingle bondPb dating of zircons firmly constrains this volcanic event as latest Carnian to early Norian (~229–223 Ma). The

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We are deeply grateful to the Editor Thomas Algeo, Reviewer Alastair Robertson, Huan Li, and an anonymous reviewer for their very useful comments and constructive criticism. We thank Zhi-Chao Liu, Xiumian Hu, Yiwei Xu and Weiwei Xue for their help in the field, Yue-Heng Yang for help in the laboratory. This work was supported by the Basic Science Center Program (41888101), the National Natural Science Foundation of China (42072133, 41672109) and the Youth Innovation Promotion Associate Project

References (107)

  • E. Garzanti et al.

    The modern Nile sediment system: processes and products

    Quat. Sci. Rev.

    (2015)
  • J. Golonka et al.

    Pangean (Late Carboniferous–Middle Jurassic) paleoenvironment and lithofacies

    Paleogeogr. Paleoclimatol. Paleoecol.

    (2000)
  • W.L. Griffin et al.

    The Hf isotope composition of cratonic mantle: LAM-MC-ICPMS analysis of zircon megacrysts in kimberlites

    Geochim. Cosmochim. Acta

    (2000)
  • X.M. Hu et al.

    Upper Jurassic–Lower Cretaceous stratigraphy in south-eastern Tibet: a comparison with the western Himalayas

    Cretac. Res.

    (2008)
  • X.M. Hu et al.

    Provenance of Lower Cretaceous Wölong volcaniclastics in the Tibetan Tethyan Himalaya: implications for the final breakup of eastern Gondwana

    Sediment. Geol.

    (2010)
  • X.M. Hu et al.

    The timing of India-Asia collision onset – facts, theories, controversies

    Earth Sci. Rev.

    (2016)
  • Y. Huang et al.

    Middle-Late Triassic bimodal intrusive rocks from the Tethyan Himalaya in South Tibet: geochronology, petrogenesis and tectonic implications

    Lithos

    (2018)
  • S.E. Jackson et al.

    The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U–Pb zircon geochronology

    Chem. Geol.

    (2004)
  • F. Jadoul et al.

    The Tethys Himalayan passive margin from Late Triassic to Early Cretaceous (South Tibet)

    J. Asian Earth Sci.

    (1998)
  • G.W. Li et al.

    Provenance of late Triassic sediments in central Lhasa terrane, Tibet and its implication

    Gondwana Res.

    (2014)
  • X.H. Li et al.

    Stratigraphy of deep-water Cretaceous deposits in Gyangze, southern Tibet, China

    Cretac. Res.

    (2005)
  • X.H. Li et al.

    Multiple sources of the Upper Triassic flysch in the eastern Himalaya Orogen, Tibet, China: implications to palaeogeography and palaeotectonic evolution

    Tectonophysics

    (2016)
  • Y.M. Liu et al.

    Provenance and tectonic setting of Upper Triassic turbidites in the eastern Tethyan Himalaya: implications for early-stage evolution of the Neo–Tethys

    Earth Sci. Rev.

    (2020)
  • Y.K. Meng et al.

    Late Triassic crustal growth in southern Tibet: evidence from the Gangdese magmatic belt

    Gondwana Res.

    (2016)
  • I. Metcalfe

    Permian tectonic framework and palaeogeography of SE Asia

    J. Asian Earth Sci.

    (2002)
  • I. Metcalfe

    Gondwana dispersion and Asian accretion: tectonic and palaeogeographic evolution of eastern Tethys

    J. Asian Earth Sci.

    (2013)
  • Y.Z. Niu et al.

    Triassic marine biogeography constrains the palaeogeographic reconstruction of Tibet and adjacent areas

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2011)
  • A. Robertson

    Rift-related sedimentation and volcanism of the north-Indian margin inferred from a Permian–Triassic exotic block at Lamayuru, Indus suture zone (Ladakh Himalaya) and regional comparisons

    J. Asian Earth Sci.

    (1998)
  • A. Robertson et al.

    Mesozoic deep-water slope/rise sedimentation and volcanism along the North-Indian passive margin: evidence from the Karamba Complex, Indus suture zone (Western Ladakh Himalaya)

    J. Asian Earth Sci.

    (1998)
  • D. Sciunnach et al.

    Subsidence history of the Tethys Himalaya

    Earth Sci. Rev.

    (2012)
  • J. Sláma et al.

    Plešovice zircon-a new natural reference material for U–Pb and Hf isotopic microanalysis

    Chem. Geol.

    (2008)
  • J.J. Veevers

    Gondwanaland from 650–500 Ma assembly through 320 Ma merger in Pangea to 185–100 Ma breakup: supercontinental tectonics via stratigraphy and radiometric dating

    Earth Sci. Rev.

    (2004)
  • C. Wang et al.

    Petrogenesis of Middle–Late Triassic volcanic rocks from the Gangdese belt, southern Lhasa terrane: implications for early subduction of Neo-Tethyan oceanic lithosphere

    Lithos

    (2016)
  • J.G. Wang et al.

    Upper Triassic turbidites of the northern Tethyan Himalaya (Langjiexue Group): the terminal of a sediment-routing system sourced in the Gondwanide Orogen

    Gondwana Res.

    (2016)
  • F.Y. Wu et al.

    Hf isotopic compositions of the standard zircons and baddeleyites used in U–Pb geochronology

    Chem. Geol.

    (2006)
  • A. Yin

    Cenozoic tectonic evolution of the Himalayan orogen as constrained by along-strike variation of structural geometry, exhumation history, and foreland sedimentation

    Earth Sci. Rev.

    (2006)
  • J.P. Bassoullet et al.

    Geological studies in the Indus Sutures Zone of Ladakh (Himalayas)

  • D.S. Chen et al.

    Late Anisian radiolarian assemblages from the Yarlung-Tsangpo Suture Zone in the Jinlu area, Zedong, southern Tibet: implications for the evolution of Neotethys

    Island Arc

    (2019)
  • J.H. Chen et al.

    Halobia fauna from Zedong of South Xizang with a discussion on the Halobia assemblages in China

    Acta Palaeontol. Sin.

    (1986)
  • J.H. Chen et al.

    Eleganuculana, new genus, and some other bivalves from the Upper Triassic of Kangmar in Xizang

    Acta Palaeontol. Sin.

    (1983)
  • J.G. Dai et al.

    Nd isotopic compositions of the Tethyan Himalayan Sequence in southeastern Tibet

    Sci. China Ser. D Earth Sci.

    (2008)
  • R.A. Davis et al.

    Principles of Tidal Sedimentology

    (2012)
  • W.R. Dickinson

    Interpreting provenance relations from detrital modes of sandstones

  • T. Dumont et al.

    Tectonics and sea-level changes recorded in Late Triassic Sequences at rifted margins of eastern and western Tethys (Northwest Australia, Leg 122; Western Europe)

  • R.J. Dunham

    Classification of carbonate rocks according to depositional textures

    AAPG Mem.

    (1962)
  • A.F. Embry et al.

    A Late Devonian reef tract on northeastern Banks Island

    NWT Bull. Can. Petrol. Geol.

    (1971)
  • N.F. Exon et al.

    Mesozoic seismic stratigraphy and tectonic evolution of the western Exmouth Plateau

    Proc. Ocean Drill. Progr. Sci. Results

    (1992)
  • D.R. Fang et al.

    Provenance of the Langjiexue Group to the south of the Yarlung-Tsangpo Suture Zone in southeastern Tibet: insights on the evolution of the Neo-Tethys Ocean in the Late Triassic

    Int. Geol. Rev.

    (2018)
  • E. Flügel

    Microfacies of Carbonate Rock: Analysis, Interpretation and Application

    (2010)
  • M. Gaetani et al.

    Multicyclic history of the northern India continental margin (NW Himalaya)

    Am. Ass. Petr. Geol. Bull.

    (1991)
  • Cited by (10)

    View all citing articles on Scopus
    View full text