Discovery of an eclogite belt in the Lhasa block, Tibet: A new border for Paleo-Tethys?

Yang, Jingsui; Xu, Zhiqin; Li, Zhaoli; Xu, Xing; Li, Tianfu; Ren, Yong’an; Li, Huaqi; Chen, Songyong; Robinson, Paul T.

doi:10.1016/j.jseaes.2008.04.001

Cited by 222 publications

(176 citation statements)

References 20 publications

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“…The SQT formed the passive northern margin of Gondwana on which sediments were deposited at various stages from the Ordovician to the Permian. Exposures of the Sumdo eclogites in the Lhasa terrane may indicate that the SQT and north Lhasa terrane together separated from Gondwana as early as the Carboniferous (Yang et al, 2009). Initial rifting and subsequent ocean spreading produced mafic rocks with ages ranging from the Ordovician to the Permian in central Qiangtang (Zhai et al, 2010(Zhai et al, , 2012(Zhai et al, , 2013.…”

Section: Ordovician To Permian (470-270 Ma)mentioning

confidence: 99%

Tectonic evolution and high-pressure rock exhumation in the Qiangtang terrane, central Tibet

et al. 2015

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Abstract. Conflicting interpretations of the > 500 km long, east-west-trending Qiangtang metamorphic belt have led to very different and contradicting models for the PermoTriassic tectonic evolution of central Tibet. We define two metamorphic events, one that only affected pre-Ordovician basement rocks and one subduction-related Triassic highpressure metamorphism event. Detailed mapping and structural analysis allowed us to define three main units that were juxtaposed due to collision of the north and south Qiangtang terranes after closure of the Ordovician-Triassic ocean that separated them. The base is formed by the Precambrian-Carboniferous basement, followed by nonmetamorphic ophiolitic mélange containing mafic rocks that range in age from the Ordovician to Middle Triassic. The top of the sequence is formed by strongly deformed sedimentary mélange that contains up to > 10 km size rafts of both unmetamorphosed Permian sediments and highpressure blueschists. We propose that the high-pressure rocks were exhumed from underneath the south Qiangtang terrane in an extensional setting caused by the pull of the northward subducting slab of the Shuanghu-Tethys. Highpressure rocks, sedimentary mélange and margin sediments were thrust on top of the ophiolitic mélange that was scraped off the subducting plate. Both units were subsequently thrust on top of the south Qiantang terrane continental basement. Onset of Late Triassic sedimentation marked the end of the amalgamation of both Qiangtang terranes and the beginning of spreading between Qiantang and north Lhasa to the south, leading to the deposition of thick flysch deposits in the Jurassic.

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Section: Ordovician To Permian (470-270 Ma)mentioning

confidence: 99%

Tectonic evolution and high-pressure rock exhumation in the Qiangtang terrane, central Tibet

et al. 2015

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“…A belt of eclogites with Permian sensitive high-resolution ion microprobe (SHRIMP) zircon ages (c. 291-242 Ma) and disrupted ultramafic rocks has been discovered in the middle of the Lhasa block (Yang et al 2009). Regional kyanite-and sillimanite-grade metamorphic rocks also occur in the southeastern part of Tibet, but it is unclear if these rocks are related to deep parts of the Lhasa terrane or to the Namche Barwa syntaxis (Greater Himalayan Sequence).…”

Section: Post-collision Thickeningmentioning

confidence: 99%

Crustal–lithospheric structure and continental extrusion of Tibet

Searle

Elliott

Phillips

et al. 2011

JGS

240

154

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Crustal shortening and thickening to c. 70-85 km in the Tibetan Plateau occurred both before and mainly after the c. 50 Ma India-Asia collision. Potassic-ultrapotassic shoshonitic and adakitic lavas erupted across the Qiangtang (c. 50-29 Ma) and Lhasa blocks (c. 30-10 Ma) indicate a hot mantle, thick crust and eclogitic root during that period. The progressive northward underthrusting of cold, Indian mantle lithosphere since collision shut off the source in the Lhasa block at c. 10 Ma. Late Miocene-Pleistocene shoshonitic volcanic rocks in northern Tibet require hot mantle. We review the major tectonic processes proposed for Tibet including 'rigid-block', continuum and crustal flow as well as the geological history of the major strikeslip faults. We examine controversies concerning the cumulative geological offsets and the discrepancies between geological, Quaternary and geodetic slip rates. Low present-day slip rates measured from global positioning system and InSAR along the Karakoram and Altyn Tagh Faults in addition to slow long-term geological rates can only account for limited eastward extrusion of Tibet since Mid-Miocene time. We conclude that despite being prominent geomorphological features sometimes with wide mylonite zones, the faults cut earlier formed metamorphic and igneous rocks and show limited offsets. Concentrated strain at the surface is dissipated deeper into wide ductile shear zones.

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“…The eclogite formed at peak metamorphic conditions of 2.7 GPa and 730 ℃, close to the phase boundary between coesite and quartz (Yang et al, 2009;Li et al, 2007). The protolith of the Lhasa eclogites was MORB-type oceanic crust (Chen et al, 2007).…”

Section: Introductionmentioning

confidence: 87%

Ultramafic blocks in Sumdo region, Lhasa block, Eastern Tibet plateau: An ophiolite unit

Chen

Yang

et al. 2009

J. Earth Sci.

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Discovery of an eclogite belt in the Lhasa block, Tibet: A new border for Paleo-Tethys?

Cited by 222 publications

References 20 publications

Tectonic evolution and high-pressure rock exhumation in the Qiangtang terrane, central Tibet

Tectonic evolution and high-pressure rock exhumation in the Qiangtang terrane, central Tibet

Crustal–lithospheric structure and continental extrusion of Tibet

Ultramafic blocks in Sumdo region, Lhasa block, Eastern Tibet plateau: An ophiolite unit

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