Mesozoic tectonic history and lithospheric structure of the Qiangtang terrane: Insights from the Qiangtang metamorphic belt, central Tibet

2014 ◽  
Author(s):  
Alex Pullen ◽  
Paul Kapp
Keyword(s):  
Lithospheric Structure ◽  
Metamorphic Belt ◽  
Tectonic History ◽  
Central Tibet ◽  
Qiangtang Terrane

scholarly journals Tectonic evolution and high-pressure rock exhumation in the Qiangtang Terrane, Central Tibet

2015 ◽  
Vol 7 (1) ◽  
pp. 329-367 ◽  
Author(s):  
Z. Zhao ◽  
P. D. Bons ◽  
G. Wang ◽  
A. Soesoo ◽  
Y. Liu
Keyword(s):  
High Pressure ◽  
Tectonic Evolution ◽  
Late Triassic ◽  
The South ◽  
Metamorphic Belt ◽  
The North ◽  
Ophiolitic Mélange ◽  
Basement Rocks ◽  
Central Tibet ◽  
Qiangtang Terrane

Abstract. Conflicting interpretations of the > 500 km long, east-west trending Qiangtang Metamorphic Belt have led to very different and contradicting models for the Permo-Triassic tectonic evolution of Central Tibet. We define two metamorphic events, one that only affected Pre-Ordovician basement rocks and one subduction-related Triassic high-pressure 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 non-metamorphic 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 un-metamorphosed Permian sediments and high-pressure 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. High-pressure 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.

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

Solid Earth ◽  
2015 ◽  
Vol 6 (2) ◽  
pp. 457-473 ◽  
Author(s):  
Z. Zhao ◽  
P. D. Bons ◽  
G. Wang ◽  
A. Soesoo ◽  
Y. Liu
Keyword(s):  
High Pressure ◽  
Tectonic Evolution ◽  
Late Triassic ◽  
The South ◽  
Metamorphic Belt ◽  
The North ◽  
Ophiolitic Mélange ◽  
Basement Rocks ◽  
Central Tibet ◽  
Qiangtang Terrane

Abstract. Conflicting interpretations of the > 500 km long, east–west-trending Qiangtang metamorphic belt have led to very different and contradicting models for the Permo–Triassic tectonic evolution of central Tibet. We define two metamorphic events, one that only affected pre-Ordovician basement rocks and one subduction-related Triassic high-pressure 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 non-metamorphic 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 high-pressure 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. High-pressure 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.

Co-seismic surface ruptures in Qiangtang Terrane: Insight into Late Cenozoic deformation of central Tibet

2019 ◽  
Vol 750 ◽  
pp. 359-378 ◽  
Author(s):  
Shuai Han ◽  
Haibing Li ◽  
Jiawei Pan ◽  
Haijian Lu ◽  
Yong Zheng ◽  
...  
Keyword(s):  
Late Cenozoic ◽  
Surface Ruptures ◽  
Central Tibet ◽  
Qiangtang Terrane ◽  
Insight Into

Late Jurassic Nb‐enriched basalts from the Bilong Co area in the southern Qiangtang Terrane, central Tibet, and their implications

2021 ◽  
Author(s):  
Jianbo Cheng ◽  
Yalin Li ◽  
Haiyang He ◽  
Siqi Xiao ◽  
Wenjun Bi ◽  
...  
Keyword(s):  
Late Jurassic ◽  
Central Tibet ◽  
Qiangtang Terrane

Passive-margin magmatism caused by enhanced slab-pull forces in central Tibet

Geology ◽  
2020 ◽  
Author(s):  
Wei Dan ◽  
Qiang Wang ◽  
William M. White ◽  
Xian-Hua Li ◽  
Xiu-Zheng Zhang ◽  
...  
Keyword(s):  
Passive Margin ◽  
Lower Plate ◽  
Isotopic Signatures ◽  
Ridge Subduction ◽  
Slab Rollback ◽  
Element Enrichment ◽  
Central Tibet ◽  
Back Arc ◽  
Ocean Ridge ◽  
Qiangtang Terrane

We report on a ca. 239 Ma mafic dike swarm intruded in the Southern Qiangtang terrane, central Tibet, that was generated on the passive continental margin of a subducting lower plate. The dikes are tholeiitic basalts and exhibit light rare earth element enrichment, modest negative anomalies in Nb and Ta, and enriched isotopic signatures. The dikes are coeval with a back-arc basin formed in the upper plate as a result of the rollback of the Paleo-Tethys oceanic slab. Thus, after ocean-ridge subduction, enhanced slab-pull forces related to slab rollback on one side of the ocean induced extension and magmatism in the passive margin on the opposite side. We argue that enhanced slab-pull forces are a previously unrecognized mechanism for the generation of lower-plate passive-margin magmatism.

Geochemistry of Eocene high-Mg# adakitic rocks in the northern Qiangtang terrane, central Tibet: Implications for early uplift of the plateau

2013 ◽  
Vol 125 (11-12) ◽  
pp. 1800-1819 ◽  
Author(s):  
J. Chen ◽  
J. Wu ◽  
J. Xu ◽  
Y. Dong ◽  
B. Wang ◽  
...  
Keyword(s):  
Adakitic Rocks ◽  
Central Tibet ◽  
Qiangtang Terrane

Closure of the Bangong–Nujiang Tethyan Ocean in the central Tibet: Results from the provenance of the Duoni Formation

2019 ◽  
Vol 89 (10) ◽  
pp. 1039-1054 ◽  
Author(s):  
Zhicai Zhu ◽  
Qingguo Zhai ◽  
Peiyuan Hu ◽  
Sunlin Chung ◽  
Yue Tang ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Suture Zone ◽  
The Tibetan Plateau ◽  
Tectonic History ◽  
Magmatic Rocks ◽  
Two Samples ◽  
Delta Sequence ◽  
History Of ◽  
Central Tibet

ABSTRACT The closure of the Bangong–Nujiang Tethyan Ocean (BNTO) and consequent Lhasa–Qiangtang collision is vital to reasonably understanding the early tectonic history of the Tibetan Plateau before the India-Eurasia collision. The timing of the Lhasa–Qiangtang collision was mainly constrained by the ophiolite and magmatic rocks in previous studies, with only limited constraints from the sedimentary rocks within and adjacent to the Bangong–Nujiang suture zone. In the middle segment of the Bangong–Nujiang suture zone, the Duoni Formation, consisting of a fluvial delta sequence with minor andesite interlayers, was originally defined as the Late Cretaceous Jingzhushan Formation and interpreted as the products of the Lhasa–Qiangtang collision during the Late Cretaceous. Our new zircon U-Pb data from two samples of andesite interlayers demonstrate that it was deposited during the latest Early Cretaceous (ca. 113 Ma) rather than Late Cretaceous. Systemic studies on the sandstone detrital model, heavy-mineral assemblage, and clasts of conglomerate demonstrate a mixed source of both Lhasa and Qiangtang terranes and ophiolite complex. Clasts of conglomerate contain abundant angular peridotite, gabbro, basalt, chert, andesite, and granite, and minor quartzite and gneiss clasts also exist. Sandstones of the Duoni Formation are dominated by feldspathic–lithic graywacke (Qt25F14L61 and Qm13F14L73), indicative of a mixture of continental-arc and recycled-orogen source origin. Detrital minerals of chromite, clinopyroxene, epidote, and hornblende in sandstone also indicate an origin of ultramafic and mafic rocks, while garnets indicate a metamorphosed source. Paleocurrent data demonstrate bidirectional (southward and northward) source origins. Thus, we suggest that the deposition of the Duoni Formation took place in the processes of the Lhasa–Qiangtang collision during the latest Early Cretaceous (∼ 113 Ma), and the BNTO had been closed by this time.

Subduction erosion and crustal material recycling indicated by adakites in central Tibet

Geology ◽  
2021 ◽  
Author(s):  
Zong-Yong Yang ◽  
Qiang Wang ◽  
Lu-Lu Hao ◽  
Derek A. Wyman ◽  
Lin Ma ◽  
...  
Keyword(s):  
Crustal Material ◽  
Convergent Margins ◽  
Nd Isotopes ◽  
Magmatic Arc ◽  
Material Recycling ◽  
Intrusive Rocks ◽  
Subducted Oceanic Crust ◽  
Subduction Erosion ◽  
Central Tibet ◽  
Qiangtang Terrane

Subduction erosion is important for crustal material recycling and is widespread in modern active convergent margins. However, such a process is rarely identified in fossil convergent systems, which casts doubt on the importance of subduction erosion through the geological record. We report on ca. 155 Ma Kangqiong (pluton) intrusive rocks of a Mesozoic magmatic arc in the southern Qiangtang terrane, central Tibet. These rocks mainly consist of trondhjemites and tonalites and are similar to slab-derived adakites with mantle-like zircon oxygen isotope compositions (δ18O = 5.2‰–5.6‰), they display more evolved Sr-Nd isotopes and higher Th/La relative to mid-oceanic ridge basalts from the Bangong-Nujiang suture, and they contain abundant amphibole and biotite. These characteristics indicate magma generation via H2O-fluxed melting of eroded forearc crust debris with subducted oceanic crust at 1.5–2.5 GPa and 700–800 °C. In addition, the intrusions are exposed <20 km north of the Bangong-Nujiang suture. Given the formation of adakites, narrow arc-suture distance, migration of the Jurassic frontal arc toward the continent interior, and other independent geological archives, we suggest that the hydrated forearc crust materials were removed from the overlying plate and carried into the mantle by subduction erosion. Our study provides the first direct magmatic evidence for a subduction erosion process in pre-Cenozoic convergent systems, which confirms an important role for such processes in subduction-zone material recycling.

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