The Middle Triassic evolution of the Bangong–Nujiang Tethyan Ocean: evidence from analyses of OIB-type basalts and OIB-derived phonolites in northern Tibet

Fan, Jian‐Jun; Cai, Li; Liu, Jin-Heng; Wang, Ming; Liu, Yiming; Xie, Chao-Ming

doi:10.1007/s00531-017-1570-x

Cited by 27 publications

(17 citation statements)

References 92 publications

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“…The start of rifting is evidenced by the initiation of separate sedimentary evolutions in the Qiangtang and Lhasa blocks, respectively, from the Triassic onward [21,22]. This is also supported by the oldest age (260-240 Ma) of mafic rocks from the ophiolites in the BNS [9,23,24]. The BNO rapidly developed and became a 5000 ± 1020 km wide ocean by the Late Triassic, as recorded by the 45.1 • ± 9.2 • paleolatitude gap between the Qiangtang and Lhasa blocks [25][26][27].…”

Section: Tectonic Evolution Of the Bangong-nujiang Oceanmentioning

confidence: 91%

“…Knowledge of the pre-Cenozoic tectonics, particularly the Lhasa-Qiangtang collision that followed the closure of the Bangong-Nujiang Ocean (BNO), are critical in understanding the formation processes of the Tibetan Plateau. While much progress has been made recently in understanding the processes of the oceanic-continental subduction and the subsequent collision between the Lhasa and Qiangtang blocks in the past decades [6][7][8][9][10][11][12][13][14][15][16], the oceanic subduction process within the BNO is still unclear.…”

Section: Introductionmentioning

confidence: 99%

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Dating Oceanic Subduction in the Jurassic Bangong–Nujiang Oceanic Arc: A Zircon U–Pb Age and Lu–Hf Isotopes and Al-in-Hornblende Barometry Study of the Lameila Pluton in Western Tibet, China

2019

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The subduction and close of the Mesozoic Bangong–Nujiang Ocean (BNO) led to a collision of the Lhasa and Qiangtang blocks, which formed the backbone of the Tibetan Plateau (the largest and highest plateau on Earth). However, the detailed subduction processes (in particular, the oceanic subduction processes) within the BNO are still not clear. Here, we focus on the plutonic complex of the oceanic arc in the Bangong–Nujiang suture (BNS) and report field observations on zircon U–Pb ages, Lu–Hf isotopes, and the Al-in-hornblende barometry of quartz diorites from the Lameila pluton in western Tibet. Zircon from the quartz diorites yielded a LA-ICP-MS U–Pb age of 164 Ma. The zircon showed very positive εHf(t) values from 10.5 to 13.9, suggesting the Lameila pluton was likely sourced from the depleted-mantle wedge, which is in contrast with contemporary (164–161 Ma) volcanic rocks in the region that had negative εHf(t) values of −7.4 to −16.2 and a magma source from partial melting of subducted sediments. The Lameila pluton showed a temperature-corrected Al-in-hornblende pressure of 3.9 ± 0.8 kbar, corresponding to an emplacement depth of 13 ± 3 km. Therefore, the thickness of the Jurassic oceanic arc crust must have doubled since the initial growth of the oceanic arc on the BNO crust, with a crustal thickness of 6.5 km during the Middle Jurassic. In combination with previous works on volcanic rocks, this study further supports a two-subduction zone model in association with the BNO during the Middle Jurassic, namely, a north-dipping BNO–Qiangtang subduction zone and an oceanic subduction zone within the BNO. The latter oceanic subduction zone produced the depleted-mantle-derived Lameila pluton and the subducted sediment-derived volcanic rocks in the fore arc.

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Section: Tectonic Evolution Of the Bangong-nujiang Oceanmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Dating Oceanic Subduction in the Jurassic Bangong–Nujiang Oceanic Arc: A Zircon U–Pb Age and Lu–Hf Isotopes and Al-in-Hornblende Barometry Study of the Lameila Pluton in Western Tibet, China

2019

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“…The Mugagangri Formation comprises slope–deep‐sea basin facies metamorphosed sandstone, shaly slate, and limestone lenses, representing mainly classic flysch deposits (J. J. Fan, Li, Liu, et al, ; J. J. Fan, Li, Wang, et al, ; Y. M. Liu et al, ).…”

Section: Geological Settingmentioning

confidence: 99%

“…For example, the opening time of the Bangong–Nujiang Ocean (BNO) may be Carboniferous (Jiang et al, ), Late Permian–Early Triassic (J. J. Fan, Li, Liu, et al, ; J. J. Fan, Li, Wang, et al, ), Triassic (Kapp et al, ), Late Triassic–Early Jurassic (D. X. Xia, ), or Middle to Late Jurassic (W. L. Wang, Aitchison, Lo, & Zeng, ; Y. X. Zhang, Zhang, et al, ; J. Zhang, Zhao, Li, Sun, Liu, et al, ).…”

Section: Introductionmentioning

confidence: 99%

Collisional processes between the Qiangtang Block and the Lhasa Block: Insights from structural analysis of the Bangong–Nujiang Suture Zone, central Tibet

Guo

et al. 2019

Geological Journal

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The Bangong–Nujiang Suture Zone (BNSZ) is one of the main suture zones in the Tibetan Plateau and indicates the existence of the Bangong–Nujiang Neo‐Tethys Ocean (BNO). It was formed by the collision between the Qiangtang and Lhasa blocks after the closure of the BNO. However, its evolutionary processes and subduction polarity remain controversial. Research on the BNSZ is of great significance for exploring plate tectonic evolution and ocean–continent connection. The scarcity of the BNSZ structural data is one of the most important reasons for the debate of the BNO tectonic evolution. Based on structural analysis in the field and combined with previous petrology and palaeomagnetic data, this paper has determined that the closure time of the BNO is progressive and scissor‐like, from Middle Jurassic in the east to Early Cretaceous in the middle and late Early Cretaceous to early Late Cretaceous in the west. There was a three‐stage deformation in the BNSZ: (a) N–S‐directed compression induced by the initial collision; (b) WNW–directed transpression related to the stress adjustment; and (c) NE–SW‐directed compression caused by the low‐angle NE‐directed subduction of the Indus–Yarlung Zangbo Ocean. The different structural pattern along the eastern segment of the BNSZ may have resulted from orogenic bending due to the later Himalayan Orocline caused by the India–Eurasia collision in the Cenozoic.

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“…The Bangong-Nujiang suture zone (BNSZ), located in the central-northern Tibetan Plateau, represents the relics of the Bangong-Nujiang oceanic lithosphere (BNO, also named as Meso-Tethys Ocean) and marks the collision zone between the Qiangtang and Lhasa terranes (Figure 1a). However, the tectonic environment of the BNSZ-ophiolite remains unclear, and previous studies have suggested that it formed in mid-ocean ridge, forearc basin, oceanic plateau, and back-arc basin settings (e.g., Fan et al, 2017;Lai & Liu, 2003;T. Liu et al, 2016;K.…”

mentioning

confidence: 99%

Petrogenesis of Early Jurassic (ca. 181 Ma) dacitic–rhyolitic volcanic rocks in the Amdo ophiolite mélange, central Tibetan Plateau: Low‐pressure partial melts of Bangong–Nujiang Tethys oceanic crust?

Zeng

et al. 2019

Geological Journal

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The identification of oceanic-crust-derived melts is critical to improving our understanding of oceanic lithosphere subduction in various geodynamic settings. However, low-pressure melts derived from the oceanic crust can be misidentified because their compositions are often indistinguishable from those of typical arc-related rocks. In this study, we report geochronological and geochemical data for the Amdo volcanic rocks in the central Tibetan Plateau. Zircon U-Pb dating indicates that they were generated in the Early Jurassic (ca. 181 Ma), simultaneous with spatially associated MORB-like rocks of the Amdo ophiolite. The Amdo volcanic rocks are characterized by high SiO 2 and Na 2 O concentrations, low MgO, K 2 O, and Fe 2 O 3 T concentrations, and low Mg# values. They are enriched in light rare earth and large-ion lithophile elements, display negative Eu, Nb, and Ta anomalies, and yield low Sr (<360 ppm) and high Y (up to 57.6 ppm) concentrations with low Sr/Y ratios (<15.4). Whole-rock Sr-Nd and zircon Hf isotopic compositions (( 87 Sr/ 86 Sr) i = 0.7040-0.7058, ε Nd (t) = +3.9to +6.8, and zircon ε Hf (t) = +13.9 to +17.9) are different from those of regional continental-crust-derived granitoids but similar to those of contemporary MORBlike rocks that occur in regional ophiolites. Furthermore, zircon from the Amdo volcanic rocks yields U/Yb ratios similar to those of oceanic zircon. These characteristics, combined with regional geological observations, indicate that the Amdo volcanic rocks are a component of the Amdo ophiolite mélange and represent low-pressure partial melts of oceanic crust, generated during incipient northward subduction of the Bangong-Nujiang oceanic lithosphere beneath the Qiangtang terrane. Our study helps to constrain the history of the Bangong-Nujiang Ocean and provides a case study on the low-pressure melting of oceanic crust.

show abstract

The Middle Triassic evolution of the Bangong–Nujiang Tethyan Ocean: evidence from analyses of OIB-type basalts and OIB-derived phonolites in northern Tibet

Cited by 27 publications

References 92 publications

Dating Oceanic Subduction in the Jurassic Bangong–Nujiang Oceanic Arc: A Zircon U–Pb Age and Lu–Hf Isotopes and Al-in-Hornblende Barometry Study of the Lameila Pluton in Western Tibet, China

Dating Oceanic Subduction in the Jurassic Bangong–Nujiang Oceanic Arc: A Zircon U–Pb Age and Lu–Hf Isotopes and Al-in-Hornblende Barometry Study of the Lameila Pluton in Western Tibet, China

Collisional processes between the Qiangtang Block and the Lhasa Block: Insights from structural analysis of the Bangong–Nujiang Suture Zone, central Tibet

Petrogenesis of Early Jurassic (ca. 181 Ma) dacitic–rhyolitic volcanic rocks in the Amdo ophiolite mélange, central Tibetan Plateau: Low‐pressure partial melts of Bangong–Nujiang Tethys oceanic crust?

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