The tectonic transition from oceanic subduction to continental subduction: Zirconological constraints from two types of eclogites in the North Qaidam orogen, northern Tibet

Zhang, L.; Chen, Ren‐Xu; Zheng, Yong‐Fei; Li, Wan-Cai; Hu, Zhaochu; Yang, Yue‐Heng; Tang, Haolan

doi:10.1016/j.lithos.2015.12.003

Cited by 66 publications

(22 citation statements)

References 102 publications

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“…Based on the existing and our new data, we explain the NQM UHP metamorphic belt as a result of north‐dipping continental subduction of the Qaidam block following earlier oceanic subduction (Zhang et al., , ; and references therein). The earlier oceanic subduction along the North Qaidam Mountains is also supported by a newly recognized arc magmatic–metamorphic belt in the northern part of the North Qaidam Mountains (Figure ).…”

Section: Discussionmentioning

confidence: 95%

“…Minor eclogite blocks from the Dulan UHP terrane yielded Cambrian protolith ages ( c . 516 Ma; Zhang, Song, et al., ; Zhang et al., ), and were interpreted as part of an ophiolite sequence (Zhang, Song, et al., ), implying possible preservation from oceanic subduction that preceded continental subduction and collision (Song et al., , ; Zhang, Song, et al., ; Zhang et al., ).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The predominant rock types in the North Qaidam UHP metamorphic belt are orthogneisses and paragneisses, which were previously considered to be derived from Late Mesoproterozoic–Early Neoproterozic (1,030–890 Ma) granite and from Mesoproterozoic sedimentary rocks, respectively (Mattinson, Wooden, Liou, Bird, & Wu, ; Song, Su, Li, Niu, & Zhang, ; Wan, Zhang, Yang, & Xu, ; Yu et al., ; Zhang, Mattinson, Meng, Wan, & Tung, ; Zhang, Roermund, Zhang, & Spiers, ; Zhang et al., ). Many authors suggested that the North Qaidam UHP metamorphic belt resulted from continental subduction, and the predominant continental materials in the belt are the product of the northward subduction of the Qaidam block (Song et al., ; Yang et al., ; Zhang et al., , ). However, some authors deduced that the North Qaidam UHP metamorphic rocks are derived from either oceanic mélange or pieces of continental margin tectonically incorporated into an oceanic subduction channel (Yin et al., and references therein).…”

Section: Introductionmentioning

confidence: 99%

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Tectonic erosion related to continental subduction: An example from the eastern North Qaidam Mountains,NWChina

Zhang

Mattinson

2018

Journal Metamorphic Geology

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Tectonic erosion has been commonly recognized in oceanic subduction zones, but evidence of tectonic erosion related to continental subduction is rarely reported. In this contribution, we suggest a tectonic erosion process along the North Qaidam Mountains of NW China during the Early Palaeozoic continental subduction. To the north of the North Qaidam ultra‐high pressure (UHP) metamorphic belt, the microcontinental Oulongbuluke Block (OB) is characterized by Precambrian metamorphic basement. New and existing zircon U–Pb data show that the OB underwent Early Palaeoproterozoic (2.4–2.3 Ga) magmatism and Late Palaeoproterozoic (c. 1.9 Ga) high‐grade metamorphic and anatectic events. The North Qaidam UHP metamorphic belt has been considered to result from the northward subduction of the Qaidam continental block consisting mainly of Meso‐Neoproterozoic orthogneiss and paragneiss. However, our new data show some gneisses enclosing eclogites in the eastern North Qaidam UHP metamorphic belt (Dulan UHP metamorphic unit) experienced 2.4–2.3 Ga magmatism and 1.9–1.8 Ga metamorphism, similar to those of the OB, prior to Early Palaeozoic UHP metamorphism. These data suggest that tectonic erosion occurred during north‐dipping subduction: the Precambrian basement from the upper plate (OB) was transported in the subduction zone to more than 80 km depth, resulting in UHP metamorphism related to Early Palaeozoic continental subduction prior to their exhumation.

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Section: Discussionmentioning

confidence: 95%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tectonic erosion related to continental subduction: An example from the eastern North Qaidam Mountains,NWChina

Zhang

Mattinson

2018

Journal Metamorphic Geology

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“…These ages are similar to those obtained by the authors from the Oulongbuluke block. Eclogites enclosed within the gneisses of the Dulan UHP unit yielded Ordovician ages, typical for the UHP metamorphism in the North Qaidam (Zhang et al., and references therein). Hence, the authors suggest a new model for the tectonic scenario that lead to the development of the North Qaidam metamorphic belt, and that tectonic erosion (sensu e.g.…”

Section: An Introduction To the Individual Papersmentioning

confidence: 99%

High‐ and ultrahigh‐pressure rocks—keys to lithosphere dynamics

Möller

Majka

Janák

et al. 2018

Journal Metamorphic Geology

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“…It is made up of HP and UHP metamorphic units, which are located between the Qilian Block to the north and the Qaidam Block to the south (e.g., Song, Niu, Su, Zhang, & Zhang, ), extending for about 400 km from north‐west of Dulan through the Xitieshan and Lüliangshan (also called Shenglikou) terranes to the Yuka terrane (Figure b). Extensive studies on HP and UHP eclogite from the North Qaidam have shown that most eclogite protoliths are Neoproterozoic within‐plate basalt (WPB) or continental flood basalt (CFB) formed in continental rift settings during the break‐up of the Rodinia supercontinent (e.g., Chen, Liu, Sun, & Liou, ; Song et al, ; Yu et al, ; Zhang, Mattinson, Yu, Li, & Meng, ), whereas a few of them are fragments from the Mesoproterozoic and Early Palaeozoic oceanic lithosphere (Ren et al, ; Song, Niu, Su, Zhang, & Zhang, ; Zhang et al, ; Zhang, Song, Zhang, & Niu, ; Zhao, Wei, Fu, Liang, & Zhao, ). Therefore, some researchers contend that the North Qaidam UHP metamorphic belt records the full Wilson cycle of continental rifting, ocean floor spreading, oceanic subduction, tectonic erosion from deep continental subduction, final collision mountain formation, and collapse between the Qaidam and Qilian blocks during the Neoproterozoic and Palaeozoic (Lu, Zhang, & Mattinson, ; Ren et al, ; Song, Niu, Su, Zhang, & Zhang, ; Zhang et al, ; Zhang, Chen, Zheng, Hu, & Xu, ; Zhang, Song, et al, ; Zhang, Zhang, Bader, Song, & Lou, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Tracking the timing and nature of protolith, metamorphism, and partial melting of tourmaline‐bearing migmatites by zircon U–Pb and Hf isotopic compositions in the Yuka terrane, North Qaidam UHP metamorphic belt

Gao

Chen

et al. 2018

Geological Journal

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An integrated study using cathodoluminescence (CL) images, U–Pb geochronology, and Hf isotopic characterization of zircons was performed on migmatites from the Yuka terrane to provide insights into the timing and nature of the protoliths, metamorphism, and partial melting of these rocks. Zircon grains separated from the migmatites have three distinct domains. Residual zircon cores in samples YKT01 and YKT02 exhibit oscillatory zoning, high Th/U ratios (0.10–0.79), steep heavy rare earth element (HREE) patterns, and mean ages of 936 ± 5 Ma and 927 ± 11 Ma, respectively, indicating that they are igneous in origin and record Neoproterozoic magmatism during the Grenvillian Orogeny. CL‐grey cores record an ultrahigh‐pressure (UHP) peak metamorphism age of 435 ± 5 Ma and have low Th/U and 176Lu/177Hf ratios, weak negative Eu anomalies, and relatively flat HREE patterns. The CL‐bright rims have steep HREE patterns with lower middle rare earth element (MREE) concentrations but higher HREE concentrations compared with the metamorphic cores and a weighted average age of 422 ± 4 Ma, which records the timing of melt crystallization. The migmatites incorporate garnet relicts coexisting with fluid inclusions and hydrous minerals like peritectic phengite and peritectic large anhedral poikilitic tourmaline in the leucosomes. Peak temperatures are less than 750°C, suggesting that the anatectic melts may be derived from melting of felsic gneiss in the presence of water. The timing of melt crystallization is ca. 13 Ma later than UHP metamorphism, indicating that the partial melting took place during the exhumation stage. The metamorphic zircon cores have higher 176Hf/177Hf(t) ratios than the residual magmatic cores, which provides powerful evidence for the generation of the metamorphic zircons through the incorporation of internal high Hf minerals other than zircon in a closed system. Anatectic rims with lower 176Hf/177Hf(t) ratios but higher 176Lu/177Hf ratios than metamorphic cores suggest that the main formation mechanism is dissolution‐reprecipitation of pre‐existing zircons. In conclusion, the elevated 176Hf/177Hf(t), TDM2 age and decreasing 176Lu/177Hf(t) ratios in the metamorphic and anatectic domains imply that the new zircons in some migmatites and granites may not reflect the Hf isotope compositions of their source rocks, accounting for the variable Hf isotope compositions in S‐type granites.

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The tectonic transition from oceanic subduction to continental subduction: Zirconological constraints from two types of eclogites in the North Qaidam orogen, northern Tibet

Cited by 66 publications

References 102 publications

Tectonic erosion related to continental subduction: An example from the eastern North Qaidam Mountains,NWChina

Tectonic erosion related to continental subduction: An example from the eastern North Qaidam Mountains,NWChina

High‐ and ultrahigh‐pressure rocks—keys to lithosphere dynamics

Tracking the timing and nature of protolith, metamorphism, and partial melting of tourmaline‐bearing migmatites by zircon U–Pb and Hf isotopic compositions in the Yuka terrane, North Qaidam UHP metamorphic belt

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