Whole-rock and zircon geochemical distinction between oceanic- and continental-type eclogites in the North Qaidam orogen, northern Tibet

Zhang, L.; Chen, Ren‐Xu; Zheng, Yong‐Fei; Hu, Zhaochu; Xu, Lijuan

doi:10.1016/j.gr.2016.10.021

Cited by 43 publications

(17 citation statements)

References 122 publications

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“…Eclogites in this belt can be divided into two types based on their protolith ages and geochemical signatures: (1) Neoproterozoic continental‐type eclogite, which is the major eclogite type in this belt. It has protolith ages of 850–750 Ma and WPB or CFB geochemical signatures and is proposed to have formed in a continental rift or an incipient oceanic basin setting related to the breakup of the supercontinent Rodinia (Chen, Liu, et al., ; Liu et al., ; Song et al., ; Xiong, Zheng, Griffin, O'Reilly, & Pearson, ; Yu, Zhang, Li, et al., ; Zhang, Chen, Zheng, Hu, & Xu, ; Zhang, Ireland, et al., ; Zhang et al., , ). The eclogite metamorphic ages (458–421 Ma) and P–T paths are comparable to their host gneisses (Chen, Liu, et al., ; Chen, Sun, & Liu, ; Chen, Sun, Liu, Zhang, & Lin, ; Chen, Sun, & Liu, ; Chen et al., ; Liu et al., ; Ren et al., ; Song, Yang, Xu, Liou, & Shi, ; Song et al., , ; Xiong et al., ; Yu, Zhang, del Real, et al., ; Yu, Zhang, Li, et al., ; Zhang, Meng, & Yang, ; Zhang et al., ), indicating they underwent continental subduction with their host gneisses; and (2) Early Palaeozoic oceanic‐type eclogite.…”

Section: Geological Settingmentioning

confidence: 99%

Metamorphic evolution of a newly identified Mesoproterozoic oceanic slice in the Yuka terrane and its implications for a multi‐cyclic orogenic history of the North QaidamUHPMbelt

Ren

Chen

Kelsey

et al. 2018

Journal Metamorphic Geology

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The North Qaidam Orogenic Belt (NQOB), lying at the northern margin of the Tibet Plateau, records two orogenic cycles: A Proterozoic cycle related to the amalgamation and breakup of the supercontinent Rodinia, and an Early Palaeozoic cycle including oceanic subduction and continental deep subduction. At present, the only information about the Proterozoic cycle is the concurrent c. 1,000-900 Ma magmatic and metamorphic events, which limited the understanding of the Proterozoic evolution of NQOB and the relationship between the Qaidam Block and other Rodinia fragments. In this study, a kyanite-bearing eclogite was identified in Yuka terrane. It has positive-slope chondrite-normalized rare earth element distribution patterns, similar to present-day N-MORB. LA-ICP-MS zircon U-Pb dating obtained a protolith age of 1,273 Ma and an eclogite facies metamorphic age of 437 Ma, which is similar to the continental deep subduction age of the Yuka terrane. Zircon Lu-Hf analysis show that the magmatic zircon cores have high eHf(t) of 8.36-15.98 and T DM1 of 1,450-1,131 Ma (M = 1,303 AE 55 Ma, consistent with its protolith age within error), indicating a juvenile crust protolith of the eclogite. The MORB-like whole-rock composition and zircon U-Pb and Lu-Hf analysis indicate that the protolith of the kyanitebearing eclogite was a Mesoproterozoic oceanic slice. P-T pseudosection analysis shows that the kyanite-bearing eclogite experienced four metamorphic stages: (1) a prograde stage with the assemblage garnet+omphacite+talc+lawsonite+phen-gite+quartz at 22.4-23.2 kbar and 585°C; (2) a peak stage with the assemblage garnet+omphacite+lawsonite+phengite+coesite at 32.5 kbar and 670°C; (3) an early retrograde stage with the assemblage garnet+omphacite+kyanite+phen-gite+coesite/quartzAElawsonite at 27.1-30.0 kbar and 670-690°C; and (4) a late retrograde stage with the assemblage garnet+omphacite+epidote+horn-blende+phengite+quartz at <18.0 kbar. The established clockwise P-T path is similar with other continental-type eclogites in this area. On the basis of the geochemical and geochronological data, as well as the P-T path, we suggest that the protolith of the kyanite-bearing eclogite was emplaced in the active margin of the Qaidam Block during the assembly of Rodinia and underwent continental deep subduction in the Early Palaeozoic. We conclude that (1) the Qaidam Block

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Section: Geological Settingmentioning

confidence: 99%

Metamorphic evolution of a newly identified Mesoproterozoic oceanic slice in the Yuka terrane and its implications for a multi‐cyclic orogenic history of the North QaidamUHPMbelt

Ren

Chen

Kelsey

et al. 2018

Journal Metamorphic Geology

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“…Zircon dating shows that the Yukahe eclogite recorded eclogite‐facies metamorphic ages of 434–430 Ma. Their protoliths have WPB or CFB and N‐MORB signatures; the former possibly formed in a continental rift environment about 850–750 Ma (Chen et al, ; Song et al, ; Zhang et al, ), and the latter may be a Mesoproterozoic oceanic slice (Ren et al, ). Meanwhile, pelitic gneiss, orthogneiss, and marble also experienced a clockwise P‐T evolution with peak metamorphic conditions of 615–754°C, 2.3–3.3 GPa (Chen, Xu, Schertl, & Zheng, ; Menold et al, ; Zhang, ) and have been subjected to synchronous UHP metamorphism (Chen, Xu, Schertl, & Zheng, ; Zhang, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…1,000-900 Ma) amphibolite to granulite facies metamorphism and Palaeozoic (ca. 460-420 Ma) HP-UHP eclogite facies metamorphism (Yang et al, 2001;Mattinson, Menold, Zhang, & Bird, 2007;Song et al, 2006Song et al, , 2012Yu, Zhang, Li, et al, 2013;Yu, Zhang, Real, et al, 2013;Yu, Li, Zhang, & Sun, 2017;Yu, Zhang, Li, & Peng, 2017;Zhang, Mattinson, et al, 2008;Zhang et al, 2017;Zhou et al, 2017). Recently, detrital zircon in metapelites from the North Qaidam UHP metamorphic belt was found to fall into three age groups, >1,100 Ma, 1,100-800 Ma, and 800-500 Ma.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…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). Although there has been much research into the U–Pb geochronology of eclogite and retrograde eclogite zircon samples, it is not easy to find geochronological information on subsequent retrogression and exhumation (Cao et al, ; Chen et al, , ; Mattinson, Wooden, Liou, Bird, & Wu, ; Mattinson, Wooden, Liou, Bird, & Wu, ; Mattinson, Wooden, Zhang, & Bird, ; Ren et al, ; Song et al, ; Song, Niu, Su, Zhang, & Zhang, ; Yu, Zhang, Sun, Li, & Gong, ; Yu, Zhang, Sun, Real, et al, ; Zhang et al, , , , ; Zhang, Ellis, et al, ; Zhang, Mattinson, Meng, Wan, & Tung, ; Zhang, Meng, & Yu, ; Zhang, Song, et al, ; Zhang, Zhang, Christy, Song, & Li, ; Zhang, Zhang, Song, & Niu, ).…”

Section: Introductionmentioning

confidence: 99%

“…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). Although there has been much research into the U–Pb geochronology of eclogite and retrograde eclogite zircon samples, it is not easy to find geochronological information on subsequent retrogression and exhumation (Cao et al, ; Chen et al, , ; Mattinson, Wooden, Liou, Bird, & Wu, ; Mattinson, Wooden, Liou, Bird, & Wu, ; Mattinson, Wooden, Zhang, & Bird, ; Ren et al, ; Song et al, ; Song, Niu, Su, Zhang, & Zhang, ; Yu, Zhang, Sun, Li, & Gong, ; Yu, Zhang, Sun, Real, et al, ; Zhang et al, , , , ; Zhang, Ellis, et al, ; Zhang, Mattinson, Meng, Wan, & Tung, ; Zhang, Meng, & Yu, ; Zhang, Song, et al, ; Zhang, Zhang, Christy, Song, & Li, ; Zhang, Zhang, Song, & Niu, ). Previous studies have found that the Yuka terrane experienced a relatively rapid and cold exhumation history compared with the Xitieshan and Lüliangshan terranes (Cao et al, ; Zhang et al, ; Zhang, Mattinson, et al, ).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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Subduction and exhumation of Luliangshan eclogite in the North Qaidam, northern Tibet: Constraints from petrology, geochemistry and phase equilibrium modelling

Peng

et al. 2020

Geological Journal

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Eclogites in the high‐pressure (HP) and ultrahigh‐pressure (UHP) belt record important information about the subduction process and evolution history of the orogenic belt. The Luliangshan eclogites surrounded by granitic gneiss or paragneiss as lenses are exposed in the western segment of the North Qaidam UHP metamorphic belt, northwestern China. Petrology, mineral chemistry, and P–T pseudosection modelling show that the eclogites have experienced a multi‐stage metamorphic process. The peak eclogite‐facies metamorphic stage, is characterized by omphacite in matrix and as inclusion in garnet, with the peak mineral assemblages of garnet + omphacite + rutile + quartz at T > 790°C and P > 25.5 kbar. The initial HP granulite‐facies retrogression is characterized by the symplectite of diopside + plagioclase around omphacite, with P–T conditions of 911°C and 16.9 kbar. The subsequent amphibolite‐facies stage is characterized by amphibole + plagioclase symplectite around the clinopyroxene, with the metamorphic conditions of 674–686°C and 6.4–6.9 kbar. Zircon U–Pb analyses yielded two metamorphic age clusters: (a) HP granulite‐facies metamorphic age of 422–425 Ma, and (b) amphibolites‐facies retrograde age of 397–420 Ma. The protolith of eclogite have geochemical characteristics similar to those of normal mid‐ocean ridge basalt (N‐MORB); and the varying εNd(t) values (−6.3 to 2.1) indicate that the Luliangshan eclogites were derived from a mantle source with rare crustal contamination. Combining these data with previous studies, a multi‐stage tectonic model can be proposed: In the Early Neoproterozoic, the protolith of the Luliangshan eclogites were emplaced into ancient continental crust; during 460–430 Ma, following the oceanic subduction, the subduction of continental crust was dragged by the oceanic slab and continue to subduct towards the Qilian Block, and metamorphosed at the depth of at least 75 km. After a long and slow exhumation process, it returned to the shallow crust.

show abstract

Whole-rock and zircon geochemical distinction between oceanic- and continental-type eclogites in the North Qaidam orogen, northern Tibet

Cited by 43 publications

References 122 publications

Metamorphic evolution of a newly identified Mesoproterozoic oceanic slice in the Yuka terrane and its implications for a multi‐cyclic orogenic history of the North QaidamUHPMbelt

Metamorphic evolution of a newly identified Mesoproterozoic oceanic slice in the Yuka terrane and its implications for a multi‐cyclic orogenic history of the North QaidamUHPMbelt

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

Subduction and exhumation of Luliangshan eclogite in the North Qaidam, northern Tibet: Constraints from petrology, geochemistry and phase equilibrium modelling

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