UHP metamorphic evolution and SHRIMP geochronology of a coesite-bearing meta-ophiolitic gabbro in the North Qaidam, NW China

Zhang, Guibin; Zhang, Lifei; Song, Shuguang; Niu, Yaoling

doi:10.1016/j.jseaes.2008.11.013

Cited by 98 publications

(62 citation statements)

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“…Compared to eclogite, the HP granulite has higher geothermal gradient, which refers to the HP granulite forming at the base of thickened crust, while the eclogite forms in the subducted crust (Konopasek, 2005). Although the first model is perfectly viable in explaining the relationship between HP granulite and the eclogite in the Dulan area, it requires both types of rock to have similar peak metamorphic condition, which is contrary to the actual observations of the studied area owing to the UHP metamorphism of eclogite (Zhang et al, 2009a(Zhang et al, ,b, 2010. Model (2) is therefore better suited to account for the separate geothermal gradients of the Dulan HP granulites and eclogites.…”

Section: Petrogenesis and Relationship Between Granulite And Eclogitementioning

confidence: 80%

“…(2) The garnet, clinopyroxene and plagioclase are in textural equilibrium and the proportion of plagioclase is too large to be ascribed to the breakdown of omphacite (Medaris et al, 2006). (3) The latest petrologic research in the area suggests that the eclogite directly retrogressed to amphibolite-faices during decompression without HP granulite-facies overprinting (Zhang et al, 2009a), which objects to the retrogressive origin of the Dulan HP granulite. (4) The inclusions of amphibole, epidote and plagioclase, together with typical zoning in garnet suggest that the HP granulite evolved from epidote-amphibolitefacies to HP granulite-facies without experiencing eclogite-facies metamorphism.…”

Section: Petrogenesis and Relationship Between Granulite And Eclogitementioning

confidence: 99%

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Petrology and P–T path of high-pressure granulite from the Dulan area, North Qaidam Mountains, northwestern China

Zhang

Real

2011

Journal of Asian Earth Sciences

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Section: Petrogenesis and Relationship Between Granulite And Eclogitementioning

confidence: 80%

Section: Petrogenesis and Relationship Between Granulite And Eclogitementioning

confidence: 99%

Petrology and P–T path of high-pressure granulite from the Dulan area, North Qaidam Mountains, northwestern China

Zhang

Real

2011

Journal of Asian Earth Sciences

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“…Recently, significant progress has been made in the study of (U)HP metamorphism in this belt, e.g., (1) in the northern belt of the Dulan terrane, coesite inclusions were found in zircons in pelitic gneiss Song et al, 2003aSong et al, , 2003bSong et al, , 2006 and coesite pseudomorphs have been identified in eclogitic garnets (Song et al, 2003a); (2) in the southern belt of the Dulan terrane, coesite inclusions and their pseudomorphs occur in garnet and omphacite in eclogites (Zhang et al, 2008a(Zhang et al, , 2009b; (3) in the Yuka terrane, coesite inclusions occur in garnet (Zhang et al, 2009c); and (4) in the Lüliangshan garnet peridotites microdiamonds occur in zircon and pyroxene-amphibole exsolution textures are common in garnets from the peridotites (Song et al, 2004(Song et al, , 2005a(Song et al, , 2005b. All of the above evidence indicates that the North Qaidam orogenic belt was subducted into the (upper) mantle where the rocks were metamorphosed in the coesite-diamond fields of the eclogite facies Song et al, 2003aSong et al, , 2003bSong et al, , 2006.…”

Section: Introductionmentioning

confidence: 99%

Petrology and SHRIMP U–Pb dating of Xitieshan eclogite, North Qaidam UHP metamorphic belt, NW China

Zhang

Roermund

et al. 2011

Journal of Asian Earth Sciences

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“…In the NQD HP/UHP metamorphic belt, except for the Dulan HP/UHP metamorphic unit [11,15,29] , coesite, polycrystalline quartz after coesite, and polycrystalline quartz+K-feldspar aggregates have not been discovered in eclogite and associated rocks of the other units including the Yuka-Luofengpo eclogite-gneiss unit and Xitieshan eclogite-gneiss unit. P-T estimates for phengite-bearing eclogites in the western segment of the …”

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confidence: 99%

Coesite in eclogite from the North Qaidam Mountains and its implications

Zhang

Meng

et al. 2009

Sci. Bull.

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Coesite provides direct evidence for ultrahigh pressure metamorphism. Although coesite has been found as inclusions in zircon in paragneiss of the north Qaidam Mountains, it has never been identified in eclogite. In this contribution, based on petrographic observations and in situ Raman microprobe spectroscopy, coesite was identified as inclusions in garnet of eclogite from the Aercituoshan, Dulan UHP metamorphic unit, north Qaidam Mountains. Coesite is partly replaced by quartz, showing a palisade texture. This is the first report on coesite in eclogite from the north Qaidam Mountains, and is also supported by garnet-omphacite-phengite geothermobarometry (2.7-3.25 GPa, 670-730℃). Coesite and its pseudomorphs have not been found in eclogites and associated rocks of other units of the north Qaidam Mountains. Further studies are required to confirm if all metamorphic units in the north Qaidam Mountains underwent the ultrahigh-pressure metamorphism.North Qaidam Mountains, Dulan, eclogite, coesite, Ultrahigh pressure metamorphismThe ultrahigh-pressure (UHP) metamorphism refers to the metamorphism above the coesite-quartz transition. Therefore, although a number of mineralogical indicators have been considered as evidence for UHP metamorphism, coesite is still one of the most direct indicators for UHP metamorphism.Over the past ten years, a new HP/UHP metamorphic terrane has been confirmed along the north Qaidam Mountains in western China [1][2][3][4][5][6][7][8][9][10][11][12][13] . It has been correlated to the south Altyn Tagh HP/UHP metamorphic terrane, and constrains a 400 km offset for the Altyn Tagh fault. Therefore, South Altyn-North Qaidam was considered as a single HP-UHP metamorphic belt truncated by a large strike-slip fault, similar to the case of the Dabie-Sulu HP-UHP metamorphic zone which was truncated by the sinistral Tanlu strike-slip fault in eastern China, and split into the Dabie and Sulu regions [14][15][16][17][18][19][20][21] . However, in contrast to Dabie-Sulu in eastern China, where UHP metamorphic evidence has been commonly recognized in different rock types, evidence of UHP metamorphism is relatively rare in the north Qaidam (NQD) and south Altyn Tagh (SAT) [11,22,23] . Up to now, coesite was only reported as inclusions in zircons of amphibolite-facies paragneiss in the Dulan area, eastern NQD. This high-pressure silica polymorph has never been positively identified in eclogite from the NQD and SAT. Although polycrystalline quartz inclusions in garnet and omphacite in the Jianggelesayi eclogite of SAT and Dulan eclogite of NQD were interpreted as pseudomorphs after coesite, the polycrystalline aggregates cannot be simply the result of a transformation from coesite because they contain small amounts of K-feldspar [24,25] .Recently, detailed field work and petrographic observations have led to the first discovery of coesite inclusions in garnet of eclogite in the northern slope of Aercituoshan, southern Dulan HP/UHP metamorphic unit, north Qaidam Mountains.

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UHP metamorphic evolution and SHRIMP geochronology of a coesite-bearing meta-ophiolitic gabbro in the North Qaidam, NW China

Cited by 98 publications

References 50 publications

Petrology and P–T path of high-pressure granulite from the Dulan area, North Qaidam Mountains, northwestern China

Petrology and P–T path of high-pressure granulite from the Dulan area, North Qaidam Mountains, northwestern China

Petrology and SHRIMP U–Pb dating of Xitieshan eclogite, North Qaidam UHP metamorphic belt, NW China

Coesite in eclogite from the North Qaidam Mountains and its implications

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