The geological characteristics of oceanic-type UHP metamorphic belts and their tectonic implications: Case studies from Southwest Tianshan and North Qaidam in NW China

Zhang, Lifei; Lü, Zeng; Zhang, GuiBin; Song, Shuguang

doi:10.1007/s11434-008-0386-2

Cited by 37 publications

(13 citation statements)

References 59 publications

(78 reference statements)

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“…(i) Only rare oceanic eclogites record UHP metamorphism, and their peak pressures are <3.2 GPa (Fig. ) (Zhang et al ., ; Agard et al ., ). Most of the associated serpentinized mantle peridotites are spinel‐facies peridotite (<80 km, e.g.…”

Section: Natural Oceanic Eclogitesmentioning

confidence: 99%

“…A third hypothesis proposes that the exhumed oceanic eclogites were dragged upward by low‐density serpentinite (Hermann et al ., ; Guillot et al ., , ; Angiboust & Agard, ). Although this model is sufficient for the oceanic eclogites associated with serpentinite, such as those in Zermatt‐Saas in the Western Alps (Angiboust & Agard, ), it cannot explain the exhumation of oceanic eclogites without serpentinite, such as those in Southwest Tianshan (Zhang et al ., ; Klemd et al ., ). Therefore, compared with the well‐accepted buoyancy exhumation model for HP–UHP rocks formed by continental subduction (Davies & von Blanckenburg, ; Ernst, ), the exhumation mechanism associated with oceanic eclogites remains one of the least‐known domains in the subduction factory (Gerya et al ., ; Gorczyk et al ., ; Krebs et al ., ; Blanco‐Quintero et al ., ; Malatesta et al ., ).…”

Section: Introductionmentioning

confidence: 99%

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Exhumation of oceanic eclogites: thermodynamic constraints on pressure, temperature, bulk composition and density

Chen

et al. 2013

Journal Metamorphic Geology

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The exhumation mechanism of high-pressure (HP) and ultrahigh-pressure (UHP) eclogites formed by the subduction of oceanic crust (hereafter referred to as oceanic eclogites) is one of the primary uncertainties associated with the subduction factory. The phase relations and densities of eclogites with MORB compositions are modelled using thermodynamic calculations over a P-T range of 1-4 GPa and 400-800°C, respectively, in the NCKFMASHTO (Na 2 O-CaO-K 2 O-FeO-MgO-Al 2 O 3 -SiO 2 -H 2 O-TiO 2 -Fe 2 O 3 ) system. Our modelling suggests that the mineral assemblages, mineral proportions and density of oceanic crust subducted along a cold P-T path are quite different from those of crust subducted along a warm P-T path, and that the density of oceanic eclogites is largely controlled by the stability of low-density hydrous minerals, such as lawsonite, chlorite, glaucophane and talc. Along a cold subduction P-T path with a geotherm of~6°C km À1 , lawsonite is always present at 1.1 to >4.0 GPa, and chlorite, glaucophane and talc can be stable at pressures of up to 2.3, 2.6 and 3.6 GPa respectively. Along such a P-T path, the density of subducted oceanic crust is always lower than that of the surrounding mantle at depths shallower than 110-120 km (< 3.3-3.6 GPa). However, along a warm subduction P-T path with a geotherm of~10°C km À1 , the P-T path is outside the stability field of lawsonite, and the hydrous minerals of chlorite, epidote and amphibole break down completely into dry dense minerals at relatively lower pressures of 1.5, 1.85 and 1.9 GPa respectively. Along such a warm subduction P-T path, the subducted oceanic crust becomes denser than the surrounding mantle at depths >60 km (>1.8 GPa). Oceanic eclogites with high H 2 O content, oxygen fugacity, bulk-rock X Mg [ = MgO/(MgO + FeO)], X Al [ = Al 2 O 3 /(Al 2 O 3 + MgO + FeO)] and low X Ca [ = CaO/ (CaO + MgO + FeO + Na 2 O)] are likely suitable for exhumation, which is consistent with the bulkrock compositions of the natural oceanic eclogites on the Earth's surface. On the basis of natural observations and our calculations, it is suggested that beyond depths around 110-120 km oceanic eclogites are not light enough and/or there are no blueschists to compensate the negative buoyancy of the oceanic crust, therefore explaining the lack of oceanic eclogites returned from ultradeep mantle (>120 km) to the Earth's surface. The exhumed light-cold-hydrous oceanic eclogites may have decoupled from the top part of the sinking slab at shallow depths in the forearc region and are exhumed inside the serpentinized subduction channel, whereas the dense-hot-dry eclogites may be retained in the sinking slab and recycled into deeper mantle.

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Section: Natural Oceanic Eclogitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exhumation of oceanic eclogites: thermodynamic constraints on pressure, temperature, bulk composition and density

Chen

et al. 2013

Journal Metamorphic Geology

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“…In the northern margin of the Tibetan Plateau, there developed an early Palaeozoic UHP metamorphic belt along the northern margin of Qaidam Block (Qaidam Basin; S. G. Song et al, ; J. Yang et al, ; J. Zhang et al, ; L. F. Zhang, Lu, Zhang, & Song, ), in which the protoliths have been strongly metamorphosed with the partial melting. By using cathodoluminescence (CL) images, U–Pb geochronology, and Hf isotope of zircons, Gao et al () carried out a study on the migmatites from the Yuka terrane to provide insights into the timing and nature of the protoliths, metamorphism, and partial melting of the rocks in the UHP belt.…”

Section: Tectonics Of Western Chinamentioning

confidence: 99%

“…Zhang, Li, Wei, Cai, & Zhang, 2008). In the northern margin of the Tibetan Plateau, there developed an early Palaeozoic UHP metamorphic belt along the northern margin of Qaidam Block (Qaidam Basin; S. G. Song et al, 2006;L. F. Zhang, Lu, Zhang, & Song, 2008), in which the protoliths have been strongly metamorphosed with the partial melting.…”

Section: Tectonics Of Western Chinamentioning

confidence: 99%

Preface: Tectonics of China

Liu

Xiao

et al. 2019

Geological Journal

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“…Earlier studies have yielded divergent results regarding the timing of orogenic processes in the North Qaidam Orogen. Based on studies of the HP/UHP metamorphic rocks, the termination of ocean–continent subduction was either at 460 Ma (Chen et al, ; Shi, Yang, Wu, Iizuka, & Hirata, ; Xiong, Zheng, Griffin, O'Reilly, & Pearson, ; Xu et al, ; Yang et al, ; Zhang, Dang, et al, ; Zhang, Wang, et al, ; Zhang, Mattinson, Meng, Yang, & Wan, ; Zhang, Yu, Meng, & Li, ) or 440 Ma (Song et al, ; Song, Niu, Su, Wei, & Zhang, ; Song, Wang, Wang, & Niu, ; Zhang, Zeng, Zhang, & Song, ); the duration of HP/UHP metamorphism during the continent–continent collision is inferred to have been either ~60 Myr (Chen et al, ; Liu et al, ; Mattinson, Menold, Zhang, & Bird, ; Mattinson, Wooden, Liou, Bird, & Wu, ; Xiong, Zheng, Griffin, O'Reilly, & Pearson, ; Xu et al, ; Zhang, Yu, Meng, & Li, ) or 15–20 Myr (Song, Niu, Su, Wei, & Zhang, ; Song, Wang, Wang, & Niu, ).…”

Section: Introductionmentioning

confidence: 99%

Geochronology and geochemistry of volcanic rocks from the Tanjianshan Group, NW China: Implications for the early Palaeozoic tectonic evolution of the North Qaidam Orogen

Sun

Algeo

et al. 2018

Geological Journal

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The widely exposed Tanjianshan volcanic rocks in the North Qaidam Orogen (NW China) encode abundant information about early Palaeozoic magma origin and tectonic evolution. This research utilizes petrological, geochemical, and geochronological methods to investigate the last volcanic cycle (Formation d) of the Tangjianshan Group, aiming to reveal the tectonic evolutionary processes of the North Qaidam Orogen. Formation d can be further divided into two major volcanic sequences, that is, Formation

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The geological characteristics of oceanic-type UHP metamorphic belts and their tectonic implications: Case studies from Southwest Tianshan and North Qaidam in NW China

Cited by 37 publications

References 59 publications

Exhumation of oceanic eclogites: thermodynamic constraints on pressure, temperature, bulk composition and density

Exhumation of oceanic eclogites: thermodynamic constraints on pressure, temperature, bulk composition and density

Preface: Tectonics of China

Geochronology and geochemistry of volcanic rocks from the Tanjianshan Group, NW China: Implications for the early Palaeozoic tectonic evolution of the North Qaidam Orogen

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