Evidence of former stishovite in UHP eclogite from the South Altyn Tagh, western China

Liu, Liang; Zhang, Junfeng; Cao, Yuting; Green, Harry W.; Yang, Wei; Xu, H.; Liao, Xiaoying; Kang, Lei

doi:10.1016/j.epsl.2017.12.023

Cited by 63 publications

(36 citation statements)

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“…The metamorphic P–T–t history of the garnetite from South Altyn orogen, involving a prograde evolution from amphibolite facies conditions (I‐A) to eclogite facies conditions (I‐B) to UHP eclogite facies conditions (II) and a possible isothermal exhuamtion to HP–UHT granulite facies conditions (III). P–T path or conditions of relevant UHP rocks from Bohemian Massif and South Altyn Tagh are presented for comparison, involving garnet–clinopyroxene rocks (H16, Haifler & Kotková, ; L05, Liu et al, ), felsic granulites (D18, Dong et al, ), garnet peridotites (W11, Wang et al, ), and eclogites (L18, Liu et al, ). The results of geothermobarometers are also presented, including those of Grt–Cpx–Pl–Qz thermobarometer (TB), X Ti in amphibole (TAmp) and ternary feldspar thermometer (Tper).…”

Section: Discussionmentioning

confidence: 99%

“…Thereafter, accumulated reports of exsolution microtextures involving pyroxene/quartz exsolution in garnet (Ye et al, ), garnet exsolution in pyroxene (Zhang & Liou, ), and C 2 /c pyroxene/K‐feldspar exsolution in clinopyroxene (Liu, Jin, et al, ; Schertl & Sobolev, ) from some UHP terranes suggest proposed pressures of > 6–7 GPa or continental subduction to the ultradeep depths over ~200 km. Moreover, the discovery of stishovite pseudomorphs/paramorphs (>9 GPa) (Liu, Zhang, et al, , Liu et al, ) have extended our views of continental subduction further to depths of 250–300 km.…”

Section: Introductionmentioning

confidence: 86%

“…The South Altyn crust should have been once subducted to the depths of > 200-220 km as evidenced by the minimum peak pressures of~6.5-7.0 GPa recovered for garnetites, or probably to~300 km ( Figure 10) as indicated by the stishovite pseudomorphs/paramorphs (>9 GPa) reported in UHP eclogites and their host rocks (Liu, Zhang, et al, 2007;Liu et al, 2018). Once detached from the subducting slab, continental slices as represented by the host felsic granulites enclosing minor garnetite-mafic granulite-garnet peridotite rocks would exhume rapidly to a thickened crust bottom.…”

Section: Geodynamic Implicationsmentioning

confidence: 99%

“…At Jianggalesayi area, eclogites containing well‐preserved coesite inclusions are interpreted to have peak conditions of 2.8–3.0 GPa/820–850 °C (Gai et al, ) and with jadeite contents of 38–43 mol% in omphacite, which are higher than those of other eclogites discovered in Baishituogelake, Piyazilekedaban and Paxialayidang (15–28 mol%, Liu et al, ) (Figure b). But the existence of former stishovite is reported in these eclogites based on long prism quartz inclusions with bamboo structures (Liu et al, ). It is also discovered in the pelitic gneisses surrounding eclogites based on the exsolved iron and aluminum oxide in quartz (Liu, Zhang, et al, ), implying peak pressures at least above ~9 GPa.…”

Section: Geological Backgroundmentioning

confidence: 99%

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P–T–t Path of Garnetites in South Altyn Tagh, West China: A Complete Record of the Ultradeep Subduction and Exhumation of Continental Crust

et al. 2020

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We report here a detailed investigation of mineral chemistry, phase modelling and geochronology for garnetites from the Bashiwake ultrahigh pressure (UHP) terrane, South Altyn Tagh, West China. Three generations of mineral assemblages including two stages of melting were identified. The first generation is represented by the zoning with decreasing grossular and increasing pyrope and multiphase inclusions in garnet core. It records an early‐stage prograde evolution from amphibolite facies to eclogite facies (1.7–2.5 GPa/710–850 °C) where the first stage of melting occurs. The second generation is characterized by the zoning in garnet mantle with increasing grossular and nearly constant pyrope, defining a later‐stage prograde evolution to UHP peak with the minimum condition of 6.5–7.0 GPa/990 °C. The pressure is consistent with that constrained from the pigeonite exsolution particularly along (401) planes in clinopyroxene. The third generation includes the presence of perthite, plagioclase along with amphibole, suggesting the decompression from eclogite facies to HP–ultrahigh‐temperature (UHT) granulite facies (~3.3–1.2 GPa/960–1020 °C) coupled with the second stage of melting. It is for the first time to get two metamorphic ages about 500 Ma and 486 Ma using in situ SIMS zircon dating which represent the prograde eclogite facies and decompressional granulite facies stages, suggesting the rocks staying at mantle depths for ~14 million years. The garnetites have recorded a complete metamorphic P–T–t history of continental ultradeep subduction to mantle depths of ~200 km or more followed by diapiring exhumation to the crust bottom.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 86%

Section: Geodynamic Implicationsmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

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P–T–t Path of Garnetites in South Altyn Tagh, West China: A Complete Record of the Ultradeep Subduction and Exhumation of Continental Crust

et al. 2020

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“…Some studies suggested that the Altun Group formed from Mesoproterozoic to Neoproterozoic, part of which experienced an early Palaeozoic tectonic thermal event (e.g., Yu et al, ). (d) The South Altyn Tagh (SAT) subduction–collision complex consists of blocks of eclogite, garnet–peridotite, and HP granulites within amphibolite‐facies gneisses exposed in the south‐western part of the Altyn Tagh, and it is a famous UHP terrane in which coesite was found in the eclogite, and stishovite paramorph was found in both the eclogite and metapelite (Gai et al, ; Liu, Zhang, Ii, Jin, & Bozhilov, ; Liu et al, ). Zircon U–Pb geochronology and Sm–Nd isotopic data from eclogites in the western segment of the SAT suggest the peak HP metamorphism occurred at ca.…”

Section: Geological Setting and Field Contextmentioning

confidence: 99%

Petrogenesis of mafic granulite in South Altyn Tagh, NW China: Constraints from petrology, zircon U–Pb chronology, and geochemistry

Zhang

et al. 2019

Geological Journal

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Mafic granulite, garnet peridotite, and garnet pyroxenite occurred as slices or lenses within dominant felsic granulite, and they together constitute a high‐pressure metamorphic terrane in the Bashiwake unit, South Altyn Tagh, Northern Tibet, China. Previous studies focused on the metamorphic evolution, and geothermobarometry results indicated that the mafic granulite has experienced high pressure/(ultra‐)high temperature (HP/(U)HT) metamorphism, followed by a medium pressure (MP) granulite‐facies overprint. However, the nature and petrogenesis of the mafic granulite in the dominant felsic granulite are poorly known. Combining the previous geothermobarometry results with the petrographic observations, mineral chemistry, and pseudosection modelling in this study, at least four stages were suggested for the metamorphic evolution of the mafic granulites in the South Altyn Tagh, including the eclogite‐facies stage (3–4 GPa, 910–1000°C), high pressure–ultrahigh temperature (HP–UHT) metamorphism, an isothermal decompression, and subsequent MP granulite‐facies overprint. The U–Pb dating of zircons yielded two age clusters: one age cluster at ca. 500 Ma, representing the retrograde age of HP–UHT metamorphism after the eclogite‐facies stage, and another age cluster of ca. 900 Ma that represented the age of the protolith for the mafic granulite. This indicated that the protolith of the mafic granulite was formed in the early Neoproterozoic and then was taken to extreme temperatures and pressures during the early Palaeozoic orogenic event. The elemental abundances of the mafic granulites in the Bashiwake area clearly indicated that they were higher in FeO and TiO2, but were significantly lower in MgO, Cr, and Ni than those of associated garnet peridotites/pyroxenites, and they showed LREE‐enriched patterns with slightly positive Eu anomalies. Sr–Nd isotopic data suggested a basaltic magmatic origin with crust contamination for the protolith of the mafic granulite. Integrating these results together with previous studies, we suggest that the mafic granulites were derived from the basaltic magma intrusion in the continental crust during the Neoproterozoic and subsequently suffered a common HP/UHT metamorphism with felsic crust rocks in the early Palaeozoic (ca. 500 Ma) after the eclogite‐facies metamorphism related to the continental collision (>500 Ma).

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In-situ high-pressure and high-temperature spectroscopic studies of phengite in ultrahigh-pressure eclogite: implications for water transport during ultra-deep continental subduction

Zhang

Kagi

et al. 2022

Phys Chem Minerals

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Evidence of former stishovite in UHP eclogite from the South Altyn Tagh, western China

Cited by 63 publications

References 49 publications

P–T–t Path of Garnetites in South Altyn Tagh, West China: A Complete Record of the Ultradeep Subduction and Exhumation of Continental Crust

P–T–t Path of Garnetites in South Altyn Tagh, West China: A Complete Record of the Ultradeep Subduction and Exhumation of Continental Crust

Petrogenesis of mafic granulite in South Altyn Tagh, NW China: Constraints from petrology, zircon U–Pb chronology, and geochemistry

In-situ high-pressure and high-temperature spectroscopic studies of phengite in ultrahigh-pressure eclogite: implications for water transport during ultra-deep continental subduction

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