Geochemical evidence from coesite-bearing jadeite quartzites for large-scale flow of metamorphic fluids in a continental subduction channel

Gao, Xiao‐Ying; Chen, Yixiang; Zheng, Yong‐Fei; Chen, Ren‐Xu; Huang, Fang; Zhang, Qiangqiang; Ji, Min; Meng, Zi-Yue

doi:10.1016/j.gca.2019.09.006

Cited by 13 publications

(2 citation statements)

References 120 publications

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“…[ 50 ] found that these white schists (T = 730°C and 4.0 GPa) have extremely heavy Mg isotopic compositions (δ 26 Mg up to +0.72‰), and suspected that the fluid could be derived from the breakdown of Mg-rich hydrous minerals such as talc and antigorite in serpentinite at the slab–mantle interface. The heavy Mg isotopic compositions (with δ 26 Mg up to +0.61‰) of the coesite-bearing jadeite quartzites from the Dabie orogen are also interpreted as being a result of the infiltration of fluid dehydrated from the breakdown of biotite in subducted metasedimentary rocks [ 51 ]. The retrograde eclogites and blueschists from southwestern Tianshan have interacted with metamorphic fluids mainly derived from subducting sediments in the subduction channel [ 52 ].…”

Section: Magnesium Isotope Fractionation During Subductionmentioning

confidence: 99%

Magnesium isotope geochemistry of the carbonate-silicate system in subduction zones

Wang

2022

National Science Review

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The lighter magnesium (Mg) isotopic signatures observed in intraplate basalts are commonly thought to result from deep carbonate recycling, provided that the sharp difference in Mg isotopic composition between surface carbonates and the normal mantle likely preserves during plate subduction. However, deep subduction of carbonates and silicates could potentially fractionate Mg isotopes and change their chemical compositions. Subducting silicate rocks that experienced metamorphic dehydration lose a small amount of Mg, and preserve the original Mg isotopic signature of their protoliths. When the dehydrated fluids dissolve carbonate minerals, they may evolve to lighter Mg isotopic compositions. The solubility of carbonate minerals in fluids decreases in the order of calcite, aragonite, dolomite, magnesite and siderite, leading to selective and partial dissolution of carbonate minerals along subduction path. At the island arc depth (70-120 km), the metamorphic fluid dissolves mainly Mg-poor calcites, and thus the fluid is difficult to modify the Mg isotopic system of the mantle wedge and associated arc basalts. At greater depth of the back arc system or continental margin (> 150 km), the supercritical fluid can dissolve Mg-rich carbonate minerals, and its interaction with the mantle wedge could significantly imprint the light Mg isotopic signature to the mantle rocks and the derivatives. Meanwhile, the carbonate and silicate remaining within the subducting slab could experience elemental and isotopic exchange, during which the silicate can obtain light Mg isotopic signature and high CaO/Al2O3, whereas the carbonates, particularly the Ca-rich limestone, shift Mg isotopes and MgO contents towards higher values. If this isotopic and elemental exchange event occurs widely during crustal subduction, subducted Ca-rich carbonates can partially transform to be Mg-rich, and a portion of recycled silicates (e.g., carbonated eclogites) can have light Mg isotopic composition alongside carbonates. Both serves as the low-δ26Mg endmember recycled back into the deep mantle, but the latter is not related to the deep carbonate recycling. Therefore, it is important to discriminate whether the light Mg isotopic signatures observed in intraplate basalts are linked to deep carbonate recycling, or alternatively, recycling of carbonated eclogites.

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Section: Magnesium Isotope Fractionation During Subductionmentioning

confidence: 99%

Magnesium isotope geochemistry of the carbonate-silicate system in subduction zones

Wang

2022

National Science Review

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“…Subduction zones are dynamic sites of mass and energy exchange between the Earth's interior and the surface [1][2][3][4]. The presence and movement of fluids and melts at a variety of scales and levels facilitates and governs geochemical cycles and fluid-enhanced deformation within subduction zones [5][6][7][8]. Geochemical studies [6,9,10] and numerical simulations [11] suggest that the fluid flow in subduction zones may be strongly channelized but not pervasive, under the control of the low permeability in subducting slabs, the high dihedral angles between fluid and minerals, and the negative rock volume change during prograde metamorphism [12,13].…”

Section: Introductionmentioning

confidence: 99%

Channelized CO2-Rich Fluid Activity along a Subduction Interface in the Paleoproterozoic Wutai Complex, North China Craton

Wang

Tian

et al. 2021

Minerals

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Greenschist facies metabasite (chlorite schist) and metasediments (banded iron formation (BIF)) in the Wutai Complex, North China Craton recorded extensive fluid activities during subduction-related metamorphism. The pervasive dolomitization in the chlorite schist and significant dolomite enrichment at the BIF–chlorite schist interface support the existence of highly channelized updip transportation of CO2-rich hydrothermal fluids. Xenotime from the chlorite schist has U concentrations of 39–254 ppm and Th concentrations of 121–2367 ppm, with U/Th ratios of 0.11–0.62, which is typical of xenotime precipitated from circulating hydrothermal fluids. SHRIMP U–Th–Pb dating of xenotime determines a fluid activity age of 1.85 ± 0.07 Ga. The metasomatic dolomite has δ13CV-PDB from −4.17‰ to −3.10‰, which is significantly lower than that of carbonates from greenschists, but similar to the fluid originated from Rayleigh fractionating decarbonation at amphibolite facies metamorphism along the regional geotherm (~15 °C/km) of the Wutai Complex. The δ18OV-SMOW values of the dolomite (12.08–13.85‰) can also correspond to this process, considering the contribution of dehydration. Based on phase equilibrium modelling, we ascertained that the hydrothermal fluid was rich in CO2, alkalis, and silica, with X(CO2) in the range of 0.24–0.28. All of these constraints suggest a channelized CO2-rich fluid activity along the sediment–basite interface in a warm Paleoproterozoic subduction zone, which allowed extensive migration and sequestration of volatiles (especially carbon species) beneath the forearc.

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Genesis of baddeleyite and high δ18O zircon in impure marble from the Tongbai orogen, Central China: insights from petrochronology and Hf–O isotope compositions

Zhou

et al. 2020

Contrib Mineral Petrol

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Geochemical evidence from coesite-bearing jadeite quartzites for large-scale flow of metamorphic fluids in a continental subduction channel

Cited by 13 publications

References 120 publications

Magnesium isotope geochemistry of the carbonate-silicate system in subduction zones

Magnesium isotope geochemistry of the carbonate-silicate system in subduction zones

Channelized CO2-Rich Fluid Activity along a Subduction Interface in the Paleoproterozoic Wutai Complex, North China Craton

Genesis of baddeleyite and high δ18O zircon in impure marble from the Tongbai orogen, Central China: insights from petrochronology and Hf–O isotope compositions

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