Iron and zinc stable isotope evidence for open-system high-pressure dehydration of antigorite serpentinite in subduction zones

Debret, Baptiste; Garrido, Carlos J.; Pons, Marie-Laure; Bouilhol, Pierre; Inglis, Edward; Sánchez‐Vizcaíno, Vicente López; Williams, Helen M.

doi:10.1016/j.gca.2020.12.001

Cited by 23 publications

(9 citation statements)

References 96 publications

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“…It is also proposed that this Atg-out front corresponds to an oxidation serpentinization front, separating the serpentinite protoliths of Atg-serpentinite and Chl-harzburgite with variable compositions that were caused by different types of melt refertilization and extents of seafloor serpentinization (Bretscher et al, 2018;Pettke & Bretscher, 2022;Piccolli et al, 2019). As mentioned above, both rock types show overlapping Al 2 O 3 , V, and Sc, indicating a similar magmatic history (Figure 4), which is also supported by the lack of systematic differences in Fe isotopes among both rock types (Debret et al, 2021). In addition to textural variations pointing to metamorphic growth of Chl-harzburgite after a serpentinite protolith (Dilissen et al, 2018(Dilissen et al, , 2021Padrón-Navarta et al, 2015), thermodynamic modeling shows that open-system serpentinite dehydration can account for the oxidation differences between the two types of rocks (Padrón-Navarta et al, 2023).…”

Section: From Atg-serpentinite To Chl-harzburgite (Stage 1-2)supporting

confidence: 74%

“…During subduction, serpentinites could have experienced cryptic metasomatism by external fluids from crustal rocks, leading to the enrichment of FMEs and related isotopes (Cannaò et al., 2015; Debret et al., 2021; Garrido et al., 2005; López Sánchez‐Vizcaíno et al., 2005). However, no systematic enrichment of FMEs among each group of samples is observed, and there are no correlations between δ 53 Cr and FMEs of the meta‐serpentinites (Figure 5).…”

Section: Discussionmentioning

confidence: 99%

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Chromium Isotope Behavior During Serpentinite Dehydration in Oceanic Subduction Zones

Xiong,

Chen,

Shen

et al. 2023

JGR Solid Earth

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Fluids released through the dehydration of serpentinite are rich in Cl‐, which enables the significant mobility of Cr in subduction zones. However, the Cr isotope behavior accompanying the mobility of Cr during serpentinite dehydration is still poorly constrained. Here, we report high‐precision Cr isotope data for a unique suite of serpentinites that represent metamorphic products at different depths in oceanic subduction zones. The low‐grade serpentinites affected by significant Cr loss during serpentinization exhibit remarkably higher δ53Cr, while samples with Cr contents > ∼1800 ppm typically preserve mantle‐like δ53Cr. Antigorite serpentinites have an average δ53Cr value of −0.17‰ ± 0.19‰ (n=12, 2SD), which is statistically lower than those of low‐grade serpentinite (‐0.05‰ ± 0.30‰, n=80, 2SD) and higher‐grade chlorite harzburgite (−0.10‰ ± 0.27‰, n=22, 2SD). This suggests that resolvable Cr isotope fractionation occurs during serpentinite dehydration, which is explained by the variability of Cr isotope behavior in the presence of Cl‐bearing fluids at different dehydration stages. No obvious Cr isotope fractionation was found during chlorite harzburgite dehydration, probably related to the limited Cr mobility in a Cl‐poor fluid. Other processes, such as melt extraction, external fluid influx and retrograde metamorphism, have negligible effects on the Cr isotope systematics of meta‐serpentinites. Fluids released by serpentinite dehydration may have a great effect on the Cr isotope heterogeneity of mantle wedge peridotites and arc magmas.

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Section: From Atg-serpentinite To Chl-harzburgite (Stage 1-2)supporting

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Chromium Isotope Behavior During Serpentinite Dehydration in Oceanic Subduction Zones

Xiong,

Chen,

Shen

et al. 2023

JGR Solid Earth

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“…1a). This interpretation is however at odds with numerous textural and geochemical evidence for the provenance of CdA and CdG metaperidotites from highly serpentinised peridotite protoliths metasomatised by crustal fluids [25][26][27] .…”

Section: Main (701 Words)mentioning

confidence: 92%

“…The pervasiveness of subducted-sediment geochemical signatures is the hallmark of arc magmatism 28 , an attribute increasingly ascribed to the interaction of slab crustal lithologies with slab fluids sourced from deserpentinisation. There is also overwhelming geochemical evidence on the role of infiltration of fluids equilibrated with metasedimentary rocks in the genesis of natural serpentinitederived metaperidotite [25][26][27][29][30][31][32][33] . However, it has not yet been investigated how the interaction of sediment-derived fluids modify the fO2 and the cargo of multivalent elements in the deserpentinisation fluids, compared to those sourced from the intrinsic (i.e.…”

Section: Main (701 Words)mentioning

confidence: 99%

Mantle wedge oxidation from deserpentinization modulated by sediment-derived fluids

et al. 2023

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The Earth's mantle is oxygen-breathing through the sink of oxidised tectonic plates at convergent margins 1,2 . Ocean floor serpentinisation increases the bulk oxidation state of iron relative to dry oceanic mantle and results in a variable intake of other redox-sensitive elements such as sulphur 2,3 . The reversibility of seafloor oxidation in subduction zones during high-pressure dehydration of serpentinite ("deserpentinisation") at subarc depths and the capacity of the resulting fluids to oxidise the mantle source of arc basalts are highly contested [4][5][6][7][8][9][10][11][12][13][14][15] .Thermodynamic modelling 8,10,15 , experiments 6,12,14 , and metaperidotite study in exhumed highpressure terrains 4,15,16 result in differing estimates of the redox state of deserpentinisation fluids, ranging from low to highly oxidant. Here we show that although intrinsic deserpentinisation fluids are highly oxidant, the infiltration of small fractions of external fluids equilibrated with metasedimentary rocks strongly modulates their redox state and oxidation-reduction capacity explaining the observed discrepancies in their redox state. Infiltration of fluids equilibrated with graphite-bearing sediments reduces the oxidant, intrinsic deserpentinisation fluids to oxygen fugacities similar to those observed in most graphite-furnace experiments and natural metaperidotites. However, infiltration of CO2-bearing fluids equilibrated with modern GLOSS generates sulphate-rich, highly oxidising deserpentinisation fluids. We show that such GLOSSinfiltrated deserpentinisation fluids can effectively oxidise the mantle wedge of cold to hot subduction zones potentially accounting for the presumed oxidised nature of the source of arc basalts.

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“…Zinc and Fe isotopes have been used to trace the nature of slab‐derived melts/fluids and element mobility in subduction zones (e.g., Z. Chen et al., 2021; Debret et al., 2016, 2021; Foden et al., 2018; S.‐A. Liu et al., 2016; Nebel et al., 2015; Pons et al., 2016; R. Xu et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

Tracing Sediment Melt Activity in the Sub‐Continental Lithosphere: Insights From Zn‐Fe Stable Isotopes

Zhang

Liu

et al. 2023

JGR Solid Earth

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Recycling of upper crustal sediments through slab subduction contributes to sub‐continental lithospheric refertilization and heterogeneity. However, the nature of recycled upper crustal components is unclear and direct evidence for sediment melt activity in the sub‐continental lithosphere is lacking. Here, we integrate major and trace elements, zircon U‐Pb dating, Sr‐Nd‐Zn‐Fe isotopic compositions of clinopyroxenites (crust‐mantle boundary) and a “glassy” xenolith from the North China Craton to relate their petrogenesis to the potential recycling of upper continental crust and provide direct insight into the sediment melt‐rock interaction. The clinopyroxenites have relatively uniform δ56Fe values (the permil deviation of the 56Fe/54Fe ratio from the IRMM014; −0.05‰–0.07‰, except for one outlier) and are not affected by melt metasomatism. The clinopyroxenites have highly variable whole‐rock δ66Zn values (the permil deviation of the 66Zn/64Zn ratio from the JMC‐Lyon standard) between 0.04‰ and 0.46‰, that closely correlate with Rb/La, K/U, Ba/Th, and Th/Nb ratios, and generate arrays that trend toward a composition similar to the “glassy” xenolith. The “glassy” xenolith has a high δ66Zn value (0.43‰ ± 0.05‰, 2SD) and a significantly low 143Nd/144Nd ratio (0.510991). This evidence implies that the “glassy” xenolith may represent a quenched sediment melt formed by the melting of carbonate‐bearing terrigenous sediments that may also be responsible for the metasomatism of clinopyroxenite xenoliths. The geochemical evidence from the “glassy” and clinopyroxenite xenoliths provides a direct evidence for the activity of sediment melt with upper continental crust components in the sub‐continental lithosphere.

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Iron and zinc stable isotope evidence for open-system high-pressure dehydration of antigorite serpentinite in subduction zones

Cited by 23 publications

References 96 publications

Chromium Isotope Behavior During Serpentinite Dehydration in Oceanic Subduction Zones

Chromium Isotope Behavior During Serpentinite Dehydration in Oceanic Subduction Zones

Mantle wedge oxidation from deserpentinization modulated by sediment-derived fluids

Tracing Sediment Melt Activity in the Sub‐Continental Lithosphere: Insights From Zn‐Fe Stable Isotopes

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