Olivine-rich veins in high-pressure serpentinites: A far-field paleo-stress snapshot during subduction

Jabaloy‐Sánchez, Antonio; Sánchez‐Vizcaíno, Vicente López; Padrón‐Navarta, José Alberto; Hidas, Károly; Gómez-Pugnaire, María Teresa; Garrido, Carlos J.

doi:10.1016/j.jsg.2022.104721

Cited by 6 publications

(2 citation statements)

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“…olivine-in, whereas the upper temperature boundary is the final disappearance of the hydrous reactant. Often, several generations of reaction products can be found in a single specimen but can be distinguished based on their chemical composition and microstructures, and can be assigned to specific dehydration reactions (Jabaloy-Sánchez et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Early release of H2O during subduction of carbonated ultramafic lithologies

Eberhard

Plümper

Frost

2023

Contrib Mineral Petrol

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To investigate the effect of carbon-bearing phases on the release of fluids in subducted serpentinites, we performed high-pressure multi-anvil experiments on representative ophicarbonate assemblages over a pressure range from 2.5 GPa to 5 GPa and from 450 °C to 900 °C, across the antigorite-out reaction. Parallel experiments were performed on carbonate-free serpentinites. In all experiments, we monitored and/or controlled the oxygen fugacity. The addition of 20 wt. % CaCO3 to a serpentinite assemblage at 2.5 GPa is found to decrease the onset of the serpentine dehydration by over 100 °C, in comparison to carbonate-free assemblages. Similarly, the final disappearance of serpentine is also affected by the presence of CaCO3. For a bulk CaCO3 content of 20 wt. %, this causes a decrease in maximum stability of antigorite by 50 °C. For a bulk CaCO3 content exceeding 25 wt. %, this difference can be as high as 100 °C in warm and 150 °C in cold subduction zones, causing antigorite to be completely dehydrated at 500 °C. This results from the reaction of CaCO3 with serpentine to form clinopyroxene and Mg-rich carbonates. This reaction, however, causes no discernible decrease in the proportion of carbonate, indicating that the amount of released carbon is insignificant. Whilst CaCO3, therefore, influences serpentine stability, there is no significant effect of hydrous phases on the carbonate stability. On the other hand, a MgCO3-bearing system shows no significant effects on the serpentinite stability field. Further experiments and oxygen fugacity calculations indicate that graphite is not stable in typical magnetite-bearing serpentinites. The reduction of carbonates to graphite would require oxygen fugacities that are 1–2 log units below those of magnetite-bearing serpentinites. This confirms earlier studies and indicates that reduction of carbonates can only occur through the infiltration of external H2-rich fluids.

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Section: Introductionmentioning

confidence: 99%

Early release of H2O during subduction of carbonated ultramafic lithologies

Eberhard

Plümper

Frost

2023

Contrib Mineral Petrol

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“…The transition from low‐grade chrysotile/lizardite to antigorite took place through the reaction: chrysotile/lizardite = antigorite + brucite (1). Widespread olivine in serpentinite results from the partial dehydration reaction: antigorite + brucite = olivine + H 2 O (2) (Jabaloy‐Sánchez et al., 2022, Figure 1). In clinopyroxene (diopside)‐bearing Atg serpentinite, relict mantle clinopyroxene (Cpx‐1) recrystallized to metamorphic clinopyroxene (Cpx‐2) through the reaction Cpx‐1 + olivine + antigorite = Cpx‐2 + chlorite + Ti‐clinohumite + H 2 O (3) (López Sánchez‐Vizcaíno et al., 2005).…”

Section: Geological Background and Samplesmentioning

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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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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