In situ Raman study and thermodynamic model of aqueous carbonate speciation in equilibrium with aragonite under subduction zone conditions

Facq, Sébastien; Daniel, Isabelle; Montagnac, Gilles; Cardon, Hervé; Sverjensky, Dimitri A.

doi:10.1016/j.gca.2014.01.030

Cited by 132 publications

(123 citation statements)

References 61 publications

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“…John et al, 2008), Frezzotti et al (2011), andFacq et al (2014), and conceivably also carbonate reduction (Galvez et al, 2013;Lazar et al, 2014), could mobilize C from slabs, particularly in regions experiencing significant fluid flux (more densely fractured rock volumes,…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Subduction zone metamorphic pathway for deep carbon cycling: II. Evidence from HP/UHP metabasaltic rocks and ophicarbonates

et al. 2015

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Exposures of low-grade metabasalts and ophicarbonates in the Northern Apennines, and their high- and ultrahigh-pressure metamorphic equivalents in the Western and Ligurian Alps and Tianshan (representing an overall peak P- T range of ~ 0.2-3.0. GPa, 200-610. °C), allow investigation of the effects of prograde metamorphic devolatilization, and other fluid-rock interactions, on degrees of retention and isotopic evolution of C in subducting oceanic crust and associated mantle rocks. Such work can inform models of C cycling at convergent margins, helping to constrain the efficiency of return of initially subducted C via arc volcanism and the fraction of this subducted C entering the deeper mantle beyond arcs. In the metabasaltic rocks, the preservation of finely disseminated carbonate with δ13C overlapping that of seafloor-altered protoliths, and the minimal mineralogical evidence of decarbonation, indicates large degrees of carbonate retention in this suite extending to UHP conditions similar to those beneath modern volcanic fronts. For many of the metabasalts, the δ18O of this carbonate can be explained by closed-system equilibration with silicate phases (e.g., garnet, clinopyroxene) during HP/UHP metamorphism. Larger volumes of carbonate preserved in interpillow regions and as breccia-filling largely escaped decarbonation, showing little or no evidence for reaction with adjacent metabasalt. Calculated devolatilization histories demonstrate that, in a closed-system model, carbonate in metabasaltic rocks can largely be preserved to depths approaching those beneath volcanic fronts (80-90km). Modeling of open-system behavior indicates that episodic infiltration of such rocks by H2O-rich fluids would have greatly enhanced decarbonation. Trends in O-C isotope composition of carbonate in some metabasaltic suites likely reflect effects of infiltration by externally-derived fluid with or without resulting decarbonation. Most carbonated ultramafic rocks similarly show little mineralogical evidence for decarbonation, consistent with calculated reaction histories, and have δ13C largely overlapping that of seafloor equivalents. However, the high-grade ophicarbonates show more restricted ranges in δ18O consistent with some control by infiltrating fluids, likely during subduction. This combination of field, petrographic, and isotopic evidence, together with calculated decarbonation histories, is consistent with minimal loss of CO2 from these rocks via decarbonation during forearc metamorphism. Combining our results with those of Cook-Kollars et al. (2014; Chemical Geology) for associated W. Alps metasedimentary rocks, we suggest that the majority of the CO2 (perhaps 80-90%, considering the full range of rock types) could be retained through forearcs in more intact volumes of subducting sediment, basalt, and ophicarbonate experiencing closed- or limited open-system conditions. Deep in forearcs and beneath arcs, decarbonation (and also carbonate dissolution) could be enhanced in shear zones and highly fractured volumes experiencin...

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Section: Accepted Manuscriptmentioning

confidence: 99%

Subduction zone metamorphic pathway for deep carbon cycling: II. Evidence from HP/UHP metabasaltic rocks and ophicarbonates

et al. 2015

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“…Their study is hampered because current geochemical models are capped at pressures of several thousand bars, the pressures reached near the center of Pluto-sized bodies. A recent model (Facq et al, 2014) has extended the predictive HKF framework to explore the solubility and speciation of carbonate species up to 80 kbar; however, this model cannot currently be used at subzero temperatures. Exoplanets, likely icy, of super-Earth size have also been discovered (Beaulieu et al, 2006).…”

Section: Other Model Considerationsmentioning

confidence: 99%

Prerequisites for explosive cryovolcanism on dwarf planet-class Kuiper belt objects

Neveu

Desch

Shock

et al. 2015

Icarus

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Explosive extrusion of cold material from the interior of icy bodies, or cryovolcanism, has been observed on Enceladus and, perhaps, Europa, Triton, and Ceres. It may explain the observed evidence for a young surface on Charon (Pluto's surface is masked by frosts). Here, we evaluate prerequisites for cryovolcanism on dwarf planet-class Kuiper belt objects (KBOs). We first review the likely spatial and temporal extent of subsurface liquid, proposed mechanisms to overcome the negative buoyancy of liquid water in ice, and the volatile inventory of KBOs. We then present a new geochemical equilibrium model for volatile exsolution and its ability to drive upward crack propagation. This novel approach bridges geophysics and geochemistry, and extends geochemical modeling to the seldom-explored realm of liquid water at subzero temperatures. We show that carbon monoxide (CO) is a key volatile for gas-driven fluid ascent; whereas CO 2 and sulfur gases only play a minor role. N 2 , CH 4 , and H 2 exsolution may also drive explosive cryovolcanism if hydrothermal activity produces these species in large amounts (a few percent with respect to water). Another important control on crack propagation is the internal structure: a hydrated core makes explosive cryovolcanism easier, but an undifferentiated crust does not. We briefly discuss other controls on ascent such as fluid freezing on crack walls, and outline theoretical advances necessary to better understand cryovolcanic processes. Finally, we make testable predictions for the 2015 New Horizons flyby of the Pluto-Charon system.

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“…The pressure range of the applicability of the HKF model it its original formulation was limited by 500 MPa (5 kbar). Recently, it was extended to 6 GPa (60 kbar) and $1500 K (1200°C) after a formulation of the relation for the dielectric constant of water valid over the same range of the state parameters Facq et al, 2014). As shown in , the extended formulation of the dielectric constant of water allows a successful reproduction of solubilities of quartz and corundum in water at temperatures up to 1073 K (800°C) and pressures up to 20 kbar in the framework of the HKF model.…”

Section: The Hkf Modelmentioning

confidence: 99%

Correlation and prediction of thermodynamic properties of nonelectrolytes at infinite dilution in water over very wide temperature and pressure ranges (2000K and 10GPa)

Plyasunov

2015

Geochimica et Cosmochimica Acta

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In situ Raman study and thermodynamic model of aqueous carbonate speciation in equilibrium with aragonite under subduction zone conditions

Cited by 132 publications

References 61 publications

Subduction zone metamorphic pathway for deep carbon cycling: II. Evidence from HP/UHP metabasaltic rocks and ophicarbonates

Subduction zone metamorphic pathway for deep carbon cycling: II. Evidence from HP/UHP metabasaltic rocks and ophicarbonates

Prerequisites for explosive cryovolcanism on dwarf planet-class Kuiper belt objects

Correlation and prediction of thermodynamic properties of nonelectrolytes at infinite dilution in water over very wide temperature and pressure ranges (2000K and 10GPa)

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