Antigorite dehydration fluids boost carbonate mobilisation and crustal CO2 outgassing in collisional orogens

Eberhard, Lisa; Pettke, Thomas

doi:10.1016/j.gca.2021.02.030

Cited by 8 publications

(6 citation statements)

References 69 publications

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“…5b and c). At these conditions, the stable carbonate after chlorite dehydration is calcite and the reaction (12) can be rewritten as This low-pressure reaction causes X(CO 2 ) values that can exceed 10%, but preserves the Ca-rich nature of carbonates as observed in contact metamorphic environments (Eberhard and Pettke 2021). Such high CO 2 contents in combination with an open system fluid flow can cause large-scale carbon release but are only relevant at lower pressures and higher temperatures than experienced in subduction zones (compare Fig.…”

Section: Phase Relations In a Ca-bearing Ophicarbonate Systemmentioning

confidence: 99%

“…However, typical PT paths of subducted carbonated serpentinites are such, that dissolved CO 2 is the main carbon species in the fluid, whereas the overall solubility is expected to be low (Tiraboschi et al 2022). Carbonated serpentinites can contain high carbonate fractions of > 50% (Driesner 1993;Pozzorini and Früh-green 1996;Eberhard and Pettke 2021) and it is, thus, unlikely that significant carbonate is removed through carbonate dissolution. Furthermore, the change in carbonate composition towards more Mg-rich endmembers with increasing temperature decreases the carbonate solubility by about two orders of magnitude (Farsang et al 2021), which helps to preserve carbonates to deeper levels in the subduction zone.…”

Section: Effect Of Carbonates On Subduction Zone Phase Relationsmentioning

confidence: 99%

“…The release of carbon from subducting slabs also occurs through dissolution of carbonate minerals in aqueous fluids (Facq et al 2014;Farsang et al 2021). At least in low-pressure environments (< 2 GPa), there is evidence that CO 2 can be released through decarbonation reactions, in the presence of aqueous fluids (Kerrick and Connolly 1998;Eberhard and Pettke 2021). Other studies suggest that more reduced carbon can be dissolved in the fluid (Sverjensky et al 2014;Vitale Brovarone et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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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: Phase Relations In a Ca-bearing Ophicarbonate Systemmentioning

confidence: 99%

Section: Effect Of Carbonates On Subduction Zone Phase Relationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Early release of H2O during subduction of carbonated ultramafic lithologies

Eberhard

Plümper

Frost

2023

Contrib Mineral Petrol

Self Cite

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“…In collisional contexts, large crustal CO 2 fluxes (Becker et al, 2008;Gaillardet and Galy, 2008;Perrier et al, 2009;Evans, 2011;Skelton, 2011;Girault et al, 2014;Menzies et al, 2018;Guo et al, 2021) can be sustained by either regional metamorphism (Groppo et al, 2013;Eberhard and Pettke, 2021) or mechano-chemical CO 2 production (Italiano et al, 2009). Metamorphic processes can operate via either 1) decarbonation reactions at relatively high temperatures within calc-silicate rocks (Groppo et al, 2013(Groppo et al, , 2017(Groppo et al, , 2020 or 2) dehydration reactions of mineral phases (Eberhard and Pettke, 2021), in which CO 2 degassing is triggered by prograde heating arising from conductive heating triggered by slab breakoff (von Blanckenburg and Davies, 1995), slab rollback (Sizova et al, 2019), or by thermal relaxation of the crust following tectonic thickening upon continent-continent collision. These processes may operate in combination and have certainly interested the past evolution of the Calabrian arc.…”

Section: Carbonmentioning

confidence: 99%

“…The conditions for metamorphic CO 2 production are thus certainly met in the study area. Because such metamorphism occurs at very slow rates, amagmatic CO 2 mobilization along convergent plate boundaries can endure over millions of years (Eberhard and Pettke, 2021).…”

Section: Carbonmentioning

confidence: 99%

Active degassing of crustal CO2 in areas of tectonic collision: A case study from the Pollino and Calabria sectors (Southern Italy)

Randazzo

Caracausi²,

Aiuppa³

et al. 2022

Front. Earth Sci.

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Carbon dioxide (CO2) is released from the Earth’s interior into the atmosphere through both volcanic and non-volcanic sources in a variety of tectonic settings. A quantitative understanding of CO2 outgassing fluxes in different geological settings is thus critical for decoding the link between the global carbon budget and different natural processes (e.g., volcanic eruption and earthquake nucleation) and the effects on the climate evolution over geological time. It has recently been proposed that CO2 degassing from non-volcanic areas is a major component of the natural CO2 emission budget, but available data are still sparse and incomplete. Here, we report the results of a geochemical survey aimed at quantifying CO2 emissions through cold and thermal springs of the tectonically active Pollino Massif and Calabrian arc (Southern Italy). The chemical ad isotopic (He and C) composition of fifty-five dissolved gas samples allows to identify two different domains: 1) a shallow system dominated by gas components of atmospheric signature (helium, hereafter He) and biogenic origin (C), and 2) a deeper system in which crustal/deep fluids (CO2 and He) are dominant. The measured He isotope ratios range from 0.03 to 1.1 Ra (where Ra is the He isotopic ratio in the atmosphere) revealing a variable atmospheric contamination. Furthermore, the He isotopic data indicate the presence of traces of mantle He contributions (2%–3%) in the thermal groundwater. The prevailing low R/Ra values reflect the addition of crustal radiogenic 4He during groundwater circulation. Using helium and carbon isotope data, we explore the possible sources of fluids and the secondary processes (dissolution/precipitation) that act to modify the chemistry of pristine volatiles. For the thermal springs, we estimate a deep C output of 2.3 x 107 to 6.1 x 108 mol year−1. These values correspond to deep CO2 fluxes per square km comparable with those estimated in several active and inactive volcanic areas and in continental regions affected by metamorphic CO2 degassing (e.g., the southern margin of the Tibetan Plateau).

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P–T–X Conditions of metamorphic systems

Groppo

2025

Treatise on Geochemistry

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Antigorite dehydration fluids boost carbonate mobilisation and crustal CO2 outgassing in collisional orogens

Cited by 8 publications

References 69 publications

Early release of H2O during subduction of carbonated ultramafic lithologies

Early release of H2O during subduction of carbonated ultramafic lithologies

Active degassing of crustal CO2 in areas of tectonic collision: A case study from the Pollino and Calabria sectors (Southern Italy)

P–T–X Conditions of metamorphic systems

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