Dating fluid infiltration and deformation in the subducted ultramafic oceanic lithosphere by perovskite geochronology

Piccoli, Francesca; Rubatto, Daniela; Ovtcharova, Maria; Hermann, Jörg; Guillong, Marcel; Brovarone, Alberto Vitale

doi:10.1016/j.chemgeo.2022.121205

Cited by 5 publications

(5 citation statements)

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“…As with many other Earth science disciplines, geochronology is on the cusp of a digital revolution. Utilizing a rapidly developing cyberinfrastructure that captures the aforementioned data and metadata will increase the longevity of radioisotopic ages and their usefulness (Deering et al, 2016;Paul et al, 2021;Piccoli et al, 2023).…”

Section: Discussionmentioning

confidence: 99%

Supplemental Material: Recommendations for the reporting and interpretation of isotope dilution U-Pb geochronological information

Condon,

al.

2024

Preprint

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Section: Discussionmentioning

confidence: 99%

Supplemental Material: Recommendations for the reporting and interpretation of isotope dilution U-Pb geochronological information

Condon,

al.

2024

Preprint

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“…It consists of a core of fresh peridotite rimmed by serpentinites that experienced Alpine metamorphism at ~550-600 °C and 2-2.5 GPa 34 . In this massif, the circulation of H2-rich fluids generated by high-pressure serpentinization of the peridotite promoted the reduction of carbonated serpentinite and the formation of abiotic methane and graphite at near peak metamorphic conditions, around 49.6 ± 1.0 Ma, and during exhumation 28,33 . This process induced strain localization, which in turn favoured fluid channelization and transport 32 .…”

Section: Geological and Structural Settingmentioning

confidence: 97%

“…The presence of jadeite and omphacite crystallizing in the matrix and the absence of albite suggests at least 1 GPa and 400 °C for the fluid-mediated brecciation (e.g., 7 39 ). Noteworthy, the methane formation in the massif was constrained between 2 GPa and 550 °C and 1 GPa and 400°C 28,33 .…”

Section: Microstructural and Microchemical Constraints Of Dilational ...mentioning

confidence: 99%

“…In this contribution, we show evidence of brecciation at the expenses of omphacite-rich rocks, hereafter referred as omphacitites, which represent the characteristic clinopyroxene of eclogite-facies mafic rocks. This rheologically strong rock type is in contact with carbonated serpentinites from which CH4-H2-rich fluids were produced at eclogite-facies conditions 28,32,33 . Mineral assemblages constrain brecciation to a depth range of 30-80 km in the Alpine subduction zone, thus consistent with the CH4 formation conditions.…”

Section: Introductionmentioning

confidence: 99%

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Methane-hydrogen-rich fluid migration triggers seismic failure in subduction at forearc depths

Brovarone

Menegon

Siron

et al. 2023

Preprint

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Metamorphic fluids and deformation zones are fundamental carriers of carbon from the deep Earth to shallower reservoirs. It is well established that water weakens rocks and contributes to trigger seismicity. Conversely, the potential effects of carbon-rich aqueous fluids on deep-seated rocks remain little studied. Some of these fluids may be reduced and transport energy sources such as natural H2 and CH4. Mechanisms and pathways capable to transport these deep energy sources towards shallower reservoirs, where they may be used by microbial life in the subsurface biosphere, remain unidentified. Here we present direct geological evidence of seismic failure of mechanically strong rock types due to the accumulation of CH4-H2-rich fluids at deep forearc depths, which ultimately reached supralithostatic pore fluid pressure. These fluids originated from adjacent reduction of carbonates by H2-rich fluids during serpentinization at eclogite-to-blueschist-facies conditions. Thermodynamic modelling predicts that the production and accumulation of carbon-rich fluids can produce overpressure much more easily than C-poor aqueous fluids, and that CH4-H2-rich fluids are more favourable to produce overpressure than CO2-rich ones. This study provides tangible evidence for the migration of deep Earth energy sources along tectonic discontinuities and suggests causal relationships with brittle failure of hard rock types that may trigger seismicity at forearc depths.

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“…Tual et al, 2022). Moreover, an existing technique can be extended to a new mineral suite, for example, the successful demonstration that U-Pb geochronology of metamorphic perovskite can be used to date deformation and fluid flow in subducted ocean lithosphere (Piccoli et al, 2023). Lastly, new technologies are being developed and introduced both to increase the range of elemental isotopes that can be analysed and to improve the spatial resolution of analyses.…”

Section: From Geochronology To Petrochronologymentioning

confidence: 99%

Some thoughts about eclogites and related rocks

Brown

2023

Eur. J. Mineral.

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Abstract. The past 40 years have been a golden age for eclogite studies, supported by an ever wider range of instrumentation and enhanced computational capabilities, linked with ongoing developments in thermobarometry and geochronology. During this time, we have made robust estimates of pressure–temperature (P–T) conditions; determined ages related to the prograde, metamorphic peak and retrograde stages; and calculated time-integrated rates of cooling and exhumation for eclogites and related rocks, including blueschists, from orogenic belts worldwide. Improvements to single mineral thermometers and new developments in elastic barometry using inclusions of one mineral in another (e.g. quartz and/or zircon in garnet), coupled with ongoing innovations in petrochronology and diffusion modelling, presage a new age for eclogite studies in which detailed quantification of metamorphic conditions and timescales will be linked to an improved understanding of processes at all scales. Since the turn of the century, numerical modelling of subduction zone and rock exhumation processes has become increasingly important. As a result, subduction and exhumation are quite well understood, but the volume of continental crust subducted to and returned from mantle conditions and the amount lost to the mantle are largely unknown. We have generated sufficient data to investigate the spatiotemporal distribution of metamorphism and secular change but not without controversy in relation to the rare occurrence of orogenic eclogites and the absence of blueschists prior to the late Neoproterozoic and the emergence of plate tectonics on Earth. Since the turn of the century, the assumption that metamorphic pressure is lithostatic has come under increasing scrutiny. Whether local variations in stress extrapolate to the crustal scale and, if so, whether the magnitude of the calculated deviations from lithostatic pressure can be generated and sustained in mechanically heterogeneous rock units remains contentious. Could the paradigm of subduction of continental lithosphere to mantle depths be simply an artefact of the lithostatic assumption? Fluid cycling in subduction zones and understanding the role of fluids in the generation of intermediate-depth earthquakes remain important topics of current research. Dry (H2O-absent) conditions are unlikely around the peak of ultrahigh-pressure (UHP) metamorphism or during exhumation, due to dehydroxylation of nominally anhydrous minerals and breakdown of hydrous minerals at P–T conditions in the realm of supercritical fluid and hydrous melt. Indeed, the presence of melt may be necessary to facilitate the exhumation of HP and UHP tectonometamorphic rock units. Finally, our ability to interrogate inclusions in superdeep diamonds should lead to a better understanding of how the deep interior and surface are linked in the context of Earth as a fully coupled system.

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Dating fluid infiltration and deformation in the subducted ultramafic oceanic lithosphere by perovskite geochronology

Cited by 5 publications

References 95 publications

Supplemental Material: Recommendations for the reporting and interpretation of isotope dilution U-Pb geochronological information

Supplemental Material: Recommendations for the reporting and interpretation of isotope dilution U-Pb geochronological information

Methane-hydrogen-rich fluid migration triggers seismic failure in subduction at forearc depths

Some thoughts about eclogites and related rocks

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