Abstract
The dehydration and decarbonation in the subducting slab are intricately related and the knowledge of the physical properties of the resulting C–H–O fluid is crucial to interpret the petrological, geochemical, and geophysical processes associated with subduction zones. In this study, we investigate the C–H–O fluid released during the progressive devolatilization of carbonate-bearing serpentine-polymorph chrysotile, with in situ electrical conductivity measurements at high pressures and temperatures. The C–H–O fluid produced by carbonated chrysotile exhibits high electrical conductivity compared to carbon-free aqueous fluids and can be an excellent indicator of the migration of carbon in subduction zones. The crystallization of diamond and graphite indicates that the oxidized C–H–O fluids are responsible for the recycling of carbon in the wedge mantle. The carbonate and chrysotile bearing assemblages stabilize dolomite during the devolatilization process. This unique dolomite forming mechanism in chrysotile in subduction slabs may facilitate the transport of carbon into the deep mantle.
Highlights
The dehydration and decarbonation in the subducting slab are intricately related and the knowledge of the physical properties of the resulting carbon and hydrogen bearing (C–H–O) fluid is crucial to interpret the petrological, geochemical, and geophysical processes associated with subduction zones
The temperature dependence of the electrical conductivity is well described by an Arrhenius relation; σ = σ0exp(− H/RT)
The in-situ electrical conductivity measurements cannot distinguish individual contributions from the chemical species of C–H–O fluid as it represents the bulk conductivity of the interconnected fluid phase
Summary
The dehydration and decarbonation in the subducting slab are intricately related and the knowledge of the physical properties of the resulting C–H–O fluid is crucial to interpret the petrological, geochemical, and geophysical processes associated with subduction zones. We investigate the C–H–O fluid released during the progressive devolatilization of carbonate-bearing serpentine-polymorph chrysotile, with in situ electrical conductivity measurements at high pressures and temperatures. The C–H–O fluid produced by carbonated chrysotile exhibits high electrical conductivity compared to carbon-free aqueous fluids and can be an excellent indicator of the migration of carbon in subduction zones. The carbonate and chrysotile bearing assemblages stabilize dolomite during the devolatilization process This unique dolomite forming mechanism in chrysotile in subduction slabs may facilitate the transport of carbon into the deep mantle. The effect of both carbon and hydrogen bearing (C–H–O) aqueous fluids on electrical conductivity remain unknown
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