Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up.
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Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments.Abstract:
Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5–10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory.read more
Citations
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Subduction Fluxes of Water, Carbon Dioxide, Chlorine, and Potassium
TL;DR: In this paper, the authors estimate that half to two thirds of subducted crustal water is later refluxed at the prism toe; most of the remaining water escapes at subarc depths, triggering partial melting.
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Journal ArticleDOI
Deep carbon cycles constrained by a large-scale mantle Mg isotope anomaly in eastern China
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TL;DR: In this article, a large-scale mantle low δ26Mg anomaly in eastern China has been delineated, suggesting the contribution of sedimentary carbonates recycled into the upper mantle, but limited into the lower mantle.
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The Global Range of Subduction Zone Thermal Structures from Exhumed Blueschists and Eclogites: Rocks Are Hotter than Models
TL;DR: In this article, the authors compare the maximum pressure P-T conditions of exhumed subduction-related metamorphic rocks with those predicted by computational thermal models of subduction systems.
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Fluid and mass transfer at subduction interfaces-The field metamorphic record
TL;DR: In this article, the authors consider records of fluid and mass transfer at localities representing various depths and structural expressions of evolving paleo-interfaces, ranging widely in structural character, the rock types involved, and the rheology of these rocks.
References
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Subduction zone metamorphic pathway for deep carbon cycling: I. Evidence from HP/UHP metasedimentary rocks, Italian Alps
TL;DR: In this article, an integrated field, petrologic and geochemical study of the devolatilization history of these rocks provides evidence regarding the extents of loss and mobility of oxidized and reduced C during subduction of sediments to depths beneath volcanic fronts, thus constraining models of the release of initially subducted C into the atmosphere via arc volcanism or contributing to the C budget of the deeper mantle.
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TL;DR: In this paper, the vertical section of the Talkeetna arc was reconstructed by determining the re-crystallization pressures at various structural levels and thermobarometry showed that the tonalites and quartz diorites intruded at ∼5-9 km into a volcanic section estimated from stratigraphy to be 7 km thick.
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The abundance of ultramafic rocks in Atlantic Ocean crust
TL;DR: In this article, a Voigt-Reuss-Hill (VRH) average model based on the average elastic properties of partially serpentinized peridotites and oceanic diabases and gabbros is used to make quantitative estimates of lithological composition from the seismic structure of the crust.