The balance between the subduction of carbonate mineral-bearing rocks into Earth’s mantle and the return of CO2 to the atmosphere by volcanic and metamorphic degassing1,2,3,4 is critical to the carbon cycle. Carbon is thought to be released from subducted rocks mostly by simple devolatilization reactions5,6,7. However, these reactions will also retain large amounts of carbon within the subducting slab and have difficulty in accounting for the mass of CO2 emitted from volcanic arcs. Carbon release may therefore occur via fluid-induced dissolution of calcium carbonate8,9,10. Here we use carbonate δ18O and δ13C systematics, combined with analyses of rock and fluid inclusion mineralogy and geochemistry, to investigate the alteration of the exhumed Eocene Cycladic subduction complex on the Syros and Tinos islands, Greece. We find that in marble rocks adjacent to two fluid conduits that were active during subduction, the abundance of calcium carbonate drastically decreases approaching the conduits, whereas silicate minerals increase. Up to 60–90% of the CO2 was released from the rocks—far greater than expected via simple devolatilization reactions. The δ18O of the carbonate minerals is 5–10 lighter than is typical for metamorphosed carbonate rocks, implying that isotopically light oxygen was transported by fluid infiltration from the surroundings. We suggest that fluid-mediated carbonate mineral removal, accompanied by silicate mineral precipitation, provides a mechanism for the release of enormous amounts of CO2 from subduction zones.
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Marty, B. & Tolstikhin, I. N. CO2 fluxes from mid-ocean ridges, arcs and plumes. Chem. Geol. 145, 233–248 (1998).
Hayes, J. M. & Waldbauer, J. R. The carbon cycle and associated redox processes through time. Phil. Trans. R. Soc. B 361, 931–950 (2006).
Dasgupta, R. & Hirschmann, M. M. The deep carbon cycle and melting in Earth’s interior. Earth Planet. Sci. Lett. 298, 1–13 (2010).
Burton, M. R., Sawyer, G. M. & Granieri, D. Deep carbon emissions from volcanoes. Rev. Mineral. Geochem. 75, 323–354 (2013).
Kerrick, D. M. & Connolly, J. A. D. Metamorphic devolatilization of subducted marine sediments and the transport of volatiles into the Earth’s mantle. Nature 411, 293–296 (2001).
Gorman, P. J., Kerrick, D. M. & Connolly, J. A. D. Modeling open system metamorphic decarbonation of subducting slabs. Geochem. Geophys. Geosyst. 7, Q04007 (2006).
Poli, S., Franzolin, E., Fumagalli, P. & Crottini, A. The transport of carbon and hydrogen in subducted oceanic crust: An experimental study to 5 GPa. Earth Planet. Sci. Lett. 278, 350–360 (2009).
Frezzotti, M. L., Selverstone, J., Sharp, Z. D. & Compagnoni, R. Carbonate dissolution during subduction revealed by diamond-bearing rocks from the Alps. Nature Geosci. 4, 703–706 (2011).
Pan, D., Spanu, L., Harrison, B., Sverjensky, D. A. & Galli, G. Dielectric properties of water under extreme conditions and transport of carbonates in the deep Earth. Proc. Natl Acad. Sci. USA 110, 6646–6650 (2013).
Manning, C. E., Shock, E. L. & Sverjensky, D. A. The chemistry of carbon in aqueous fluids at crustal and upper-mantle conditions: Experimental and theoretical constraints. Rev. Mineral. Geochem. 75, 109–148 (2013).
Connolly, J. A. D. Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation. Earth Planet. Sci. Lett. 236, 524–541 (2005).
Manning, C. E. Thermodynamic modeling of fluid-rock interaction at mid-crustal to upper-mantle conditions. Rev. Mineral. Geochem. 76, 135–164 (2013).
Bröcker, M. & Franz, L. Rb–Sr isotope studies on Tinos Island (Cyclades, Greece): Additional time constraints for metamorphism, extent of infiltration-controlled overprinting and deformational activity. Geol. Mag. 135, 369–382 (1998).
Marschall, H. R., Altherr, R., Gméling, K. & Kasztovszky, Z. Lithium, boron and chlorine as tracers for metasomatism in high-pressure metamorphic rocks: A case study from Syros (Greece). Min. Petrol. 95, 291–302 (2009).
Dragovic, B., Samanta, L. M., Baxter, E. F. & Selverstone, J. Using garnet to constrain the duration and rate of water-releasing metamorphic reactions during subduction: An example from Sifnos, Greece. Chem. Geol. 314–317, 9–22 (2012).
Trotet, F., Vidal, O. & Jolivet, L. Exhumation of Syros and Sifnos metamorphic rocks (Cyclades, Greece) New constraints on the P–T paths. Eur. J. Mineral. 13, 901–920 (2001).
Miller, D. P., Marschall, H. R. & Schumacher, J. C. Metasomatic formation and petrology of blueschist-facies hybrid rocks from Syros (Greece): Implications for reactions at the slab–mantle interface. Lithos 107, 53–67 (2009).
Ague, J. J. Extreme channelization of fluid and the problem of element mobility during Barrovian metamorphism. Am. Mineral 96, 333–352 (2011).
Syracuse, E. M., van Keken, P. E. & Abers, G. A. The global range of subduction zone thermal models. Phys. Earth Planet. Inter. 183, 73–90 (2010).
Bickle, M. J. Transport mechanisms by fluid flow in metamorphic rocks: Oxygen and strontium decoupling in the Trois Seigneurs Massif—a consequence of kinetic dispersion? Am. J. Sci. 292, 289–316 (1992).
Tracy, R. J., Rye, D. M., Hewitt, D. A. & Schiffries, C. M. Petrologic and stable-isotopic studies of fluid-rock interactions, south-central Connecticut: I. the role of infiltration in producing reaction assemblages in impure marbles. Am. J. Sci. 283A, 589–616 (1983).
Putnis, A. & John, T. Replacement processes in the Earth’s crust. Elements 6, 159–164 (2010).
Breeding, C. M., Ague, J. J. & Bröcker, M. Fluid–metasedimentary rock interactions in subduction-zone mélange: Implications for the chemical composition of arc magmas the chemical composition of arc magmas. Geology 32, 1041–1044 (2004).
De Capitani, C. & Petrakakis, K. The computation of equilibrium assemblage diagrams with Theriak/Domino software. Am. Mineral. 95, 1006–1016 (2010).
Holland, T. J. B. & Powell, R. An internally consistent data set for phases of petrological interest. J. Metam. Geol. 16, 309–343 (1998).
Rea, D. K. & Ruff, L. J. Composition and mass flux of sediment entering the world’s subduction zones: Implications for global sediment budgets, great earthquakes, and volcanism. Earth Planet. Sci. Lett. 140, 1–12 (1996).
Plank, T. & Langmuir, C. H. The chemical composition of subducting sediment and its consequences for the crust and mantle. Chem. Geol. 145, 325–394 (1998).
Johnston, F. K. B., Turchyn, A. V. & Edmonds, M. Decarbonation efficiency in subduction zones: Implications for warm Cretaceous climates. Earth Planet. Sci. Lett. 303, 143–152 (2011).
Bebout, G. E. & Barton, M. D. Tectonic and metasomatic mixing in a high-T, subduction-zone mélange—insights into the geochemical evolution of the slab–mantle interface. Chem. Geol. 187, 79–106 (2002).
Penniston-Dorland, S. C., Sorensen, S. S., Ash, R. D. & Khadke, S. V. Lithium isotopes as a tracer of fluids in a subduction zone mélange: Franciscan Complex, CA. Earth. Planet. Sci. Lett. 292, 181–190 (2010).
We thank C. M. Breeding, M. Bröcker, E. L. Donald and D. E. Wilbur for discussions and field work; M. E. Galvez for perspectives on fluid inclusions; R. A. Berner, O. Beyssac, C. P. Chamberlain, B. Marty and D. Rumble for insights regarding carbon cycling; G. W. Olack for assistance with the stable isotope analyses; J. O. Eckert, Jr, for assistance with the FEG-EPMA; and H. Marschall for insightful comments. J.J.A. thanks the Reservoirs and Fluxes Community of the Deep Carbon Observatory for supporting a workshop on Tectonic Fluxes of Carbon. Funding provided by the US National Science Foundation Directorate of Geosciences (EAR-0105927, EAR-0744154) is gratefully acknowledged.
The authors declare no competing financial interests.
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Ague, J., Nicolescu, S. Carbon dioxide released from subduction zones by fluid-mediated reactions. Nature Geosci 7, 355–360 (2014) doi:10.1038/ngeo2143
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