Carbon Cycle in Subduction Zones: Experimental Constraints in Fluid-Saturated MORB Eclogites

Details Carbon Cycle in Subduction Zones: Experimental Constraints in Fluid-Saturated MORB Eclogites Carbon Cycle in Subduction Zones: Experimental Constraints in Fluid-Saturated MORB Eclogites

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja....12638c&link_type=abstract

EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #12638

Statistics

Computation

Scientific paper

Graphite and/or carbonates are stable in eclogite mafic systems, according to both natural evidences and experimental and computed data (Yaxley and Green, 1994; Molina and Poli, 2000). In this work, the stability of C-bearing phases in metamorphosed oceanic crust is discussed as a function of fO2, expected to be the main factor controlling fluid speciation in subduction zone. We performed experiments using a piston-cylinder apparatus, at pressures up to 3 GPa and temperatures to 730^oC. Experiments were carried out on seeded gels in the model system Na2O-CaO-FeO-MgO-Al2O3-SiO2 , in the presence of a C-O-H fluid at variable C-O-H ratios generated from mixtures of oxalic acid dihydrate and silver oxalate. The double capsule technique was employed to control fH2 with Ni-NiO (NNO) and hematite-magnetite (HM) buffers. In agreement with Molina and Poli (2000), a large amphibole-carbonate phase field is present at NNO oxygen fugacities at P <= 2 GPa. At 2.5-2.6 GPa amphibole breaks down. Omphacite is stable up to 3.0 GPa, coexisting with fassaite at 2.2 GPa in CO2 -rich bulk compositions, where garnet is absent. A fine-grained Na-melilite is stable at 2.2-2.4 GPa, containing up to 15 wt.% Na2O. Graphite is ubiquitous at P >= 2.2 GPa, with dolomite and aragonite at HM oxidation conditions and aragonite at NNO-buffered conditions. At pressures above 2.4 GPa carbonates disappear, being graphite the only C-bearing solid phase. Thermodynamic computations on fluid speciation in graphite buffered systems support experimental results, suggesting that carbonates can be stable at values of log fO2 close to NNO buffer at P <= 2.0 GPa, whereas at higher pressures their stability is permitted only by highly oxidizing conditions (3-4 log units lower than HM) in H2 O-poor bulk compositions. The experimental results demonstrate that transfer of carbon from the subducting slab to either the deep slab or to the mantle wedge via fluid flow is strongly related to the actual oxygen fugacity conditions attained in subduction zones. J.F. Molina and S. Poli, Earth. Planet. Sci. Lett., 176, 295-310 (2000). G.M. Yaxley and D.H. Green, Earth. Planet. Sci. Lett., 128, 313-325 (1994).

Affiliated with

Also associated with

No associations

Rating

Carbon Cycle in Subduction Zones: Experimental Constraints in Fluid-Saturated MORB Eclogites does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Carbon Cycle in Subduction Zones: Experimental Constraints in Fluid-Saturated MORB Eclogites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carbon Cycle in Subduction Zones: Experimental Constraints in Fluid-Saturated MORB Eclogites will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-845569