Fig. 2: Experimental CO2 contents and thermodynamic modelling of fluids. | Nature Communications

Fig. 2: Experimental CO2 contents and thermodynamic modelling of fluids.

From: Subducted organic matter buffered by marine carbonate rules the carbon isotopic signature of arc emissions

Fig. 2: Experimental CO2 contents and thermodynamic modelling of fluids.The alternative text for this image may have been generated using AI.

a CO2 concentration (molality) in experimental aqueous fluids interacting with (i) aragonite-only (blue), (ii) graphite-only (grey) and (iii) graphite + aragonite (magenta). Typical analytical uncertainty is 1 mol%. Dashed line: CO2 content predicted by thermodynamic modelling of graphite-saturated COH fluids. Run duration (h) is shown at the top of each bar. RRO: run buffered by Re–ReO2 (ΔFMQ ≈ +2) instead of ferrosilite + magnetite + coesite; b fO2 vs. pH diagram at 3 GPa and 700 °C generated by thermodynamic modelling (Deep Earth Water model26,28) of aqueous fluids in equilibrium with aragonite-only (blue dot), graphite-only (grey dot) and aragonite + graphite (magenta dot). Black solid lines: saturation curves. Coloured dots: experimental conditions at fO2 buffered by ferrosilite + magnetite + coesite. Grey field: CO2(aq) is the dominant carbon-bearing species; it is adjacent to Ca(HCO3)+-dominated field at higher pH and to CH4(aq)-dominated field at lower fO2 values. Neutral pH is shown for reference with a dashed line. Calculations are performed at 3 GPa, 700 °C and fH2 buffered by ferrosilite + magnetite + coesite + H2O (equivalent to log (fO2 /1 bar)= −13.36; ΔFMQ = +0.61).

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