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The effect of iron content and dissolved O 2 on dissolution rates of clinopyroxene at pH 5.8 and 25°C: Preliminary results

A.R. Hoch·M.M. Reddy·J.I. Drever
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Abstract

Dissolution experiments using augite (Mg 0.87 Ca 0.85 Fe 0.19 Na 0.09 Al 0.03 Si 2 O 6 ) and diopside (Mg 0.91 Ca 0.93 Fe 0.07 Na 0.03 Al 0.03 Si 2 O 6 ) were conducted in flow-through reactors (5-ml/h flow rate). A pH of 5.8 was maintained by bubbling pure CO 2 through a solution of 0.01 M KHCO 3 at 25°C. Two experiments were run for each pyroxene type. In one experiment dissolved O 2 concentration in reactors was 0.6 (±0.1) ppm and in the second dissolved O 2 was 1.5 (±0.1) ppm. After 60 days, augite dissolution rates (based on Si release) were approximately three times greater in the 1.5 ppm. dissolved O 2 experiments than in the sealed experiments. In contrast, diopside dissolution rates were independent of dissolved O 2 concentrations. Preliminary results from the augite experiments suggest that dissolution rate is directly related to oxidation of iron. This effect was not observed in experiments performed on iron-poor diopside. Additionally, dissolution rates of diopside were much slower than those of augite, again suggesting a relationship between Fe content, Fe oxidation and dissolution rates.

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A.R. Hoch, M.M. Reddy, J.I. Drever. 1996. The effect of iron content and dissolved O 2 on dissolution rates of clinopyroxene at pH 5.8 and 25°C: Preliminary results. https://doi.org/10.1016/s0009-2541(96)00050-2

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