C. Fauguerolles, T. Castelain, Johan Villeneuve, Michel Pichavant
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引用次数: 0
Abstract
Abstract. New hydrothermal experiments in rapid-quench pressure vessels have been performed to investigate the effect of redox state on the serpentinization reaction. The experimental hydrogen fugacity (fH2) was controlled by monitoring the mobility of H2 in the reacting system (internal vs. external fH2 control). This was achieved by using either Au (H2 impermeable) or AgPd (H2 permeable) capsules and Ar pressurizing gas to control fH2. The experiments were performed with either San Carlos olivine powders or Åheim dunite chips. Water / rock mass ratios of 1–2, a total pressure of 50 MPa, and temperatures of 300 and 350 °C were investigated. Experimental durations of 30, 45, or ≈80 d were imposed. Serpentine production is observed in almost all experiments but is favored at 300 °C under external fH2 control. The serpentine–magnetite assemblage is observed in Au capsules (high fH2) at 300 °C, while the serpentine–hematite(–magnetite) is observed in AgPd capsules (low fH2). At 350 °C, less H2 is produced than at 300 °C and the serpentine–hematite(–magnetite) assemblage is present in both Au and AgPd capsules. Brucite is absent and this is interpreted to reflect both the initially oxidizing conditions and relatively low serpentine production in our experiments. Differences in product phase assemblages found in this study imply that natural serpentinization reaction mechanisms vary with redox conditions, and consequences for H2 production fluxes and rates can be expected. The high-fH2 (reduced) internally controlled experiments simulate low-permeability “closed” oceanic hydrothermal systems. The low-fH2 (oxidized) externally controlled experiments are analogous to “open” oceanic hydrothermal systems where serpentinization is driven by tectonically aided infiltration of an external fluid.
期刊介绍:
EJM was founded to reach a large audience on an international scale and also for achieving closer cooperation of European countries in the publication of scientific results. The founding societies have set themselves the task of publishing a journal of the highest standard open to all scientists performing mineralogical research in the widest sense of the term, all over the world. Contributions will therefore be published primarily in English.
EJM publishes original papers, review articles and letters dealing with the mineralogical sciences s.l., primarily mineralogy, petrology, geochemistry, crystallography and ore deposits, but also biomineralogy, environmental, applied and technical mineralogy. Nevertheless, papers in any related field, including cultural heritage, will be considered.