[MIS11-P07] A coupled experimental and thermodynamic study of chondrite-water interaction under anoxic condition
Keywords:chondrite, saponite, pyrrhotite
The experiments up to 7 months showed that the water-rock reactions caused a series of mineral alterations and production of H2(aq), especially at 80 °C. X-ray diffraction analysis revealed that the formation of pyrrhotite was notable during the first few days in the experiment, which was likely resulted from the dissolution of troilite. In contrast, precipitation of saponite was evident after 100 days in the experiment, which was probably caused by the dissolution of Si-rich glass in the synthetic chondrites. Transmission electron microscope observation revealed that the saponite and secondary Si-rich amorphous phases densely covered the surface of the original olivine, glass, pyroxene, and troilite. These results imply that amorphous silica precipitated after the formation of pyrrhotite, followed by the precipitation of saponite. A part of these mineral assemblages obtained from our experiment was inconsistent with those predicted from the thermodynamic equilibrium calculations, suggesting that some metastable alteration minerals occur in the chondrite-water system before the complete equilibrium is achieved.