Multiple generation magmatic and hydrothermal processes in a Martian subvolcanic environment based on the analysis of Yamato-000593 nakhlite meteorite

We studied the occurrence of secondary minerals and inferred their formation in the Yamato-000593 Martian meteorite using multiple technological approaches such as electron probe micro analysis, optical microscope, Raman spectroscopy, scanning electron microscopy, as well as Fourier transform-infrared microscopy and spectroscopy. Two separate hydrothermal alteration events and their sequence of formation (based on superpositional relationship) can be identified: an elevated temperature phase producing high-temperature sulfidic hydrothermal alteration and a lower temperature hydrothermal alteration phase by iron-rich fluids. This meteorite shows signatures more compatible with magmatic effects, rather than impact-induced hydrothermal alteration, as has been proposed earlier. The sulfidic alteration probably formed by magmatic hydrothermal fluids, whereas iron-rich hydrothermal fluid circulation after a possible early impact event has also been proposed, when the fluids cooled down to 50 °C. Most of the secondary minerals formed at alkaline-neutral conditions, and the few observed signatures (clay–silica-bearing veins, siderite-iron-oxide veins) of briny conditions are probably from local spatial effects in larger cavities. The ferrous minerals (hematite and siderite) along the fractures could be crystallized from Fe-HCO₃-bearing fluids. Alternatively, the primary magmatic minerals could have been oxidized easily (Fe-rich olivines, magnetite) during the cooling to iron oxides (hematite, goethite). The results suggest the possible existence of at least ephemerally habitable environments on Mars, mainly at volcanically heated locations. Following published geochemical models, the carbonates formed within acidic-circumneutral condition, which was followed by formation of phyllosilicates in alkaline condition.