Contrasting Olivine Alteration Scenario in the Deccan Continental Flood Basalt, India: Implications for Mars

The olivine of the Deccan Traps basalts undergoes aqueous alteration to iddingsite along fractures, irrespective of their forsterite (Fo) content. Low Fo olivine typically displays wide and relatively straight fractures, while picritic (high Fo) olivine shows serrated (saw-tooth) fractures, indicative of an in situ dissolution process. Low Fo olivine attributes a relatively higher degree of aqueous alteration as compared to high Fo under low-temperature conditions. The clay minerals associated with low Fo experienced mildly reducing conditions, reflecting multiple aqueous alteration events. High Fo in picritic basalts is characterized by a lower pH and water-to-rock ratio than low Fo in tholeiitic basalts. The higher concentration of Si in the clay mineral saponite suggests an acidic hydrothermal alteration process. Geochemical modeling suggests a closed system operating at low temperatures. Although the total duration of alteration was brief in both scenarios, low Fo underwent alteration over a longer period, resulting in a similar quantity of altered products. These findings may provide insights into the alteration processes of Mars by defining geochemical conditions and hydrodynamic properties. This may also reveal whether Martian meteorites (Nakhlites) mineral cracks changed in a single event or multiple occurrences. While terrestrial analogs differ in essential mineral composition (such as Fe and Mg levels), the alteration products and conditions closely resemble those of Martian meteorites, helping to understand Mars' water-crust interaction. Additionally, phyllosilicates/clay minerals may induce the preservation of biosignatures on Mars, which remains a top priority of ongoing missions.