火星陨石和火星表面泥岩中蚀变过程对比研究

Alteration minerals record the aqueous conditions and climate changes in Mars geological history. They are key to revealing the habitable environments on Mars, as well as the most signification objects of Mars exploration mission and Martian meteorite investigations. We present here detailed studies of alteration minerals in a Martian regolith breccia NWA7034, a Nakhlite meteorite MIL03346, and Sheepbed mudstone detected by Mars Curiosity rover. We compared the inventory of hydrous minerals in these rocks, and determined the formation mechanisms and conditions of smectite, Fe-oxides/hydroxides, and CaSO₄ found in these rocks. We concluded that NWA7034, MIL03346, and Sheepbed mudstone were all altered during diagenesis or after lithification. However, the secondary alteration processes they experienced are distinct with each other. NWA7034 were mostly altered by oxidization and heating. For the meteorite MIL03346, secondary minerals are mostly present in veining within brittle fractures in the mafic minerals and mesostasis. This indicates the vein-filling alteration products result from hydrothermal fluid introduced by an impact event. Compared with two Martian meteorites, the Sheepbed mudstone in Gale crater is more altered with Chemical Index of Alteration (CIA) of 47 and 50. The original debris with basaltic mineral composition experienced at least two stages of secondary alterations: olivine altered to smectite and magnetite during diagenetic processes, and CaSO₄ veins formation after lithification. This result suggests aqueous conditions in various geological setting are different, and chemical weathering under different climate conditions could produce diverse alteration mineral assemblages. This study summarized the secondary mineral found by Mars missions and in Martian meteorites and their possible origins. It could help understand the formation of secondary minerals and future data interpretation in the China Tianwen-1 Mars mission.