A simple inorganic process for formation of carbonates, magnetite, and sulfides in Martian meteorite ALH84001

We show experimental evidence that the zoned Mg-Fe-Ca carbonates, magnetite , and Fe sulfides in Martian meteorite ALH84001 may have formed by simple, inorganic processes. Chemically zoned carbonate globules and Fe sulfides we re rapidly precipitated under low-temperature (150 degreesC), hydrothermal, and non-equilibrium conditions from multiple fluxes of Ca-Mg-Fe-CO2-S-H2O solutions that have different compositions. Chemically pure, single-domain, defect-free magnetite crystals were formed by subsequent decomposition of previously precipitated Fe-rich carbonates by brief heating to 470 degreesC . The sequence of hydrothermal precipitation of carbonates from flowing CO2 -rich waters followed by a transient thermal event provides an inorganic ex planation for the formation of the carbonate globules, magnetite, and Fe su lfides in ALH84001. In separate experiments, kinetically controlled C-13 en richment was observed in synthetic carbonates that is similar in magnitude to the C-13 enrichment in ALH84001 carbonates.