CARBONATES IN MARTIAN METEORITE ALH84001 - A PLANETARY PERSPECTIVE ONFORMATION TEMPERATURE

We have re-examined the formation temperature of carbonates in ALH8400 1, accounting for the prior evolution of the stable isotopes used in t he analysis. Oxygen and carbon in the atmosphere likely have become is otopically fractionated due to various nonthermal loss mechanisms oper ating throughout geologic time. Taking this previous evolution into ac count, we derive a formation temperature from oxygen isotope thermomet ry of 40-250 degrees C. This range of temperatures represents a lower limit; an increase in groundwater salinity could further raise the del ta(18)O of the groundwater, as seen in terrestrial hydrothermal system s, allowing for an even higher temperature of formation derived from t he isotopic data.