Calcium carbonate and sulfate of possible extraterrestrial origin in the EETA 79001 meteorite

Two varieties of Ca-carbonate were found in a total of three interior (2-cm depth) samples of glass inclusions from the shergottite meteorite, Elephant Moraine, Antarctica, A79001. Two of the samples, including the largest deposit around a vug near the center of the meteorite (8-cm depth), contained veins of granular calcite with significant magnesium (avg. atomic Mg/(Mg + Ca) = 0.14-0.15 ) and phosphorus (avg. atomic P/Ca = 0.04 ), either as Mg-calcite with dissolved P or as calcite with very finely intergrown Mg-bearing phosphate. The second variety, which occurred in a third sample with a previously documented high concentration of trapped gases, consisted of disseminated 10-20 μm, anhedral grains of nearly pure CaCO ₃ and was intimately associated with laths and needles of Ca-sulfate (possibly gypsum). The coexisting carbonate and sulfate appeared to be partially decrepitated, relict grains that were trapped during rapid solidification of quench-textured pyroxene and glass. For at least the latter occurrence, textural relationships clearly indicate a pre-terrestrial origin for the salts. All evidence considered, it is probable that both varieties of Cacarbonate (and the Ca-sulfate) formed on a planetary body (probably Mars) before the meteorite fell on Earth.