Oxygen isotope thermometry of DaG 476 and SaU 008 martianmeteorites: Implications for their origin

We report the equilibration temperatures derived from the oxygen isotope thermometry of pyroxene-olivine pair from the Dar al Ghani (DaG) 476 (1200 +105/-90°C) and Sayh al Uhaymir (SaU) 008 (1430 +220/-155°C) meteorites showing a difference of over 200°C at the face values. Regardless of the large associated uncertainties, contrasting geochemical and isotopic characteristics such as oxygen fugacities, hydrogen isotopic compositions (referred to as the D/H ratios), olivine abundances, presence of merrillite and/or apatite, and their chlorine contents between the two meteorites are observed in the literature. These opposing features lend support to the idea that the relative difference observed in the estimated temperatures is probably real and significant, thus providing insights into the Martian mantle magmatism. Based on our temperature estimation and previous magmatic models, we propose that SaU 008 could have been originated from a deeper depleted mantle source. However, DaG 476 may have been produced by the partial melting of the entrained pockets of the depleted mantle similar to that of the SaU 008’s source at a relatively shallower depth. Both meteorites erupted as a relatively thick lava flow or a shallow intrusion at approximately the same time followed by a launch initiated by a single meteoritic impact 1.1 million years (Ma) ago.