Uniform oxygen fugacity of shergottite mantle sources and an oxidized martian lithosphere

Characterization of achondritic cosmic spherules from the Widerøefjellet micrometeorite collection (Sør Rondane Mountains, East Antarctica)

“…Righter and Drake (1996) suggested that the oxygen fugacity levels of martian basalts (f(O 2 ) = À1.25 DIW, where DIW represents the oxygen fugacity levels relative to the iron-wu ¨stite buffer) are slightly higher than those of eucritic basalts (f(O 2 ) = À2.2 DIW), which implies that siderophile and chalcophile elements were more oxidized during the petrogenesis of basaltic shergottites. However, a recent study demonstrated that oxygen fugacity levels within shergottites vary considerably more than initially reported (i.e., f(O 2 ) = À3.7 to À0.2 DIW; Nicklas et al, 2021). Consequently, these elements tend to be more enriched in basaltic shergottites compared to basaltic eucrites.…”

MAGMARS: A Melting Model for the Martian Mantle and FeO‐Rich Peridotite

“…Finally, starting mixes were pre-conditioned at FMQ −0.5 and 1000°C for 72 hr in a gas-mixing furnace. The final 𝐴𝐴 𝐴𝐴O 2 is set to FMQ −2.5 by the graphite capsule during the experiments (Medard et al, 2008), which is close to the average 𝐴𝐴 𝐴𝐴O 2 of the Martian mantle (Nicklas et al, 2021). The basaltic compositions were then mixed with 50-66 wt.% of a peridotite composition-the Dreibus and Wänke (1985) starting material used for direct melting experiments (Collinet et al, 2015).…”

Early differentiation processes on Mars inferred from silicon isotopes

“…Samples analysed in this study include ten martian meteorites which belong to the shergottite group (LAR06319, LAR12011, RBT04262, NWA856, NWA480, EET790010-A and B, Zagami and NWA), one meteorite from the nakhlite group (MIL03346) and one from the chassignite group (NWA2737) (see Supplementary Materials, Tables S1 and S2). The three different groups share similar oxygen isotope composition expressed as D 17 O (Clayton and Mayeda, 1983) and show homogeneous redox state within each group (Stolper et al, 1979;Wadhwa, 2001;Herd, 2003) although a recent study argues for a homogeneous f O2 in the martian mantle (Nicklas et al, 2021). The relatively young crystallization age of shergottites, between 170 and 341 Ma (see compilation by McSween and McLennan, 2014) compared with other extraterrestrial materials means that the formation of SNC are associated with relatively recent igneous processes that could be related to Mars mantle-crust evolution (Bogard and Johnson, 1983;Udry et al, 2014;Filiberto, 2017;Day et al, 2018;Mezger et al Udry et al, 2020).…”

“…Mysen et al, 1984) with oxidized magma being more depolymerized. It has been documented that enriched shergottites are characterized by greater fO 2 (Herd, 2003), although this interpretation has recently been questioned (Nicklas et al, 2021). Thus, one could imagine that the corresponding modification of melt structure directly affecting the bond length of Si-O in the melt could directly impact the d 30 Si of magmas.…”