Valence state partitioning of vanadium between olivine-liquid: estimates of the oxygen fugacity of Y980459 and application to other olivine-phyric martian basalts

The valence state of vanadium ([V.sup.2+], [V.sup.3+], [V.sup.4+], and [V.sup.5+]) is highly sensitive to variations in redox conditions of basaltic magmas. Differences in valence state will influence its partitioning behavior between minerals and basaltic liquid. Using partitioning behavior of V between olivine and basaltic liquid precisely calibrated for martian basalts, we determined the oxidation state of a primitive (olivine-rich, high Mg no.) martian basalt (Y980459) near its liquidus. The behavior of V in the olivine from other martian olivine-phyric basalts (SaU005, DaG476, and NWA1110) was documented. The combination of oxidation state and incompatible-element characteristics determined from early olivine indicates that correlations among geochemical characteristics such as [fo.sub.2], LREE/HREE, initial [sup.87]Sr/[sup.86]Sr, and initial [[epsilon].sub.Nd] observed in many martian basalts is also a fundamental characteristic of these primitive magmas. These observations are interpreted as indicating that the mantle sources for these magmas have a limited variation in [fo.sub.2] from IW to IW + 1 and are incompatible-element depleted. Moreover, these mantle-derived magmas assimilated a more oxidizing (>IW+3), incompatible-element enriched, lower-crustal component as they ponded at the base of the martian crust. Keywords: Shergottite, olivine, vanadium, valence state partitioning