Redox equilibria of iron and silicate melt structure: Implications for olivine/melt element partitioning

Petrogenetic linkages among Martian basalts: Implications based on trace element chemistry of olivine

“…The cause of this apparent relationship has not been satisfactorily explained. The experimental study by Herd et al (Forthcoming) concluded that changes in fO 2 on the scale observed in Martian basalts did not affect the olivine/ melt partitioning behavior of Ni or Co; the combined data of Herd et al (Forthcoming) and Mysen (2006) show that oxygen fugacity influences on Ni and Co partitioning in olivine are only significant above ∼IW + 3. In almost all olivine in Martian basalts, little Fe-Mg subsolidus re-equilibration has occurred; since diffusion rates in olivine are generally Fe ∼ Mg > Co > Ni (Ito et al 1999) the changes in slope cannot be attributed to differences in the degree of subsolidus reequilibration and differences in diffusivities of Ni, Co, and Mn.…”

Olivine/melt transition metal partitioning, melt composition, and melt structure—Melt polymerization and Qn-speciation in alkaline earth silicate systems

“…The DHvs. Z/r 2 relationship from experimental results from the systems Na 2 O-CaO-MgO-FeO-Fe 2 O 3 -Al 2 O 3 -SiO 2 (Mysen, 2006) and CaO-MgO-Al 2 O 3 -SiO 2 (Mysen, 2007b) is also linear (Fig. 7), but the DH from these latter two systems is significantly less sensitive to the ionic potential of the m-cation than the DH-values determined for the present, Al-free system.…”

“…In summary, in order to characterize effects of melt composition on mineral/melt partitioning behavior, the Mysen (2006Mysen ( , 2007b Fig. 7.…”

“…Ionic radii, r, for from Prewitt (1969, 1970) assuming 6-fold coordination with oxygen. Dashed line-data from Mysen (2006Mysen ( , 2007b principal melt structural parameter needing quantitative understanding is how the abundance of the individual Q nspecies depends on melt composition (temperature and pressure). Melt compositional variables that affect mineral/melt partition coefficients can then be treated in terms of how these same variables govern the Q n -abundance behavior in silicate melts and how the elements of interest are bonded to oxygen in these structural units.…”

Olivine/melt transition metal partitioning, melt composition, and melt structure—Influence of Al3+ for Si4+ substitution in the tetrahedral network of silicate melts

“…Point (ii) relates to the proportion of individual Q-species and how their type and abundance are governed by the overall degree of melt polymerization, NBO/T, and the ionization potential of individual networkmodifying cations that form bonding with nonbridging oxygen in the Q-species (e. g, Mysen et al, 1982;Stebbins, 1987;Maekawa et al, 1991;Mysen, 1997;Jones et al, 2001;Lee and Stebbins, 2003). These aspects of Q-speciation behavior affect crystal/liquid partitioning behavior (Mysen and Dubinsky, 2004;Mysen and Shang, 2005;Mysen, 2006Mysen, , 2007a.…”