S.M. Brown , T.L. Grove
Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139

We examine the fO₂-dependent melting conditions of the Apollo 14 yellow intermediate-Ti ultramafic glasses and the melting processes that formed the full suite of lunar yellow ultramafic glasses. Multiple saturation experiments indicate that the Apollo 14 yellow glass would have been in equilibrium with residual olivine and low-Ca pyroxene near 1530°C and 2.4 GPa at ΔIW = +2. At ΔIW = -2, the multiple saturation point moves to greater depth and higher temperature to 1580°C and 3.0 GPa. Combining the results of this study with that of [26] on more Ti-rich Apollo orange and red glass indicates that the fO2-induced change in multiple saturation pressure correlates with the Fe-Ti# (molar (FeO + TiO₂*)/(MgO + FeO + TiO₂*), where TiO₂* = all Ti calculated as Ti⁴⁺) of the liquid. Further, a decrease in the olivine Fe-Mg exchange coefficient at lower fO2 suggests that Fe²⁺ is complexing more efficiently with Ti³⁺ at the expense of Mg in the melt than it did with Ti⁴⁺ at higher fO₂.

Reference
Brown SM, Grove TL (2015) Origin of the Apollo 14, 15, and 17 yellow ultramafic glasses by mixing of deep cumulate remelts. Geochimica et Cosmochimica Acta (in Press)
Link to Article [ http://www.sciencedirect.com/science/article/pii/S0016703715005293]
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