Experimental Crystallization of the Lunar Magma Ocean, Initial Selenotherm and Density Stratification, and Implications for Crust Formation, Overturn and the Bulk Silicate Moon Composition

Eleven isobaric experimental series simulate the fractional crystallization of a 1150 km deep lunar magma ocean. Crystallization begins at 1850 oC with olivine (to 32 per cent solidified, pcs), followed 1600 by olivine+opx±Cr-spinel 62 1210 cpx+plagioclase±olivine±Ti-spinel 97 pcs) and 1060 quartz+cpx+plagioclase+Ti-spinel, leaving 1.8 wt% residual that crystallizes minor K-feldspar apatite in addition. Melt compositions remain near 45 SiO2, while FeO increases from 11 to 26 wt%, TiO2 peaks 4 Ti-spinel saturation. The available liquid lines descent yields an overall sequence olivine→opx→cpx+plagioclase→quartz→FeTi-oxide. Plagioclase appears concomitantly cpx, result low ocean floor pressures (≤ 1 GPa) after 66-76 % olivine+opx-fractionation. A few FeTi-oxides form mostly once quartz+plagioclase+cpx-cotectic is reached, cumulates densities ≤3740 kg/m3. Scaled full ocean, plagioclase 210-120 depth, mainly as function bulk Al2O3. As buoyancy driven plagioclase-cpx separation likely limited, these depths may correspond primordial crustal thickness. Allowing for complete flotation quartz+plagioclase+cpx+FeTi-oxide±olivine cotectic 95-70 crust anorthosite quartz-gabbro, far excess 35-50 observed. This supports overturn layers, re-melting dense gabbroic harzburgitic cumulate mantle leading further mixing differentiation. We posit such complex density induced convection led marble cake primitive fairly evolved reprocessed next each other.