The origin of the Moon has been attributed to a giant impact involving a Mars-sized asteroid and the proto-Earth. Energy liberated in this catastrophic event was sufficient to melt a substantial portion of the Moon, a likely cause of a global “Lunar Magma Ocean". This LMO developed early at ca. 4.5 Ga and its crystallization appears to have produced an anorthositic crust and deep cumulate rocks forming the lunar upper mantle, known from their product of partial melting: mare basalts. Direct evidence on how the LMO evolved as it cooled and crystallized remains a major issue. Petrologic models for the solidification of the LMO are derived mainly from thermodynamic phase relationships. The crystallization sequence predicted by these models is olivine, opx ± olivine, olivine + cpx ± plag, cpx + plag, cpx + plag + ilmenite. However, the exact composition of late-stage products during the crystallisation of the LMO remains poorly known. The timing for plagioclase accumulation by flotation, that probably occurred at the top of the LMO to form the lunar crust, is undoubtedly related to the density of the magma. It is rather uncertain whether plagioclase has floated throughout its crystallization story or only at precise degree of evolution when a maximum magma density was reached. What occurs during this critical early period of the Moon differentiation sets the stage for all subsequent events. The objective of this project is to perform new experiments in a range of pressure, with sophisticated equipments allowing the control of important parameters such as starting compositions, temperature and oxygen fugacity. New models for how the LMO evolved as it crystallized during its late-stage evolution will be developed and constrained with observations on mare basalts. How do starting composition, pressure, oxygen fugacity and fluids influence this liquid line of descent? How was generated the anorthositic crust and what is the composition of its complementary mantle cumulates?
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