THE OBJECTIVE OF THIS RESEARCH PROGRAM IS TO USE PHASE EQUILIBRIUM EXPERIMENTS TO DETERMINE THE PHYSICAL CONDITIONS OF MELTING OF LUNAR MAGMA OCEAN (LMO) CUMULATES. A SERIES OF CUMULATE COMPOSITIONS THAT SPAN THE MIDDLE TO LATE STAGES OF LMO SOLIDIFICATION HAVE BEEN SELECTED FOR INVESTIGATION. WE WILL MELT THE LUNAR MAGMA OCEAN CUMULATES OVER A RANGE OF PRESSURES (0.5 3.5 GPA) AND TEMPERATURES (1060 1680 C). WE WILL SYSTEMATICALLY INVESTIGATE THE INFLUENCE OF VARYING THE AMOUNTS OF TRAPPED LIQUID. THE EXPERIMENTS WILL BE CARRIED OUT USING BOYD-ENGLAND END-LOADED PISTON CYLINDERS IN BOTH IRON AND GRAPHITE CAPSULES IN ORDER TO EXPLORE THE EFFECTS OF VARYING FO2 IN THE HIGH TI AND HIGH FE COMPOSITIONS. WE WILL THEN USE THE EXPERIMENTALLY DETERMINED PRESSUREDEPENDENT MELT COMPOSITIONS AS INPUTS INTO A QUANTITATIVE 3-COMPONENT MAJOR ELEMENT CUMULATE REMELT MIXING MODEL WHICH WILL ALSO TAKE FRACTIONAL CRYSTALLIZATION INTO ACCOUNT. THIS MODEL WILL CONSTRAIN THE PROCESSES THAT GAVE RISE TO THE ORIGIN OF AND COMPOSITIONAL VARIABILITY WITHIN THE 25 LUNAR ULTRAMAFIC GLASS GROUPS.