OBJECTIVES: THE DISTRIBUTION OF RARE EARTH ELEMENTS (REE) BETWEEN MAJOR ROCK-FORMING MINERALS DEPENDS ON TEMPERATURE PRESSURE AND MINERAL COMPOSITION. THE PRIMARY GOALS OF THIS PROPOSED STUDY ARE TWOFOLD: (1) TO USE TEMPERATURE- AND COMPOSITION DEPENDENT MINERAL-MELT AND MINERAL-MINERAL REE PARTITION COEFFICIENTS TO INFER MAGMATIC AND SUBSOLIDUS PROCESSES EXPERIENCED BY MAFIC AND ULTRAMAFIC ROCKS FROM THE MOON (LUNAR FERROAN ANORTHOSITES AND MG-SUITE ROCKS) MARS AND HED METEORITES AND (2) TO EXPLORE THEIR IMPLICATIONS FOR THE AGE AND THE THERMAL AND MAGMATIC EVOLUTION OF PARENT BODIES. GIVEN THE UBIQUITOUS PRESENCE OF PLAGIOCLASE AND PYROXENE IN CUMULATE ROCKS FROM THE MOON MARS AND HED METEORITES WE PLAN TO DEVELOP A REE-INPLAGIOCLASECLINOPYROXENE THERMOMETER AND A REE-IN-PLAGIOCLASE-ORTHOPYROXENE THERMOMETER FOR MAFIC AND ULTRAMAFIC ROCKS IN THIS PROPOSED STUDY. A REE-IN-TWO PYROXENE THERMOMETER WAS RECENTLY DEVELOPED IN PI S LAB FOR MAFIC AND ULTRAMAFIC ROCKS. PART OF THIS PROPOSED STUDY WILL FOCUS ON ITS FURTHER CALIBRATION IN FE-RICH SYSTEMS AND ITS PLANETARY APPLICATION. DUE TO THEIR SLOW DIFFUSION RATES TRIVALENT REE HAVE HIGHER CLOSURE TEMPERATURES THAN DIVALENT CA MG AND FE IN PYROXENE AND PLAGIOCLASE. THE DIFFERENCES IN TEMPERATURES BETWEEN THE REE-BASED THERMOMETERS AND THE DIVALENT CATION-BASED THERMOMETERS WILL BE USED TO INFER COOLING RATES OF THE CUMULATE ROCKS. THE LATTER CAN SHED NEW LIGHT ON THE THERMAL HISTORY OF THE PARENT BODIES. RELEVANCY: MAFIC AND ULTRAMAFIC ROCKS ARE UBIQUITOUS IN INNER SOLAR SYSTEM BODIES. ABUNDANCES AND DISTRIBUTIONS OF REE IN THESE MAFIC AND ULTRAMAFIC ROCKS PROVIDE IMPORTANT CLUES TO UNDERSTANDING THE CHEMICAL AND THERMAL EVOLUTION OF PLANETARY INTERIORS THROUGH TIME. THIS PROPOSED STUDY IS DIRECTLY RELEVANT TO THE SCOPES OF SOLAR SYSTEM WORKINGS BY PRODUCING NEW MINERAL-MELT REE PARTITIONING DATA AND DEVELOPING THREE NEW THERMOMETERS FOR PLANETARY MATERIALS BY EXAMINING THE MEASURED SM-ND AGES OF LUNAR HIGHLANDS SAMPLES THE BY ANALYZING PLANETARY MATERIALS AND BY PROVIDING NEW METHODS FOR ASSESSING THE THERMAL AND CHEMICAL EVOLUTION OF PLANETARY MANTLE AND LITHOSPHERE. METHODOLOGY: LABORATORY CRYSTAL GROWTH EXPERIMENTS WILL BE CONDUCTED IN THE SYSTEM PLAGIOCLASE-PYROXENE-BASALT OVER A RANGE OF TEMPERATURES (1050~1400 C) PRESSURES (0~2 GPA) AND (EVOLVED) MELT COMPOSITIONS. MAJOR AND TRACE ELEMENT ABUNDANCES IN QUENCHED RUN PRODUCTS WILL BE ANALYZED USING AN ELECTRON MICROPROBE AND A LASER ABLATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (LA-ICP-MS) AT BROWN UNIVERSITY. TOGETHER WITH PUBLISHED HIGH QUALITY PLAGIOCLASE-MELT AND PYROXENE-MELT TRACE ELEMENT PARTITIONING DATA WE WILL DEVELOP INTERNALLY CONSISTENT LATTICE STRAIN MODELS FOR REE PARTITIONING IN THE AFOREMENTIONED MINERAL-MELT SYSTEMS USING A NONLINEAR LEAST SQUARES REGRESSION METHOD. WITH LABORATORY CALIBRATED TEMPERATURE- AND COMPOSITION-DEPENDENT MINERAL-MINERAL REE PARTITIONING MODELS WE WILL BE ABLE TO CALCULATE TEMPERATURES FOR THE MAFIC AND ULTRAMAFIC ROCKS USING MEASURED PLAGIOCLASEPYROXENE REE PARTITION COEFFICIENTS. WE WILL ASSESS EFFECTS OF DISEQUILIBRIUM CRYSTALLIZATION DIFFUSION AND SUBSOLIDUS RE-EQUILIBRATION ON REE ABUNDANCES IN COEXISTING PLAGIOCLASE AND PYROXENES IN THE CUMULATE SAMPLES THROUGH NUMERICAL SIMULATIONS AND EXAMINE THEIR IMPLICATIONS FOR THE MEASURED SM-ND AGES AND INFERRED PARENTAL MELT COMPOSITIONS. AS PART OF PLANETARY APPLICATIONS WE PLAN TO MEASURE REE AND OTHER ELEMENT ABUNDANCES IN COEXISTING PLAGIOCLASE AND PYROXENES IN SELECTED LUNAR SAMPLES MARTIAN AND HED METEORITES AS WELL AS MAFIC AND ULTRAMAFIC CUMULATES FROM THE BUSHVELD LAYERED INTRUSION USING THE LA-ICP-MS AND ELECTRON MICROPROBE. TERRESTRIAL LAYERED INTRUSION STUDY WILL HELP US TO FURTHER TEST AND BETTER UNDERSTAND THE REE-BASED THERMOMETERS AND TO AID OUR PLANETARY INTERPRETATION.