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Thirty-five years ago, a bulk-rock INAA and mineral EPMA study concluded high-Ti basalt fragment 71597 resulted from significant olivine accumulation (Murali et al., 1977; Warner, 1977). Cumulates of this nature are relatively underrepresented in the lunar sample collection, and may provide unique insights into mare volcanic processes. We utilize in-situ mineral trace element abundances to add a higher level of fidelity in constraining the processes that affected this sample. In addition, aspects of crystallization kinetics and the nature of olivine accumulation (e.g., gravitational settling during a single, large flow vs. magma mixing) can be addressed by quantitative petrography (via crystal size distributions) and crystal stratigraphy (via mineral geochemistry).
Microscale details and changes in basalt evolution are recorded in core-to-rim and inter-crystal compositional variations, and can only be constrained by in-situ techniques. Equilibrium liquid trace element compositions can be used to constrain a petrogenetic model. In addition to characterizing trace element variations in major phases, we analyzed seven melt inclusions (7-70 μm) contained in olivine and ilmenite, and a region of mesostasis. These silicate melt inclusions theoretically record a snapshot of magma composition during entrainment. Late-stage mesostasis, on the other hand, may represent the last dregs of crystallizing magma. By incorporating melt inclusion variation and mesostasis composition, we aim to build a robust petrogenetic model for this unique sample.
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