Evidence for open magmatic system processes recorded in the crystal cargoes of lunar basalts

A. J. Gawronska , C. L. McLeod, M. Loocke, B. Shaulis

Basaltic magmatism is fundamental to planetary evolution and establishment of planetary crusts. Decades of terrestrial-based research indicate that basaltic magmatic systems often comprise of a series of discrete magma batches with distinct geochemical compositions. The crystal cargos of magmas erupted from such systems provide evidence of this. Within this framework, we investigate textures and mineral compositions of select Apollo basaltic samples to advance our understanding of extraterrestrial magmatic system evolution. We find that samples 10057, 12043, 15085, and 70017 contain reversely zoned clinopyroxene grains in textural disequilibrium alongside grains that do not record disequilibrium textures or reverse elemental stratigraphies; additionally these samples contain reversely zoned feldspars alongside grains normally zoned in An content and Sr. These populations are reflective of magma mixing processes and introduction of antecrysts, indicating the existence of multiple populations is a result of changing melt conditions. The identified textures are consistent with generation in systems whose architectures comprise multiple distinct magma lenses, where material was transported between distinct environments via porous flow and mobilized by influx of hot, primitive magma. Future work should consider this magmatic framework when investigating the role of crust-forming basaltic magmatism on the Moon and on other planets.