Phenocryst Fabric in Lunar Basalt Sample 12052 from the Ocean of Storms

Pyroxene phenocrysts in Apollo 12 sample 12052, a porphyritic basalt, have a weak, planar preferred orientation and a lineation as determined by crystal-elongation measurements and universal-stage measurements in orthogonal thin sections. The structures are probably the result of laminar flow. Numerous vugs and the flow foliation in sample 12052 suggest crystallization as a surface flow or a near-surface sill. Flowage appears to have ceased by the time of crystallization of the variolitic groundmass of the sample. The fabric data suggest a two-stage crystallization of sample 12052.