Petrology of Apollo 11 sample 10071 - A differentiated mini-igneous complex.

Sample 10071,33 is a thin section of Apollo 11 ferrobasalt showing an unusual dual texture. The major portion of the sample is very similar to other fine grained Apollo 11 basalts, but the thin section also includes materials with a distinct variolitic texture. The two areas are separated by a sharp boundary and the mineralogy and composition of the two textural types are quite distinct. The mineralogy and chemistry of the variolitic portion show it to be the product of rapid cooling of a liquid, intermediate between the typical Apollo 11 ferrobasalt and the associated Si and K-rich mesostasis. This liquid is the result of fractional crystallization of a magma of composition closely corresponding to the major portion of the 10071 system, followed by crystal-liquid separation. The sample provides strong and direct evidence for igneous differentiation on the lunar surface.