Preliminary petrographic description and geologic implications of the Apollo 17 Station 7 boulder consortium samples

Preliminary petrographic description and mineral composition of four hand samples (77135, 77115, 77075 and 77215) are presented. 77135, 77115, and 77075 all crystallized from fragment-laden melts; they are similar in textures but differ in grain size. 77135 and 77115 are pigeonite feldspathic basalts. On the basis of geologic and petrographic evidence, 77115 and 77075 are related; they formed, cooled, and consolidated before being engulfed in the vesicular 77135. The impact or igneous origin of the melts from which these rocks crystallized cannot be determined. 77215 is a shocked, strongly sheared and granulated microbreccia consisting of three major lithologies dominated by mineral clasts of orthopyroxene and calcic plagioclase. The orthopyroxene clasts contain coarse exsolved blebs of augite, suggesting a deep-seated origin. The major, minor, and trace element compositions of 77135, 77115, and 77075 are in general similar. They represent a major highland rock type, perhaps more important than anorthosites.