A pristine eucrite-like gabbro from Descartes and its exotic kindredA coarse-grained plagioclase-pyroxene gabbro (61224,6) with a cumulate texture suggestive of a slowly cooled plutonic rock was recovered from the 4-10 mm fraction of an Apollo 16 soil. The rock is uncommonly poor in feldspar and rich in Na for a lunar highlands lithology. Trace element analyses show extremely low siderophile element concentrations which confirm the pristine character indicated by the texture. The composition of 61224,6 is compared with those of 3 other pristine, exceptionally mafic, nonmare gabbros and of certain eucrites. 61224,6 and the three other gabbros have notable chemical differences but share relatively high ratios of Ti/Sm and Sc/Sm which suggest a possible genetic relationship. We conclude that 61224,6 represents a Na-rich cumulate from a layered intrusion within the highlands crust.
Document ID
19820038742
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Marvin, U. B. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Warren, P. H. (New Mexico, University Albuquerque, NM, United States)