Luna 16: Relative proportions and petrologic significance of particles in the soil from Mare Fecunditatis
Abstract
We have classified some 2380 lithic and vitreous particles from levels A and Γ(G) of the Luna 16 core-tube sample. The proportions of particle types in the two levels are very similar, indicating a well-mixed regolith. Light-colored, non-mare materials in the soil consist of anorthositic fragments similar to those from Apollo 11, a Ti, K, P-poor gabbro not reported from earlier missions, and their vitreous equivalents. KREEP-rich norites and their glassy counterparts are very rare. Luna 16 mare basalts have a more restricted variety of textures than do the basalts from the Apollo 11 and 12 missions and contain pyroxenes that fall into two groups on plots of TiO 2 vs. Fe/(Fe + Mn + Mg). TiO 2 is high in cores of type 1 pyroxenes, but falls sharply toward grain boundaries, probably reflecting depletion of TiO 2 in the melt by simultaneous ilmenite crystallization. Type 2 pyroxenes have lower and less variable TiO 2, but are more strongly zoned in Fe/Mg and reach higher Fe/Mg ratios than type 1 pyroxenes. Fragments with type 1 pyroxenes appear to be early crystallizing portions of a series of flows whose later stage pyroxenes are dominantly type 2. Cindery glass and breccia matrix compositions are not identical to the bulk regolith composition but contain higher normative plagioclase, indicating a greater non-mare component than is present in the bulk soil. The most likely source of non-mare material at the Luna 16 landing site is the crater Langrenus, 140 km in diameter and 280 km southeast of the landing site. It appears that a substantial part of the cindery glass found in the Luna 16 soil may have been derived from soils containing a larger component of Langrenus ejecta than is present in the Luna 16 bulk soil sample.
- Publication:
-
Earth and Planetary Science Letters
- Pub Date:
- January 1972
- DOI:
- 10.1016/0012-821X(72)90104-5
- Bibcode:
- 1972E&PSL..13..286R