Modal Petrology and Mineral Chemistry of the <1 mm Size Fraction of Lunar Regolith in Apollo 17 Drive Tube Section 73002

Abstract

AbstractThe Apollo 17 mission returned samples from the Taurus‐Littrow Valley of the Moon. Key features of the site are a basaltic valley floor partially enclosed by South Massif and North Massif mountains and the Sculptured Hills, which consist of feldspar‐rich highland lithologies. A recently opened soil core sampled an inferred landslide deposit at the base of South Massif. Study of a suite of polished grain mounts of six size fractions of <1 mm material from 14 depth intervals of the ∼18 cm soil column shows that all size fractions from the upper 5–6 cm are richer in agglutinates, an indicator of surface exposure, than the deeper material, which is among the most agglutinate‐poor Apollo 17 regolith reported. Regolith breccia, crystalline melt breccia, and noritic igneous rocks are the most abundant fragment types. Nonmare rock types found range from anorthosites to ultramafic rocks and include rare types such as dunites, pyroxenites, and granitic fragments rich in potassium feldspar and silica. Mare basalt, glasses, and agglutinates are minor components throughout. The observations are consistent with the deposition of the highland‐dominated material in a landslide, which did not preserve any previous stratigraphy, followed by in situ maturation, with only minor additions of mare lithologies from nearby basaltic regolith, due to the inefficiency of lateral transport on the Moon.