Petrogenesis of Luna 16 aluminous Mare basalts

Abstract

Bulk compositionspetrology and mineralogy of > 0.5 mm Luna 16 aluminous mare basalt particles are described. The data rule out any close genetic relationships between Luna 16 and other major types of lunar mare basalts. Compared to high‐Ti mare basaltsthe Luna 16 basalts contain lower TiO2 (5.1 wt %) and Ta (∼ 0.8 ppm) and higher Al2O3 (13.3 wt %) and REE (∼ 30‐70X chondrites) abundancessuggesting that the Luna 16 source rocks crystallized later than (i.e. stratigraphically above) the ilmenite‐bearing high‐Ti basalt cumulate source rocks. The REE pattern for the Luna 16 basalts requires that the source material from which they were derived crystallized from a light REE enriched magma.

Cratering History and Lunar Chronology

“…A small amount of feldspathic highland material is present (e.g., Keil et al 1972). The tiny mare basalt fragments available from the Luna 16 regolith appear to be mainly a coherent chemical group that is more aluminous than typical mare basalts and with intermediate Ti contents (4-5% TiO 2 ) (Grieve et al 1972;Keil et al 1972;Kurat et al 1976;Ma et al 1979); they probably represent a single flow or related flows. The basalt fragments are all fine-grained, suggesting either a thin flow or a series of similar, overlapping thin flows.…”

New Views of Lunar Geoscience: An Introduction and Overview

“…old. Mare basalts from this landing site are among the most Fe-and Mg-poor basalt samples returned from the Moon and, with ~13.5% Al 2 O 3 , are the most Al-rich basalts yet sampled (e.g., Ma et al 1979). More information about the Luna 16 site can be found in McCauley and Scott (1972).…”

Volcanism in Mare Fecunditatis and Mare Crisium: Ar-Ar age studies

“…The robotic mission drilled to a depth of 35 cm and collected ϳ100 g of material from the upper regolith layer. Most of the fragments obtained were basaltic (Vinogradov, 1971) with an aluminous (ϳ13 wt.% Al 2 O 3 ), low Ti (ϳ5 wt.% TiO 2 ) chemical composition (Ma and Schmitt, 1979). Until recently, the age of only three fragments had been determined; this number has now been increased to 13 by Cohen et al (2001) and the present study.…”

“…The difference in J value between the two monitors within the same vial is ϳ1%, which is ϳ3 times higher than the uncertainty on an individual J value. Therefore, a 1% uncertainty has been used in calculating individual step ages (given in the Electronic Annex), and 1.4% uncertainty on J, introduced from the error on the age determination of the Hb3gr monitor (1072 Ϯ 11 Ma;Turner et al, 1971;Roddick, 1983), is included for calculation of the total and plateau ages.…”