The petrology, geochemistry, and age of lunar regolith breccias Miller Range 090036 and 090070: Insights into the crustal history of the Moon

Abstract

Meteorites ejected from the surface of the Moon as a result of impact events are an important source of lunar material in addition to Apollo and Luna samples. Here, we report bulk element composition, mineral chemistry, age, and petrography of Miller Range (MIL) 090036 and 090070 lunar meteorites. MIL 090036 and 090070 are both anorthositic regolith breccias consisting of mineral fragments and lithic clasts in a glassy matrix. They are not paired and represent sampling of two distinct regions of the lunar crust that have protoliths similar to ferroan anorthosites. 40Ar‐39Ar chronology performed on two subsplits of MIL 090070,33 (a pale clast impact melt and a dark glassy melt component) shows that the sample underwent two main degassing events, one at ~3.88 Ga and another at ~3.65 Ga. The cosmic ray exposure data obtained from MIL 090070 are consistent with a short (~8–9 Ma) exposure close to the lunar surface. Bulk‐rock FeO, TiO2, and Th concentrations in both samples were compared with 2‐degree Lunar Prospector Gamma Ray Spectrometer (LP‐GRS) data sets to determine areas of the lunar surface where the regolith matches the abundances observed on the sample. We find that MIL 090036 bulk rock is compositionally most similar to regolith surrounding the Procellarum KREEP Terrane, whereas MIL 090070 best matches regolith in the feldspathic highlands terrane on the lunar farside. Our results suggest that some areas of the lunar farside crust are composed of ferroan anorthosite, and that the samples shed light on the evolution and impact bombardment history of the ancient lunar highlands.

Investigating the shock histories of lunar meteorites Miller Range 090034, 090070, and 090075 using petrography, geochemistry, and micro‐FTIR spectroscopy

“…) and the parent hand specimen‐sized meteorite samples (Korotev ) are cross‐cut by millimeter‐sized vein networks infilled with glassy feldspathic melt (see also the “dark melt” discussed in the section studied by Calzada‐Diaz et al. ). These melt vein networks are heterogeneous, having patchy mafic and felsic regions (see Figs.…”

“…; Calzada‐Diaz et al. ). They are good case study examples of impact modified lunar highlands crust as they contain a range of clasts (largely feldspathic) and impact melt veins, and are dominantly fine‐grained, indicating they have experienced multiple impact modification events throughout their history.…”

Petrogenesis of lunar impact melt rock meteorite Oued Awlitis 001

“…To account for this scenario, we did least-squares comparison of OA 001's bulk rock composition (Table 1) with the Lunar Prospector's 5°c -ray spectrometer data (Prettyman et al 2006). Previously, this technique has been used to constrain the provenances of regolith breccias on the Moon's surface (e.g., Joy et al 2010Joy et al , 2011Jolliff et al 2014;Wittmann et al 2014b;Calzada-Diaz et al 2015;Zeng et al 2018). Our match algorithm compared Lunar Prospector 5°c-ray spectrometer data to that of OA 001, computed an error-weighted sum of squares of differences, and divided this result by the number of components to give a reduced v 2 /m value.…”

“…; Calzada‐Diaz et al. , ). Our study aims to refine this approach for the identification of potential source craters for OA 001 by including the analysis of high‐resolution Lunar Reconnaissance Orbiter Camera (LROC) images and Diviner nighttime temperature distribution and rock abundance maps (Robinson et al.…”

“…Provenance studies for lunar meteorites are performed routinely based on the comparison of chemical data from small chips of lunar rocks to the composition of large regions on the Moon as determined by the Lunar Prospector c-ray spectrometer (e.g., Jolliff et al 2000Jolliff et al , 2014Korotev et al 2003;Korotev 2005;Joy et al 2010Joy et al , 2011Joy et al , 2014Mercer et al 2013;Wittmann et al 2014b;Calzada-Diaz et al 2015. Our study aims to refine this approach for the identification of potential source craters for OA 001 by including the analysis of high-resolution Lunar Reconnaissance Orbiter Camera (LROC) images and Diviner nighttime temperature distribution and rock abundance maps Hayne et al 2017).…”