New maps of mafic mineral abundances in global mare units on the Moon

Abstract

Lunar surface mineralogy plays a crucial role in characterizing the distribution and abundance of silicate minerals, providing pivotal insights into the geological evolution of the Moon. Existing lunar mineral distribution maps are primarily derived from the calibration of Apollo and Luna sample datasets, which are predominantly older than 3.0 Ga. However, these maps lack critical constraints from younger mare basalt samples, limiting their ability to fully represent the mineralogical diversity of lunar mare units. In this work, we present updated global mineral abundance maps for olivine (OLV), high-Ca pyroxene (HCP), and low-Ca pyroxene (LCP) on the global mare units using the partial least squares regression (PLS) algorithm applied to Moon Mineralogy Mapper data, incorporated the distinctive 2.0-Ga Chang’e-5 lunar samples as a new calibration reference. The revised maps indicate mean HCP, LCP, and OLV abundances of 48.4 wt%, 38.2 wt%, and 13.2 wt%, respectively, among global mare units. Our results reveal a systematic trend of HCP enrichment and OLV depletion in younger mare basalts, which correlates with variations in TiO₂ content and model ages. HCP abundance follows a Gaussian distribution, increasing from low-Ti to high-Ti units, whereas LCP exhibits an inverse trend. OLV abundance only shows a slightly decrease from medium-Ti to low-Ti units. From a geochemical perspective, mare units become progressively enriched in HCP with increasing FeO content and decreasing Mg#, while less evolved mare units, characterized by higher LCP abundances, retain higher Mg# and lower FeO content. In the new maps, the localized variations in mineral abundances are possibly related to subsurface materials excavated by impact events, highland ejecta deposits, and space weathering.