Evidence for Late-Imbrian and Eratosthenian Mare Volcanism from the Grimaldi Basin on the nearside of the Moon: Implications for Lunar Mantle Heterogeneity and Thermal Evolution 01/01/2025

Earth and Space Sciences

Mare basalts on the Moon are believed to have been formed by remelting of the lunar interior after the initial differentiation episode through serial magmatism. Our study investigated the spectral and chemical characteristics and ages of the nearside mare basaltic units from the Grimaldi basin, namely Mare Grimaldi and Mare Riccioli, using orbital remote sensing data. Distinct and younger basaltic units of higher FeO, TiO2, and olivine abundances are characteristics of the Mare Grimaldi and Mare Riccioli. The crater size-frequency distribution technique revealed that at least two phases of basaltic magmatism spanning ~3.5 to 1.5 Ga (Late Imbrian–Eratosthenian) have occurred in the Grimaldi basin. The main phase of low to intermediate-Ti basaltic volcanism occurred at ~3.5 Ga ago in both the units, was followed by the eruption of low to intermediate-Ti basalts in the Mare Riccioli at ~3.2 Ga ago. The younger Late-phase event of high to intermediate-Ti basaltic volcanism occurred at ~2.05 Ga and ~1.5 Ga ago in the Mare Grimaldi and Mare Riccioli, respectively. The new results from the present study show that mare volcanism was active in the Grimaldi basin during the main (3.5-3.2 Ga)- and late (2.05-1.5 Ga)-phase volcanic history of the Moon.

Fig. 1. a) LROC-WAC mosaic of the western limb of the Moon, centered on the Grimaldi basin at 5°S, 68°W. The white rectangle on the image outlines the area chosen for the present study. b-e) FeO and TiO2 variations in the Mare Grimaldi and Mare Riccioli. f-h) Model ages of the Mare Grimaldi and Mare Riccioli basaltic units determined based on the CSFD technique.