Compositional diversity in the Mare Marginis and Mare Smythii: An insight into the volcanism in the region

The Marginis-Smythii region of the eastern limb of the Moon is a unique geological setting with the presence of equally widespread volcanism both inside and outside of an impact basin. Mare Marginis (13.3°N, 86.1°E) is a large mare deposit lying north of the pre-Nectarian Smythii Basin (13.3°N, 86.1°E). The basalts from Mare Marginis are deposited in a topographically low area outside an impact basin, i.e. the Smythii Basin. The Marginis-Smythii region is important to understand the geological controls on basalt emplacement on the Moon. In this study, we carry out a detailed investigation of the Mare Marginis and Mare Smythii basalts using the Moon Mineralogy Mapper (M³) data to understand the compositional diversity of the basalt deposits. Our study reveals that the basalts in the Mare Marginis can be divided into two distinct units: i) the central and eastern Marginis basalts that are spectrally similar to the Mare Smythii basalts, and ii) the western lacus, described as Margins west which is a small basalt deposit in the western fringes of Mare Marginis having a spectral composition different from the rest of Mare Marginis and Mare Smythii. We report that the volcanism in this compositionally distinct unit of Marginis west occurred up to ∼3.1 Ga when volcanism was still active in the Smythii Basin. We found that the volcanism in Mare Marginis was influenced by both; Crisium and Smythii Basins implying that the pre-existing structures in the lunar crust generated by large-scale impacts play an important role in the volcanism on the Moon.