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 degrees N, 86.1 degrees E) is a large mare deposit lying north of the pre-Nectarian Smythii Basin (13.3 degrees N, 86.1 degrees 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.