  The mineralogy of mare basalts reflects the chemical composition of the magma
source, as well as the physical and chemical environment of the rock's
formation. It is significant for understanding the thermal evolution of the
Moon. In this study, the spatial distribution of the mineralogy of the lunar
northern nearside basalts was mapped using the Moon Mineralogy Mapper (M3)
data. The study area, which is an elongated mare, Mare Frigoris and northern
Mare Imbrium, was mapped and characterized into 27 units based on multi-source
data, including spectrum, terrain, and element abundance. We extracted 177 M3
spectra from fresh craters. Spectral parameters such as absorption center and
band area ratio (BAR) were obtained through data processing. The variation of
mafic mineral of this region was acquired by analyzing these parameters. The
basaltic units in eastern Mare Frigoris, which are older, have been found to be
dominated by clinopyroxene with lower CaO compared to the returned lunar
samples; this is similar to older basaltic units in Mare Imbrium. The basaltic
units of western Mare Frigoris and Sinus Roris which are younger have been
found to be rich in olivine. The late-stage basalts in Oceanus Procellarum and
Mare Imbrium show the same feature. These wide-spread olivine-rich basalts
suggest the uniqueness in the evolution of the Moon. Geographically speaking,
Mare Frigoris is an individual mare, but the magma source region have
connections with surrounding maria in consideration of mineral differences
between western and eastern Frigoris, as well as mineral similarities with
maria at the same location.
