Abstract
The Nectarian-aged Crisium basin exhibits an extremely thin crust and complicated lunar geological history. This large multi-ring impact basin is characterized by prolonged lunar volcanism ranging from the Imbrian age to the Eratosthenian period, forming the high-Ti mare unit, low-Ti mare basalts, and very low-Ti mare unit. We produced an updated geological map of the Crisium basin and defined four mare units (Im1: 3.74 Ga; Im2: 3.49 Ga; Im3: 3.56 Ga; EIm: 2.49 Ga) in terms of distinct composition and mineralogy. Olivine was widely determined in the Ti-rich Im1, implying the hybridization source in the lunar mantle with the occurrence of small-scale convective overturn. The major phase of low-Ti basaltic volcanism occurred c.a. 3.5 Ga, forming Im2 and Im3 in the western area. The youngest mare unit (EIm) has slight variations of pyroxene compositions, implying a decrease of calcic content of basaltic volcanisms with time. Later, distal material transports from large impact events in highlands could complicate the mixing of local mare basalts in the Copernicus age, especially the Im3 unit. The identified olivine-bearing outcrops and widely Mg-rich materials (Mg# > 70, where Mg# = molar 100 × Mg/(Mg + Fe)) in the western highlands, assumed to be the occurrence of the Mg-suite candidates, require future lunar exploration missions to validate.
Highlights
Among the most prominent landforms on the Moon, large impact basins have a relatively complex topographic expression and mineralogical composition [1,2]
We systematically studied the detailed geologic context, including geomorphology, reflectance spectra, composition, mineralogy and chronology around the Crisium basin, producing a newly updated geological map of the Crisium basin
Olivine signatures were widely determined in the Ti-rich Im1 unit, implying the hybridization source in the lunar mantle with the occurrence of small-scale convective overturn
Summary
Among the most prominent landforms on the Moon, large impact basins have a relatively complex topographic expression and mineralogical composition [1,2]. A large impact basin usually consists of concentric rings formed during catastrophic impact events. These basins are commonly surrounded by old, heavily cratered terrain, representing the residue of the ancient lunar crust. The interior floors of these basins, especially for these on the lunar nearside, are usually filled with subsequent, multi-phase mare lava flows from the partially melted lunar mantle. The mare plains could be contaminated by highland materials ejected by small-body impact events and other basin-forming events, leading to the compositional and mineralogical heterogeneity due to later mixing. In mare basalt-filling basins, the lunar crust is extremely thin on the lunar nearside from the GRAIL dataset [6]. Most lunar basins have been characterized in terms of mineralogy and composition
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