Mineralogical variation of the late stage mare basalts

Abstract

The last major phases of lunar volcanism occurred mainly in Oceanus Procellarum and Mare Imbrium and produced spectrally unique medium‐ and high‐titanium basalts. The composition and distribution of these basalts provide a record of the late stage thermal evolution of the Moon. To study the spectral and mineralogical variations of the late stage mare basalts, 31 distinct units were mapped employing a range of remote sensing data. Their inferred mineralogical characteristics were studied by analyzing the spectral features of small, fresh craters derived from the Moon Mineralogy Mapper (M3) data. The strongest olivine spectral signatures were found around Lichtenberg crater, while the units with the lowest olivine/pyroxene ratio occurred mainly in the southern Kepler crater and some local areas. In Oceanus Procellarum, the olivine/pyroxene ratio decreases progressively from the Lichtenberg crater to the southern units. The northern and southern units within Mare Imbrium have higher olivine/pyroxene ratios than the central ones. The inferred abundance of olivine appears to vary stratigraphically, with the younger flows being more olivine rich. However, the stratigraphically younger units around Euler crater in Mare Imbrium, which present as dark red hues in the integrated band depth image of M3, were found to have lower olivine/pyroxene ratios than the units around Lichtenberg crater (shown as light red hues) in Oceanus Procellarum. It could be interpreted that the late stage mare basalts around Lichtenberg crater originated from a more olivine‐rich source than those around Euler crater.

The Thickness and Volume of Young Basalts Within Mare Imbrium

“…Depending on whether apparent flow fronts existed or not, Wu et al () divided the late‐stage basaltic units into two groups, namely, Upper Eratosthenian basalts (UEm), which have discernible flow fronts, and Lower Eratosthenian basalts (LEm), whose flow fronts are invisible. Zhang et al () sketched the late‐stage basalts within the western mare into 31 different units based on albedo and hue differentiations by using various data sets, including M 3 , Clementine, and LROC WAC images. The divisions of basaltic units in this research (Figure ) followed the division of Eratosthenian basalts in the northwestern Imbrium by Wu et al (), and we made some modifications after Zhang et al ().…”

“…Zhang et al () sketched the late‐stage basalts within the western mare into 31 different units based on albedo and hue differentiations by using various data sets, including M 3 , Clementine, and LROC WAC images. The divisions of basaltic units in this research (Figure ) followed the division of Eratosthenian basalts in the northwestern Imbrium by Wu et al (), and we made some modifications after Zhang et al ().…”

“…On the basis of previous studies (Wu et al, ; Zhang et al, ), 17 basaltic units have been finally recognized within the Eratosthenian basalts through the application of various remote lunar data sets. The well‐preserved individual flow fronts of several late‐stage basaltic flows, clearly observed in the low‐Sun illumination images and shaded relief pictures (Figure ), were applied here to sketch the stratigraphic boundaries of these flows.…”

“…To illustrate the differences with Zhang et al (), the northern U24 was detailed into UEm1–UEm4, and some recognized lava flows (UEm5a–UEm5f) have been added in the south based on visible flow fronts. The LEm1 unit was taken as a whole rather than dividing it into three units (U29, U30, and U31) (Zhang et al, ). Additionally, the boundaries of the LEm9–LEm11 units were slightly changed according to the hue variation of the four pictures in Figure .…”

Geology and Scientific Significance of the Rümker Region in Northern Oceanus Procellarum: China's Chang'E‐5 Landing Region

“…Located in northern Oceanus Procellarum (Figure ), the Rümker region is in the northwest part of the PKT (Figure ; Haskin, ; Jolliff et al, ). Its extended and complex geologic history includes multiple volcanic episodes, each differing in element composition and mineral assemblages (e.g., Hiesinger et al, , ; Morota et al, ; Pieters, ; Zhang et al, ).…”