Remote sensing and geological studies of the Hadley‐Apennine region of the Moon

Abstract

Abstract-We have used data from the Clementine and Lunar Prospector spacecraft in conjunction with reflectance spectra collected with Earth-based telescopes to study the geology of the HadleyApennine portion of the lunar Imbrium basin. The Apennine Mountains and the Imbrium backslope are composed of Imbrium basin ejecta with a noritic or anorthositic norite composition. We find that the two major facies of Imbrium ejecta, the Apenninus material and the Alpes Formation, differ in iron and titanium content. "Pure" anorthosite has tentatively been identified in the ejecta of the crater Conon, based on low-iron content. A difference in Th and rare earth element (REE) abundance between the northeast Apennine Mountains (lower) and the southwest Apennines (higher) is noted. Pyroclastic deposits are common in the region and are dominated by mare basalt material, probably plug rock ejected in vulcanian eruptions. The Apennine Bench Formation, which is likely to be a deposit of non-mare volcanic material, has an Fe, Ti and Th composition consistent with that of Apollo 15 KREEP basalt samples thought to be fragments of the Bench. Aristillus crater is a Th and REE hot spot, and the stratigraphy of the impact target site has been reconstructed from knowledge of the composition of the crater interior and exterior deposits. We infer that the target consisted of highland basement, KREEP plutonics and volcanics, and both high-and low-Ti mare basalt.

Lunar surface geochemistry: Global concentrations of Th, K, and FeO as derived from lunar prospector and Clementine data

“…The TiO 2 -sensitive FeO derivation using CSR data yields FeO concentrations that more accurately match high-Fe/ low-Ti mare-basalt-rich surfaces. The slightly higher FeO contents produced using this algorithm are important for remote sensing studies of basalts with similar high-FeO low-TiO 2 compositions (e.g., Gillis and Spudis, 2000;Blewett and Hawke, 2001). Also, the modified algorithm produces FeO concentrations for the northern farside highlands that are consistent with the feldspathic meteorite compositions (Table 7).…”

“…Results from this work may have important implications on interpreting local and regional geology. For example, having accurate Th concentrations is important for modelling the distribution of Thrich Imbrium antipodal ejecta within South Pole-Aitken Basin , and the characterization of surface geology by geochemical unmixing of LP-GRS Th data using compositions of known lithologic materials (e.g., Blewett and Hawke, 2001;Chevrel et al, 2002). In addition, theories of Table 6.…”

Properties of the Hermean regolith: V. New optical reflectance spectra, comparison with lunar anorthosites, and mineralogical modelling

“…Figure 3 shows the NOT spectrum along with the extended visible spectrum of McCord et al (1972) and an IRCVF (near-infrared circular-variable-filter) spectrum. Blewett and Hawke (2001) found the IRCVF spectrum to have a "1 µm" mafic mineral absorption band centered near 982 nm with a depth of ∼ 10%. The NOT spectrum follows the previous spectra well in the 460-800 nm region, with a similar slope.…”

A laser-ablation ICP-MS study of Apollo 15 low-titanium olivine-normative and quartz-normative mare basalts

“…These features are evident from dark-mantled deposits and terraces along the Apennine front (Ryder, 1989), the massive Hadley Rille lava tube (Howard et al, 1972), and the consistency in mare basalt regolith compositions (<1.5 wt. % TiO 2 ) at the Apollo 15 site (Blewett and Hawke, 2001).…”