5:15 PM - 7:15 PM
[MGI29-P04] Classification of Lunar Samples using Principal Component Analysis
Keywords:Lunar samples, PCA
The surface evolution of the Moon has been elucidated by detailed petrological and geochemical analyses of lunar returned lunar samples and meteorites [e.g., 1-5]. The surface materials experienced various types of phenomena, elemental fractionation in the initial magma ocean, secondary shock metamorphism such as late stage heavy bombardment, and mare volcanism. The record of these geological events has been studied in detail by petrology, mineralogy, whole-rock chemistry and isotopic analysis [4,5]. The first step in lunar rock analysis is to identify the rock type. The classification of individual lunar samples and lunar meteorites has been established on the basis of petrological and mineralogical observations using polished thin sections and whole-rock chemical compositions, but the relationships among samples have not been systematically understood. In this study, we compile the whole-rock chemical compositions of Apollo samples and perform principal component analysis (PCA) to derive the classification and relationships among the samples. Analytical data of lunar samples and lunar meteorites were extracted from papers and Astromat [6] to create a database. Ten oxides SiO2, TiO2, Al2O3, Cr2O3, FeO, MnO, CaO, MgO, Na2O, and K2O (wt.%) were extracted from the total rock chemical composition data.
The result of the PCA indicates that the lunar meteorites classified as anorthosite are plotted close to the Apollo 16 samples, which contain mostly highland materials. Brecciated felspathic meteorites are widely distributed and do not match typical types of Apollo samples. This may be due to the mixing of different types of rock fragments. Basaltic meteorites are similar to the Apollo 14, 15, and 17 samples which were collected from mare regions and contain volcanic materials (basalt) and impact melts.
Although we have succeeded in making a rough classification of the lunar rocks, to establish a clearer classification, we need to clarify the end members of the lunar rocks to understand mixed materials in breccias. We also have a problem with interlaboratory errors in the data sets.
References
[1] Lucey et al., 1998, Journal of Geophysical Research-Planets, 103, 3679-3699. [2] Jolliff et al., 2000, Journal of Geophysical Research, 105, 4197-4216. [3] Warren, 1993, American Mineralogist 78, 360-376. [4] Korotev, 1994, Geochimica et Cosmochimica Acta, 58, 3931-3969. [5] Niihara et al., 2019, Meteoritics and Planetary Science 54, 675-698. [6] The Astromaterials Data System (Astromat). URL: https://www.astromat.org/
The result of the PCA indicates that the lunar meteorites classified as anorthosite are plotted close to the Apollo 16 samples, which contain mostly highland materials. Brecciated felspathic meteorites are widely distributed and do not match typical types of Apollo samples. This may be due to the mixing of different types of rock fragments. Basaltic meteorites are similar to the Apollo 14, 15, and 17 samples which were collected from mare regions and contain volcanic materials (basalt) and impact melts.
Although we have succeeded in making a rough classification of the lunar rocks, to establish a clearer classification, we need to clarify the end members of the lunar rocks to understand mixed materials in breccias. We also have a problem with interlaboratory errors in the data sets.
References
[1] Lucey et al., 1998, Journal of Geophysical Research-Planets, 103, 3679-3699. [2] Jolliff et al., 2000, Journal of Geophysical Research, 105, 4197-4216. [3] Warren, 1993, American Mineralogist 78, 360-376. [4] Korotev, 1994, Geochimica et Cosmochimica Acta, 58, 3931-3969. [5] Niihara et al., 2019, Meteoritics and Planetary Science 54, 675-698. [6] The Astromaterials Data System (Astromat). URL: https://www.astromat.org/