Mare basalt and other clasts in Yamato lunar meteorites Y-791197, -82192 and -82193

• Main Authors: Cyrena Anne Goodrich, Klaus Keil
• Format: Report
• Language: English
• Published: Institute of Meteoritics, Department of Geology, University of New Mexico 1987
• Subjects: Yamato; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2120; http://id.nii.ac.jp/1291/00002120/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2120&item_no=1&attribute_id=18&file_no=1

A study of lithic clasts >0.1mm in size in new thin-sections of the lunar meteorites Y-791197,-82192 and -82193 revealed that Y-791197 and -82192 may contain components of low-Ti mare basalt, which has not previously been identified in any of the four known lunar meteorites. Of eleven clasts from Y-791197,one is a very low-Ti (VLT) mare basalt, four are ferroan mafic lithologies that are either low-Ti mare basalts or polymict breccias with a large component of low-Ti mare basalt, three are ferroan anorthositic rocks, and three are magnesian granulitic breccias. In Y-82192 and -82193 magnesian clasts, most of which are polymict, are relatively more abundant. Of nine clasts from Y-82192,one is a possible low-Ti mare basalt, two are ferroan mafic lithologies that are either low-Ti mare basalts or polymict breccias with a large component of low-Ti mare basalt, and six are more magnesian polymict breccias. Of four clasts from Y-82193,three are magnesian polymict breccias and one may be a fragment of a pristine Mg-suite lithology. The presence of a significant mare basalt component in at least three of the four lunar meteorites is consistent with orbital geochemical data that suggest that the farside highlands have a 30% component of mare basalts that may predate the final heavy lunar bombardment. The lunar meteorites need not be derived from a source region near visible maria. Available data are insufficient to say whether all four lunar meteorites were derived from a single impact.