Basaltic fragments in lunar feldspathic meteorites: Connecting sample analyses to orbital remote sensing |
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| Authors: | Katharine L. ROBINSON Allan H. TREIMAN Katherine H. JOY |
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| Affiliation: | 1. Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Blvd., Houston, Texas 77058, USA;2. Center for Lunar Science and Exploration, NASA Lunar Science Institute;3. Present address: HIGP/UHNAI, University of Hawai’i at Manoa, 1680 East West Rd., Honolulu, HI 96822, USA;4. The Centre for Planetary Sciences at UCL/Birkbeck, The Joint UCL‐Birkbeck Research School of Earth Sciences, Gower Street, London, WC1E 6BT, UK;5. IARC, Department of Mineralogy, The Natural History Museum, London, Cromwell Road, SW7 5BD, London, UK |
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| Abstract: | Abstract– The feldspathic lunar meteorites contain rare fragments of crystalline basalts. We analyzed 16 basalt fragments from four feldspathic lunar meteorites (Allan Hills [ALHA] 81005, MacAlpine Hills [MAC] 88104/88105, Queen Alexandra Range [QUE] 93069, Miller Range [MIL] 07006) and utilized literature data for another (Dhofar [Dho] 1180). We compositionally classify basalt fragments according to their magma’s estimated TiO2 contents, which we derive for crystalline basalts from pyroxene TiO2 and the mineral‐melt Ti distribution coefficient. Overall, most of the basalt fragments are low‐Ti basalts (1–6% TiO2), with a significant proportion of very‐low‐Ti basalts (<1% TiO2). Only a few basalt clasts were high‐Ti or intermediate Ti types (>10% TiO2 and 6–10% TiO2, respectively). This distribution of basalt TiO2 abundances is nearly identical to that obtained from orbital remote sensing of the moon (both UV‐Vis from Clementine, and gamma ray from Lunar Prospector). However, the distribution of TiO2 abundances is unlike those of the Apollo and Luna returned samples: we observe a paucity of high‐Ti basalts. The compositional types of basalt differs from meteorite to meteorite, which implies that all basalt subtypes are not randomly distributed on the Moon, i.e., the basalt fragments in each meteorite probably represent basalts in the neighborhood of the meteorite launch site. These differences in basalt chemistry and classifications may be useful in identifying the source regions of some feldspathic meteorites. Some of the basalt fragments probably originate from ancient cryptomaria, and so may hold clues to the petrogenesis of the Moon’s oldest volcanism. |
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