New Insights into the Complex History of Lunar Highlands: Alha 81005 under Reinvestigation
نویسنده
چکیده
Introduction: Lunar meteorites come from random sites on the Moon (including areas not visited by Apollo or Lunar missions) and so are crucial for understanding the development of the whole moon, and as ground truth for lunar remote sensing. Data from the Lunar Prospector and Clementine spacecraft show that, relative to the Apollo and Luna landing sites, most of the lunar surface has low abundances of FeO and incompatible elements [3; 4], with an average composition more like that of the feldspathic lunar meteorites [5]. We have started a re-investigation ALHA81005 to improve our understanding of unsampled areas of the Moon and enlarge our knowledge of lunar highland rock types and the Moon’s early history. Sample and Method: Antarctic meteorite Allan Hills A81005 is a ploymict, anorthositic regolith breccia from the lunar highlands [6,7]. Its clasts include granulites, FAN, mare basalts, impact melts, and impact glasses. Clasts described here were analyzed from the polished thin section ALHA81005,9. Mineral analyses were performed using an electron microprobe (Cameca SX100) at NASA JSC. Operating conditions were 15kV accelerating voltage, 20nA, focused beam and a measuretime of 20-40s per element. Standards included well characterized natural and synthetic materials. Lithic and Mineral Clasts: ALHA 81005 contains a wide range of rock and mineral fragments, most of which are granulites and anorthosites [13,7]. Other rock types are rare, and some mineral fragments must represent other lithologies.
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Granulite Clasts of Intermediate Mg* in Lunar Meteorite Alha 81005: Chemical Compositions and Origins
Lunar highland meteorites contain fragments of metamorphic granulites with a wide range of Mg* (molar Mg/(Mg+Fe)) [1], between that of Mg-suite plutonics and magnesian anorthositic granulites (MAG), and those of ferroan anorthosites (FAN), Figure 1 [2,3]. The intermediate-Mg* granulites have been inferred (explicitly or implicitly) to represent mixtures of FAN and MAG or Mg-suite rocks. To test...
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