Geochemistry and petrography of the MacAlpine Hills lunar meteorites

Conference · Fri Nov 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

OSTI ID:5142709

Lindstrom, M M; McKay, D S ^[1]; Wentworth, S J; Martinez, R R; Mittlefehldt, D W ^[2]; Wang, Mingsheng; Lipschutz, M E ^[3]

---

1. Johnson Space Center, Houston, TX (United States)
2. Lockheed Engineering and Science Co., Houston, TX (United States)
3. Purdue Univ., West Lafayette, IN (United States)

MacAlpine Hills 88104 and 88105 are anorthositic lunar meteorites recovered from the same area in Antarctica which are demonstrated to be paired samples of the same fall. Petrographic studies of matrix and clasts show that mAC88104/5 is a polymict breccia dominated by impact melt clasts. It contains a small amount of highland impact glass and very few regolith glass spherules. It is better classified as a fragmental breccia than a regolith breccia. The bulk composition is ferroan (mg{prime} = 63) and highly aluminous (Al{sub 2}O{sub 3} = 28%). REE and other incompatible element concentrations are very low. Compositions of anorthositic, granulitic, and impact melt breccia clasts are very similar to, but distinct from, matrix composition. MAC88104/5 is very similar in composition to the other anorthositic lunar meteorites, but each of the meteorites is distinct. The anorthositic lunar meteorites, especially MAC88104/5 and Y82192/3/86032, are very similar to North Ray Crater feldspathic fragmental breccias in composition and petrography. These fragmental lunar meteorites may have been ancient, deeply buried breccias from the megaregolith. Comparisons of chemical petrographic features and exposure histories suggest that the twelve lunar meteorites were derived from two to nine, but probably four to seven, impact onto the lunar surface. Discrepancies between the proportions of lunar meteorites and results of Apollo missions may be due to unrepresentative sampling. Lunar meteorites provide valuable new information on the nature of the lunar crust.

• DOE Contract Number: FG02-80ER10725
• OSTI ID: 5142709
• Report Number(s): CONF-9003166--
• Conference Information: Journal Name: Geochimica et Cosmochimica Acta; (United States) Journal Volume: 55:11
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ANORTHOSITES
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
EVALUATION
GABBROS
GEOLOGIC HISTORY
IGNEOUS ROCKS
LUNAR MATERIALS
MATERIALS
METEORITES
ORIGIN
PETROGENESIS
PETROGRAPHY
PLUTONIC ROCKS
ROCKS