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The Apollo 17 “melt sheet”: Chemistry, age and Rb/Sr systematics

1977; Elsevier BV; Volume: 33; Issue: 3 Linguagem: Inglês

10.1016/0012-821x(77)90090-5

1385-013X

Stephen R. Winzer, D. F. Nava, P. J. Schuhmann, R. K. L. Lum, S. Schuhmann, M. M. Lindstrom, David Lindström, J. A. Philpotts,

Space Exploration and Technology

Major, minor and trace element compositions, age data and Rb/Sr systematics of Apollo 17 boulders have been compiled, and additional analyses performed on a norite breccia clast (77215) included in the Apollo 17, Station 7 boulder. The Apollo 17 boulders are found to be identical or nearly so in major, minor and trace element composition, suggesting that they all originated as an impact melt analogous to melt sheets found in larger terrestrial craters. The matrix dates (40Ar/39Ar) and Rb/Sr systematics available suggest that this impact melt formed by a single impact about 4 b.y. ago. This impact excavated, shocked, brecciated and melted norites, norite cumulates and possibly anorthositic gabbros and dunites about 4.4 b.y. old. The impact was likely a major one, possibly the Serenitatis basin-forming event.