U-Th-Pb systematics of selected samples from Apollo 17, Boulder 1, Station 2
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Abstract
Nine U-Th-Pb whole-rock analyses of selected brecciated materials from sample 72215 and one analysis of a pigeonite basalt clast from 72275 are presented. Both samples are from Boulder 1, Apollo 17. These data supplement previous Boulder 1 U-Th-Pb analyses of samples 72275 and 72255. U and Th concentrations indicate that most of the samples contain a moderate to large KREEP component. Samples containing the least KREEP are a noritic clast (72255,49; Civet Cat clast) and an anorthositic clast (72275,117). Evidence for the migration of Pb from Pb-rich matrix material into relatively Pb-poor clasts is presented for two clasts.
Most of the Boulder 1 data define a linear trend that intersects concordia at ∼ 3.9 and 4.4 b.y. when plotted on a U-Pb concordia diagram. The presence of one anorthositic clast distinctly off this trend indicates that a simple two-stage U-Pb evolution history is inadequate to explain all the data. Accordingly physical significance is only attached to the lower concordia intercept age of 3.9–4.0 b.y. The older concordia intercept age of ∼ 4.4 b.y. is interpreted to reflect an averaging of events both older and younger than 4.4 b.y.
The data suggest that significant differentiation and/or metamorphism occurred ∼ 4.2 b.y. ago. The age of this event, however, is not accurately defined by these data.
Publication type | Article |
---|---|
Publication Subtype | Journal Article |
Title | U-Th-Pb systematics of selected samples from Apollo 17, Boulder 1, Station 2 |
Series title | The Moon |
DOI | 10.1007/BF00569676 |
Volume | 14 |
Issue | 3-4 |
Year Published | 1975 |
Language | English |
Publisher | Springer |
Description | 9 p. |
First page | 463 |
Last page | 471 |
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