| タイトル | Pieces of the ancient lunar crust - Ages and composition of clasts in consortium breccia 67915 |
| 著者（英） | Groegler, N.; Marti, K.; Geiss, J.; Taylor, G. J.; Eberhardt, P.; Jost, D. T.; Aeschlimann, U.; Laul, J. C.; Ma, M.-S.; Schmitt, R. A. |
| 著者所属（英） | California Univ.|Bern Univ.|Oregon State Univ.|New Mexico Univ.|Battelle Northwest Labs. |
| 発行日 | 1983-11-15 |
| 言語 | eng |
| 内容記述 | The composition and chronology of clasts representing three minor lithologies in consortium breccia 67915 are discussed. The lithologies studied are: sodic ferrogabbro, pristine troctolitic anorthosite (67915,26), and granulitic troctolitic anorthosite (67915,67). These lithologies were presumed to represent samples of the ancient lunar crust. The pristine troctolitic anorthosite, a typical member of the pristine anorthosite suite, contains little or no trapped liquid consistent with its two-phase mineralogy. The plagioclase separates have Ar-39-Ar-40 plateau ages of 4.10 + or - 0.06 b.y., and a final rise in the age pattern may represent a 'memory' of the earlier evolution. The granulitic troctolitic anorthosite, which has 13 times larger REE abundances, displays a continuous rise of the Ar-40/Ar-39 ratio. The last 25 percent of the Ar-39 release data establish a minimum age of over 3.5 b.y., but the Pu-244/Nd chronology suggests an age of about 4.3 b.y. The sodic ferrogabbro samples, which appear to be members of the Mg-gabbronorite group of pristine rocks, show large Ar losses but indicate plateaus in the low-temperature data, suggesting a metamorphic event more recently than 260 m.y. ago, a time that is consistent with the North Ray impact event 50 m.y. ago. |
| NASA分類 | LUNAR AND PLANETARY EXPLORATION |
| レポートNO | 84A18464 |
| 権利 | Copyright |
| URI | https://repository.exst.jaxa.jp/dspace/handle/a-is/400003 |
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