| タイトル | Disturbances in the Isotopic Record of Asuka 881394 |
| 本文（外部サイト） | http://hdl.handle.net/2060/20110016407 |
| 著者（英） | Nyquist, L. E.; Bogard, D. D. |
| 著者所属（英） | NASA Johnson Space Center |
| 発行日 | 2011-01-01 |
| 言語 | eng |
| 内容記述 | Asuka 881394 is a unique achondrite with a granulitic texture, very calcic approximately An(sub 98) plagioclase, and pigeonite that has not inverted to orthopyroxene. First thought to be a eucrite, recent Oisotopic studies show it has a closer affinity to angrites . Initial isotopic studies provided evidence for now extinct A-26, Mn-53, and Sm-146. A recent study confirmed an early chronology with an absolute Pb-207 - Pb-206 age of 4566.5 +/- 0.2 Ma, a new measurement of the Al-Mg formation interval as 3.7 +/- 0.1 Ma since Al-26/Al-27 = approximately 4.63 x 10(exp -5) for the E60 CAI, and a Mn-Cr formation interval of -6.0 +/- 0.2 Ma relative to LEW86010 ("LEW"). Absolute ages relative to age anchors presented by were 4563.4 +/- 0.2 Ma by Al- Mg and 4564.6 +/- 0.5 Ma by Mn-Cr. These ages are in good, but not perfect, agreement with the Pb-207 - Pb-206 age. Perhaps the most direct comparison of the early chronology of A881394 as determined by various workers is provided by reported Al-26/Al-27 values of 1.18 +/- 0.14, 1.28 +/- 0.07, and 2.1 +/- 0.4 x 10(exp -6). Analyses of mineral separates by TIMS and MC-ICPMS6] agree well, but the higher value obtained by in situ SIMS analysis is significant in light of the slight inconsistency between absolute ages inferred from the short-lived chronometers and the Pb-207 - Pb-206 age. We examine the possibility that inconsistencies in the earliest fine-scale chronology of Asuka 881394 may be related to isotopic "disturbances" observed in Ar-39 - Ar-40, Rb-97 - Sr-87, and Sm-147 - Nd-143 chronometers. |
| NASA分類 | Lunar and Planetary Science and Exploration |
| レポートNO | JSC-CN-24924 |
| 権利 | Copyright, Distribution as joint owner in the copyright |
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