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Record 26 of 7618
Neodymium, strontium and chromium isotopic studies of the LEW86010 and Angra dos Reis meteorites and the chronology of the angrite parent body
Author and Affiliation:
Nyquist, L. E.(NASA Johnson Space Center, Houston, TX, United States)
Bansal, B.(Lockheed Engineering and Science Co., Houston, TX, United States)
Wiesmann, H.(Lockheed Engineering and Science Co., Houston, TX, United States)
Shih, C.-Y.(Lockheed Engineering and Science Co., Houston, TX, United States)
Abstract: Neodymium, stontium, and chromium isotopic studies of the LEW86010 angrite established its absolute age and the formation interval between its crystallization and condensation of Allende CAIs from the solar nebula. Pyroxene and phosphate were found to contain approximately 8% of its Sm and Nd inventory. A conventional Sm-147-Nd-143 isochron yielded an age of 4.53 +/- 0.04 Ga (2 sigma and Epsilon(sub Nd sup 143)) = 0.45 +/- 1.1. An Sm-146-Nd-142 isochron gives initial Sm-146/Sm-144 = 0.0076 +/- 0.0009 and Epsilon (sub Nd sup 142) = -2.5 +/- 0.4. The Rb-Sr analyses give initial Sr-87/Sr-86 Iota(sub Sr sup 87) = 0.698972 +/- 8 and 0.698970 +/- 18 for LEW and ADOR, respectively, relative to Sr-87/Sr-86 = 0.71025 for NBS987. The difference, Delta Iota(sub Sr Sup 87), between Iota (sub sr sup 87) for the angrites and literature values for Allende CAIs, corresponds to approximately Ma of growth in a solar nebula with a CI chondrite value of Rb-87/Sr-86 = 0.91, or approximately 5 Ma in a nebula with solar photospheric Rb-87/Sr-86 = 1.51. Excess Cr-53 from extinct Mn-53(t(sub 1/2) = 3.7 Ma)in LEW86010 corresponds to initial Mn-53/Mn-55 = 4.4 +/- 1.0 x 10(exp -5) for the inclusions as previously reported by the Paris group (Birck and Allegre, 1988). The Sm-146/Sm-144 value found for LEW86010 corresponds to solar system initial (Sm-146/Sm-144) = 0.0080 +/- 0.0009 for crystallization 8 Ma after Allende, the difference between Pb-Pb ages of angrites and Allende, or 0.0086 +/- 0.0009 for crystallation 18 Ma after Allende, using the Mn-Cr formation interval. The isotopic data are discussed in the context of a model in which an undifferentiated 'chondritic' parent body formed from the solar nebula approximately Ma after Allende CAIs and subsequently underwent differentiation accompanied by loss of volatiles. Parent bodies with Rb/Sr similar to that of CI, CM, or CO chondrites could satisfy the Cr and Sr isotopic systematics. If the angrite parent body had Rb/Sr similar to that of CV meteorites, it would have to form slightly later, approximately 2.6 Ma after the CAIs, to satisfy the Sr and CR isotopic systematics.
Publication Date: Nov 01, 1994
Document ID:
19950035641
(Acquired Dec 28, 1995)
Accession Number: 95A67240
Subject Category: LUNAR AND PLANETARY EXPLORATION
Document Type: Journal Article
Publication Information: Meteoritics; p. p. 872-885; (ISSN 0026-1114); 29; 6
Publisher Information: United States
Financial Sponsor: NASA; United States
Organization Source: NASA Johnson Space Center; Houston, TX, United States
NASA; Washington, DC, United States
Description: 14p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: CHROMIUM ISOTOPES; CHRONOLOGY; METEORITIC COMPOSITION; NEODYMIUM ISOTOPES; STRONTIUM ISOTOPES; CHEMICAL COMPOSITION; MASS SPECTRA; PETROLOGY; PHOSPHATES; PYROXENES; SOLAR CORONA
Imprint And Other Notes: Meteoritics vol. 29, no. 6 p. 872-885 November 1994
Miscellaneous Notes: Research sponsored by NASA
Availability Source: Other Sources
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