Osmium isotope evidence for uniform distribution of s- and r-process components in the early solar system

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doi: 10.1016/j.epsl.2007.05.017
Authors:Yokoyama, Tetsuya; Rai, Vinai K.; Alexander, Conel M. O'D.; Lewis, Roy S.; Carlson, Richard W.; Shirey, Steven B.; Thiemens, Mark H.; Walker, Richard J.
Author Affiliations:Primary:
University of Maryland, College Park, Department of Geology, College Park, MD, United States
Other:
University of California, San Diego, United States
Carnegie Institution of Washington, United States
University of Chicago, United States
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 259(3-4), p.567-580. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:2007
Note:In English. Includes appendices. 53 refs.; illus., incl. 3 tables
Summary:We have precisely measured Os isotopic ratios in bulk samples of five carbonaceous, two enstatite and two ordinary chondrites, as well as the acid-resistant residues of three carbonaceous chondrites. All bulk meteorite samples have uniform 186Os/188Os, 188Os/189Os and 190Os/189Os ratios, when decomposed by an alkaline fusion total digestion technique. These ratios are also identical to estimates for Os in the bulk silicate Earth. Despite Os isotopic homogeneity at the bulk meteorite scale, acid insoluble residues of three carbonaceous chondrites are enriched in 186Os, 188Os and 190Os, isotopes with major contributions from stellar s-process nucleosynthesis. Conversely, these isotopes are depleted in acid soluble portions of the same meteorites. The complementary enriched and depleted fractions indicate the presence of at least two types of Os-rich components in these meteorites, one enriched in Os isotopes produced by s-process nucleosynthesis, the other enriched in isotopes produced by the r-process. Presolar silicon carbide is the most probable host for the s-process-enriched Os present in the acid insoluble residues. Because the enriched and depleted components present in these meteorites are combined in proportions resulting in a uniform chondritic/terrestrial composition, it requires that disparate components were thoroughly mixed within the solar nebula at the time of the initiation of planetesimal accretion. This conclusion contrasts with evidence from the isotopic compositions of some other elements (e.g., Sm, Nd, Ru, Mo) that suggests heterogeneous distribution of matter with disparate nucleosynthetic sources within the nebula.
Sections:Geochemistry; Meteorites and tektites
Subjects:Allende Meteorite; Carbonaceous chondrites; Chondrites; CM chondrites; Cosmochemistry; CR chondrites; CV chondrites; Dhajala Meteorite; Elephant Moraine Meteorites; Enstatite chondrites; Geochemical anomalies; H chondrites; Insoluble residues; Metals; Meteorites; Murchison Meteorite; Ordinary chondrites; Osmium; Planetesimals; Platinum group; Presolar grains; Renazzo Meteorite; Solar nebula; Stony meteorites; Tagish Lake Meteorite; Allegan Meteorite; EET 92042; Nucleosynthesis; Pillistfer Meteorite; R-process; S-process; Silicon carbide; Yilmia Meteorite
Abstract Numbers:07M/3821
Record ID:2008016679
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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