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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Osmium isotope anomalies in chondrites: Results for acid residues and related leachates
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Osmium isotope anomalies in chondrites: Results for acid residues and related leachates

机译：球粒陨石中的is同位素异常：酸残渣和相关渗滤液的结果

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We have investigated Os isotope anomalies in acid residues enriched in insoluble organic matter (IOM) extracted from ten primitive chondrites, acid leachates and residues of these fractions, as well as acid leachates of bulk chondrites. Osmium isotopic compositions of bulk carbonaceous, ordinary and enstatite chondrites are also reported. Consistent with prior results, bulk chondrites have homogeneous Os isotope compositions for s-, r-, and p-process nuclides that are indistinguishable from terrestrial, at the current level of resolution. In contrast, nearly all the IOM-rich residues are enriched in s-process Os, evidently due to the preferential incorporation of s-process enriched presolar grains (most likely presolar SiC). Presolar silicate grains that formed in red giant branch (RGB) or asymptotic giant branch (ACB) stars are also likely hosts of additional s-process Os in chondrites. Consistent with one prior study, Os released by weak acid leaching of bulk chondrites is slightly to strongly enriched in r-process nuclides, of which the carrier may be fine-grained presolar silicates formed in supernovae or unidentified solar phases. Collectively, the different, chemically concentrated components in these meteorites are variably enriched in s-, r-, and possibly p-process Os, of which the individual carriers must have been produced in multiple stellar environments. The lack of evidence for Os isotopic heterogeneity among bulk chondrites contrasts with evidence for isotopic heterogeneities for various other elements at approximately the same levels of resolution (e.g., Cr, Mo, Ru, Ba, Sm, and Nd). One possible explanation for this is that the heterogeneities for some elements in bulk materials reflect selective removal of some types of presolar grains as a result of nebular processes, and that because of the strong chemical differences between Os and the other elements, the Os was not significantly affected. Another possible explanation is that late-stage injection of isotopically distinct materials into the nebula led to heterogeneous distribution of some elements. Osmium may not have been affected because of a lack of isotopic contrast with the pre-injection, well mixed nebula.
机译：我们研究了从十种原始球粒陨石中提取的富含不溶性有机物（IOM）的酸残渣中的Os同位素异常，酸浸出物和这些馏分的残留物以及大块状球粒陨石中的酸浸出物。还报告了块状碳质，普通和顽辉长晶球陨石的iso同位素组成。与先前的结果一致，在当前的分辨率水平下，块状球状陨石的s，r和p过程核素具有均匀的Os同位素组成，与陆地没有区别。相反，几乎所有富IOM的残余物都在s过程Os中富集，这显然是由于优先加入了s过程富集的前太阳晶粒（最可能是前太阳SiC）。在红巨星分支（RGB）或渐近巨星分支（ACB）恒星中形成的太阳前硅酸盐晶粒也可能是球粒陨石中其他S过程Os的宿主。与一项先前的研究一致，散装球粒陨石的弱酸浸出所释放的Os在r过程核素中略有或强烈富集，其中的载体可能是超新星形成的细粒前太阳硅酸盐或未知的太阳相。总的来说，这些陨石中不同的，化学浓缩的成分在s-，r-和p-过程Os中可变地富集，其中各个载体必须已经在多个恒星环境中产生。缺乏块状陨石中Os同位素异质性的证据，与分辨率近似相同（例如Cr，Mo，Ru，Ba，Sm和Nd）的其他各种元素的同位素异质性的证据形成对比。对此的一种可能解释是，散装材料中某些元素的异质性反映了由于星云状过程而选择性去除了某些类型的前太阳晶粒，并且由于Os与其他元素之间存在强烈的化学差异，所以Os不是受到严重影响。另一个可能的解释是，将同位素不同的物质后期注入星云会导致某些元素的分布不均。 with可能没有受到影响，因为与注射前的混合星云缺乏同位素对比。

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