早期内太阳系对分化原行星中异常硫同位素的起源。
Early inner solar system origin for anomalous sulfur isotopes in differentiated protoplanets.
机构信息
Department of Geology, University of Maryland, College Park, MD 20742;
School of Geography and Earth Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada;
出版信息
Proc Natl Acad Sci U S A. 2014 Dec 16;111(50):17749-54. doi: 10.1073/pnas.1418907111. Epub 2014 Dec 1.
Achondrite meteorites have anomalous enrichments in (33)S, relative to chondrites, which have been attributed to photochemistry in the solar nebula. However, the putative photochemical reactions remain elusive, and predicted accompanying (33)S depletions have not previously been found, which could indicate an erroneous assumption regarding the origins of the (33)S anomalies, or of the bulk solar system S-isotope composition. Here, we report well-resolved anomalous (33)S depletions in IIIF iron meteorites (<-0.02 per mil), and (33)S enrichments in other magmatic iron meteorite groups. The (33)S depletions support the idea that differentiated planetesimals inherited sulfur that was photochemically derived from gases in the early inner solar system (<∼2 AU), and that bulk inner solar system S-isotope composition was chondritic (consistent with IAB iron meteorites, Earth, Moon, and Mars). The range of mass-independent sulfur isotope compositions may reflect spatial or temporal changes influenced by photochemical processes. A tentative correlation between S isotopes and Hf-W core segregation ages suggests that the two systems may be influenced by common factors, such as nebular location and volatile content.
球粒陨石中的硫同位素（33）相对球粒陨石存在异常富集，这归因于太阳星云的光化学作用。然而，推测的光化学反应仍然难以捉摸，以前也没有发现预测的伴随（33）S 亏损，这可能表明关于（33）S 异常的起源，或者整个太阳系硫同位素组成的错误假设。在这里，我们报告了 IIIF 铁陨石中（33）S 异常亏损的情况（<-0.02‰），以及其他岩浆铁陨石群中（33）S 的富集。（33）S 亏损支持这样一种观点，即分化的星子继承了源自早期内太阳系气体的光化学硫（与 IAB 铁陨石、地球、月球和火星一致）。无质量依赖硫同位素组成的范围可能反映了受光化学过程影响的空间或时间变化。S 同位素与 Hf-W 核分异年龄之间的暂定相关性表明，这两个系统可能受到共同因素的影响，例如星云位置和挥发性物质含量。
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