Sr stable isotope composition of Earth, the Moon, Mars, Vesta and meteorites

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• 作者：Fré ; dé ; ric Moynier ; Arnaud Agranier ; Dominik C. Hezel ; Audrey Bouvier
• 关键词：meteorites ; Sr isotopes ; MC-ICP-MS ; cosmochemistry
• 刊名：Earth and Planetary Science Letters
• 出版年：2010
• 出版时间：1 December 2010
• 年：2010
• 卷：300
• 期：3-4
• 页码：359-366
• 全文大小：367 K

文摘

High-precision stable Sr isotopic variations (⁸⁸Sr/⁸⁶Sr) are reported in a variety of terrestrial samples, martian and lunar meteorites, HED, undifferentiated primitive meteorites, chondrules and refractory inclusions. Almost all the whole-rock samples are isotopically indistinguishable at a 50 parts per million (ppm) level. The exceptions are CV and CO chondrites which are isotopically light and for which we believe that their isotopic composition is controlled by the proportion of refractory material. Five separated chondrules and one refractory inclusion from Allende are isotopically light, with δ^88/86Sr fractionations up to −1.73‰, whereas the matrix is enriched in the heavy isotopes (δ^88/86Sr = + 0.66‰). The depletion in heavy isotopes observed in chondrules and refractory inclusions could be attributed to the condensation of a material already depleted in Sr, however, in that case more than 60 % of the original material would be unaccounted. We propose instead that isotopic fractionation by electromagnetic sorting of ionized heavy Sr from neutral Sr in the early solar system for the origin of the fractionation observed in refractory inclusions and redistribution of Sr by aqueous alteration for the origin of the fractionation observed in chondrules and matrix. We conclude that CV and CO chondrites are not the primary building blocks for Earth and Mars.