Vanadium isotopic difference between the silicate Earth and meteorites
Vanadium isotopic difference between the silicate Earth and meteorites
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DOI：
10.1016/j.epsl.2013.12.030
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发表时间：
2014-03
影响因子：
5.3
通讯作者：
S. Nielsen;J. Prytulak;B. Wood;A. Halliday
中科院分区：
文献类型：
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作者：
S. Nielsen;J. Prytulak;B. Wood;A. Halliday
有人认为，元素钒(V)的稳定同位素组成为太阳系发育早期高能辐射的影响提供了一个潜在的指示器。这样的辐射将产生50V的微量同位素，而丰度为51V的同位素的丰度是51V的400倍(Gounelle等人，2001年，Lee等人，1998年)。与碳质球粒陨石和普通球粒陨石以及来自火星和小行星4灶神星的非球粒陨石相比，硅酸盐地球的钒同位素组成在∼0.8‰下富集了51V。尽管V被岩心形成所贫化，但实验表明，金属和硅酸盐之间没有同位素分馏，这可以解释观察到的地球和地外物质之间V同位素组成的差异。陆地钒同位素偏移量的核合成来源与块状陨石中其他核合成产生的同位素的异常不一致，这些异常比钒更易变(Burkhardt等人，2011年，Carlson等人，2007年，Trquier等人，2009年)。此外，V同位素不太可能受到挥发作用、母体改变或地球ʼS表面的冲击侵蚀的影响。因此，造成同位素差异的原因尚不清楚。一种可能性是，地球ʼS的同位素较重的V反映了太阳系形成初期照射的物质的亏损。无论是什么原因，50V的地球电压赤字意味着，不同陨石的混合物不可能完全重建地球。
It has been argued that the stable isotopic composition of the element vanadium (V) provides a potential indicator of the effects high-energy irradiation early in Solar System development. Such irradiation would produce enrichment in the minor isotope,50V compared with the 400 times more abundant51V (Gounelle et al., 2001, Lee et al., 1998). Here we show that the vanadium isotopic composition of the silicate Earth is enriched in51V by ∼0.8‰ compared with carbonaceous and ordinary chondrites as well as achondrites from Mars and the asteroid 4 Vesta. Although V is depleted by core formation, experiments reveal no isotopic fractionation between metal and silicate that could account for the observed difference in V isotope composition between terrestrial and extraterrestrial materials. Nucleosynthetic provenance of the terrestrial vanadium isotope offset is inconsistent with anomalies of other nucleosynthetically produced isotopes in bulk meteorites, which are more variable than vanadium (Burkhardt et al., 2011, Carlson et al., 2007, Trinquier et al., 2009). Furthermore, V isotopes are unlikely to have been affected by volatilization, parent body alteration or impact erosion of Earthʼs surface. Therefore, the cause of the isotopic difference is unclear. One possibility is that Earthʼs isotopically heavier V reflects a deficit in material irradiated during the initial stages of Solar System formation. Whatever the cause, the terrestrial deficit in50V implies that bulk Earth cannot be entirely reconstructed by mixtures of different meteorites.