Nucleosynthetic vanadium isotope heterogeneity of the early solar system recorded in chondritic meteorites
Nucleosynthetic vanadium isotope heterogeneity of the early solar system recorded in chondritic meteorites
复制标题
DOI：
10.1016/j.epsl.2018.10.029
复制
发表时间：
2019
影响因子：
5.3
通讯作者：
S. Nielsen;M. Auro;K. Righter;D. Davis;J. Prytulak;Fei Wu;J. Owens
中科院分区：
文献类型：
--
作者：
S. Nielsen;M. Auro;K. Righter;D. Davis;J. Prytulak;Fei Wu;J. Owens
钒（V）同位素被假设通过产生少量的50 V同位素来记录早期太阳系的辐射过程。然而，由于V只有两个稳定同位素，因此很难将辐照与其他过程区分开来，例如稳定同位素分馏和核合成异质性，这些过程也可能导致V同位素变化。在这里，我们进行了第一次详细的调查V同位素在普通和碳质方解石调查任何变化的起源。我们还进行了三个实验室的互校准，这证实了不同的化学分离协议不诱导V同位素分析文物，只要使用中等分辨率的多接收器电感耦合等离子体质谱（MC-ICPMS）测量样品。钒同位素组成（51 V/50 V）的碳质方解石与以前报道的核合成衍生过剩的54 Cr。51 V和54 Cr是它们各自元素中最富中子的元素，这可能表明富含r过程同位素的太阳前颗粒是V-Cr同位素相关的主要原因。普通球粒陨石群和地球的钒同位素比值与54 Cr形成较弱的相关性，其斜率与碳质球粒陨石不同。碳质和非碳质陨石在钒铬同位素空间的偏移量与铬、钛、氧、钼和钌同位素的差异相似，据推测，这反映了早期太阳系中存在两个物理上分离的储层。地球的V同位素组成比迄今为止测量的任何陨石都重。因此，钒同位素支持地球吸积模型，其中地球的很大一部分是由我们的陨石收藏中不存在的材料形成的。
Vanadium (V) isotopes have been hypothesized to record irradiation processes in the early solar system through production of the minor50V isotope. However, because V only possesses two stable isotopes it is difficult to distinguish irradiation from other processes such as stable isotope fractionation and nucleosynthetic heterogeneity that could also cause V isotope variation. Here we perform the first detailed investigation of V isotopes in ordinary and carbonaceous chondrites to investigate the origin of any variation. We also perform a three-laboratory inter-calibration for chondrites, which confirms that the different chemical separation protocols do not induce V isotope analytical artifacts as long as samples are measured using medium resolution multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS). Vanadium isotope compositions (51V/50V) of carbonaceous chondrites correlate with previously reported nucleosynthetically derived excesses in54Cr. Both51V and54Cr are the most neutron-rich of their respective elements, which may suggest that pre-solar grains rich in r-process isotopes is the primary cause of the V–Cr isotope correlation. Vanadium isotope ratios of ordinary chondrite groups and Earth form a weaker correlation with54Cr that has a different slope than observed for carbonaceous chondrites. The offset between carbonaceous and non-carbonaceous meteorites in V–Cr isotope space is similar to differences also reported for chromium, titanium, oxygen, molybdenum and ruthenium isotopes, which has been inferred to reflect the presence in the early solar system of two physically separated reservoirs. The V isotope composition of Earth is heavier than any meteorite measured to date. Therefore, V isotopes support models of Earth accretion in which a significant portion of Earth was formed from material that is not present in our meteorite collections.