Confirmation of mass-independent Ni isotopic variability in iron meteorites
Confirmation of mass-independent Ni isotopic variability in iron meteorites
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DOI：
10.1016/j.gca.2011.08.030
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发表时间：
2011-12
影响因子：
5
通讯作者：
R. Steele;T. Elliott;C. Coath;M. Regelous
中科院分区：
文献类型：
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作者：
R. Steele;T. Elliott;C. Coath;M. Regelous
我们报告了对12块铁陨石的内归一化镍同位素比率的高精度分析。我们对60Ni/61Ni、62Ni/61Ni和64Ni/61Ni的测量归一化为58Ni/61Ni，并以万分之几(‱)表示，相对于NISTSRM986为ε60Ni5861、ε62Ni5861和ε64Ni5861，分别变化0.146、0.228和0.687。典型分析的精密度分别为0.03‱、0.05‱和0.08‱，分别为ε60Ni5861、ε62Ni5861和ε64Ni5861，与我们的样品重复性相当。我们指出，这种与质量无关的Ni同位素变异性不能归因于干扰、仪器或自然质量相关分馏的不准确校正、核场位移效应控制的分馏，也不能归因于宇宙线散裂的影响。因此，这些结果证明了在块状陨石样品中存在与质量无关的镍同位素不均一性，正如Regelous等人以前提出的那样。(2008年)(EPSL 272,330-338)，但我们的新分析更精确，并包括64Ni的测定。有趣的是，我们发现地球上的物质并没有产生均匀的内部标准化的镍同位素组成，正如Young等人所指出的那样。(2002)(GCA 66,1095-1104)，可能是使用指数(动力学)定律和原子质量来归一化所有分馏过程的预期结果。认证的镍同位素标准物质NISTSRM986在本研究中定义为零，而橄榄岩JP-1和DTS-2给出了适用于块状硅酸盐地球的比例，并且相对于NISTSRM986，ε60Ni5861、ε62Ni5861和ε64Ni5861的产量偏差分别为−0.006‱、0.036‱和0.119‱。在铁陨石分析中，ε64Ni5861与ε62Ni5861有很强的正相关关系，斜率为3.03±0.71。铁陨石中镍同位素异常的变化与Ia型超新星进入原太阳星云的核合成成分的不均匀分布相一致。
We report high-precision analyses of internally-normalised Ni isotope ratios in 12 bulk iron meteorites. Our measurements of60Ni/61Ni,62Ni/61Ni and64Ni/61Ni normalised to58Ni/61Ni and expressed in parts per ten thousand (‱) relative to NIST SRM 986 as ε60Ni5861,ε62Ni5861and ε64Ni5861, vary by 0.146, 0.228 and 0.687, respectively. The precision on a typical analysis is 0.03‱, 0.05‱ and 0.08‱ for ε60Ni5861, ε62Ni5861and ε64Ni5861, respectively, which is comparable to our sample reproducibility. We show that this ‘mass-independent’ Ni isotope variability cannot be ascribed to interferences, inaccurate correction of instrumental or natural mass-dependent fractionation, fractionation controlled by nuclear field shift effects, nor the influence of cosmic ray spallation. These results thus document the presence of mass-independent Ni isotopic heterogeneity in bulk meteoritic samples, as previously proposed by Regelous et al. (2008) (EPSL 272, 330–338), but our new analyses are more precise and include determination of64Ni. Intriguingly, we find that terrestrial materials do not yield homogenous internally-normalised Ni isotope compositions, which, as pointed out by Young et al. (2002) (GCA 66, 1095–1104), may be the expected result of using the exponential (kinetic) law and atomic masses to normalise all fractionation processes. The certified Ni isotope reference material NIST SRM 986 defines zero in this study, while appropriate ratios for the bulk silicate Earth are given by the peridotites JP-1 and DTS-2 and, relative to NIST SRM 986, yield deviations in ε60Ni5861, ε62Ni5861and ε64Ni5861of −0.006‱, 0.036‱ and 0.119‱, respectively. There is a strong positive correlation between ε64Ni5861and ε62Ni5861in iron meteorites analyses, with a slope of 3.03±0.71. The variations of Ni isotope anomalies in iron meteorites are consistent with heterogeneous distribution of a nucleosynthetic component from a type Ia supernova into the proto-solar nebula.