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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Nickel isotope heterogeneity in the early Solar System
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Nickel isotope heterogeneity in the early Solar System

机译：早期太阳系中的镍同位素异质性

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摘要

We report small but significant variations in the Ni-58/Ni-61-normalised Ni-60/Ni-61 and Ni-62/Ni-61 ratios (expressed as epsilon Ni-60 and epsilon Ni-62) of bulk iron and chondritic meteorites. Carbonaceous chondrites have variable, positive epsilon Ni-62 (0.05 to 0.25), whereas ordinary chondrites have negative epsilon Ni-62 (-0.04 to -0.09). The Ni isotope compositions of iron meteorites overlap with those of chondrites, and define an array with negative slope in the epsilon Ni-60 versus epsilon Ni-62 diagram. The Ni isotope compositions of the volatile-depleted Group IVB irons are similar to those of the refractory CO, CV carbonaceous chondrites, whereas the other common magmatic iron groups have Ni isotope compositions similar to ordinary chondrites. Only enstatite chondrites have identical Ni isotope compositions to Earth and so appear to represent the most appropriate terrestrial building material. Differences in epsilon Ni-62 reflect distinct nucleosynthetic components in precursor solids that have been variably mixed, but some of the epsilon Ni-60 variability could reflect a rachogenic component from the decay of Fe-60. Comparison of the epsilon Ni-60 of iron and chondritic meteorites with the same epsilon Ni-62 allows us to place upper limits on the Fe-60/Fe-56 of planetesimals during core segregation. We estimate that carbonaceous chondrites had initial Fe-60/Fe-56 <1 x 10(-7). Our data place less good constraints on initial Fe-60/Fe-56 ratios of ordinary chondrites but our results are not incompatible with values as high as 3 x 10(-7) as determined by in-situ measurements. We suggest that the Ni isotope variations and apparently heterogeneous initial Fe-60/Fe-56 results from physical sorting within the protosolar nebula of different phases (silicate, metal and sulphide) that carry different isotopic signatures.
机译：我们报告了散装铁的Ni-58 / Ni-61归一化Ni-60 / Ni-61和Ni-62 / Ni-61比值（表示为εNi-60和εNi-62）的微小但显着变化。粒状陨石。碳质球粒陨石的ε-NiNi-62为正值（0.05至0.25），而普通球粒陨石的ε-NiNi-62为负值（-0.04至-0.09）。铁陨石的Ni同位素组成与球粒陨石的Ni同位素组成重叠，并在epsilon Ni-60与epsilon Ni-62图中定义了具有负斜率的阵列。挥发性贫化的IVB组铁的Ni同位素组成与难熔的CO，CV碳质球粒陨石相似，而其他常见的岩浆铁基团的Ni同位素组成与普通球粒陨石相似。只有顽辉陨石球粒陨石具有与地球相同的Ni同位素组成，因此似乎代表了最合适的陆地建筑材料。 εNi-62的差异反映了已混合混合的前体固体中独特的核合成成分，但某些ε60 Ni 60的可变性可能反映了Fe 60衰变引起的致发性成分。将铁陨石的ε-60和具有相同ε-62的粒状陨石进行比较，可以使我们在核心分离过程中对小行星的Fe-60 / Fe-56设置上限。我们估计碳质球粒石的初始Fe-60 / Fe-56 <1 x 10（-7）。我们的数据对普通球粒陨石的初始Fe-60 / Fe-56比值的约束不太好，但是我们的结果与通过现场测量确定的高达3 x 10（-7）的值并不矛盾。我们认为，Ni同位素的变化和明显的非均质的Fe-60 / Fe-56最初是由带有不同同位素特征的不同相（硅酸盐，金属和硫化物）的原生质星云内的物理分选产生的。

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