Heavy nitrogen in Bencubbin—a light-element isotopic anomaly in a stony-iron meteorite
Heavy nitrogen in Bencubbin—a light-element isotopic anomaly in a stony-iron meteorite
复制标题
Bencubbin 中的重氮——石铁陨石中的轻元素同位素异常
作者：
I. Franchi;I. Wright;C. Pillinger
到目前为止，轻元素同位素异常仅限于原始球粒陨石。Bencubbin是在澳大利亚发现的一种不寻常的角砾岩，含有60-75%的金属，硅酸盐和球粒陨石碎屑1 - 4，在一个激波焊接的基体中5,6，已经被证明含有前所未有的富集（2倍）15N，可能是一种在太阳星云中逃脱均质化的核合成产物。本库宾的氮几乎全部富集，δ15N最大值为+ 1033‰。氮存在于两种耐酸成分中，其中一种比另一种更耐酸，它们以不同的比例存在于金属和硅酸盐中。较强的抗性成分可能是碳质成分，具有异常低的C:N比，并且没有异常的碳同位素组成（δ13C≃+25%‰）。另一个可能的宿主是一种富含铬的硫化物，这表明在超新星中进行了处理。
Until now, light-element isotopic anomalies have been confined to primitive chondritic meteorites. Bencubbin, an unusual breccia found in Australia, comprising 60–75% metal with silicate and chondritic clasts1–4 in a shock-welded matrix5,6, has been shown7–9 to contain an unprecedented enrichment (by a factor of 2) of 15N, presumably a nucleosynthetic product which escaped homogeniz-ation in the solar nebula. Here we show that virtually all the nitrogen in Bencubbin is enriched, with a maximum δ15N of +1,033‰. The nitrogen resides in two acid-resistant components, one more so than the other, which are present in different proportions in the metal and silicate. The more resistant component could be carbonaceous, with an unusually low C:N ratio and without an anomalous carbon isotopic composition (δ13C ≃ +25%‰). Another possible host is a chromium-rich sulphide, which would indicate processing in a supernova10.