EXTRATERRESTRIAL PLATINUM GROUP NUGGETS IN DEEP-SEA SEDIMENTS
EXTRATERRESTRIAL PLATINUM GROUP NUGGETS IN DEEP-SEA SEDIMENTS
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DOI：
10.1038/309693a0
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发表时间：
1984-01-01
期刊：
影响因子：
64.8
通讯作者：
WHEELOCK, MM
中科院分区：
文献类型：
--
作者：
BROWNLEE, DE;BATES, BA;WHEELOCK, MM
铁的宇宙球体，由围绕着铁镍金属核心的氧化铁组成，是在世纪前的HMS探测器1航行中发现的。这些球体是由大气中的陨石金属熔化而形成的，这一点得到了各种证据的支持，包括元素组成2、亚稳氧化物浮氏体3的存在、与实验室中产生的类似物的相似性4以及暴露于宇宙射线5产生的53 Mn含量。我们在这里报告一个以前未被承认的性质的领域。事实上，最常见的大于300微米的球体并不包含FeNi金属核，而是包含几乎完全由铂族元素组成的微米大小的熔核。这些元素似乎是在进入大气层时熔融的陨石金属氧化而浓缩的。这一过程在很大程度上取决于大气中氧气的相对丰度，地质记录中的金块首次出现可能提供了一个标志，表明氧气丰度何时达到目前水平的一半。
Iron cosmic spheres, composed of iron oxides surrounding a FeNi metal core, were discovered more than a century ago during the voyage of the HMSChallenger1. That tbe spheres originated by atmospheric melting of meteoritic metal is supported by a variety of evidence, including elemental composition2, the presence of the metastable oxide wustite3, similarity to analogues produced in the laboratory4and content of53Mn produced by exposure to cosmic rays5. We report here a previously unrecognized property of the spheres. The most common spheres larger than 300 µm do not, in fact, contain FeNi metal cores, but instead contain a micrometre-sized nugget composed almost entirely of platinum group elements. These elements appear to have been concentrated by the oxidation of molten meteoritic metal during atmospheric entry. This process is critically dependent on the relative abundance of oxygen in the atmosphere, and the first appearance of the nuggets in the geological record may provide a marker indicating when the oxygen abundance attained half of its present level.