Distribution of sulfur isotopes, selenium and cobalt in the Yanahara ore deposits, Okayama-Ken, Japan
Distribution of sulfur isotopes, selenium and cobalt in the Yanahara ore deposits, Okayama-Ken, Japan
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日本冈山县柳原矿床中硫同位素、硒和钴的分布
DOI：
10.2343/geochemj.2.137
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发表时间：
1968
影响因子：
0.8
通讯作者：
H. Sakai
中科院分区：
文献类型：
--
作者：
M. Yamamoto;Nagashi Ogushi;H. Sakai
对冈山县柳原黄铁矿矿床的硫同位素、钴、硒和镍的分布进行了研究。硫化物（主要是黄铁矿）中的 Co/Fe 比值分别在 (0.02-34.7) × 10-4 范围内变化，Se/S 比值在 (0.32-38.4) × 10-5 范围内变化，而陨石硫的 δ34S 值几乎均匀分布在平均值 +2.8‰ 附近。 Kabu 矿体是最大的矿床之一，其中的钴呈明确的带状结构分布，Co/Fe 比从矿体东南边缘 (Gari-Ko) 向西侧逐渐减小。尽管钴和硒在矿体内分馏明显，但柳原矿床中Co/Fe和Se/S比值的加权平均值与地壳中的非常相似，而矿床中Ni/Fe比值远小于地壳中的值。矿床的同位素和微量元素化学特征与基于矿浆分步结晶的理论预期相一致。矿石岩浆可能是从后来的 Yanahara 侵入岩中分离出来的。当磁黄铁矿与黄铁矿共存时，钴似乎在黄铁矿中富集，而硒则出现相反的趋势。然而，富集似乎仅发生在两种矿物的接触处，并且怀疑在磁黄铁矿形成期间和/或之后边界周围的微量元素发生短程化学交换或重排。
The Yanahara pyritic ore deposits, Okayama-Ken, was investigated for the distribution of the sulfur isotopes, cobalt, selenium and nickel. The Co/Fe ratio in sulfides, mostly pyrites, varies in the range (0.02-34.7) × 10-4 and the Se/S ratio in the range (0.32-38.4) × 10-5, respectively, while δ34S values with respect to the meteoritic sulfur are almost uniformly distributed around the average, +2.8‰. Cobalt in the Kabu ore body, one of the biggest in the deposits, is distributed in a well defined zonal structure, the Co/Fe ratio decreasing from the south-eastern margin (Gari-Ko) toward the western side of the ore body. Despite of the significant intra-ore body fractionation of cobalt and selenium, the weighted averages of the Co/Fe and Se/S ratios in the Yanahara deposits are very similar to those in the crust, while the Ni/Fe ratio in the ore deposits is much smaller than that in the crust. These features in the isotopic and trace element chemistry of the deposits are shown to be compatible with those theoretically expected on the basis of fractional crystallization of an ore magma. An ore magma may have been separated from a later differentiate of the Yanahara intrusives. When pyrrhotite coexists with pyrite, cobalt seems to be enriched in pyrite, whereas the opposite trend is apparent for selenium. However, the enrichment seems to occur only at the contact of the two minerals, and short range chemical exchange or rearrangement of the trace elements around the boundary is suspected during and/or after the formation of pyrrhotite.