Mineralogy and composition of Kuroko deposits from northeastern Honshu and their possible modern analogues from the Izu-Ogasawara (Bonin) Arc south of Japan: Implications for mode of formation
Mineralogy and composition of Kuroko deposits from northeastern Honshu and their possible modern analogues from the Izu-Ogasawara (Bonin) Arc south of Japan: Implications for mode of formation
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DOI：
10.1016/j.oregeorev.2008.09.005
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发表时间：
2008-12
影响因子：
3.3
通讯作者：
G. Glasby;K. Iizasa;M. Hannington;H. Kubota;K. Notsu
中科院分区：
文献类型：
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作者：
G. Glasby;K. Iizasa;M. Hannington;H. Kubota;K. Notsu
本州东北部的黑子矿床是研究火山成因块状硫化物矿床的重要类型存款。然而，这些矿床没有被详细研究，因为20世纪80年代初和知识的形成模式，现在是过时的。本文对伊豆-小笠原弧上的12个黑子矿床样品、12个日出存款矿床样品和6个水予海山样品进行了27种元素的分析。黑矿存款中Cd>Sb>Ag>Pb>Hg>As>Zn>Cu高度富集，Au>Te>Bi>Ba>Mo中等富集，In>Tl稍富集，Fe不明显富集。在这些矿床中，元素组合的模式相似：Zn-Pb与As、Sb、Cd、Ag、Hg、Tl和Au; Fe-Cu-Ba与As、Sb、Ag、Tl、Mo、Te和Au; Si-Ba与Ag和Au; CaSO 4。这些矿床中亲铜元素的富集与这些元素从寄主岩石中的热液沥滤相一致，在Kuroko矿床中，寄主岩石主要是流纹岩-英安岩，在日出存款中主要是流纹岩，在Suiyo海山存款中主要是英安岩-流纹岩。然而，这种模式的元素富集也类似于安山质火山的火山气凝析物中观察到的。这表明，可能有一个显着的岩浆贡献的热液流体的组成，负责形成的黑矿矿床，虽然它还不可能量化这两个来源的元素的相对贡献。成分数据表明，日出和水予海山矿床在成分上更接近东北本州的Kuroko矿床，而不是来自冲绳海槽JADE站点的海底热液矿床，平均而言，其Pb、Zn、Sb、As和Ag的浓度明显高于这些矿床。尽管与Myojin Knoll和Suiyo Seamount（活弧火山）相比，Kuroko矿床形成所在的Hokuroku盆地与冲绳海槽（陆内裂谷弧后盆地）的构造背景更相似，但Myojin Knoll和Suiyo Seamount的海底热液矿床似乎比冲绳海槽的海底热液矿床更接近Kuroko存款。目前的数据与Urabe和Marumo [Urabe，T.，Marumo，K.，1991.日本黑矿型矿床的新模式Episodes 14，246-251].
The Kuroko deposits of NE Honshu are a key type deposit for the study of volcanogenic massive sulfide deposits. However, these deposits have not been studied in detail since the early 1980's and knowledge of their mode of formation is now dated. In this study, we present the analysis of 12 samples of the Kuroko deposits, 12 samples of submarine hydrothermal minerals from the Sunrise deposit and 6 samples from Suiyo Seamount, both of which are located on the Izu-Ogasawara (Bonin) Arc, for 27 elements. For the Kuroko deposit, Cd>Sb>Ag>Pb>Hg>As>Zn>Cu are highly enriched, Au>Te>Bi>Ba>Mo are moderately enriched, In>Tl are somewhat enriched and Fe is not significantly enriched relative to the average continental crust. Within each of these deposits, a similar pattern of element associations is apparent: Zn–Pb with As, Sb, Cd, Ag, Hg, Tl and Au; Fe–Cu–Ba with As, Sb, Ag, Tl, Mo, Te and Au; Si–Ba with Ag and Au; CaSO4. The enrichment of the chalcophilic elements in these deposits is consistent with hydrothermal leaching of these elements from the host rocks which are dominantly rhyolite–dacite in the case of the Kuroko deposits, rhyolite in the case of the Sunrise deposit and dacite–rhyolite in the case of the Suiyo Seamount deposit. However, this pattern of element enrichment is also similar to that observed in fumarolic gas condensates from andesitic volcanoes. This suggests that there may be a significant magmatic contribution to the composition of the hydrothermal fluids responsible for the formation of the Kuroko deposits, although it is not yet possible to quantify the relative contributions of these two sources of elements. The compositional data show that Sunrise and Suiyo Seamount deposits are much closer compositionally to the Kuroko deposits from NE Honshu than are the submarine hydrothermal deposits from the JADE site in the Okinawa Trough which contain, on average, significantly higher concentrations of Pb, Zn, Sb, As and Ag than each of these deposits. In spite of the greater similarity in tectonic setting of the Hokuroku Basin in which the Kuroko deposits formed to the Okinawa Trough (intracontinental rifted back-arc basin) compared to Myojin Knoll and Suiyo Seamount (active arc volcanoes), it appears that submarine hydrothermal deposits from Myojin Knoll and Suiyo Seamount are closer analogues of the Kuroko deposit than are those from the Okinawa Trough. The present data are consistent with the magmatic hydrothermal model for the formation of Kuroko-type deposits as formulated by Urabe and Marumo [Urabe, T., Marumo, K., 1991. A new model for Kuroko-type deposits of Japan. Episodes 14, 246–251].