Metalliferous black slates consisting of black slates and interbedded coaly slates in the Okcheon Metamorphic Belt of South Korea were analyzed for redox-sensitive trace elements and rare earth elements (REEs) to examine their depositional conditions. Our data show that the coaly slates have elevated concentrations of redox-sensitive trace metals (U, V, Mo, and Cr), low Mn contents, high V/(V + Ni), V/Cr, and U/Th ratios, and high total organic carbon (TOC) contents. A general tendency of positive correlation between TOC and trace metals was established. The results suggest that the coaly slates were developed under a strongly reducing environment, while the black slates were deposited under a suboxic-oxic condition. The REE patterns of the coaly slates typically show positive Eu and negative Ce anomalies compared to the North American Shale Composite reference and they are essentially inherited from submarine hydrothermal fluids under high temperature reducing condition. The enrichment of the redox-sensitive elements including V (up to 3,564 ppm) and Mo (up to 358 ppm) may have been controlled by direct hydrothermal input of metals into the rift basin from hydrothermal vents, proximal from the vent sites, as supported by textural evidences, and the metals could have been fixed from seawater by means of scavenging process via exhalative oxide particles in a hydrothermal plume. The sorption of metals from seawater under anoxic conditions into organic-rich sediments occurred as well. The metal enrichments in the black slates seem to have been achieved in somewhat similar way to black shales in South China.

中文翻译：

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韩国Okcheon变质带中含金属的黑色板岩中对氧化还原敏感的微量元素的沉积环境

分析了韩国Okcheon变质带中含金属的黑色板岩和层状煤板岩中的氧化还原敏感的痕量元素和稀土元素（REEs），以检查其沉积条件。我们的数据表明，煤板岩具有较高的氧化还原敏感性痕量金属（U，V，Mo和Cr）浓度，低Mn含量，高V /（V + Ni），V / Cr和U / Th比，以及高的总有机碳（TOC）含量。建立了总有机碳和痕量金属之间正相关的总体趋势。结果表明，煤板岩是在强烈还原的环境下发育的，而黑板岩是在低氧-高氧条件下沉积的。与北美页岩复合参考相比，煤岩板岩的REE模式通常表现出正Eu异常和Ce负异常，并且它们基本上是从高温还原条件下的海底热液中继承而来的。可以通过将金属直接从热液喷口向裂谷盆地中的热液输入（靠近喷口部位）来控制氧化还原敏感元素（包括V（高达3,564 ppm）和Mo（高达358 ppm））的富集。根据结构上的证据，这些金属本来可以通过清除过程通过热液羽流中的呼出氧化物颗粒从海水中固定下来的。在缺氧条件下，海水中的金属也被吸附到富含有机物的沉积物中。