Origins of Molybdenum, Nickel, Gold and Platinum-Group Metals in Cambrian Black Shales of Southern China

在中国南方，一种不寻常的金属组合， 钼、镍、铂族金属和金， 下寒武统黑色页岩。 这些金属尤其 集中在薄层和块状硫化物的透镜体中。Fan et （1973; 1978）报告页岩和相关块状物的价值 钼含量超过2%的硫化物层。2%镍，3%锌，700 ppb Au，200-400 ppb Pt，200-400 ppb Pb和50 ppb Ir。在某些情况下，金属 价值等于或接近于常规的矿石品位， 存款 例如，在贵州省遵义市附近的一个煤矿， 钼现在是从一个页岩结核中提取的， 硫化床 这是世界上唯一一个 从页岩中回收战略金属。 黑色页岩中的Ni- 钼铂金Au矿床分布于中国南方10个省 中国（Chen等人，1982年），并可能构成的金属资源， 巨大的经济潜力。 矿化包括金属 其通常以两种不同的关联出现：即，经典 多金属热液矿床（Zn、Au、Mo）， 与镁铁质火成岩有关的火成岩/气成岩矿床 岩石（Ni，Pt，Pd）。 考虑场域关系和文本 Chen（1988 a，B）所描述的特征，存在很好的可能性 多金属硫化物透镜体和矿床的形成 寒武纪典型的火山成因海底喷流岩。 将寻求支持这一假设的其他证据 在拟议的研究中。 但考虑到 钼等矿石的特殊地球化学行为 在碱性溶液中，也有可能 矿石金属的引入分两个阶段：（1）早期 含贵金属的球状Fe-Ni硫化物的沉淀 其次是（2）晚期 大量Mo和其他元素的表生沉淀 现代风化过程中的金属，而壮观的“塔” 中国南方岩溶地貌形成（动员 在晚前寒武纪的深层风化作用中， 因子）。 研究金属分布，结构关系， 流体包裹体和同位素的样品从关键地点， 寒武纪硫化物透镜体发育的贵州、云南和湖南 在发育良好的塔状喀斯特地形中的页岩， 将有助于区分这些可能性， 确定是否有两个阶段的矿石 沉积在中国南部的页岩中。 分析主机和 现代风化带和古风化带中及附近的围岩 裂缝将被用来评估表生的可能影响， 钼和其他元素从矿源层中活化。

In southern China an unusual association of metals including molybdenum, nickel, platinum group metals and gold occurs in Lower Cambrian black shales. These metals are especially concentrated in thin beds and lenses of massive sulfides. Fan et al. (1973; 1978) report values for shales and associated massive sulfides beds exceeding 2% Mo. 2% Ni, 3% Zn, 700 ppb Au, 200-400 ppb Pt, 200-400 ppb Pb and 50 ppb Ir. In several cases metal values are at or near what would be ore grades in conventional deposits. For example, at one mine near Zunyi, Guizhou province, molybdenum is now being extracted from a shale-hosted nodular sulfide bed. This is the only place in the world from which this strategic metal is recovered from shale. Black shale-hosted Ni- Mo-Pt-Au deposits can be traced across ten provinces in southern China (Chen et al., 1982) and may constitute a metal resource of great economic potential. The mineralization includes metal which normally occur in two distinct associations: i.e., classic polymetallic hydrothermal deposits (Zn, Au, Mo) and igneous/pneumatolitic deposits associated with mafic igneous rocks (Ni, Pt, Pd). Considering the field relations and textural features described by Chen (1988a, b), there is good possibility that the polymetallic sulfide lenses and beds were developed as classic volcanogenic submarine exhalites during the Cambrian. Additional evidence in support of this hypothesis will be sought during the proposed study. However, taking into account the peculiar geochemical behavior of molybdenum and certain other ore constituents in alkaline solutions, it is also possible that the ore metals were introduced in two stages: (1) early precipitation of precious metal-bearing nodular Fe-Ni sulfide exhalites from submarine hot springs, followed by (2) late supergene precipitation of significant amounts of Mo and other metals during modern weathering while the spectacular "tower" karst topography of southern China was formed (Mobilization of metals by deep weathering during the Late Precambrian may also be a factor). Studies of metal distributions, textural relations, fluid inclusions and isotopes for samples from key locations in Guizhou, Yunnan and Hunan where sulfide lenses occur in Cambrian shales in the midst of well-developed tower karst topography, will help to distinguish between these possibilities by establishing whether or not there were two stages of ore deposition in the shales of southern China. Analyses of host and country rocks in and near the modern weathering zone and ancient fractures will be used to assess the probable impact of supergene mobilization of Mo and other elements from source beds.