西非金矿床类型及时空分布规律
Genetic types of gold deposits in Western Africa and their temporal and spatial distribution
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摘要: 西非素有"黄金海岸"之称, 近年西非金矿勘查和产量不断突破新高, 已超过南非成为非洲最重要的产金区。通过系统总结西非156个有储量数据的金矿山信息发现, 西非已发现金矿储量全球占比超7%, 未来可能成为全球金矿开采与供应的重要一极。成因类型上以造山型金矿为主, 且成矿流体具有富水含碳为特征。砾岩型金矿次之, 独居特色, 其他类型矿床数量较少。西非金矿时间分布上具有广泛分布、高度集中的特点。古元古代埃布尼造山运动(2.2.~2.0 Ga)对金矿的形成具有绝对控制作用, 其他时期金矿数量相对较少。西非金矿空间分布广泛, 且具有明显的丛聚性分布特征, 集中分布于西非克拉通内的莱奥地盾区, 其他地区零星出露。根据西非金矿成矿地质背景与空间分布规律, 划分了23个Ⅳ成矿带。上述研究不仅有助于深入了解西非金矿成矿地质条件及矿床分布规律, 也对该区下步的找矿勘查部署具一定的指示意义, 更可能为该区金矿理论研究提供启示。Abstract: West Africa is known as the "Gold Coast". In recent years, the gold in West Africa prospecting exploration and production has continuously broken new highs, and it has surpassed South Africa to become the most important gold-producing region in Africa. In order to understand the geological conditions and their temporal and spatial distribution of gold deposits in West Africa, this paper systematically sorts out and summarizes 156 gold deposits in West Africa. A comprehensive study found that West Africa has discovered gold reserves accounting for more than 7% of the world, and will become an important pole of global gold mining and supply in the future. In terms of genetic type, the gold orogenic type deposit is the main type in West Africa, and its ore-forming fluid is characterized by the enrichments of water and carbon. The conglomerate type gold deposit is the second important genetic type, which is an unique type in West Africa. The gold deposits in West Africa are widely distributed and highly concentrated in time. The Eburnean Orogeny (2.2 ~2.0 Ga) in Paleoproterozoic has an absolute control on the formation of gold deposits in West Africa, and relatively few gold deposits formed in other periods. The gold deposits in West Africa are widely distributed in space and have obvious cluster distribution characteristics, which are concentrated in the Leo shield area within the West Africa Craton. Whereas, the other areas are sporadically exposed. According to the geological background and spatial distribution of gold deposits in West Africa, 23 Ⅳ metallogenic belts are firstly divided in this area. The above research is not only helpful to understand the metallogenic geological conditions and distribution rules of gold deposits in West Africa, but also could supply some indication on the next prospecting and exploration deployment, and also may provide some enlightenment for the theoretical research of gold deposits in this area.