贵州晴隆丁头山铅锌矿床硒超常富集新发现及其地质意义

位于扬子板块西南缘的川滇黔接壤区,处于全球特提斯成矿域和环太平洋成矿域交汇部位、峨眉山大火成岩省内,成矿背景极其特殊,形成了独具特色的优势紧缺矿产(铅锌)、战略性关键矿产(稀散元素)为代表的大型-超大型矿床及相关的成矿系统。黔西北地区是川滇黔富稀散元素铅锌特色成矿系统的重要组成部分之一,近年来找矿不断取得重要突破。位于黔西北成矿区南部的丁头山铅锌矿床,是近期找矿突破的一个代表。通过对丁头山矿床闪锌矿LA-ICPMS原位微量元素分析,发现了该矿床Se显著超常富集现象,所测试的90个测点中w(Se)介于19.7×10-6～172×10-6,平均含量81.0×10-6,显著高于Se的地壳丰度(0.05×10-6)和整个扬子板块周缘同类型矿床硫化物的w(Se)(通常50×10-6),暗示其成矿环境极为特殊,很可能与研究区成矿背景有关。通过相关分析,发现丁头山矿床闪锌矿中Se并非直接替代Zn,而是很可能与Cd、In和Fe一起联合置换Zn,即Fe+Cd+Se+In?4Zn,是一种新的替代方式。丁头山矿床Se超常富集新发现,对理解稀散元素共生分异与超常富集成矿作用具有重要意义,同时表明丁头山矿区及外围具有良好的Se资源潜力,应加强系统勘查和深入研究工作。

New discovery of extraordinary enrichment of selenium in Dingtoushan Pb-Zn deposit, Qinglong City, Guizhou Province, and its geological significance

Located in southwestern Yangtze Block, the Sichuan-Yunnan-Guizhou border area (SYG) is situated at the intersection of the global Tethys ore-forming domain and the Pacific Rim ore-forming domain, and within the Emeishan large igneous province. Rare shortage (Pb-Zn) and critical minerals (dispersed elements) formed large-scale and ultra-large scale ore deposits and related metallogenic systems. Northwest Guizhou area is one of the important components of the SYG dispersed elements-rich Pb-Zn metallogenic province. The Dingtoushan Pb-Zn deposit, located in the southern part of the northwest Guizhou dispersed elements-rich Pb-Zn metallogenic area, is a representative of recent prospecting breakthroughs. Through LA-ICPMS in-situ trace elements analysis of sphalerite from the Dingtoushan deposit, the authors found that the selenium in this deposit is extraordinary enriched, and the Se values in 90 analytical points are between 19.7×10^-6 and 172×10^-6, with an average value of 81.0×10^-6, which are significantly higher than the Se crustal abundance (0.05×10^-6) and the Se content of the same type of deposits around the Yangtze Block (usually<50×10^-6), implying that its metallogenic environment is very special. This is probably related to the geological background. Through correlation analysis, the authors also found that Se in sphalerite from the Dingtoushan deposit is not a direct replacement for Zn, but it is likely to replace Zn together with Cd, In and Fe, that is, Fe+Cd+Se+In↔4Zn, which is a new replacement form. The new discovery of extraordinary enrichment of selenium in the Dingtoushan Pb-Zn deposit is of great significance for understanding the associated differentiation and superabundant enrichment, and it also shows that the Dingtoushan mining area and its periphery have good selenium resource potential. Hence, the ore exploration and in-depth research should be strengthened.