紫金山矿田Cu-Fe-S矿物的EPMA和LA-ICP-MS微区元素分析及地质意义

EPMA and LA-ICP-MS micro-analysis of Cu-Fe-S minerals in Zijinshan orefield:implications for ore genesis

应用EPMA和LA-ICP-MS微区分析技术,首次揭示了紫金矿田中铜铁硫化物的主、微量元素分布特征。研究表明紫金山铜金矿浅部蓝辉铜矿石的铜矿物具有富Se的特征,其中铜蓝中的Se最高可达1.57%,并出现Se的成分环带特征。LA-ICP-MS的微量元素分析表明蓝辉铜矿和久辉铜矿中含较高的Au(>1×10-6)和Ag,是金、银的重要载体,同时含较高含量的Bi、Sn、As和Se,与次生富集成因存在着显著的区别。紫金山铜金矿和龙江亭铜矿的斑铜矿是重要的Ag和Bi载体,不同阶段的斑铜矿的微量元素有差异,高硫化阶段的斑铜矿Bi含量较高,而中低硫化阶段的斑铜矿Ag和Sn含量较高。黄铜矿含少量的Ag,但出现了较高的In(约30×10-6),是铟的重要载体。高硫化阶段的黄铁矿具有更高的Cu和Ni。此外,矿石矿物中普遍含有较高的Se、Te、Ge和As,均表明紫金山矿田的矿床与火山活动的热液作用紧密相关。紫金山铜金矿床中出现的W、Sn、Mo、Bi和In元素异常带是一种指示斑岩型矿化向高硫化型矿化过渡的地球化学标志,指示紫金山深部具有潜在的斑岩成矿潜力。

This paper would first present the distribution of minor and trace elements in the Cu-Fe-S minerals in the deposits of Zijinshan orefield by using EPMA and LA-ICP-MS micro-analysis. The results show copper minerals from the upper Zijinshan open-pit have the distinct high Se contents, of which covellite develops the good shape of selenium zoning with the highest Se of 1. 57%. LA-ICP-MS micro-analysis showed that the digenite and djurleite contain significant concentration of Au （〉 1 × 10^-6） and Ag, and are the major gold- carrier, in which also have different trace element signatures with significant concentration of Bi, Se, and Sn compared to the secondary digenite. Bornite is the major carriers of silver and bismuth in Zijinshan orefield, and contanins alternative concentration of Bi and Ag in different mineralized stage. Bornite contains higher Bi and less Ag and Sn in the high sulfidation stage when compared to the low-middle sulfidation stage. Chalcopyrite contains less Ag but highest In contents （-30× 10^-6）, is the major indium-carrier. Besides, ore minerals in Zijinshan orefield all contain significant concentration of Se, Te, Ge and As, which implies that the mineralization in Zijinshan district was intimately related to the volcanism. The occurrence of anomalous zone of W, Sn, Mo, Bi and In in Zijinshan orefield is a potential geochemical indicator of transition between porphyry and high sulfidation mineralization, which indicates a porphyry mineralization in the depth of Zijinshan.