安徽庐枞盆地西湾铅锌矿床闪锌矿中镉的赋存状态和富集机制研究

镉(Cd)是一种重要的关键金属元素, 对国家安全和新兴产业发展具有重大意义。闪锌矿是最具经济意义的富镉矿物, 查明闪锌矿中镉的赋存状态, 对研究镉的富集机制具有重要的意义; 但受限于研究手段, 闪锌矿纳米尺度上镉的赋存状态研究仍相对薄弱。西湾矿床是长江中下游成矿带庐枞矿集区内新发现的大型铅锌矿床, 矿床中产出富镉闪锌矿。本次研究使用LA-ICP-MS对闪锌矿进行原位微量元素含量和Mapping分析, 查明闪锌矿微米尺度镉的分布规律; 在此基础上使用扫描透射电镜(STEM)查明纳米级闪锌矿的微观形貌和高分辨原子像, 明确纳米尺度镉的赋存状态。研究结果表明, 西湾矿床闪锌矿中镉含量的变化范围为2186×10^-6~9859×10^-6, 镉在闪锌矿中分布不均匀, 闪锌矿孔洞发育的区域相对富镉, 而闪锌矿均质区域相对贫镉。通过高分辨原子像的晶面间距和原子线扫描结果, 确定西湾矿床闪锌矿中Cd原子以原位替代Zn原子的形式赋存在闪锌矿晶格中, 未发现纳米级镉的独立矿物。对比金顶和牛角塘等富镉铅锌矿床, 长江中下游成矿带的铅锌矿床中平均镉含量不高, 推测成矿带可能缺乏充足的镉物质来源。

Occurrence state and enrichment mechanism of cadmium in sphalerite of Xiwan lead-zinc deposit in Luzong basin,Anhui Province,China

Cadmium (Cd) is an important key metal mineral resource that is of significant implications for national security and emerging industries' development. Sphalerite is the most economically significant Cd-rich mineral, therefore, finding out the occurrence state of cadmium in sphalerite is of great significance for studying the enrichment mechanism of cadmium. However, limited by research means, the research on the occurrence of cadmium in sphalerite at the nanoscale is relatively weak. The Xiwan deposit is a large lead-zinc deposit newly discovered in the Luzong basin of the Middle-Lower Yangtze River Metallogenic Belt (MLYRMB). In this study, LA-ICP-MS was used to carry out in situ trace element content and mapping analysis on sphalerite to reveal the distribution of cadmium in sphalerite on the micron scale. On the basis, scanning transmission electron microscope (STEM) was used to photograph the micro morphology and high-resolution atomic phase of nano sphalerite to find out the occurrence state of cadmium in nano scale. The research results show that the content of cadmium varies from 2186×10-6 to 9859×10-6, and the distribution of cadmium in sphalerite is uneven. The area with holes in sphalerite is rich in cadmium while the homogeneous area is relatively poor in cadmium. Based on the crystal plane spacing of high-resolution atomic image and atomic line scanning results, it is determined that Cd atoms in sphalerite of Xiwan deposit exist in sphalerite lattice in the form of in-situ replacement of Zn atoms, and no nano scale independent minerals were found. Compared to Cd-rich lead-zinc deposits such as Jinding and Niujiaotang, lead-zinc deposits in the MLYRMB generally have relatively low cadmium content. It is speculated that there may be a lack of sufficient sources of cadmium material within the MLYRMB.