Distribution, speciation and enrichment processes of germanium in high grade Mississippi Valley type Pb-Zn deposits

Mississippi Valley type (MVT) Pb-Zn deposits are becoming the main supply of germanium resources worldwide. In such deposits, sphalerite (ZnS) mineral is the main Ge-hosting mineral, which can show very contrasted Ge-contents (0-500 ppm). Such variability strongly questions the deposition conditions during the formation of the deposit. Understanding the deposit formation processes is of great importance to efficiently and sustainably exploit these rare metal deposits. In this proposal we wish to use μ-XRF mapping coupled to high-resolution μ-XANES/EXAFS at the Ge K-edge in order to, 1) identify the distribution of Ge in various sphalerite minerals showing different colors and formation stages in the deposit, 2) characterize the crystal chemistry of Ge in sphalerite (i.e., speciation and substitution modes), 3) study enrichment mechanisms of Ge in these high grade Ge-rich Pb-Zn deposits.

密西西比河谷型（Mississippi Valley type, MVT）铅锌矿床现已成为全球锗资源的主要供给来源。在这类矿床中，闪锌矿（sphalerite, ZnS）是锗的主要赋存矿物，其锗含量差异悬殊（0~500 ppm）。这种显著的含量变异，对矿床形成过程中的沉积成矿条件提出了诸多疑问。明晰矿床的形成过程，对于高效且可持续地开发这类稀有金属矿床至关重要。本项目拟采用锗K边（Ge K-edge）的微区X射线荧光（μ-XRF）成像结合高分辨微区X射线吸收近边结构（μ-XANES）/扩展X射线吸收精细结构谱（EXAFS）技术，以实现以下三个研究目标：1）厘清矿床中不同颜色、不同形成阶段的各类闪锌矿内锗的分布特征；2）阐明闪锌矿中锗的晶体化学特性（即赋存状态与置换方式）；3）探究这类富锗高品位铅锌矿床中锗的富集机制。