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.