Juan Bello-Rodriguez, PhD

J. Bello-Rodríguez¹, D. Gregory¹, M. Reynolds^2
1Earth Sciences department, University of Toronto, Toronto, Ontario, Canada
²Northwest Territories Geological Survey, Yellowknife, NWT, Canada

Germanium (Ge) is crucial in advancing technology, especially fiber optics and high-efficiency solar cells. It is commonly recovered as a byproduct of zinc (Zn) production, which poses potential future supply risks, defining it as a critical mineral. Ge is frequently sourced from sediment-hosted Zn-Pb deposits but the deposit-scale distribution and enrichment mechanisms within these deposits remain poorly understood. To help fill this knowledge gap, we use macro- to nano-scale analytical methods to examine the Ge-bearing Zn-Pb-Ag Prairie Creek deposit in Northwest Territories, Canada. We aim to refine the genetic model of this deposit and identify key factors influencing Ge accumulation.

The Prairie Creek deposit exhibits two main mineralization styles: 1) stratiform and 2) quartz-carbonate vein, hosted in Ordovician to Devonian sedimentary rocks. Using whole-rock geochemical analysis, we determined that only the stratiform style is significantly enriched in Ge (up to 300 ppm). The results show a strong correlation between Ge and Zn, indicating that Ge content is associated with Zn-bearing mineral phases. EMPA analysis of the three major ore minerals—galena (PbS), sphalerite (ZnS), and pyrite (FeS₂)—suggests that sphalerite is the primary host for Ge. At least two generations of sphalerite (Sp I and Sp II) occur in the stratiform mineralization. LA-ICP-MS analysis of sphalerite reveals significant Ge enrichment (up to 2600 ppm) exclusively in Sp I, whereas Sp II exhibits much lower Ge concentrations (0.5 to 100 ppm). Trace element mapping shows a spatial correlation between Cu and Ge within sphalerite crystals, with spot analysis identifying a 2:1 Cu ratio. This suggests a possible relationship in their substitution mechanisms. Notwithstanding, atom probe tomography indicates that Ge primarily occurs as nano-inclusions, likely Cu-Ge sulphide minerals, within Sp I, rather than substituting for Zn in the sphalerite crystal lattice.

This work will provide valuable insights into the behavior of Ge in hydrothermal fluids within sedimentary environments, directly guiding strategies to enhance mineral exploration and extraction for Ge-bearing deposits in the Northwest Territories. By refining these strategies, it aims to better meet global demand for Ge and contribute to a sustainable future.