Juan Bello-Rodriguez, PhD
J. Bello-Rodriguez1, D. Gregory1, M. Reynolds2
1Department of Earth Sciences, University of Toronto,Toronto, Ontario, Canada
2Northwest Territories Geological Survey, Yellowknife, NWT, Canada
The Ge-bearing Zn-Pb-Ag Prairie Creek deposit is located in the Mackenzie Mountains, NWT, adjacent to the Selwyn Basin. This region is recognized as a highly prospective area for Zn and Pb, and more recently for Ge. Ge is globally sourced from sediment-hosted Zn-Pb deposits and is mostly hosted in sphalerite (ZnS). However, the deposit-scale distribution of Ge and the local conditions that allow its enrichment remain poorly understood. Here, we investigate the trace element and sulphur isotope geochemistry of sphalerite from the Prairie Creek Deposit to refine the genetic model and elucidate the key factors influencing Ge accumulation.
The Prairie Creek deposit exhibits two main styles of mineralization: 1) stratabound massive sulfides (SMS) and 2) quartz-carbonate veins (MQV), hosted in Ordovician to Devonian sedimentary rocks (Fraser, 1996; Paradis, 2007). SMS mineralization contains mostly pyrite, sphalerite, and galena, with minor calcite and quartz, whereas MQV mineralization consists primarily of calcite and quartz with variable pyrite, sphalerite, galena, and tetrahedrite. At least two generations of sphalerite (Sp I and Sp II) are present in both styles, distinguished by texture, color, and size. LA-ICP-MS analysis of sphalerite reveals significant Ge enrichment (up to 2600 ppm) exclusively in Sp I from SMS, while Sp II from SMS and both Sp generations from MQV exhibit much lower Ge concentrations (0.1 to 100 ppm). Trace element mapping in SMS Sp I shows a spatial correlation between Ge and other elements, including Cu, Ag, and Tl. However, only Cu shows a consistent positive relationship in spot analyses, suggesting a potential substitution mechanism between Cu, Ge, and Zn. In contrast, TEM analysis indicates that Ge primarily occurs as nano-inclusions, likely Cu-Zn-Fe-Ge sulphides.
Furthermore, we are collecting in situ sulphur isotope data in sphalerite from SMS and MQV, using Secondary-Ion Mass Spectrometry (SIMS). This will allow us to distinguish the source of sulphur and reconstruct the physicochemical conditions influencing Ge incorporation in the Prairie Creek deposit.
This work will provide valuable insights into the behavior of Ge in hydrothermal fluids within sedimentary environments through combined trace element and sulphur isotope geochemistry. Ultimately, guiding strategies to enhance mineral exploration and extraction of Ge-bearing deposits in the Northwest Territories.