Project of the Week: Excellon Resources - Silver City Project (2022 Update)

11th January 2022

Happy New Year everyone!

I hope you all enjoyed time with friends, family, pets, and partners. The great thing about geology is that we can take some time away from the rocks, celebrating holidays, sharing meals, or sleeping in after a New Year’s feast, and those rocks just stay right there. And they stay for a long time! While the European mining sector may be snoozing, those rocks are waiting - and they certainly know that in the Erzgebirge mining district in Germany! One of the longest lived and most mining friendly districts in Europe, the Erzgebirge in Saxony, Germany has seen over 800 years of continuous mineral extraction for a range of resources including tungsten, zinc, copper, silver, and lead, among others.

Excellon Resources (TSX:EXN | NYSE:EXN | FRA:E4X2) became the latest company to join the fray in the Erzgebirge mining district when it picked up the option of the Silver City Project from Globex Resources in 2019. Located just 5 km north of Freiberg, Germany, the Silver City project, operated by the Excellon subsidiary, Saxony Silver Corp, is easily accessible by road throughout the year. Despite fantastic infrastructure and mining-friendly Saxon government, no modern precious metal exploration has taken place at this deposit. Let’s take a look at the new findings at Excellon’s newest project which includes the Bräunsdorf (165km2), Mohorn (57 km2), Oederan (63 km2), and Frauenstein (57 km2) licenses (Fig. 1).

Figure 1. Map of the Free State of Saxony, in eastern Germany. Dresden, the capitol of the region, is located about 60 km from the Erzgebirge Mining District.

The Silver City project at the Bräunsdorf license area hosts a suite of epithermal Ag-Au and Pb-Zn-Cu occurrences which strike over 36 km, with 12 historic mining camps located. The most recently operated is the Halsbrücke mine, which operated periodically for more than 300 years from 1602 to 1945 producing 10.3 Moz of silver. The Bräunsdorf project, on the periphery of the Freiberg epithermal vein system, is identified as one of the richest zones of the intermediate epithermal Ag deposits that make up the district (Burisch et al., 2019). Deformation of the crust during the Variscan Orogeny (~400 - 340 Ma) resulted in the uplift of the Paleozoic and Neoproterozoic basement rocks which host the epithermal mineralization that occurred later, around 275 ± 16 Ma (Swinkels et al., 2021, references within). The epithermal veins at the Bräunsdorf project dip to the northwest (45°-70°), cutting across metasedimentary units dominated by a gneiss unit surrounded by schists and phyllites (Fig. 2).  The most favorable zones for mineralization are the gneiss, schist, and mafic volcanic units, which host mineralization along lithological contacts as vein stockworks and local replacement.

Figure 2. Map of the bedrock geology and drilling results from the Bräunsdorf project. Modified from NI 43-101 Report

The mineralization consists of quartz-carbonate veins that are accompanied by significant sulfide and sulfosalt mineralization in different stages. The most valuable stage of mineralization produced Ag-bearing sulfosalt minerals such as freibergite (yes, named for the Freiberg deposits!) along with zinc sulfides (sphalerite). Boiling of a hydrothermal fluid triggered the precipitation of these minerals in extensional veins, similar to what occurred at the world-class Mexican silver deposits (check out Guanajuato Silver’s project at El Cubo). The vein and replacement mineralization at the Bräunsdorf project occurred near the boiling zone of an epithermal system and increases in silver content with shallower depths and distance from the core of the system.

Figure 3. Generalized model for intermediate- and low-sulfidation epithermal systems, along with samples from the Bräunsdorf license which correspond to the boiling zone of the epithermal deposit model.

This bodes well for Excellon Resources, who have defined several new targets around the historical mines. Already, drilling from the 2020 and 2021 campaigns has yielded multiple ore zones and Ag-bearing veins, including the discover of a 1.3m interval with 1,043 g/t silver at the Grauer Wolf target. Another exciting target is the Trinity location, which is thought to host the most distal sections of Ag mineralization (Fig. 4). Trinity focuses on those same lithological contacts which have proven so bountiful across the entire district. Airborne magnetic survey indicates that the Trinity target may host the same structural contact that holds the major silver vein at Grauer Wolf. Definitely something to keep an eye on in 2022!

Figure 4. RTP Airborne Magnetic survey map with major contacts and the newly established mafic trend, which has led to big new discoveries in the district in recent years. Veins in dark blue are known mineralized veins from the district.

In 2021, over 12 km of drill core were extracted, marking the second stage of Excellon’s drill program at Bräunsdorf. As this drilling program concludes, with final work left at Grauer Wolf, Excellon is looking forward to the 2022 campaign, set to kick off in July. Following the step-out drilling recommended by consultants and team geologists, around 9,000 m will be drilled at the Grauer Wolf, Peter Vein, and Reichenbach targets. An additional 2,100 m will be drilled along known structures hosted in other license areas around the Bräunsdorf area. Additional soil chemistry and geophysical surveys are planned, and Excellon will move forward with an advanced structural analysis of their licenses to better predict the location and continuation of known silver veins (News Release, Jan 5th ,2022). Stay tuned and up to date, as Excellon Resources welcomes us to the new Silver City!

For more on the history of the Freiberg Silver district, check out Spotlight's new mini-documentary series, premiering on Monday 17th January at 14:00 here:

https://youtu.be/Dsr1eBr0urg

References:

Burisch, M., Hartmann, A., Bach, W., Krolop, P., Krause, J. and Gutzmer, J., 2019. Genesis of hydrothermal silver-antimony-sulfide veins of the Bräunsdorf sector as part of the classic Freiberg silver mining district, Germany. Mineralium Deposita, 54(2), pp.263-280.

Swinkels, L.J., Schulz-Isenbeck, J., Frenzel, M., Gutzmer, J. and Burisch, M., 2021. Spatial and Temporal Evolution of the Freiberg Epithermal Ag-Pb-Zn District, Germany. Economic Geology.

News Release, Jan. 5, 2022, Excellon Resources http://www.excellonresources.com/news/details/index.php?content_id=317

NI 43-101 Report for the Silver City Project, September 17th, 2021 http://www.excellonresources.com/_resources/silvercity/Silver-City-Technical-Report.pdf

Silver City Technical Presentation, October 202, Excellon Resources -http://www.excellonresources.com/_resources/presentation/2021-10-Silver-City-Tech-Presentation.pdf?v=0.2

Spotlight's team recently spent 4 days with Excellon's teams touring the Silver City project.

Aaron Hantsche

View posts by Aaron Hantsche
Aaron Hantsche recently obtained his PhD in Geology from the University of Geneva in Switzerland, where he studied distal Pb-Zn skarn deposits in southern Bulgaria. Magmatic-hydrothermal deposits are his primary focus, with a bent towards geochemical vectoring tools and field geology. In addition to his work as a geologist, Aaron is a director for the science communication platform, Ore Deposits Hub. His passion for mineral deposits and geo-communication led him to join the Spotlight Mining writing team in October 2021.