In June 2020, District Metals acquired 100% of the Tomtebo Property located in the prolific Bergslagen Mining District of south central Sweden from EMX Royalty Corp. (TSX-V:EMX). The Bergslagen is known for world class polymetallic mines such as Boliden’s Garpenberg and Lundin Mining’s Zinkgruvan. The size and scale of these mines has only been revealed within the last two decades through a better understanding of the associated polymetallic VMS/SedEx mineralizing systems, and through advances in drilling and mining technology.
Tomtebo is an advanced exploration property with the following highlights:
- Tomtebo covers an area of 5,144 ha, and is located 175 km northwest from Stockholm in Sweden.
- The forest and agricultural lands within Tomtebo are well traversed with roads, railway, and power lines. Sweden has numerous deep water ports, and five smelters are active in the Nordic region.
- Boliden’s Garpenberg Mine is located 25 km to the southeast, and the historic Falun Mine is located 25 km to the northwest. Lundin’s Zinkgruvan Mine is located 175 km to the southwest.
- Tomtebo contains the same host rocks, structure, alteration, and mineralization as the Garpenberg, Falun, and Zinkgruvan Mines.
- Two historic mines, and numerous mineralized showings are situated along more than a 17 km trend on the property. Mineralization at the historic Tomtebo and Lovas Mines appears to be open in all directions.
- Modern systematic exploration has never been carried out on the Tomtebo Property.
Figure 1: Location Map
Figure 2: Property Map
Bergslagen Mining District
The Bergslagen District is composed largely of supracrustal rocks dominated by felsic metavolcanic successions with limestones and calcsilicates, along with pre- to post-tectonic intrusive rocks located in south central Sweden. The region was folded and metamorphosed to upper amphibolite facies during the Svecofennian orogeny (1.9 to 1.8 Ga).
The district hosts thousands of mineral occurrences, including polymetallic Zn-Pb-Ag-Cu-Au sulphide and iron oxide deposits, Fe oxide skarn, banded iron formation, Fe oxide apatite, Mn oxide, and subordinate granite-pegmatite–hosted molybdenite and W skarn deposits1.
Figure 3: Bergslagen Mining District
Table 1: Bergslagen District Production, Reserves, and Resources
|Mine/Deposit||Tonnage of Production, Reserve, or Resource with Grades|
|Falun Mine1||28.1 Mt Production at 2–4% Cu, 2-4 g/t Au, 4% Zn, 1.5% Pb, 13–25 g/t Ag|
|Garpenberg Mine2||54.4 Mt Production at 132 g/t Ag, 4.9% Zn, 2.0% Pb, 0.3 g/t Au|
|Garpenberg Mine2||89.5 Mt P&P at 94 g/t Ag, 2.8% Zn, 1.3% Pb, 0.3 g/t Au, 0.04% Cu|
|Garpenberg Mine2||36.6 Mt M&I at 90 g/t Ag, 2.8% Zn, 1.4% Pb, 0.35 g/t Au, 0.06% Cu|
|Garpenberg Mine2||25.5 Mt Inferred at 57 g/t Ag, 2.5% Zn, 1.4% Pb, 0.4 g/t Au, 0.07% Cu|
|Tomtebo Mine3||0.12 Mt Production at 4.4% Cu|
|Lovas Mine4||0.33 Mt Production at 3.5% Zn, 2.5% Pb, 30g/t Ag|
|Zinkgruvan Mine5||19.3 Mt Production at 9.9% Zn, 4.0% Pb, 84 g/t Ag
0.9 Mt Production at 2.0% Cu
|Zinkgruvan Mine5||11.9 Mt P&P at 7.9% Zn, 2.9% Pb, 63 g/t Ag|
|Zinkgruvan Mine5||5.2 Mt P&P at 1.8% Cu, 0.2% Zn, 26 g/t Ag|
|Zinkgruvan Mine5||15.7 Mt M&I at 9.3% Zn, 3.7% Pb, 84 g/t Ag|
|Zinkgruvan Mine5||5.0 Mt M&I at 2.3% Cu, 0.3% Zn, 32 g/t Ag|
|Zinkgruvan Mine5||9.4 Mt Inferred at 8.5% Zn, 3.5% Pb, 81 g/t Ag|
|Zinkgruvan Mine5||0.2 Mt Inferred at 2.3% Cu, 0.3% Zn, 25 g/t Ag|
|Sala Mine1||5.0 Mt Production at 150-3000 g/t Ag, 12% Zn, 1.5% Pb|
|Stollberg (Gransgruvan Mine)6||6.7 Mt Production at 7.7% Zn, 2.6% Pb, 60 g/t Ag|
|Stollberg (Tvistbo Mine)7||0.58 Mt Production at 3.3% Zn, 2.6%, 22 g/t Ag|
|Saxberget Mine3||6.43 Mt Production at 42.2 g/t Ag, 0.4 g/t Au, 0.9% Cu, 2.2% Pb, 7.1% Zn|
|Lovisagruvan Mine8||1.15 Mt Production at 9.4% Zn, 5.3% Pb, 10-20 g/t Ag|
Mining on the Tomtebo Property can be traced back to the mid-seventeenth century. Two historic mines, and numerous mineralized prospects are situated along more than a 17 km trend on the property. Historic production at the Tomtebo Mine comprised 120,000 tonnes at 4.4% Cu3, and historic production at the Lovas Mine comprised 330,000 tonnes at 3.5% Zn, 2.5% Pb, and 30g/t Ag4. Mining depths reached down to approximately 200 m, and based on available cross sections and long sections, mineralization at the historic Tomtebo and Lovas Mines appears to be open in all directions. Comparatively, mining operations at Boliden’s Garpenberg Mine and Lundin’s Zinkgruvan Mine are currently at depths of 1250 m and 1200 m, respectively.
State owned Stora AB (Stora) conducted development drilling in the 1960’s and 1970’s from exploration drifts at the 200 m level that was used to estimate a historic resource in 1983 from surface to 200 m depth at the historic Tomtebo Mine comprised 385,000 tonnes grading 0.67% Cu, 1.84% Pb, 3.72% Zn, 0.66 g/t gold, and 55 g/t Ag9. This is a historic resource estimate for the purposes of NI 43-101, and a Qualified Person has not done sufficient work to classify the historic estimate above as current mineral resources or mineral reserves, and District is not treating the historical estimate as current mineral resources or mineral reserves. This historic resource was estimated in 1983 by Birger Hellegren in a Technical Report on the Tomtebo Mine, and it does not include any categories prescribed by NI 43-101. The key assumptions, parameters and methods used to prepare the historical estimate are not known. The Company is not aware of any more recent estimates or data relating to the historical estimate. District Metals considers these results as indications of the presence of mineralization on the property, and will use the information to guide future exploration.
The Oscarsgruvan zone is situated at the north end of the Tomtebo Mine, and is dominated by silver-zinc-lead mineralization with lesser copper-gold mineralization. The holes highlighted in Figures 4 and 5 accompanied by Table 2 below show strong mineralization associated with semi-massive and massive sulphides over a dip extent of 200 m and strike extent of 170 m that remains open.
Figure 4: Plan View of Tomtebo Mine
Figure 5: Long Section Facing South from North End of Tomtebo Mine
Table 2: Oscarsgruvan Zone Historical Drill Results
|Drill Hole||Depths and Interval||Historical Assay Results|
|Hole ID||Azimuth||Dip||Hole Type||From (m)||To (m)||Interval (m)||Ag (g/t)||Au (g/t)||Cu (%)||Zn (%)||Pb (%)||AgEq (g/t)||ZnEq (%)|
- True widths of the reported mineralized intervals have not been determined.
- Metal prices used in USD for metal equivalent calculations were based on $15.00/oz for Ag, $1650/oz for Au, $2.15/lb for Cu, $0.85/lb for Zn and $0.75/lb for Pb.
- AgEq equals = (Ag g/t x 0.76) + (Au g/t × 96.8) + (Cu% × 24.08) + (Zn% × 36.10) + (Pb% × 28.77)
- ZnEq equals = (Zn% x 0.93) + (Ag g/t × 0.02) + (Au g/t x 1.70) + (Cu% × 2.23) + (Pb% × 0.74)
- Metal equivalent calculations assume the following recoveries: 76.1% silver, 92.9% zinc, 83.9% lead, 88.0% gold, and 88.0% copper, which are derived from the Garpenberg and Zinkgruvan Mines.
- na - not assayed
- These drill results are historical in nature. District has not undertaken any independent investigation of the sampling nor has it independently analyzed the results of the historical exploration work in order to verify the results. The author of the NI 43-101 Technical Report on the Tomtebo Property has completed historical data verification and validation work, and has concluded that the historical drill results at the Tomtebo Mine do not conform to the presently accepted industry standards. District considers these historical drill results relevant as the Company will use this data as a guide to plan future exploration programs. The Company also considers the data to be reliable for these purposes, however, the Company's future exploration work will include verification of the data through drilling.
Stora operated the Falun Mine located 25 km to the northwest of Tomtebo, and the Swedish Geological Survey reported that the intention of Stora’s development drilling at the historic Tomtebo Mine was to bring it into production after the closure of the Falun Mine. Stora’s plans to develop the Tomtebo Property in 1990’s were abandoned due to a shift in business focus to forestry.
Recent Exploration Work
In 2006, approximately 20% of the Tomtebo Property was flown with SkyTEM (airborne electromagnetic survey), which at that time only had a depth penetration of approximately 200 m. The 2006 SkyTEM survey and a 2007 Induced Polarization (IP) survey was coincident with mineralization at the historic Tomtebo Mine at shallow depths, and also identified sub-parallel untested conductive anomalies.
In 2011, confirmatory drilling was conducted at the historic Tomtebo Mine with two shallow holes (less than 200 m deep each). Multiple untested projections of striking, dipping and plunging mineralization, and untested mineralized showings and conductive anomalies remain on the property.
1 Allen, R.L., Lundström, I., Ripa, M., and Christofferson, H., 1996, Facies analysis of a 1.9 Ga, continental margin, back-arc, felsic caldera province with diverse Zn-Pb-Ag-(Cu-Au) sulfide and Fe oxide deposits, Bergslagen region, Sweden: Economic Geology, v. 91, p. 979–1008.
3 Ed. Eilu, Pasi, 2012, Geological Survey of Finland, Special Paper 53, Metallogenic areas in Sweden.
4 Geological Survey of Sweden report grb_097, 1997.
5 Daffern, T., Ellis, R., King, P., Richardson, S., Glucksman, E., Beveridge, A., 2017, NI 43-101 Technical Report for the Zinkgruvan Mine, Sweden, Wardell Armstrong International.
6 Raat, H., Jansson, N.F., and Lundstam, E., 2013, The Gränsgruvan Zn-Pb-Ag deposit, an outsider in the Stollberg ore field, Bergslagen, Sweden: Geology Applied to Mineral Deposits, Biennial Meeting, 12th, Uppsala, Sweden, August 12–15, 2013, Proceedings, p. 12–15.
7 Kopparberg Mineral (unpub. annual report, 2012)
8 Jansson, N.F., Sädbom, S, Allen, R.L, Billström, K, Spry, P.G., 2018, The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis: Economic Geology (2018) 113 (3): 699–739.
9 Technical Report on Tomtebo Mine, Birger Hellegren, 1983.