Gumsberg VMS Project - Bergslagen district
The strategically situated Gumsberg project consists of five exploration licenses in the Bergslagen Mining District of southern Sweden totaling over 18,300 hectares, where multiple zones of Volcanogenic Massive Sulfide (VMS) style mineralization occur. The VMS mineralization at Gumsberg was mined from the 13th century through the early 1900’s, with over 30 historic mines present on the property, most notably the Östrasilverberg mine which was the largest silver mine in Europe between 1300 and 1590. Despite its long- lived production history, relatively little modern exploration has taken place on the project.
New geologic interpretations, geophysical surveys and reconnaissance drilling by Boreal and partner Eurasian Minerals have led to the identification of multiple exploration targets, near the historic workings.
The Gumsberg Project is a highly prospective drill project situated in the world class Bergslagen mining district between the past producing Falun and Saxberget mines and the active Garpenberg Mine (Boliden) and Zincgruvan (Lundin) mines (Figure 1). The Gumsberg project contains approximately 27 kilometers of stratigraphy prospective for VMS containing base and precious metal mineralization. In 1939, 9 holes (728 meters) were drilled to test the depth extent of several prospects with outcropping VMS and related surface mineralization. An additional 12 holes were drilled during the Second World War and in 1958. Historical drilling data is shown in Figure 2. Boreal’s work at Gumsberg is focused on advancement of the multiple mineralized trends on the property.
In 2016 high priority, shallow drill targets were generated through a combination of mapping, sampling, geophysical surveys and compilation of historic drill data from the area. A reconnaissance diamond drilling campaign targeted exhalative-type lead-zinc-silver mineralization and replacement style zinc-lead mineralization. Four holes drilled along the > 2 kilometer long Vallberget-Loberget trend of historic mines (one of the key mineralized trends on the Gumsberg property) intersected significant intervals of mineralization (see Eurasian Mineral news release September 8th, 2016).
Results included 2.8 meters of 17.9% Zn, 6.9% Pb, 0.5% Cu, and 68.9 g/t Ag in drill hole GB16-2 at a depth of 32 meters below surface, and 3.0 meters of 9.2% Zn, 3.0% Pb, and 12.8 g/t Ag in drill hole GB16-5 at a depth of 22 meters below surface. Both drill intercepts cut exhalative style VMS mineralization, with true widths estimated to be 80-90% of the reported intervals. Replacement style mineralization was intersected by drill hole GB16-1 with an interval of 5.7 meters of 6.5% Zn (true width unknown).
The drill results demonstrate that multiple horizons of exhalative VMS style mineralization are present in the stratigraphy and contain interbedded zones of replacement style mineralization. Drilling results and a cross section from the 2016 drill program can be viewed in Figure 3 and Figure 4. Additionally, the program identified untested zones of copper-rich mineralization accompanied by pyrrhotite and intense chlorite alteration that are interpreted to represent “feeder” type structures to the exhalite and replacement styles of VMS mineralization which will be the focus of future exploration drilling.
Figure 1: The Location of Gumsberg Project, Bergslagen District, Southern Sweden
1 Grade-Tonnage information obtained from Mineral deposits and metallogeny of Fennoscandia, Geological Survey paper of Finland, Special Paper 53. Pasi Eilu Editor. 401 p. 2012.
2 Garpenberg has a proven resource of 19.7 Mt @ 96 g/t Ag, 0.3 g/t Au, 0.04% Cu, 1.6% Pb, and 3.8% Zn and a probable resource of 56.7 Mt @ 99 g/t Ag, 0.3 g/t Au, 0.05% Cu, 1.4% Pb, and 2.9% Zn (Boliden 2016 Annual Report: http://www.boliden.com/investor-relations/reports-and-presentations/annual-reports/)
Figure 2: Historical Drill Intercepts from the Gumsberg Property
Figure 3: Drill Intercepts from the 2016 Gumsberg Drill
|BH2-M||40.8||42.26||1.46||1.46m @ 20.7% Zn, 0.2% Pb||Mellangruvan|
|BH11||78.7||88.5||9.8||9.8m @ 22.9% Zn, 0.7% Pb||Mellangruvan|
|BH12||93||96.35||3.35||3.35m @ 7.3% Zn, 0.2% Pb||Mellangruvan|
|BH14||96.53||97.3||0.77||0.77m @ 30.7% Zn, 7% Pb||Mellangruvan|
|BH15||5.4||8||2.6||2.6m @ 3.5% Zn, 0% Pb||Mellangruvan|
|33.02||34.4||1.38||1.38m @ 3.5% Zn, 1.8% Pb|
|BH16||36.9||39.57||2.67||2.67m @ 10.3% Zn, 5.3% Pb||Mellangruvan|
|BH17||93.7||94.73||1.03||1.03m @ 34.3% Zn, 22.7% Pb||Mellangruvan|
|BH1-H||42.7||44.2||1.5||1.5m @ 24.3% Zn, 15.7% Pb||Hoppet|
|BH22||52.61||54.05||1.44||1.44m @ 17.2% Zn, 0.1% Pb||Hoppet|
|57.46||61.21||3.75||3.75m @ 17.1% Zn, 1.9% Pb|
|73-24||92.55||93.65||1.1||1.1m @0.71% Cu, 0.14% Zn, 8ppm Ag||Stora Lobersget|
|95.5||97||1.5||1.5m @0.44% Cu, 0.53% Zn, 14ppm Ag, 0.2ppm Au|
|98.17||99.84||1.67||1.67m @0.4% Cu, 0.14% Zn, 4ppm Ag|
|23.95||25.05||1.1||1.1m @ 0.68% Zn, 4ppm Ag, 0.2ppm Au|
|92.74||94.46||1.72||1.72m @1.43% Cu, 0.56% Zn, 8ppm Ag, 0.1ppm Au|
|95.65||97.17||1.52||1.52m @0.65% Cu, 10ppm Ag|
|73-27||58.78||59.95||1.17||1.17m @1.72% Zn, 4ppm Ag, 0.1ppm Au||Stora Lobersget|
|61.47||62.07||0.6||0.6m @1.11% Zn, 8ppm Ag, 0.1ppm Au|
|73-28||17.02||19.35||2.33||2.33m @0.79% Zn, 6ppm Ag, 0.1ppm Au||Stora Lobersget|
|19.35||20.5||1.15||1.15m @0.23% Zn, 4ppm Ag, 0.1ppm Au|
|73-29||51.52||52.1||0.58||0.58m @0.08% Cu||Stora Lobersget|
|73-33||56.56||57.38||0.82||0.82m @1.37% Zn, 0.82% Pb, 20ppm Ag, 0.1ppm Au||Hedvig|
|98.98||99.85||0.87||0.87m @8.5% Zn, 5.88% Pb, 78ppm Ag, 0.3ppm Au|
|73-34||29.6||32.35||2.75||2.75m @0.78% Zn, 6ppm Ag, 0.1ppm Au||Hedvig|
|37.7||39.4||1.7||1.7m @3.17% Zn, 14ppm Ag, 0.1ppm Au|
|73-35||159.17||160.5||1.34||1.34m @1.76% Zn||Hedvig|
|169.5||171.1||1.6||1.6m @ 0.95% Zn|
|171.1||172.5||1.35||1.35m @1.97% Zn, 0.88% Pb, 10ppm Ag, 0.1ppm Au|
|205.45||206.9||1.46||1.46m @2.8% Zn, 2.12% Pb, 20ppm Ag, 0.2ppm Au|