Åtvidaberg – Base- Precious Metals
- The licence area covers 225 square kilometres (“km²”) and is in the Bergslagen area, southern Sweden. The licence is valid for three years from the 30 May 2016.
- Bergslagen is one of Europe’s oldest mining districts and yielded a substantial portion of Sweden’s mineral wealth in the 1800-1900s, with several large mines and hundreds of smaller mines producing copper, zinc, lead, gold, silver, and iron ore. Current operating mines in the area include Boliden’s Garpenberg and Lundin Mining’s Zinkgruvan.
- Most of southern Bergslagen has seen little modern exploration, yet it hosts Bersbo, one of Sweden’s largest early copper mines, and Zinkgruvan, Sweden’s most important zinc mine.
- Other than at Zinkgruvan, exploration activity in Bergslagen has predominantly focused on finding new outcropping ore bodies. Some historic mining areas have not been mapped here since the early 1900s.
- The ore types that Beowulf is exploring for are amenable to modern exploration methods, and the Company hopes to build a detailed picture of what lies at shallow depth. The southern Bergslagen district comprises strong potential for the types of volcanogenic massive sulphide (“VMS”) deposits typical to the area, namely exhalative style, exemplified by the nearby Zinkgruvan mine, and replacement-reaction style, exemplified by the Falun mine.
- The licence area is divided in two by the north-northwest south-southeast striking Loftahammer-Linköping deformation zone. In both lithotectonic domains the geology consists of a sequence of metavolcanic rocks that are intruded by several granitic suites. Mineralisation in the Bersbo mine area is characterised by copper-zinc mineralisation, with some evidence of gold and silver, together with pyrrhotite, that is stratabound in interlayered felsic and mafic volcanic rocks. The mines in this area are marked by narrow aeromagnetic anomalies.
- In the western Mormors area, there are four former mines where mineralisation occurs in deformation zones in potassium-altered gneisses. The host rocks are altered to quartz-biotite-garnet schists in which chalcopyrite occurs as veins and lenses. The Mormor-type mineralisation is not obviously associated with aeromagnetic anomalies.
- Beowulf has created a Geographic Information System (“GIS”) Database, capturing significant historical data for the area. Beowulf has also established an expert team who are familiar with the area, geological setting, and style of deposit we are exploring for.
- Bersbo contains 15 small historic mines that occur at the contact of felsic and mafic volcanic rocks associated with a geophysical airborne magnetic high anomaly. The Bersbo ore occurs stratabound within interlayered felsic and mafic metavolcanic rocks. The ore is often associated with pyrrhotite, which means that aeromagnetic data can be used to trace potential mineralisation.
- The former Grönhög underground mine, situated in Bersbo, extracted copper and zinc to a depth of 250 metres (“m”).
- Mine waste dumps examined at Grönhög were found to be very rich in sphalerite, the principal ore of zinc. This suggests that past mining may have focused on copper, and that zinc ore may still be present, with the potential of undiscovered ore zones below the 250m level where mining ceased.
- “Grab” samples of sphalerite have yielded up to 19.7 per cent zinc, while waste samples with chalcopyrite, have yielded up to 1.7 per cent copper.
- Mormor contains at least 14 historic mines over a mineralised zone 5km in length and 1.5km in width. Two of the largest mines in operation were Malmviksgruvan and Mormorsgruvan.
- The ore in the Mormors area is not consistently linked to high magnetic susceptibility minerals, with aeromagnetic data for the area showing that former mines do not lie on magnetic high anomalies, but rather on the gradients.
- In contrast, electromagnetic data shows that the former mines lie on high conductivity zones, possibly resulting from the presence of conductive copper mineralisation, together with abundantly evident pyrite.
- Mineralisation occurs in retrograde shear zones in potassium-altered felsic rocks. The host rocks are often enriched in biotite and quartz, are garnet-bearing, and often show intense deformation.
- Intense alteration by silification in metavolcanics west of the Mormors mine area appears to be accompanied by an increase in magnetite, but, as yet, no significant mineralisation has been identified.
- Examination of several large waste dumps at the Malmviksgruvan mine confirmed the presence of chalcopyrite, the principal ore of copper, in thin veins contained in a pink host rock with high concentrations of potassium, possibly because of hydrothermal alteration commonly associated with this type of mineralisation.
- Mining at Malmviksgruvan ceased at approximately 150m depth, due to water ingress, and therefore it seems probable that ore will continue below this depth
- Examination of mine waste dumps at the Mormorsgruvan mine showed traces of chalcopyrite in thin veins in a quartzo-feldspathic-granitoid rock. Historic sections for the mine show the orebody to extend over 300m in length and to a depth of 407m.
- Two waste dump samples from the area have yielded 4.42 per cent and 8.46 per cent copper.
- Quartz-veined samples from dumps at Mormorsgruvan have yielded up to 2.05 ppm gold.