お知らせ • Oct 18
District Metals Corp. Commences Drilling At the Stollberg Property in Sweden
District Metals Corp. announced the commencement of core drilling at the high grade polymetallic Stollberg Property located 35 km to the southwest of the Tomtebo Property within the Bergslagen Mining District of south-central Sweden. The Stollberg-Tomtebo Properties are being explored in collaboration with Boliden Mineral AB. Highlights: A total of 2,200 m of drilling in five to six holes is planned at the historic Gränsgruvan Mine (operated from 1943 to 1978) located within the Stollberg Property. All drill holes will be followed up by Boliden's in-house, state of the art, down-hole, three component electromagnetic (DHEM) survey. The Stollberg Property contains similar host rocks, structure, alteration, and mineralization styles as the Garpenberg Mineralized Trend, which gives significant support in making a similar new discovery. The Stollberg Mineralized Trend is located in the Bergslagen region of the Fennoscandian shield. The Stollberg Trend comprises a 5.0 km long steeply east-dipping belt of manganese-rich, magnetite and Zn-Pb-Ag sulphide deposits hosted by marble, skarn and hydrothermally altered meta-volcanic rocks. The deposits have been mined continuously from medieval times until 1982. Most deposits in the Stollberg Mineralized Trend occur along the N-S striking eastern limb of an upright to steeply east-dipping, steeply south plunging syncline. The historic Gränsgruvan Zn- Pb-Ag Mine is located 2.0 km west of the historic Stollberg workings and is interpreted to be stratigraphically equivalent, representing the western limb of the syncline. The core of the syncline comprises meta-sediments, which are separated from the mineralized horizon by 800 m of massive to banded rhyolitic meta-volcanic rocks. These hanging-wall rocks are generally not strongly altered but locally contain abundant patchy, calc-silicate aggregates and local zones of elevated cordierite, muscovite and quartz, interpreted as regional metamorphosed syn-volcanic alteration zones. Proximal to the mineralized horizon on the eastern limb, gradation into biotite and quartz rocks with abundant porphyroblasts (locally more than 50 vol.%) of garnet, gahnite, cordierite, andalusite, sillimanite and amphibole is observed. These grade further eastward into marble and skarn, which is the main host to mineralization. Formation of these polymetallic deposits directly followed a major rhyolitic, volcanic eruption and formation of a submarine caldera. The earliest mineralization comprised exhalative iron oxides concurrent with limestone formation. Post-caldera subsidence and burial induced a shift in style of mineralization, whereby the limestone became a trap to replacement-type magnetite and Zn-Pb- Ag sulphide mineralization. The polymetallic sulphide mineralization is dominated by sphalerite (Zn), pyrrhotite, arsenopyrite and lesser chalcopyrite (Cu) and pyrite. They grade irregularly into semi-massive and locally massive sulphide bodies, which are considerably richer in galena (Pb-Ag). Average grades in the mined deposits ranged between 0.5 to 5.0% Zn, 0.5 to 15.6% Pb, and 5 to 320 g/t Ag2,3,4. Boliden acquired the historic Gränsgruvan Zn-Pb-Ag Mine in 1972 and produced 0.26 Mt at 4.8% Zn, 2.1% Pb and 29 g/t Ag down to -225 m depth until mine closure in 19784. Boliden restarted exploration activities in the Stollberg Mineralized Trend in 2000. The newly discovered mineralization at the Västansjö deposit is situated on the eastern limb of the Stollberg syncline. A mineral resource estimate, compliant with SveMin's procedures, was delineated by Boliden in 20165. Similarities in structural setting, alteration and mineralization style to the marble-skarn hosted Zn-Pb-Ag-(Cu-Au) deposit of Garpenberg imply potential for finding significant mineralization at the Stollberg Property.