Bjurträskmineraliseringen, en Zn-Cu massiv sulfidmineralisering i Bjurträsk, Skelleftefältet, Sverige

Abstract: The Bjurträsk mineralization, a Zn-Cu rich volcanic-hosted massive sulphide (VHMS) - deposit, is located in central part of the Skellefte district. The district represents a remnant of a volcanic arc formed at 1.90-1.86 Ga and hosts more than 85 sulphide deposits whereas 5 mines are currently in operation. The investigated area covers approximately 2 x 1 km where studies of the different rock types, alteration and stratigraphic position of the mineralization relative to a neighboring VHMS deposit, Bjurliden, have been undertaken. The Bjurträsk area is dominated by dacitic to rhyolitic rocks alternating with basaltic units. The study area is affected by deformation and strong alteration, locally up to amphibolites facies where porphyroblasts of gahnite, garnet and andalusite are prominent. The alteration patterns follow and are most intense along the N-S trending transfer fault in the Bjurträsk area and to some extent also the NW-SE trending reverse fault, indicating that these fault zones have acted as conduits for hydrothermal fluids. The comparison with geochemical data of Bjurliden rocks shows that there is not a specific rock unit in the Skellefte Group stratigraphy in this area that host the VHMS-deposits, but that deposition is more structurally controlled and that intersections between transfer faults and inverted normal fault zones may be potential targets for exploration for new VHMS-deposits.