Conceptual modelling and prospecting criteria for stratiform Zn-Pb-Ag-(Cu) mineralisations in Bergslagen

Purpose and goal
The project has developed new exploration criteria and a revised genetic model for stratiform Zn-Pb-Ag deposits in Bergslagen. The emphasis has been on constraining the stratigraphic and structural context, as well as geochemical and mineralogical vectors to ore. This type of knowledge is a prerequisite for discovering new mineralisation at active mines such as Zinkgruvan and Lovisa, and new deposits in other parts of Bergslagen. The results of the project are beneficial to future exploration work in the area and may stimulate new discoveries.

Structure and implementation
The project illustrates the importance of integrating geochemical and mineralogical data with detailed stratigraphic and structural analysis during exploration. Combining these in several study areas has led to an improved understanding of the nature of the ore-forming systems. Data integration has e.g. led to improved knowledge on the mechanisms of sulphide precipitation, elemental dispersion and redox variations on the seafloor, the importance of syn-sedimentary structures, as well as how prospective stratigraphic intervals can be identified.

Results
The results allow prospective areas to be narrowed down with more precision than before, to which future exploration efforts can be focused. The zonation models developed, as well as geochemical and geological criteria, allow geochemical anomalies to be evaluated and followed-up with better accuracy. The results indicate that volcanic processes were of secondary importance to the establishment of calm, anoxic sedimentary basins for forming stratiform Zn-Pb-Ag deposits and associated stratabound Cu-(Co-Ni) deposits. This drastically affects exploration strategies.