Alteration patterns of the Kristineberg area as revealed by 3D geochemical modelling

The Palaeoproterozoic Skellefte mining district in northern Sweden is one of the most important mining regions in Europe and, as a result of decades of exploration in this area, there is an extensive collection of geochemical analyses from drill holes in this area. This research compiles data from over 3,000 samples from the Kristineberg area of this district to create an overview of the alteration patterns in 3D, and, for the first time ever, this data is being compared with the regional structural 3D model, which has also been developed for this area, to determine to what extent the current structure dominates the alteration pattern. Structurally-constrained 3D interpolations of calculated alteration indexes of drill core and outcrop samples from the hydrothermally altered zones in this area reveals an excellent correlation (from surface to c. 1,000 m depth) between the zones of most intense alteration and the localization of massive sulphide deposits. The results furthermore suggest that most of the alteration zones at surface are continuous with alteration zones at depth (possibly even deeper than 1,000 m). Comparison of the geometries and spatial distribution of these 3D interpolation volumes with 3D-modelled regional faults and lithological contacts in the Kristineberg area suggest that the regional distribution of alteration zones is controlled to a significant extent by the regional structure of the area, in particular by major S-dipping faults. Consequently, the structurally- constrained 3D geochemical model presents a new and exciting tool for the identification of prospective 3D volumes in the Kristineberg area for deep exploration. In addition, the 3D approach will allow quantifications of the total budget of mass gain and loss during hydrothermal alteration in the Kristineberg area, which will allow fundamental questions regarding the nature of the hydrothermal systems and the source of elements to be answered.Godkänd; 2014; 20140521 (reichm