Analysis of the fractal clustering of ore deposits in the Spanish Iberian Pyrite Belt

The Iberian Pyrite Belt (IPB) contains one of the greatest known concentrations of volcanic-hosted massive sulfides (VHMS) on Earth. Investigation of the spatial attributes of the mineralization using fractal methods, over a range of scales, and integrated within a GIS provides new information, of potential import to the exploration of VHMS deposits. At the mine-scale, stockworks, which act as feeders for hydrothermal fluids, show vein thickness distributions that are power-law (Dt ≈ 0.65 in one dimension) at length scales from about 10−2 to 102 m. Box-counting of veins indicates a capacity dimension (Dc) in the range of 1.60–1.65 in two dimensions, which is consistent with the vein thickness data. At larger scales, in the range 103 to 105 m, the distribution of mines and mineral prospects can be modelled as a fractal dust. When all the known mineral deposits and prospects are analyzed they have a capacity dimension Dc ≈ 1.3. The VHMS deposits alone have a capacity dimension Dc ≈ 0.9, indicating that they are clustered, with some indication that the ‘world-class’ deposits may be even more clustered. The different fractal analyses are integrated with information from geological and geophysical maps using a GIS. The distribution of prospects has been simulated using a simple multifractal model of the ore concentration and is constrained by known geological controls. Such a model has been implemented through the GIS.

Research highlights
► Geometry of stockworks of VHMS deposits from the IPB is fractal.
► Vein thickness distribution in stockworks is power-law at a mine-scale.
► The distribution of VHMS deposits and prospects is clustered on a regional scale.
► The spatial distribution of VHMS deposits can be simulated as multifractal systems.
► Multifractals and geological constraints modelled through GIS aid to prospectivity.