Quantitative mineral resource assessment of undiscovered PGE resources in Finland

摘要

Most of the known platinum group element (PGE) resources in Finland are in contact-type and reef-type deposits in 2.45 Ga mafic–ultramafic layered intrusions. These intrusions are also estimated to contain the majority of possibly existing, yet undiscovered PGE resources in Finland. The undiscovered Pt, Pd, Au, Ni, and Cu resources in contact-type and reef-type deposits were estimated down to 1000 m depth using a three-part quantitative assessment method. This included the delineation of 19 contact-type and 24 reef-type permissive tracts, the formulation of a grade-tonnage model for the contact-type deposits and a separate model for each reef-type tract, estimation of the number of undiscovered deposits for each permissive tract, and Monte Carlo simulation to estimate the frequency distributions of metal tonnages in the undiscovered deposits. The expected number of undiscovered contact-type deposits is 29 and that of reef-type deposits is 23. At the 50% probability level, the total undiscovered PGE resources of Finland are estimated to be at least 5600 t Pt, 12,000 t Pd, 430 t Au, 4.2 Mt Ni, and 5.7 Mt Cu. At the 90% probability level, the corresponding tonnages are 720 t Pt, 1700 t Pd, 59 t Au, 0.87 Mt Ni, and 0.91 Mt Cu. More than 80% of the Pt+Pd in the undiscovered resources are estimated to be in reef-type deposits. The known PGE resources in Finland are 259 t Pt+Pd in six contact-type deposits, plus 69 t Pt+Pd in the atypical Kevitsa deposit. These figures indicate that the presently known deposits account for approximately 2% of the total assessed PGE resources in Finland. They suggest that significant potential exists for the discovery of additional PGE resources in the country.