Probabilistic ore systems modeling: a new tool for quantitative risk analysis and decision-making in mineral exploration

We present a new method for translating ore deposit models into a flexible, probabilistic decision-making structure that is based on the critical processes of ore formation: (1) extraction of ore components from crustal or mantle sources, (2) fluid- or melt-assisted transport of ore components from source regions to trap zones, (3) formation of 'trap' zones that can focus melt or fluid migration and accommodate large amounts of metal, and (4) operation of the physicochemical processes that promote and sustain the deposition of metal from fluids or melts passing through a particular trap site. Our modeling approach integrates these critical processes with concepts of probability theory and decision analysis, with the principal objective of making ore deposit models more quantitative, amenable for management of risk and uncertainty and suitable for communication of geological concepts to managers or financial stakeholders who do not have a geoscience background. We constructed probabilistic models for lode-gold, porphyry copper, stratiform lead-zinc and magmatic nickel-sulfide systems. These models are based on our assessment of the current state of knowledge and our personal views, prejudices and experience. However, users can easily modify the model templates to suit their own beliefs, knowledge or specific local circumstances. We do not imply that our modeling approach is superior to others, but simply that the resulting ore systems models are flexible, probabilistic and internally consistent, and structured according to previously published petroleum and mineral systems approaches.