Aspects of Mineral Exploration Thinking

Editor’s note: The aim of the Geology and Mining series is to introduce early career professionals and students to various aspects of mineral exploration, development, and mining in order to share the experiences and insight of each author on the myriad of topics involved with the mineral industry and the ways in which geoscientists contribute to each. Abstract Successful exploration requires an understanding of ore deposit models, the experience to recognize ore guides in an outcrop, nonlinear thinking, and some intuition. Models, using porphyry Cu deposits as examples, combine magmatic and hydrothermal processes; however, process and the results of process are different. Models provide important understanding of process but are not ore guides and do not drive discoveries; models function as rules that inhibit prediscovery exploration thinking. Results of the genetic process are recorded in descriptive models that do not reflect the considerable geologic variations existing between the hundreds of known porphyry Cu deposits. Discoveries and discovery cycles are driven by nonlinear thinking about ore guides visible in outcrop, not by genetic or descriptive models. Reality in an outcrop typically departs from generalized models. Reinterpretations that lead to drilling prospects rejected by previous exploration groups is what makes many discoveries. Increasingly, field-portable instruments for mineral and chemical analyses will add efficiencies. The most important product of early exploration work is the geologic map, defined here as a decision-making document. Mapping of ore guides in any ore-forming system invariably leads to sampling of outcrops where high grading can help geologists rig the odds in their favor. However, the objective is a highly profitable mine, not just a high-grade sample. That means the mineralization must be sufficiently continuous to build the inventory of recoverable metal required for a profitable mine, regardless of grade. High grade gets you interested, but continuity gets the mine. The principal intangible in any discovery is intuition, often described as nothing more or less than recognition, and it invariably involves experience. Perhaps the only tangible expression of intuition is displayed by individuals or teams that are unwilling to abandon a complex prospect, a behavior often described in case histories as tenacity.