Evaluation of the fluid-inclusion crushing-stage as an aid in exploration for mesothermal gold-quartz deposits

Abstract

Case studies in the Wabigoon and Uchi Archaean greenstone belts of Canada demonstrate that the liquid CO 2-bearing fluid inclusions, which are diagnostic of mesothermal gold-quartz-carbonate-sulphide deposits, may be reliably and reproducibly detected in the field by crushing-stage analysis. The technique alone cannot distinguish veins of different ore grade in a given exploration terrain, but after preliminary crushing tests to assess the composition of local metamorphic fluids, samples from potentially auriferous mesothermal deposits may be inexpensively and unequivocally identified in the field. The most powerful application of the crushing-stage is in geochemical surveys of sediments in which diagnostic fluid inclusions in quartz may offer a much wider exploration target than the related gold anomaly. Unmistakable haloes of liquid CO 2-bearing fluid inclusions are rapidly detectable in the wall rocks surrounding mesothermal veins. The haloes are spatially as extensive as the alteration mineral assemblages, and thus in field situations where outcrop is sparse or highly weathered, crushing analysis may aid in targeting areas for more detailed exploration.