Exploring for carbonate-hosted ore deposits using carbon and oxygen isotopes

Carbonate‐hosted ore deposits often have very limited mineralogical and lithogeochemical alteration halos, as the highly reactive carbonate host rocks neutralize acidic hydrothermal fluids, limiting the ability of those fluids to cause hydrothermal alteration or transport pathfinder elements into the surrounding rocks. However, carbon and oxygen stable isotope ratios in the rocks surrounding carbonate‐hosted ore deposits often record large alteration halos (on the order of hundreds of meters to kilometers) which can be used to identify and vector toward ore bodies. In this contribution we review the theory of carbon and oxygen isotope alteration during hydrothermal fluid flow, and present various case studies carried out over the last 50 years which demonstrate stable isotope alteration in carbonate‐hosted ore deposits. In particular, it is clear that world‐class ore deposits, such as the Mount Isa Cu ore bodies, and the Carlin Trend gold deposits, are surrounded by very large (3–8 kilometre) oxygen isotope alteration halos. We discuss advances in analytical technology that make stable isotope analysis a practical tool for mineral exploration, and highlight potential future advances. Finally, practical details of sampling, and factors to consider before carrying out a stable isotope study are outlined.