THE ROLE OF REGIONAL GROUNDWATER FLOW IN THE FORMATION OF SEDIMENT-HOSTED ORE DEPOSITS

Most of the world's largest deposits of iron, copper, lead, zinc, uranium, and gold are found in ancient sedimentary rocks, and many of these deposits were formed by the migration of deep groundwater in sedimentary basins. Geochemical and petrologic aspects of these sediment-hosted ore deposits were mostly well known by the middle part of the 20th century, but the geohydrologic aspects resulting in their formation and subsequent alteration/weathering were not understood until much later. As hydrogeologists began to quantify the physics of regional groundwater flow (based on field observations, flow net construction, physical and electrical analogs, and numerical modeling), a clearer picture began to emerge on how these ore deposits likely formed. The pioneering studies of Toth-Freeze-Witherspoon on the theory and geologic manifestations of regional groundwater provided the foundation for later studies.

In this presentation, I review a few case studies to illustrate the remarkable success that has been made in applying the regional flow theory of Professor Joe Toth to the study of hydrothermal/sediment-hosted ores.