Ore deposits and related mineral alteration are often associated with silica-rich igneous rocks. These igneous intrusions have been hypothesized to evolve one or more water and chlorine-rich fluid phases, which contribute to mineral alteration and nearby ore deposition. The hydrochloric acid (HCl) concentration within this magmatic volatile phase has been shown to influence mineral stability, the behavior of metals and the mechanisms of ore precipitation. The extent to which HCl influences these processes is unknown because there is a dearth of experimental data with which to test current hypotheses on the extent to which volatile phases influence mineral alteration and metal transport. A succession of experiments will be conducted to address this lack of fundamental knowledge.
This study will examine the activity of HCl at pressures and temperatures of the magmatic-hydrothermal system, 600-750C, where metals are partitioned from a crystallizing felsic melt and deposited in the high-temperature portion of the system. Additionally, the proposed research will compile important data regarding the activity of HCl in both high-salinity brines and supercritical fluids in select mineral systems. Our study will address these systems collectively over a range of salinities within the vapor-undersaturated brine and supercritical fluid phase fields at temperatures from 600-750C and 50-140 MPa with applications to the broader magmatic-hydrothermal system. An undergraduate student and a graduate student will participate in this research project and will be trained in experimental geology, thermodynamics, and geochemistry. The graduate students will also mentor the more junior members involved in this project. The results of this research can provide direct economic benefits by improving existing metal exploration models associated with high-temperature ore deposits.
