An intergrated physical and chemical model for silica transport and deposition in sub-seafloor magmatic-hydrothermal environments

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The Earth is a geologically active system in which new crust is continuously being generated at mid-ocean ridge spreading centers. Cold seawater flows into the sub-seafloor, is heated, and interacts with the basalt, altering the composition of both the rocks and the seawater. As a result, hydrothermal activity at oceanic spreading centers exerts a major influence on ocean chemistry and significantly affects the composition of oceanic lithosphere that is eventually recycled back into the mantle at subduction zones. These same mid-ocean ridge hydrothermal systems are often associated with the formation of valuable mineral deposits that are important sources of copper, zinc and silver. Because the silica content of hydrothermal fluids being vented onto the seafloor is often used to indicate the temperature and depth of the base of the hydrothermal system, i.e., at the top of the magma chamber, this research examines the role of immiscibility on silica transport and deposition in the submarine hydrothermal environment through the development of modeling software and computer simulations. Work involves incorporating thermodynamic data for relevant dissolved aqueous species into a newly developed transport code called FISHES which includes the effects of boiling (i.e., phase separation) and two phase flow. The result should be a dramatic improvement of our ability to infer sub-seafloor conditions based on vent fluid chemistry and to predict where economic mineral occurrences.