Phase Separation in the Aftermath of Subseafloor Magmatic Events: An Experimental Study of Processes of Acid-Generation, Aqueous Speciation, and Vapor-Phase Transport of Fe

ABSTRACT-0751771 (Seyfried)

Intellectual Merit: This research provides an integrated series of experiments that allow the assessment of liquid-vapor partitioning, acid generating processes, and the role of redox variation on vapor-transport of Fe in NaCl-bearing systems from 380 to 500 C and 250 to 350 bars. These are important for reactions in which hot geothermal waters interact with rocks, causing mineral dissolution and precipitation as well as the generation of deep hot brines. Experiments will build from a simple NaCl-H2O-HCl system to those that include Ca and Fe where hydrolysis effects that generate acidity can be examined. Vapor transport of Fe will be determined during a series of magnetite-bearing experiments with dissolved H2 at fixed values from 2 to 100 mm/kg and concentrations greater or equal to those observed in hydrothermal systems. For the work, a novel new reactor will be developed that permits sampling of vapor and brine phases and that is fitted with in-situ chemical sensors that allow the activity of HCl in the vapor phase to be determined. Aqueous speciation, vapor-liquid partitioning, and mineral solubility effects on the composition of vapors and brines will be determined.

Broader Impacts: Broader impacts of the work include: the generation of essential data and parameters for use in a wide range of disciplines ranging from geothermal energy generation to earth science to chemical engineering to reactive transport modeling in high temperature water-rock systems. The development of the titanium reactor with in-situ chemical sensors is an important technological development and increases the infrastructure for science. The work also supports graduate and undergraduate training and the likelihood that students from groups whose gender or race is under-represented in the sciences will be engaged.