Experimental Simulations of Basalt-fluid Interaction at Supercritical Hydrothermal Condition (400°C – 500bar)

• Published in: Procedia earth and planetary science Vol. 17; pp. 770 - 773
• Main Authors: Passarella, Mauro, Mountain, Bruce W., Seward, Terry M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2017
• Subjects: basalt-fluid interaction; distilled water; experimental geochemistry; geothermal brine; hydrothermal; supercritical; hydrothermal; experimental geochemistry; distilled water; supercritical; basalt-fluid interaction; geothermal brine
• ISSN: 1878-5220; 1878-5220
• DOI: 10.1016/j.proeps.2017.01.022

Two experimental simulations of basalt-fluid interaction under supercritical hydrothermal conditions have been carried out to examine the relationship between fluid and secondary mineral compositions with respect to pressure-temperature conditions and time. Fresh basalt was reacted with distilled water and geothermal brine at 400°C, 500bar using a flow-through high P-T hydrothermal apparatus. Results indicate that high silica concentrations, which reached quartz saturation, early in the experiments are due to the dissolution/devitrification of volcanic glass. Low pH is attributed to the release of sulfur from the glass. In the basalt-distilled water experiment, an assemblage of grossular - amphibole (possibly actinolite) - diopside was identified while in the brine experiment hornblende - biotite appeared as secondary phases. Fluid compositions are reasonably consistent with known mineral equilibria implying that reaction rates are extremely rapid at these conditions.