Silica-water interaction in the geothermal field shown in the data of the deep drillings

Abstract

Water-Rock Interaction has an important role for spatial and temporal change of permeability in the Earth’s crust. In the geothermal field, the permeable-impermeable boundary is at around 3 km depth because of high geothermal gradient. This boundary consists of the local minimum value of quartz solubility in the Kakkonda geothermal field, Japan, due to the phase change of H₂O. In this study, quartz solubility is calculated to reveal the relationship between the permeability and dissolution-precipitation of silica minerals in the deep drilling wells in Italy, Iceland, and U.S.A., which recorded overpressure at the bottoms of them.