Contribution of the Paragenetic Sequence of Clay Minerals to Re-Examination of the Alteration Zoning in the Krafla Geothermal System

This paper revisits the clay mineralogy of “smectite” alteration zone in Krafla geo-thermal field via study an exploratory well which temperatures range from 40 °C to 215 °C. The consists several mineral assemblages superimposed time and space, resulting different stages water-rock interaction. Trioctahedral minerals (chlorite, corrensite smectite) are observed throughout studied section. These can form nearly closed systems as replacements groundmass minerals/glass after interactions with resident stagnant fluids not far chemical equilibrium (neutral basic pH conditions) or direct precipitation geothermal fluids. They locally by Al phases (smectite, illite/smectite kaolinite), result intense leaching host rocks due their interaction low under strong W/R ratios. absence mineralogical zoning is explained fact that hydrothermal strongly dependent on very recent hydrodynamics. current fluid circulation generates trioctahedral clays at depth cannot be distinguished pervasive earlier alteration. only easily detectable signature activity most relevant for exploration presence dioctahedral since it indicates activity.