Mineralogical Evolution of a Hydrothermal System II: Heat Sources -- Fluid Interactions

Abstract

Interaction between hot intrusive rocks and hydrous fluids establish and maintain high temperature hydrothermal activity. Mineralogical evidence from the Geitafell Central Volcano SE-Iceland show s that heat extraction form hot intrusive rocks may proceed via supercritical and/or superheated fluid layers into the hydrostatically controlled hydrothermal system hosted by the basaltic volcanics. In the case example two types of metamorphic and hydrothermal minerals assemblages resulted: A. The development of an inner aureole of hornfels and an outer aureole of skarn mineral at the contacts of large intrusive bodies (gabbros); the skarn minerals being produced from supercritical fluid and, B. The development of secondary mineral assemblages within shallow level intrusive, of higher grade than those existing within the host rocks at the same depths; apparently produced from superheated steam within the intrusive rocks.