Understanding of magmatic geothermal systems from studies of exhumed systems in continental and oceanic settings

Abstract

We contribute to the understanding of the relationships between geothermal fluid flow and geological structures studying analogous examples of exhumed geothermal systems developed in continental (Elba Island, Italy) and oceanic settings (Geitafell, Iceland). The adopted methodology follows the classical approach of structural geology, petrography and fluid inclusion studies. In both cases, field studies indicate that geothermal fluids-related hydrothermal mineralization is localized in fault damage zones which thickness is controlled by lithology and structural level. Permeable geological bodies, hydraulically connected to the main fault zones, can host hydrothermal ore deposits, indicating that fluids were channeled through the faults and were laterally stored. At Elba Island, fluid inclusion studies from veins collected at deep structural levels indicate a clear magmatic origin and P-T conditions compatible with supercritical conditions. At Geitafell, fluid inclusions studies from field and boreholes samples indicate that supercrital conditions might be occurred in the thermometamorphic aureole, close to the magmatic intrusion.