Resumen de Geochemistry of hydrothermal systems: thermal springs of Ourense

Dawn L. Lopez, Pedro Araujo Nespereira, Isabel Delgado Outeiriño, José Ángel Cid Araújo , Gonzalo Astray Dopazo

• The thermal waters of Ourense in Galicia, Spain, have been investigated to determine their mineral equilibrium conditions. Ourense is located in the valley that Miño River has eroded in the intrusive and metamorphic rocks of the region. The area is intercepted by two fault systems that determine the water circulation in the region, with NW trending faults as the permeable features that transfer water and heat to the bottom of the valley. Equilibrium activity diagrams have been constructed to determine the equilibrium conditions of these waters with respect to the mineral assemblage K-feldspar, muscovite, clinochlore, calcite, and quartz. Waters circulating throughout granite and schist seem to approach equilibrium conditions with respect to this mineral assemblage approaching equilibrium temperatures close to 140-160 ˚C.

  The waters circulating from the North to the Miño River and throughout granite are probably describing a longer and deeper paths allowing them to reach conditions closer to equilibrium and producing mature waters.