Aproximacion a la hidrodinamica de los sistemas hidrotermales Liquido - dominantes asociados a yacimientos de Au-Ag. Aplicacion teorica al sector Almagrera - Herrerias (Almeria)

Los yacimientos epitermales del sector Almagrera-Herrerías parecen originados por un sistema hidrotermal asociado a celdas convectivas superficiales alimentadas por aguas meteóricas/marinas y magmáticas. La simulación matemática de un teórico sistema hidrotermal convectivo muestra la coincidencia entre las zonas mineralizadas conocidas con las zonas de descarga y acumulación de masa predecidas por el modelo. Todo ello, y la existencia de un sistema hidrotermal aún en activo, explica el interés de localizar zonas de descarga del sistema hidrogeológico actual, con el fin de profundizar en la génesis de los yacimientos conocidos y localizar posibles nuevos depósitos.

MgO/Ag(001) interface structure and STM images from first principles

The interface of MgO/Ag(001) has been studied with density functional theory applied to slabs. We have found that regular MgO films show a small adhesion to the silver substrate, the binding can be increased in off-stoichiometric regimes, either by the presence of O vacancies at the oxide film or by a small excess of O atoms at the interface between the ceramic to the metal. By means of theoretical methods, the scanning tunneling microscopy signatures of these films is also analyzed in some detail. For defect free deposits containing 1 or 2 ML and at low voltages, tunnelling takes place from the surface Ag substrate, and at large positive voltages Mg atoms are imaged. If defects, oxygen vacancies, are present on the surface of the oxide they introduce much easier channels for tunnelling resulting in big protrusions and controlling the shape of the image, the extra O stored at the interface can also be detected for very thin films.