El potencial didáctico del afloramiento granítico de El Berrocal (Geoparque Sierra Norte de Sevilla)procesos sin-magmáticos

Abstract

One of the most representative geomorphologies of the Sierra Norte de Sevilla Geopark is the one that is developed on gra- nitic rocks (e.g., Moreno et al., 2008) and still, the geosites catalogue of the Geopark does not include any that illustrate about the magmatic processes that took place during the genesis of such rocks. To advance in this issue, we present here the detailed cartography of an outcrop of the El Berrocal granite (Almadén de la Plata). The high quality of this outcrop allows one to directly observe several magmatic structures. The El Berrocal pluton is mostly composed of leucocratic granite, which shows in the studied outcrop several centi- to decimetric bodies of tonalite. Lobulated contacts suggest both phases were in the magmatic state when they get in contact. A detailed analysis of these contacts reveals opposite relative viscosity relations- hips, although those indicating a higher viscosity of the granitic magma predominate. These include some cooling margins in the tonalite, as well as granite back-veining. These observations suggest that when interaction between magmas occurred, the temperature of the system would be slightly below the viscosity inversion temperature between two systems with different compositions. Therefore, we believe this is an outcrop with a high didactic potential for igneous processes, helpful to show the development of a magmatic interaction zone by the intrusion of a tonalitic syn-plutonic dyke into a granitic magma chamber.