Abstract
This paper deals with four practically unknown, important aspects of Ordovician palaeovolcanic rocks outcropping in the area of Lago-Fontaron (province of Lugo, Spain): a) geometry in depth of volcaniclastic rocks, b) restored geology of the same units, c) detailed petrographic study and d) fundamental geochemistry and geotectonic interpretation of the altered volcaniclastic rocks. Despite the intense alteration of these rocks, collected data suggest a withinplate alkali-basalt activity in the area. The data also appear to suggest that an intense volcaniclastic activity, with eruption linked to syn-rift fractures, took place simultaneously to the sedimentation of the transitional layers of Luarca slates. The petrographic and chemical nature of the volcanics, therefore, appear to point to an extensive geodynamic framework in the Ordovician period in this area.
