Monte Amiata is a Pleistocenic volcano located in southern Tuscany at about 40 km NW of Vulsini volcanoes, where the Tuscan and the Roman magmatic provinces overlap. It is composed by trachydacitic to olivine latitic lava flows and domes emplaced in a very short time (between 305 and 231 ka; Laurenzi et al., 2015) and grouped into the “Basal Trachydacitic Complex” (BTC), the “Dome and Lava flow Complex” (DLC) and the “Olivine Latite final lavas” (OLF; Conticelli et al., 2015). The three main petrographic features are: 1) the presence of sanidine megacrysts, mostly visible in the rocks emplaced during the second phase of the volcanic activity (Ferrari et al., 1996); 2) the occurrence of abundant rounded fine-grained magmatic enclaves, which suggest that a possible mingling process occurred at Monte Amiata; 3) the presence of mafic olivine latitic lava flows, characterized by an intermediate composition between the early silica-rich volcanic rocks and the most mafic enclaves hosted in Monte Amiata volcanic,rocks. Here, we report the preliminary data about the origin, the evolution and the distribution of the magmatic enclaves hosted by Monte Amiata lavas. In order to do this, thin sections were studied under the optical microscope, chemical analyses were performed, and statistical survey on the distribution of the magmatic enclaves and their variations in size was made. These preliminary results suggest that Monte Amiata mafic enclaves vary in composition and increase in size and abundance from those hosted by domes and lavas with the highest silica contents to those with the lowest silica contents.
Study of the Monte Amiata mafic enclaves: a window into the evolution of its volcanic system
Valeriani L.
;Conticelli S.
2021-01-01
Abstract
Monte Amiata is a Pleistocenic volcano located in southern Tuscany at about 40 km NW of Vulsini volcanoes, where the Tuscan and the Roman magmatic provinces overlap. It is composed by trachydacitic to olivine latitic lava flows and domes emplaced in a very short time (between 305 and 231 ka; Laurenzi et al., 2015) and grouped into the “Basal Trachydacitic Complex” (BTC), the “Dome and Lava flow Complex” (DLC) and the “Olivine Latite final lavas” (OLF; Conticelli et al., 2015). The three main petrographic features are: 1) the presence of sanidine megacrysts, mostly visible in the rocks emplaced during the second phase of the volcanic activity (Ferrari et al., 1996); 2) the occurrence of abundant rounded fine-grained magmatic enclaves, which suggest that a possible mingling process occurred at Monte Amiata; 3) the presence of mafic olivine latitic lava flows, characterized by an intermediate composition between the early silica-rich volcanic rocks and the most mafic enclaves hosted in Monte Amiata volcanic,rocks. Here, we report the preliminary data about the origin, the evolution and the distribution of the magmatic enclaves hosted by Monte Amiata lavas. In order to do this, thin sections were studied under the optical microscope, chemical analyses were performed, and statistical survey on the distribution of the magmatic enclaves and their variations in size was made. These preliminary results suggest that Monte Amiata mafic enclaves vary in composition and increase in size and abundance from those hosted by domes and lavas with the highest silica contents to those with the lowest silica contents.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
