The Monte Amiata volcano is located in southern Tuscany, at the geographical overlap of the Tuscan magmatic province with the Roman magmatic province. It is a small Pleistocenic volcano made up prevalently by viscous lava flows and domes ranging in composition from trachydacites to olivine latites. The volcanic rocks emplaced in a very short period of time, between 305 and 231 ka (Laurenzi et al., 2015). Lava flows and domes are grouped into three main complexes, one for each stage of activity: the “Basal Trachydacitic Complex” (BTC), the “Dome and Lava flow Complex” (DLC) and the “Olivine Latite final lavas” (OLF; Conticelli et al., 2015; Marroni et al., 2015). The most important petrographic characteristics of Monte Amiata volcanic rocks are represented by: i) the occurrence of sanidine megacrysts, mostly confined in the rocks emplaced in concomitance with the second stage of the Monte Amiata volcanic activity (DLC); ii) the occurrence of rounded fine-grained mafic enclaves with cuspidate margins convex toward the host, which constitute proof of the mingling process that took place at Monte Amiata and that possibly triggered the eruptions of these highly viscous magmas; iii) the occurrence of mafic olivine latitic lava flows, emplaced as the final product of the volcanic activity and characterised by an intermediate composition between the early silica-rich volcanic rocks and the most mafic enclaves hosted by Monte Amiata volcanic rocks. Here, we present the preliminary results about the origin, the evolution, and the distribution of the mafic enclaves hosted by the Monte Amiata lavas and domes. To do this, thin sections were studied under the petrographic microscope, chemical analyses of whole rocks and enclaves and their rock-forming minerals were carried out. A statistical survey on the magmatic enclaves distribution and their size variations was also made. These preliminary results suggest that Monte Amiata mafic enclaves change in composition and increase in size and abundance from those hosted by domes and lavas with the highest silica contents to those hosted by domes and lavas with the lowest silica contents.
Study of the origin, the evolution, and the distribution of Monte Amiata mafic enclaves
Valeriani L.
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2021-01-01
Abstract
The Monte Amiata volcano is located in southern Tuscany, at the geographical overlap of the Tuscan magmatic province with the Roman magmatic province. It is a small Pleistocenic volcano made up prevalently by viscous lava flows and domes ranging in composition from trachydacites to olivine latites. The volcanic rocks emplaced in a very short period of time, between 305 and 231 ka (Laurenzi et al., 2015). Lava flows and domes are grouped into three main complexes, one for each stage of activity: the “Basal Trachydacitic Complex” (BTC), the “Dome and Lava flow Complex” (DLC) and the “Olivine Latite final lavas” (OLF; Conticelli et al., 2015; Marroni et al., 2015). The most important petrographic characteristics of Monte Amiata volcanic rocks are represented by: i) the occurrence of sanidine megacrysts, mostly confined in the rocks emplaced in concomitance with the second stage of the Monte Amiata volcanic activity (DLC); ii) the occurrence of rounded fine-grained mafic enclaves with cuspidate margins convex toward the host, which constitute proof of the mingling process that took place at Monte Amiata and that possibly triggered the eruptions of these highly viscous magmas; iii) the occurrence of mafic olivine latitic lava flows, emplaced as the final product of the volcanic activity and characterised by an intermediate composition between the early silica-rich volcanic rocks and the most mafic enclaves hosted by Monte Amiata volcanic rocks. Here, we present the preliminary results about the origin, the evolution, and the distribution of the mafic enclaves hosted by the Monte Amiata lavas and domes. To do this, thin sections were studied under the petrographic microscope, chemical analyses of whole rocks and enclaves and their rock-forming minerals were carried out. A statistical survey on the magmatic enclaves distribution and their size variations was also made. These preliminary results suggest that Monte Amiata mafic enclaves change in composition and increase in size and abundance from those hosted by domes and lavas with the highest silica contents to those hosted by domes and lavas with the lowest silica contents.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
