Transtensional shear zones controlling volcanic eruptions: the Middle Pleistocene Mt Amiata volcano (inner Northern Apenines, Italy)

The Mt Amiata volcano is characterized by the SW-NE alignment of the eruption centres, as well as other Italian Pleistocene volcanoes. We carried out a structural and kinematic analysis in a broad stripe comprehending the eruption centres and the substratum, towards NE and SW. The results point out that a transtensional left-lateral brittle shear zone affects the pre-Neogene substratum, the Middle Pleistocene volcanic rocks and the Late Pleistocene travertines. This transtensional structure is active since the Early Pliocene. It controlled the location of the eruption centres through pull-apart structures, thus providing the deep structural channels for the uprising of magma to the surface. The Mt Amiata volcano represents a key study area to investigate the Pleistocene to Present relationships between tectonics and magmatism in the Tyrrhenian area. © 2010 Blackwell Publishing Ltd.