Surface deformation induced by pluton emplacement: the case of Amiata (Italy)

Abstract

The Amiata area was uplifted during the Pliocene as a consequence of pluton emplacement in an extensional setting. In the Middle Pleistocene, a fissural eruption filled a depression within the uplifted area. Field analysis and analogue models are integrated to study the surface deformation induced by the emplacement of the buried pluton. Field work recognized a domed overburden, ≈2.5 km high and 35 × 50 km wide. Analogue models of pluton emplacement show three stages at the surface, which consist of: doming, development of a crestal depression and apical extrusion. Theoretical calculations suggest that the bending stresses and the stretching of the brittle layer during doming induce the development of the apical depression in experiments and nature. This, in turn, is responsible for a localized decompression, enhancing extrusion. The integrated data suggests that doming, crestal depression and fissural volcanism at Amiata are sequential features due to pluton emplacement in an extensional setting.