Cenozoic volcanism and tectonics in the southern Tyrrhenian sea: space-time distribution and geodynamic significance

Short-lived magmatic episodes separated in space and time are recognizable in the southern portion of the Tyrrhenian sea and on the island of Sardinia. Distinct episodes of subduction-related calcalkaline are volcanism can be identified: on the island of Sardinia during the Oligo-Miocene (32-13 Ma), in the central part of the Tyrrhenian basin during the Pliocene (5-2 Ma), and in the active Aeolian are, the southeastern basin margin, from the middle Pleistocene to Holocene (1-0 Ma). The composition of the orogenic magmatic products in these arcs indicates the existence of a geochemical polarity of interarc type above a NW-dipping subducted slab. NW-SE migration of calcalkaline volcanic activity was accompanied by the opening of the interarc Vavilov and Marsili sub-basins in late Tortonian to early Pliocene and in the upper Pliocene, respectively. During these time intervals, volcanic activity was mainly confined within the sub-basins with emplacement of MORE-like basalts. Rift-related intra-plate volcanism occurred in the Pliocene (5-2 Ma), following the opening of the Vavilov basin, and resumed in the Quaternary (1.2-0.1 Ma) following the opening of the Marsili basin, This volcanism has a large areal distribution covering the island of Sardinia, the western Tyrrhenian margin, the Vavilov basin, the supposed central Tyrrhenian are and, sporadically, the Marsili volcanic seamount. The identified magmatic cycles allow constraints to be placed on the geodynamic evolution of the Tyrrhenian backarc basin which appears to be controlled by a rolling back subducted slab that becomes progressively steeper in time. (C) 1999 Elsevier Science Ltd. All rights reserved.