HR: 1340h
AN: T13B-0468    [Abstracts]
TI: Insights Into Deformation of a Subduction Channel During the Transition From Accretion to Collision
AU: * Remitti, F
EM: remitti.francesca@unimore.it
AF: Universita' di Modena e Reggio Emilia, Largo Sant'Eufemia, 19, Modena, 41100 Italy
AU: Vannucchi, P
EM: paolav@GEO.UNIFI.IT
AF: Universita' di Firenze, Via La Pira, 4, Firenze, 50121 Italy
AU: Bettelli, G
EM: bettelli.giuseppe@unomore.it
AF: Universita' di Modena e Reggio Emilia, Largo Sant'Eufemia, 19, Modena, 41100 Italy
AB: A mèlange of Miocenic age (Sestola-Vidiciatico Unit) exposed on the Adriatic side of the Northern Apennines, Italy, has been formed during the transition from subduction to collision and it is sandwiched between the former accretionary Ligurian prism and the foreland deposits. The mèlange is made up of slices of the former accretionary prism (shales, limestones and sandstones with deformation styles ranging from coherent to disrupted or block-in-matrix fabric), sedimentary breccias due to gravitational reworking of the same units and shales, sandstones and marlstones coeval with the underthrust foreland deposits. These units have been deposited in a tectonically active environment and then transported along the dècollement to reach temperatures of at least 150° C. The marly components show pervasive brittle fracturing leading to the loss of the primary bedding, while the shales developed scaly fabric. On the contrary sandstone layers show little amounts of deformation accommodated by soft-sediment and brittle structures. This evidence testifies the control of the lithology (and lithification rate) on the onset and concentration of deformation. Soft-sediment boudinage of the layers is followed by hydroplastic conjugate shearing surfaces with no grain breakage evolving to concentrated grain breaking on the surface. The next stage is the discontinuous (crack and seal) opening of extensional fractures (P_f > σ₃) Finally, the whole mèlange is cut by a spaced network of shearing surfaces coated with calcite showing a characteristic crack and seal growth. The nature, spatial relationship and the evolution of the micro and mesostructures seem to indicate a role progressively more active of P_f while deformation tends to concentrate in more spaced structures and movement become discontinuous in time
DE: 8010 Fractures and faults
DE: 8021 Melanges
DE: 8030 Microstructures
SC: Tectonophysics [T]
MN: Fall Meeting 2005