Evolución de la corteza en limite de placas convergentes.

The thermal–mechanical evolution of crustal orogenic belts at convergent plate boundaries: A reappraisal of the orogenic cycle

Olivier Vanderhaeghe

Como evoluciona la corteza en zonas de convergencia, dependiendo de la interacción entre las diferentes fuerzas y condiciones existentes.

Dynamics of crustal wedges, orogenic plateaus, metamorphic core complexes and rifts.

Thermal–mechanical evolution of the crust at plate boundaries and the crustal tectonic cycle. The thermal–mechanical evolution of the crust at plate boundaries and the crustal tectonic cycle are illustrated by the evolution of crustal thickness and Moho temperature as a function of time. The first stage of the thermal–mechanical evolution of the crust at convergent plate boundaries is characterized by the development of a crustal wedge under a low-geothermal gradient dominated by subduction. A steady-state is reached if mass redistribution by erosion counterbalances crustal accretion. If, not thermal maturation of the crustal wedge is responsible for the weakening of the lower crust which leads to the wedge/plateau transition. At this stage, the basal traction force decomposes into Ftw beneath the plateau and Fts along its edges. A steady-state is reached if accretion is balanced by gravity-driven lateral flow of the weakened crust. A modification of the lithospheric-scale dynamics boundary condition causes the switch from crustal thickening to thinning and the mode of crustal extension ranges from metamorphic core complex to rift as a function of the rheologic state of the crust. Crustal thinning is associated with isothermal decompression and is followed by thermal subsidence.

Deformación en Italia a partir de medidas de GPS

Evidence of large scale deformation patterns from GPS data in the Italian subduction boundary doi:10.1016/j.epsl.2011.09.034
R. Devoti, A. Esposito, G. Pietrantonio, A. R. Pisani, F. Riguzzi

We present the velocity field in Italy derived from over 300 continuous GPS stations operated in the 1998–2009 time span. The GPS network maps the whole country with a mean inter-site distance of about 50 km and provides a valuable source of data to study the ongoing deformation processes in the central Mediterranean. The estimated horizontal and vertical velocity fields show major significant features and also less known second-order kinematic features. A general uplift characterizes the whole Apennines and Alpine belts that follow the topographic ridge, whereas the Po Plain shows a gradually increasing subsidence from west to east. The Apennines belt displays a distinctive extension (50–80 10−9 yr−1)while compressive tectonic regimes characterize northern Sicily, eastern Alps and the northeast front of the northern Apennines (25–50 10−9 yr−1). Second-order deformation patterns, on large scale wavelength (~100 km) have been detected on the accretionary prism of central and southern Apennines that are highly correlated with other geophysical data (Vp anomalies, seismic anisotropy, etc.) and related to deep rooted sections (70–100 km), marked by different subduction regimes. Apparently at this scale-length the observed deformations are governed by the lithosphere as a whole. We interpret these deformations as a result of different subduction mechanisms, such as variations of the subduction rollback velocity affecting different segments of the subduction zone and/or to mantle flows in proximity of the slab edges. Further south, in central-southern Sicily, we detect a
contraction of (−1.1±0.2) mm/yr that probably accommodates part of the Africa–Eurasia convergence on the outer thrust front of the Apennines–Maghrebides belt. This hypothesis agrees with an independent analysis of the seismicity associated to the Sicilian Basal Thrust, thought to be still active. The ITRF2005 estimates of the new GPS velocity field are available also in SINEX format as supplementary file S1.