Charles Gumiaux

Interactions between plutonism and detachments during Metamorphic Core Complex formation, Serifos Island (Cyclades, Greece)

In order to better understand the interactions between plutonic activity and strain localization during metamorphic core complexes formation the Miocene granodioritic pluton of Serifos (Cyclades, Greece) is studied. This pluton (11.6-9.5 Ma) intruded the Cycladic Blueschists during thinning of the Aegean domain along a system of low-angle normal faults belonging to the south-dipping West Cycladic Detachment System (WCDS). Based on structural fieldwork, together with microstructural observations and anisotropy of magnetic susceptibility (AMS), we recognize a continuum of deformation from magmatic to brittle conditions within the magmatic body. This succession of deformation events is kinematically compatible with the development of the WCDS. The architecture of the pluton shows a marked asymmetry resulting from its interaction with the detachments. We propose a tectonic scenario for the emplacement of Serifos pluton and its subsequent cooling during the Aegean extension. (1) A first stage corresponds to the metamorphic core complex initiation and associated southwestward shearing along the Meghalo Livadhi detachment. (2) In a second stage the Serifos pluton has intruded the dome at shallow crustal level, piercing through the ductile/brittle Meghalo Livadhi detachment. Southwest-directed extensional deformation was contemporaneously transferred upward in the crust along the more localized Kavos Kiklopas detachment. (3) A third stage was marked by syn-magmatic extensional deformation and strain localization at the contact between the pluton and the host rocks resulting in narrow shear zones nucleation which (4) continued to develop after the pluton solidification.

Tectonic inversion of an asymmetric graben: Insights from a combined field and gravity survey in the Sorbas basin

The formation of sedimentary basins in the Alboran domain is associated with the exhumation of metamorphic core complexes over a ca. 15u2009Ma period through a transition from regional late-orogenic extension to compression. An integrated study coupling field analysis and gravity data acquisition was performed in the Sorbas basin in the southeastern Betic Cordillera. Detailed field observations revealed for the first time that extensional tectonics occurred before shortening in this basin. Two extensional events were recorded with NW-SE to N-S and NE-SW kinematics respectively; the first of which being likely responsible for the basin initiation. Tectonic inversion of the basin then occurred around 8u2009Ma in an overall ca. N-S shortening context. 2D-gravity sections reveal that the basin acted as an active depocenter as the basin floor locally exceeding 2u2009km-depth is characterized by a marked asymmetric architecture. Based on this integrated study, we explore a new evolutionary scenario which can be used as a basis for interpretations of the Neogene tectonic history of the southeastern Betics.