Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary.
New field data integrated by fission-track (FT) analysis unravel
an innovative scenario for the post-Variscan evolution of the
eastern Anti-Atlas. This area, unaffected by Meso-Cenozoic
tectonics according to most workers, is crosscut by crustal
faults bearing evidence of a polyphase deformation history.
Apatite FT ages, ranging between 284 and 88 Ma, point to fast
Neogene exhumation and unravel contrasting cooling paths
across major faults. Results show that the study area was buried
beneath 2 km of allochthonous Variscan units, now eroded. The
eastern Anti-Atlas acted as the southern shoulder of the Atlasic
rift in the Mesozoic, and underwent a dextral transpressional
structuring of Neogene age followed by sub-meridian shortening.
The southern front of Atlasic deformation is therefore
located inside the Anti-Atlas region, and it is still active
The paleogeography of Neotethys during its closure is still a matter of debate, This study provides new insights on the Neotethys closure by the discovery in the Intra-Pontide Suture Zone (Turkey) of an accretionary complex that recorded a Late Jurassic (~163 Ma) amphibolite-facies metamorphism. These results are discussed in the framework of the accretionary events that occurred at the southern margin of Laurasia. The resulting picture supports a new model in which the Vardar suture zone, in the Balkans, and the Intra-Pontide suture zone, in Anatolia, represent remnants of the same elongate oceanic basin
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