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The thrust zone of the Ligurian Penninic basal contact (Monte Fronté, Ligurian Alps, Italy)
No full textThis paper presents a geological map and interpretative cross-sections, which illustrate the structure of a major fault zone of the Alps, that is, the Ligurian segment of the Penninic Basal Contact (PBC), which led to the emplacement of the orogenic wedge onto the European crust. Chaotic deposits, whose origin is debated, characterize the footwall of this complex thrust zone. The lower part of the sequence containing chaotic deposits consists of low deformed paraconglomerates and exotic megablocks embedded with turbidites. Conversely, the highly deformed upper part of the sequence englobes fragments of substratum-derived succession and is bounded by thrust planes. The nature of these chaotic deposits suggests an origin by gravitational processes related to the unstable front of the advancing wedge associated with offscraping of tectonic slices during the thrusting of allochtonous nappes along the PBC thrust zon
The M. Sotta Piedmont Unit (Central Ligurian Alps): new stratigraphic and structural framework
No full text2D-thermo-mechanical modelling of spatial P-T variations in heterogeneous shear zones
Full text linkWe present a suite of two-dimensional thermo-mechanical
simulations of a compositionally heterogeneous shear zone
characterized by viscous matrix and inclusions. The experiments
have been performed using a visco-elasto-plastic 2D finite difference
code that reproduces the stress, strain, temperature and pressure
variations occurring within the shear zone at lithospheric scale. From
here, we extrapolated and discuss the results of a narrow (<10 km)
domain where strong inclusions with respect to a weaker matrix are
inserted. The experimental setting simulates the geological conditions
common to several (ultra-) high-pressure (U-HP) rocks worldwide.
Particularly, we shaped the model in order to roughly reproduce the
distribution of the (U)HP ultramafic rocks of the Adula-Cima Lunga
nappe system. Results indicate that significant overpressure (up to
0.3 GPa) within the strong inclusions and viscous shear heating (up
to 100°C) can be generated already with a short time of deformation
(ca. 1.2 Myr) in small rock units. These data suggest that, in specific
structural domains, pressure and temperature deviations may play a
not trivial role in the pressure-temperature-time paths recorded by
the rocks through the metamorphic reactions
Carta Geologica della Regione Liguria alla scala 1:10000; 228140 Calizzano, Progetto CARG Foglio 228 Cairo Montenotte.
No full textU-Pb chronological constraints for the late- and post-orogenic episodes in the Ligurian Variscides
No full textU-Pb dating and geodynamic implication of post-Variscan magmatism in the Briançonnais Domain (Ligurian Alps, Italy).
No full textThe Permian volcanic record in the Ligurian Alps (Northern Italy): from the Variscan towards the Alpine cycle.
No full text
Carta Geologica della Regione Liguria alla scala 1:10000; 228130, Monte Spinarda. Progetto CARG, Foglio 228 Cairo Montenotte
No full textU–Pb zircon geochronological and petrographic constraints on late to post-collisional Variscan magmatism and metamorphism in the Ligurian Alps, Italy
No full textIn the Ligurian Alps, the Barbassiria massif (a Variscan basement unit of the Brianconnais domain) is made up of orthogneisses derived from K-rich rhyolite protoliths and minor rhyolite dykes. However, on account of subsequent Alpine deformation and a related blueschist facies metamorphic overprint that are pervasive within the Barbassiria Orthogneisses, little evidence of the earlier Variscan metamorphism is preserved. In this study, new UPb laser ablationinductively coupled plasmamass spectrometry (LAICPMS) dating of zircon from the Barbassiria Orthogneisses and dykes was undertaken to unravel the relationships between protolith magmatism and the Variscan metamorphic overprint. The results suggest a protolith age for the Barbassiria Orthogneisses of similar to 315320 Ma (i.e., Early/Late Carboniferous), and constrain the age of a subsequent rhyolite dyke emplacement event to 260.2 +/- 3.1Ma (i.e., Late Permian). The Variscan high-temperature (greenschistamphibolite facies) metamorphic event that affected the Barbassiria Orthogneisses was likely associated with both tectonic burial and compression during the final stages of the Variscan collision during the Late Carboniferous period. Emplacement of late-stage rhyolite dykes that cut the Barbassiria Orthogneisses is linked to a diffuse episode of Late Permian rhyolite volcanism that is commonly observed in the Ligurian Alps. The age of this dyke emplacement event followed a similar to 1015Ma Mid-Permian gap in the volcano-sedimentary cover sequence of the Ligurian Alps, and represents the post-orogenic stage in this segment of the Variscides
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