Structure and metamorphism of the Gran Paradiso massif, western Alps, Italy

Brouwer, Fraukje M.; Vissers, R. L. M.; Lamb, William M.

doi:10.1007/s00410-002-0357-6

Cited by 40 publications

(48 citation statements)

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“…The rectangle shows the location of the study area. massif, outcropping to the SE of the P-L oceanic unit, again belongs to the Briançonnais domain and represents the internal basement massif situated in our study area (Brouwer et al 2002). The "Internal Massifs" are interpreted to paleogeographically represent the most internal basement units, situated next to the P-L oceanic unit.…”

Section: Geological Settingmentioning

confidence: 99%

Tectonic evolution of the Briançonnais units along a transect (ECORS-CROP) through the Italian-French Western Alps

Bucher¹,

Ulardic

Bousquet³

et al. 2004

Eclogae geol. Helv.

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Based on new structural data from an area in the Italian-French Western Alps, situated between the Petit Saint Bernard pass and the Gran Paradiso massif, the large-scale geometry of the tectonic features is established for the tectonic units derived from the Briançonnais paleogeographic domain. Based on this, and other new data on the metamorphic evolution and geochronology of the area, a consistent model for the tectonic evolution for the Briançonnais domain is proposed. A nappe stack consisting of, from bottom to top, Zone Houillère unit, Ruitor unit, Internal unit and Piemont-Ligurian oceanic unit, was affected by three deformation phases. The third phase of deformation (35-31 Ma), referred to as post-nappe folding, is responsible for the formation of two large-scale folds: the Ruitor and Valsavaranche mega-folds. An overturned nappe stack, characterized by foreland-dipping foliations, is found between the axial planes of these two mega-folds. No evidence was found for back-thrusting, postulated by many previous authors. The individual thrusts between the tectonic units were active during a second phase of deformation (43-35 Ma), characterized by top-NW to -NNW shearing. This D2 is related to nappe stacking and accompanied by substantial exhumation. Thrusting becomes relatively younger towards the external parts of the study area. We emphasize that extension played no significant role in the exhumation of the highpressure units of the Italian-French Alps. The contacts between the tectonic units were already active during the first phase of deformation (50-43 Ma), which is related to subduction and peak pressures.

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Section: Geological Settingmentioning

confidence: 99%

Tectonic evolution of the Briançonnais units along a transect (ECORS-CROP) through the Italian-French Western Alps

Bucher¹,

Ulardic

Bousquet³

et al. 2004

Eclogae geol. Helv.

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“…Brouwer et al, 2002;Wei and Powell, 2003;Meffan-Main et al, 2004;Wei and Powell, 2004;Gabudianu Radulescu et al, 2009;. The timing of HP metamorphism is a matter of debate, with available geochronological data for the eclogite facies event varying from 43±0.5 Ma (Meffan-Main et al, 2004) to 33.7±1.6 Ma (Gabudianu Radulescu et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…It overprints an earlier HP structural fabric, which is locally preserved in mafic and metasedimentary lithologies as a folded schistosity containing relics of garnet, phengite, glaucophane and chloritoid (Le Bayon and Ballèvre, 2006;. Estimates for P-T conditions during the albite-epidote amphibolite facies overprint range from 0.4-0.6 GPa, 500-550°C (Borghi et al, 1996;Brouwer et al, 2002) to 0.95-1.15 GPa, 600-625°C ). These variations may reflect different structural levels within the nappe.…”

Section: Introductionmentioning

confidence: 99%

Dating deformation in the Gran Paradiso Massif (NW Italian Alps): Implications for the exhumation of high-pressure rocks in a collisional belt

Rosenbaum

Menegon

Glodny

et al. 2012

Lithos

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The Gran Paradiso massif, situated in the internal part of the Western Italian Alps, records a complex tectono-metamorphic history involving high-pressure metamorphism and subsequent exhumation during retrograde metamorphism. The exact timing of deformation and, consequently, the geodynamic evolution of this part of the Western Alps is still debated and is addressed here by the application of Rb/Sr geochronology, 40 Ar/ 39 Ar step heating and 40 Ar/ 39 Ar total fusion dating techniques. forming an extruding wedge. The kinematics associated with this wedge involved topto-W shearing within the Gran Paradiso nappe (e.g. Pont area shear zones) and top-to-E shearing at the top of the extruding wedge (e.g. Orco shear zone). Subsequent deformation (after ~34 Ma) was characterised by coaxial strain involving orogenicscale backfolding and backthrusting.

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“…A pressure of 12-14 kbar at 500-5508C represents the minimum P-T conditions estimated for the eclogite facies event (Ballèvre, 1988;Benciolini et al, 1984;Brouwer et al, 2002). Moreover the Al-and Mg-rich micaschists (called 'whiteschists' or 'silvery micaschists') record eclogite facies conditions at 21 -23 kbar and 540-5708C (Vidal, Parra, & Trotet, 2001;Wei, Powell, & Zhang, 2003;Gabudianu Radulescu et al, 2011).…”

Section: Gran Paradiso Unitmentioning

confidence: 99%

“…Lenses of mafic rocks, derived from pre-Alpine amphibolites (Ballèvre, 1988;Battiston et al, 1984;Benciolini, Martin, & Tartarotti, 1984;Brouwer, Vissers, & Lamb, 2002;Dal Piaz & Lombardo, 1986) or from Late Palaeozoic gabbros (Gasco, Borghi, & Gattiglio, 2010;Pognante, Talarico, Rastelli, & Ferrati, 1987) occur in the paragneisses. Remnants of a thin Mesozoic metasedimentary cover lay over this pre-Triassic basement (Elter, 1960(Elter, , 1972Polino & Dal Piaz, 1978).…”

Section: Gran Paradiso Unitmentioning

confidence: 99%

Petro-structural map of the Money Unit (Gran Paradiso Massif, Valnontey valley, Western Alps)

et al. 2013

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Structure and metamorphism of the Gran Paradiso massif, western Alps, Italy

Cited by 40 publications

References 0 publications

Tectonic evolution of the Briançonnais units along a transect (ECORS-CROP) through the Italian-French Western Alps

Tectonic evolution of the Briançonnais units along a transect (ECORS-CROP) through the Italian-French Western Alps

Dating deformation in the Gran Paradiso Massif (NW Italian Alps): Implications for the exhumation of high-pressure rocks in a collisional belt

Petro-structural map of the Money Unit (Gran Paradiso Massif, Valnontey valley, Western Alps)

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