Evolution of the Ligurian Tethys in the Western Alps: Sm/Nd and U/Pb geochronology and rare-earth element geochemistry of the Montgenèvre ophiolite (France)

Costa, Sylvie; Caby, Renaud

doi:10.1016/s0009-2541(00)00334-x

Cited by 57 publications

(46 citation statements)

References 32 publications

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“…However, one difficulty with this model lies in the fairly long age discrepancy between the Lago Nero-Replatte radiolarites and the Chenaillet intrusives. This age hierarchy does not only concern our locality: Traversiera radiolarites (late Bathonian-early Callovian in age [21]) which are in a similar structural position on the westernmost part of the Piemonte zone, are also older than the Chenaillet s.s. youngest magmatic rocks [10]. In accordance with our second proposition, authors have previously stressed the differences between the two thrust sheets such as their metamorphic grade and considered that they had a distinct tectonic history [4].…”

Section: Comparison With Local Radiometric Ages and Implicationssupporting

confidence: 81%

“…Albitites are interpreted as either fractionated mantle-derived magmas of tholeitic character [30] or the final differentiation product of a MORB-type mantle source [10]. These results support the model of asymmetric mantle-denudation by an oblique detachment fault [1] implying that the newly formed lherzolite-gabbro oceanic domain probably remained close to the spreading center and therefore experienced slow cooling and low spreading rates.…”

Section: Comparison With Local Radiometric Ages and Implicationssupporting

confidence: 63%

“…Geochronological studies on the Chenaillet-Montgenèvre magmatic rocks [10] provide an isochron age of 198 ± 22 Ma on gabbros, while zircons from a leucodioritic vein within gabbros are 156 ± 3 Ma and an albitite lens within mantle rocks display concordant ages at 148 ± 2 Ma. Albitites are interpreted as either fractionated mantle-derived magmas of tholeitic character [30] or the final differentiation product of a MORB-type mantle source [10].…”

Section: Comparison With Local Radiometric Ages and Implicationsmentioning

confidence: 99%

“…However, no local age control from these various units was documented until recently. Radiometric dating was achieved on Chenaillet gabbros and intrusives by Costa and Caby [10] but sedimentary rocks from the area were still devoid of direct age control due to the technical difficulties of extracting diagnostic microfossils from metasediments. Remarkably, radiolarians from the Mongenèvre area were initially studied in thin sections by Italian paleontologists more than a century ago: in 1890, Parona documented a radiolarian fauna from the siliceous schists of Cesana [11] while in 1912 Squinabol described an assemblage interpreted at the time as latest Jurassic in age [12].…”

Section: Introductionmentioning

confidence: 99%

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Alpine ocean seafloor spreading and onset of pelagic sedimentation: new radiolarian data from the Chenaillet-Montgenèvre ophiolite (French-Italian Alps)

Cordey

Bailly

2007

Geodinamica Acta

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Radiolarians of Middle Jurassic age (tentatively middle Bathonian) provide the first direct age determination from oceanic sediments associated with the Chenaillet-Montgenèvre ophiolite (Piemonte zone, French-Italian Alps). This datum obtained from radiolarites of the Lago NeroReplatte thrust sheet is older than those previously established on ophiolite sedimentary covers from this segment of the western Alps. It also shows that Lago Nero-Replatte basal radiolarites are anterior to the youngest intrusives from the overlying Chenaillet s.s. thrust sheet. This chronological relationship implies either a late seafloor spreading-related magmatic activity in places younger than adjacent initial pelagic sedimentation, or more likely that the Lago Nero-Replatte and the Chenaillet s.s. thrust sheets are distinct and distant pieces of lithosphere that were eventually stacked together: the Lago Nero-Replatte unit was trapped within the accretionary wedge while the Chenaillet s.s., of a younger age and in a more distal position with regards to the European margin, was obducted. Regionally, the Lago Nero-Replatte sediments appear to be coeval to other Bathonian supraophiolitic radiolarites exposed in the western Alps. These results strengthen the Bathonian correlation of widespread seafloor spreading in both western Tethys and the central Atlantic ocean.

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Section: Comparison With Local Radiometric Ages and Implicationssupporting

confidence: 81%

Section: Comparison With Local Radiometric Ages and Implicationssupporting

confidence: 63%

Section: Comparison With Local Radiometric Ages and Implicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alpine ocean seafloor spreading and onset of pelagic sedimentation: new radiolarian data from the Chenaillet-Montgenèvre ophiolite (French-Italian Alps)

Cordey

Bailly

2007

Geodinamica Acta

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“…Ohnenstetter et al 1981;Bill et al 1997;Rubatto 1998;Rubatto et al 1998). However, Pinet et aL Caby (1995); Costa & Caby (1997), from their studies of the Queyras and MontGenbvre ophiolites, concluded that intrusion and intra-oceanic deformation of gabbros clearly predate extrusion of the overlying pillow basalts. The occurrence of radiolarite beneath basalt (Bortolotti et al 1991) also confrms that basalts postdate gabbros in many cases.…”

Section: Time Gap Between Gabbro Crystallization and Superficial Basamentioning

confidence: 99%

Non-volcanic rifted margins, continental break-up and the onset of sea-floor spreading: some outstanding questions

Boillot

Froitzheim

2001

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During the last 20 years, regional studies on the West Iberia margin and on the former margins of the Tethys have considerably advanced the understanding of processes related to continental break-up and the onset of sea-floor spreading. However, some questions remain outstanding. To tentatively answer these, a coherent interpretation of available data is proposed, based on the detachment fault concept applied to the continental as well as the oceanic lithosphere, and on the hypothesis of a multi-staged rifting process. The interpretation addresses the nature of the lower crust beneath non-volcanic passive margins, the origin of ophicalcites, the probable time gap between syn-or post-rift crystallization of gabbros and extrusion of basalts on the sea floor, and the significance of dipping reflectors within oceanic lithosphere adjacent to non-volcanic passive margins. The interpretation also considers the symmetry v. asymmetry of continental rifting and break-up, the location of the ocean-continent boundary, and the possible association of magnetic quiet zones with ultramafic sea floor (serpentinized peridotite) bordering non-volcanic passive margins.

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What drives Alpine Tethys opening? Clues from the review of geological data and model predictions

et al. 2018

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Permo‐Triassic remnants (300–220 Ma) of high‐temperature metamorphism associated with large gabbro bodies occur in the Alps and indicate a high thermal regime compatible with lithospheric thinning. During the Late Triassic–Early Jurassic, an extensional tectonics leads to the break‐up of Pangea continental lithosphere and the opening of Alpine Tethys Ocean (170–160 Ma), as testified by the ophiolites outcropping in the Central–Western Alps and Apennines. We revise geological data from the Permian to Jurassic of the Alps and Northern Apennines, focusing on continental and oceanic basement rocks, and predictions of existing numerical models of post‐collisional extension of continental lithosphere and successive rifting and oceanization. The aim is to test whether the transition from the Permo‐Triassic extensional tectonics to the Jurassic opening of Alpine Tethys occurred. We enforce the interpretation that a forced extension of 2 cm/year of the post‐collisional lithosphere results in a thermal state compatible with the Permo‐Triassic high‐temperature event suggested by pressure and temperature conditions of metamorphic rocks and widespread igneous activity. Extensional or transtensional tectonics is also in agreement with the generalized subsidence indicated by the deposition of sedimentary successions with deepening upward facies occurred in the Alps from the Permian to Jurassic. Furthermore, a rifting developed on a thermally perturbed lithosphere agrees with a hyperextended configuration of the Alpine Tethys rifting and with the duration of the extension necessary to the oceanization. The review supports the interpretation of Alpine Tethys opening developed on a lithosphere characterized by a thermo‐mechanical configuration inherited by the post‐Variscan extension which affected Pangea during the Permian and Triassic. Therefore, a long‐lasting period of active extension can be envisaged for the breaking of Pangea supercontinent, starting from the unrooting of the Variscan belts, followed by the Permo‐Triassic thermal high, and ending with the crustal break‐up and the formation of the Alpine Tethys Ocean.

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Evolution of the Ligurian Tethys in the Western Alps: Sm/Nd and U/Pb geochronology and rare-earth element geochemistry of the Montgenèvre ophiolite (France)

Cited by 57 publications

References 32 publications

Alpine ocean seafloor spreading and onset of pelagic sedimentation: new radiolarian data from the Chenaillet-Montgenèvre ophiolite (French-Italian Alps)

Alpine ocean seafloor spreading and onset of pelagic sedimentation: new radiolarian data from the Chenaillet-Montgenèvre ophiolite (French-Italian Alps)

Non-volcanic rifted margins, continental break-up and the onset of sea-floor spreading: some outstanding questions

What drives Alpine Tethys opening? Clues from the review of geological data and model predictions

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