2-D numerical study of hydrated wedge dynamics from subduction to post-collisional phases

Regorda, Alessandro; Roda, Manuel; Marotta, Anna; Spalla, Maria Iole

doi:10.1093/gji/ggx336

Cited by 12 publications

(18 citation statements)

References 72 publications

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“…The numerical models were performed by using SubMar code (Marotta, Spelta, & Rizzetto, 2006) and successive versions (Marotta et al, 2018;Regorda, Roda, Marotta, & Spalla, 2017;Roda et al, 2012). The dynamics of the crust-mantle system were investigated by numerical integration of the three fundamental equations of conservation of mass, momentum, and energy, which include the extended Boussinesq approximation (e.g., Christensen & Yuen, 1985) for incompressible fluids.…”

Section: Model Set-upmentioning

confidence: 99%

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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Section: Model Set-upmentioning

confidence: 99%

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

et al. 2018

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“…To better understand the meaning of the two different pre-D2 stages, we compare their PT estimates with the PT conditions predicted by continental crustal markers of a numerical model of convergence (Regorda et al, 2017), from the oceanic subduction to the continental collision ( Fig. 13).…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

“…Comparison between PT metamorphic conditions recorded by the two rock types, metamorphic field gradients and PT predictions recorded by crustal markers at different stages of a numerical model of Variscan convergence (from subduction to postcollisional stages,Regorda et al, 2017). V o is the initial geotherm of the numerical model.…”

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Pre-Alpine contrasting tectono-metamorphic evolutions within the Southern Steep Belt, Central Alps

Roda

Zucali

et al. 2018

Lithos

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In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are preserved. Between Valtellina and Val Camonica, a poly-metamorphic rock association occurs, which belongs to the Austroalpine units and includes two classically subdivided units: the Languard-Campo nappe (LCN) and the Tonale Series (TS). The outcropping rocks are low to medium grade muscovite, biotite and minor staurolite-bearing gneisses and micaschists, which include interlayered garnet-and biotite-bearing amphibolites, marbles, quartzites and pegmatites, as well as sillimanite-bearing gneisses and micaschists. Permian intrusives (granitoids, diorites and minor gabbros) emplaced in the metamorphic rocks. We performed a detailed structural, petrological and geochronological analysis focusing on the two main lithotypes, namely, staurolite-bearing micaschists and sillimanitebearing paragneisses, to reconstruct the Variscan and Permian-Triassic his

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“…The time span covered by the four phases covers the same time span of one cycle model (now on "models SS") after Regorda et al (2017), which is characterised by two tectonic phases: (1) an initial oceanic subduction (phase 1) lasting 51.5 Myr (from 425 to 373.5 Ma), with a prescribed velocity of 5 cm/yr; (2) a post-collisional phase (phase 2) lasting 78.5 Myr (from 425 to 295 Ma).…”

Section: Model Setupmentioning

confidence: 99%

“…Models also account for mantle hydration associated to the dehydration of H 2 O-satured MORB basalt, which transport water in their hydrous phases up to 300 km deep, as implemented in Regorda et al (2017). The maximum depth at which dehydration takes place is identifiable by the depth of the deepest oceanic marker in the stability field of lawsonite.…”

Section: Model Setupmentioning

confidence: 99%

How many subductions in the Variscan orogeny? Insights from numerical models

Regorda¹,

Lardeaux

Roda³

et al. 2020

Preprint

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The Variscan belt is the result of the Pangea accretion, a prominent feature of the European continental lithosphere (von Raumer et al., 2003) . The debate on the number of oceans and the geodynamic evolution of the Variscan belt is still open (Faure et al., 2009; Franke et al., 2017). Two scenarios have been proposed:<ol><li> Monocyclic scenario: assumes a single long-lasting south-dipping subduction of a large oceanic domain. Armorica remained more or less closed to Gondwana during its northward drift, in agreement with lack of biostratigraphic and paleomagnetic data that suggests a narrow oceanic domain (lesser than 1000 km; Matte, 2001; Lardeaux, 2014); </li> <li> Polycyclic scenario: this geodynamic reconstruction envisages two main oceanic basins opened by the successive northward drifting of two Armorican microcontinent and closed by two opposite subductions (Lardeaux, 2014; Franke et al., 2017). The northern oceanic basin is identified as the Saxothuringian ocean, while the southern basin is identified as the Medio-European ocean (Lardeaux, 2014). </li> </ol>Models of single and double subduction have been developed to verify which scenario better fits with Variscan P-T evolutions from the Alps and the French Central Massif (FCM). From the comparison between model predictions and natural Variscan P-T-t estimates results that data from the Alps with high P/T ratios better fit with the double subduction model, supporting that a polycyclic scenario is more suitable for the Variscan belt evolution. Differently, data from the FCM with high P/T ratios that fit with both models have poorly constrained geological ages and, therefore, are not suitable to actually discriminate between mono- and polycyclic scenarios (Regorda et al., 2020). Moreover, the predictions of the models open to the possibility that rocks of the Upper Gneiss Unit of the FCM could derive from tectonic erosion of the upper plate and not only from the ocean-continent transition of the lower plate.ReferencesFaure M., Lardeaux J.-M. and Ledru P.; 2009: A review of the pre-Permian geology of the Variscan French Massif Central. Comptes Rendus Geoscience, 341, 202-213.Franke W., Cocks L.R.M. and Torsvik T.H.; 2017: The Palaeozoic Variscan oceans revisited. Gondwana Research, 48, 257-284.Lardeaux J.-M.; 2014: Deciphering orogeny: a metamorphic perspective. Examples from European Alpine and Variscan belts. Part II: Variscan metamorphism in the French Massif Central &#8211; A review. Bull. Soc. g&#233;ol. France, 185(5), 281-310.Matte P.; 2001: The Variscan collage and orogeny (480-290 Ma) and the tectonic definition of theArmorica microplate: A review. Terra Nova, 13(2), 122-128.Regorda A., Lardeaux J-.M., Roda M., Marotta A.M. and Spalla M.I.; 2020: How many subductions in the Variscan orogeny? Insights from numerical models. Geoscience Frontiers, 10.1016/j.gsf.2019.10.005.von Raumer J. F., Stampfli G.M. and Bussy, F.; 2003: Gondwana-derived microcontinents &#8211; the constituents of the Variscan and Alpine collisional orogens. Tectnophysics, 365, 7-22.

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2-D numerical study of hydrated wedge dynamics from subduction to post-collisional phases

Cited by 12 publications

References 72 publications

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

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

Pre-Alpine contrasting tectono-metamorphic evolutions within the Southern Steep Belt, Central Alps

How many subductions in the Variscan orogeny? Insights from numerical models

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