Deciphering orogeny: a metamorphic perspective. Examples from European Alpine and Variscan belts

Lardeaux, Jean‐Marc

doi:10.2113/gssgfbull.185.2.93

Cited by 37 publications

(24 citation statements)

References 217 publications

(202 reference statements)

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“…Penninic domain consists of a mélange of crustal slices deriving from both pre-Alpine continental and Mesozoic oceanic lithosphere, the latter tectonically sampled from the subducted Alpine Tethys Ocean (e.g., Malatesta, Crispini, Federico, Capponi, & Scambelluri, 2012;Malatesta, Gerya, Crispini, Federico, & Capponi, 2013;Platt, 1986;Polino, Dal Piaz, & Gosso, 1990;Roda, Marotta, & Spalla, 2010;Roda, Spalla, & Marotta, 2012;Spalla, Lardeaux, vittorio Dal Piaz, Gosso, & Messiga, 1996;Spalla, Gosso, Marotta, Zucali, & Salvi, 2010;Stöckhert & Gerya, 2005). In contrast, ophiolites do not occur in the Austroalpine domain although they are tectonically coupled together with Mesozoic sediments along the external boundary of the domain, under high-pressure (HP) metamorphic conditions (Lardeaux, 2014;Roda et al, 2012;Spalla et al, 1996) Variscan metamorphic imprints are widely recorded in the Alpine continental crust ( Figure 1) and consist of eclogite, granulite, and amphibolite facies rocks Table S3 [Colour figure can be viewed at wileyonlinelibrary.com] conditions (Donatio, Marroni, & Rocchi, 2013;Marroni & Pandolfi, 2007).…”

Section: Tectonic Evolution and Metamorphic And Magmatic Recordsmentioning

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: Tectonic Evolution and Metamorphic And Magmatic Recordsmentioning

confidence: 99%

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

et al. 2018

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“…The Sesia-Lanzo Zone (SLZ) represents the largest portion ( ̴ 90 × 20 km) of Austroalpine continental crust that has been eclogized during the Alpine subduction and now exposed in the axial zone of the Western Alps (Babist, Handy, Konrad-Schmolke, & Hammerschmidt, 2006;Compagnoni et al, 1977;Dal Piaz, Hunziker, & Martinotti, 1972;Delleani et al, 2013;Lardeaux, 2014;Manzotti, Ballèvre, Zucali, Robyr, & Engi, 2014;Regis et al, 2014;Venturini, Martinotti, Armando, Barbero, & Hunziker, 1994;Zucali et al, 2002). The SLZ is bounded by rocks of the Penninic domain to the northwest, and the Canavese Line (Periadriatic Line (PL)) to the southeast, which separates the SLZ from the Southern Alps (Figure 1(A)).…”

Section: Geologic Outlinementioning

confidence: 99%

Analysis of fabric evolution and metamorphic reaction progress at Lago della Vecchia-Valle d’Irogna, Sesia-Lanzo Zone, Western Alps

et al. 2017

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The Lago della Vecchia-Valle d'Irogna rocks are part of the Eclogitic Micaschists Complex (EMC) of the Sesia-Lanzo Zone, western Austroalpine domain. The 1:10,000 scale map includes metaintrusive, minor micaschist, banded gneiss, and metabasic boudins. The multiscale structural analysis reveals successive magmatic and tectono-metamorphic stages: during M0 the metaintrusive protoliths emplaced; D1 took place under eclogite-facies conditions; during D2 stage, a pervasive foliation developed under retrograde blueschist-facies conditions; D3-D4 and D5 structures developed under greenschist-facies conditions; during M6 andesitic dykes intruded. The mapped degree of fabric evolution (FE) and metamorphic transformation (MT) related to D2-foliation shows that the MT was not only controlled by bulk rock and mineral compositions, but also by FE. The development of a pervasive blueschist-facies D2-foliation is in contrast with the eclogitic dominant fabric generally recorded in the EMC. This difference suggests that FE and MT are potentially responsible for km-scale heterogeneities in the tectono-metamorphic record.ARTICLE HISTORY

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“…a,b) that are dominated by subduction‐related Alpine eclogite facies imprints, locally re‐equilibrated under exhumation‐related greenschist facies metamorphism (e.g. Ernst & Dal Piaz, ; Cartwright & Barnicoat, ; McNamara et al ., ; Lardeaux, ). The ZSZ, together with the Combin Zone (CZ), forms the oceanic suture of the Western European Alps (e.g.…”

Section: Geological Settingmentioning

confidence: 99%

Ocean floor and subduction record in the Zermatt‐Saas rodingites, Valtournanche, Western Alps

Zanoni

Rebay

Spalla

2016

Journal Metamorphic Geology

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Multiscale structural analysis and petrological modelling were used to establish the pressure‐peak mineral assemblages and pressure–temperature (P–T) conditions recorded in the rodingites of the upper Valtournanche portion of the oceanic Zermatt‐Saas Zone (ZSZ; Western Alps, northwestern Italy) during Alpine subduction. Rodingites occur in the form of deformed dykes and boudins within the hosting serpentinites. A field structural analysis showed that rodingites and serpentinites record four ductile deformation stages (D1–D4) during the Alpine cycle, with the first three stages associated with new foliations. The most pervasive fabric is S2 that is marked by mineral assemblages in serpentinite indicating pressure‐peak conditions, involving mostly serpentine, clinopyroxene, olivine, Ti‐clinohumite and chlorite. Three rodingite types can be defined: epidote‐bearing, garnet–chlorite–clinopyroxene‐bearing and vesuvianite‐bearing rodingite. In these, the pressure‐peak assemblages coeval with S2 development involve: (i) epidoteII + clinopyroxeneII + Mg‐chloriteII + garnetII ± rutile ± tremoliteI in the epidote‐bearing rodingite; (ii) Mg‐chloriteII + garnetII clinopyroxeneII ± vesuvianiteII ± ilmenite in the garnet–chlorite–clinopyroxene‐bearing rodingite; (iii) vesuvianiteII + Mg‐chloriteII + clinopyroxeneII + garnetII ± rutile ± epidote in vesuvianite‐bearing rodingite. Despite the pervasive structural reworking of the rodingites during Alpine subduction, the mineral relicts of the pre‐Alpine ocean floor history have been preserved and consist of clinopyroxene porphyroclasts (probable igneous relicts from gabbro dykes) and Cr‐rich garnet and vesuvianite (relicts of ocean floor metasomatism). Petrological modelling using thermocalc in the NCFMASHTO system was used to constrain the P–T conditions of the S2 mineral assemblages. The inferred values of 2.3–2.8 GPa and 580–660 °C are consistent with those obtained for syn‐S2 assemblages in the surrounding serpentinites. Multiscale structural analysis indicates that some ocean floor minerals remained stable under eclogite facies conditions suggesting that minerals such as vesuvianite, which is generally regarded as a low‐P phase, could also be stable in favourable chemical systems under high‐P/ultra‐high‐pressure (HP/UHP) conditions. Finally, the reconstructed P–T–d–t path indicates that the P/T ratio characterizing the D2 stage is consistent with cold subduction as estimated in this part of the Alps. The estimated pressure‐peak values are higher than those previously reported in this part of ZSZ, suggesting that the UHP units are larger and/or more abundant than those previously suggested.

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Deciphering orogeny: a metamorphic perspective. Examples from European Alpine and Variscan belts

Cited by 37 publications

References 217 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

Analysis of fabric evolution and metamorphic reaction progress at Lago della Vecchia-Valle d’Irogna, Sesia-Lanzo Zone, Western Alps

Ocean floor and subduction record in the Zermatt‐Saas rodingites, Valtournanche, Western Alps

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