Petrological and geochronological investigations on the individual nappes of the Meran-Mauls nappe stack (Austroalpine unit/South Tyrol, Italy)

Pomella, Hannah; Costantini, Daniel; Aichholzer, Paul; Reiser, Martin; Schuster, Ralf; Tropper, Peter

doi:10.17738/ajes.2022.0002

Cited by 3 publications

(1 citation statement)

References 42 publications

(91 reference statements)

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“…The temperatures reached during the Neoalpine Orogenesis were not high enough to reset ZFT (ZFT ages of 118 to 41 Ma). The reconstruction of the remaining nappes of the UANS, located south of the western TW, is based on the tectonic model of Pomella et al (2022) west and southwest of the BNF. For the data basis of the tectonic model, we refer to their publication.…”

Section: Manuscript Submitted To Agu Tectonicsmentioning

confidence: 99%

2-D kinematic restoration of the western Tauern Window, Eastern Alps using thermochronological and P-T constraints

Rudmann,

Tanner,

Stipp

et al. 2024

Preprint

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The Penninic and Subpenninic nappe stack of the Tauern Window (TW) in the European Alps was formed by collision between Europe (Subpenninic) and the Adria margin (Austroalpine), and finally exhumed by the northward push of the Dolomites Indenter in the Miocene. In this study, we kinematically restore a cross-section along the trace of the Brenner Base Tunnel, concentrating mainly on the Subpenninic (Venediger duplex; VD). We integrate zircon fission-track data (ZFT) as a temporal constraint for the termination of viscous deformation and test different geothermal gradients (GG). P-T-t data are used to define (i) the depth of brittle-viscous transition (ca. 300°C) and (ii) pre-indenter depth. First, we displace the VD down along the Sub-Tauern ramp below the 300°C isotherm. To that time, a GG of 50°C/km prevailed. ZFT ages reveal that viscous folding of the VD terminated at ca. 17 ± 2 Ma. Unfolding of the VD, while conserving surface area, yield that the model is extended by ca. 70 km (i.e. thus equaling indenter shortening), which means that the VD was not affected by W-E extension or lateral extrusion. Reconstruction of the hanging-wall nappes (Austroalpine and Penninic nappes) above the restored VD reveals that the total pre-indenter thickness of their northern limbs was 35–50% more than it is today. We interpret this as tectonic thinning, which was mainly caused by the Brenner normal fault. Our model shows that tectonic processes can explain the exhumation of the western TW; erosional denudation seems to play only a minor part.

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Section: Manuscript Submitted To Agu Tectonicsmentioning

confidence: 99%

2-D kinematic restoration of the western Tauern Window, Eastern Alps using thermochronological and P-T constraints

Rudmann,

Tanner,

Stipp

et al. 2024

Preprint

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The Meran-Mauls Fault: Tectonic switching from compression to transpression along a restraining bend of the Periadriatic Fault

Zanchetta

Montemagni

Mascandola

et al. 2023

Journal of Structural Geology

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The metabasites from the Texel Unit (Austroalpine nappe stack): markers of Cretaceous intracontinental subduction and subsequent collision

Tropper,

Tribus,

Pomella

et al. 2023

Austrian Journal of Earth Sciences

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Eclogites in the Texel Unit (Austroalpine nappe stack; Eastern Alps, South Tyrol, Italy) represent the westernmost out-crops of the E-W striking Eoalpine High-Pressure Belt (EHB). East of the Tauern Window, the EHB forms part of a Cretaceous intracontinental south-dipping subduction/collision zone. The impetus of this contribution is to extend the geothermo-barometric data of the eclogites from the EHB using conventional geothermobarometry and multi-equilibrium calculations as well as Zr-in-rutile/titanite geothermometry and to put the P-T results of eclogites and amphibolites from the Texel Unit into the geodynamic framework. The investigated samples of this study are from the Spronser- and the Saltaus valleys (S-Tyrol) in the Austroalpine Texel Unit. The Texel Unit is composed mainly of paragneisses with minor intercalations of micaschists, orthogneisses, amphibolites and subordinately eclogites. The amphibolites from the Spronser valley contain the mineral assemblage amphibole + plagioclase + garnet + clinozoisite/epidote + quartz + titanite ± ilmenite ± rutile ± apatite ± calcite. Chemical zoning in plagioclase and amphibole shows two main growth stages: an older P-dominated stage (e.g. albite and barroisite cores) and a younger amphibolite-facies stage. The core of the amphiboles shows barroisite composition, the rim can be chemically classified as hornblende, edenite, tschermakite and pargasite. Geothermobarometric calculations with multi-equilibrium geothermobarometry (THERMOCALC v.3.21) yield temperatures of 600–654°C and pressures of 0.98–1.17 GPa for the same samples. The eclogites from the Saltaus valley contain the peak mineral assemblage omphacite + amphibole + garnet + clinozoisite/epidote + muscovite + quartz + titanite ± ilmenite ± rutile. Thermobarometric calculations, were performed in the system CaO-FeO-MgO-Na2O-Al2O3-FeO-SiO2-H2O with the assemblage clinopyroxene + garnet + amphibole + clinozoisite/epidote + muscovite + quartz ± H2O. The calculations involved an H2O-absent invariant point (mode-1 calculation) as well as two types of average P-T mode-2 calculations. The obtained average P-T H2O-absent mode 1 P-T conditions are 1.89 ± 0.18 GPa and 578 ± 60°C. Using the average P-T mode-2 two types of calculations were done: (1) calculations without amphiboles but with H2O present, which yield mean P-T conditions of 1.95 ± 0.28 GPa and 601 ± 55°C and (2) calculations with amphiboles but without H2O, which yield mean P-T conditions of 1.95 ± 0.26 GPa and 666 ± 77°C. Calculations using THERMOCALC v.3.33 yield similar results with slightly higher pressures of 0.3 GPa. Based on the present geothermobarometric data in conjunction with available mineral ages the eclogites represent the Eoalpine intracontinental subduction stage whereas the amphibolites reflect the subsequent, P-accentuated stage of decompression associated with the subsequent Eoalpine collisional stage.

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Petrological and geochronological investigations on the individual nappes of the Meran-Mauls nappe stack (Austroalpine unit/South Tyrol, Italy)

Cited by 3 publications

References 42 publications

2-D kinematic restoration of the western Tauern Window, Eastern Alps using thermochronological and P-T constraints

2-D kinematic restoration of the western Tauern Window, Eastern Alps using thermochronological and P-T constraints

The Meran-Mauls Fault: Tectonic switching from compression to transpression along a restraining bend of the Periadriatic Fault

The metabasites from the Texel Unit (Austroalpine nappe stack): markers of Cretaceous intracontinental subduction and subsequent collision

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