The Schwarzhorn Amphibolite (Eastern Rätikon, Austria): an Early Cambrian intrusion in the Lower Austroalpine basement

Nilius, Nils-Peter; Froitzheim, Nikolaus; Nagel, T.; Tomaschek, Frank; Heuser, Alexander

doi:10.1515/geoca-2016-0008

Cited by 3 publications

(1 citation statement)

References 29 publications

(43 reference statements)

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“…Laser ablation inductively coupled mass spectrometry analyses were carried out using a Resonetics RESOlution M50‐E 193 nm excimer‐laser coupled to a Thermo Scientific ELEMENT XR SF‐ICP‐MS. U‐Pb data for zircon was collected following an adaption of methods previously used in our lab (Nilius et al, ). Material was ablated for 30 s with a laser spot size of 33 μm (44 μm) at 8 Hz and a fluency of ~7 J/cm 2 .…”

Section: Methodsmentioning

confidence: 99%

Kinematics and Age of Syn‐Intrusive Detachment Faulting in the Southern Alps: Evidence for Early Permian Crustal Extension and Implications for the Pangea A Versus B Controversy

Pohl

Froitzheim²,

Obermüller³

et al. 2018

Tectonics

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Permian basin formation and magmatism in the Southern Alps of Italy have been interpreted as expressions of a WSW-ENE-trending, dextral megashear zone transforming Early Permian Pangea B into Late Permian Pangea A between~285 and 265 Ma. In an alternative model, basin formation and magmatism resulted from N-S crustal extension. To characterize Permian tectonics, we studied the Grassi Detachment Fault, a low-angle extensional fault in the central Southern Alps. The footwall forms a metamorphic core complex affected by upward-increasing, top-to-the-southeast mylonitization. Two granitoid intrusions occur in the core complex, the synmylonitic Val Biandino Quartz Diorite and the postmylonitic Valle San Biagio Granite. U-Pb zircon dating yielded crystallization ages of 289.1 ± 4.5 Ma for the former and 286.8 ± 4.9 Ma for the latter. Consequently, detachment-related mylonitic shearing took place during the Early Permian and ended at~288 Ma, but kinematically coherent brittle faulting continued. Considering 30°anticlockwise rotation of the Southern Alps since Early Permian, the extension direction of the Grassi Detachment Fault was originally~N-S. Even though a dextral continental wrench system has long been regarded as a viable model at regional scale, the local kinematic evidence is inconsistent with this and, rather, supports N-S extensional tectonics. Based on a compilation of >200 U-Pb zircon ages, we discuss the evolution and tectonic framework of Late Carboniferous to Permian magmatism in the Alps.

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Section: Methodsmentioning

confidence: 99%

Kinematics and Age of Syn‐Intrusive Detachment Faulting in the Southern Alps: Evidence for Early Permian Crustal Extension and Implications for the Pangea A Versus B Controversy

Pohl

Froitzheim²,

Obermüller³

et al. 2018

Tectonics

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Pre-Alpine tectonic evolution of the Eastern Alps: From Prototethys to Paleotethys

Neubauer

Liu

Dong

et al. 2022

Earth-Science Reviews

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The Wechsel Gneiss Complex of Eastern Alps: an Ediacaran to Cambrian continental arc and its Early Proterozoic hinterland

et al. 2020

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Many metamorphosed basement complexes in the Alps are polymetamorphic and their origin and geological history may only be deciphered by detailed geochronology on the different members including oceanic elements like ophiolites, arc successions, and continental passive margin successions. Here we present a case study on the Lower Austroalpine Variegated Wechsel Gneiss Complex and the overlying low-grade metamorphosed Wechsel Phyllite Unit at the eastern margin of Alps. The Wechsel Gneiss Complexes are known to have been overprinted by Devonian metamorphism, and both units were affected by Late Cretaceous greenschist facies metamorphism. New U–Pb zircon ages reveal evidence for two stages of continental arc-like magmatism at 500–520 Ma and 550–570 Ma in the Variegated Wechsel Gneiss Complex. An age of ca. 510 Ma of detrital zircons in metasedimentary rocks also constrain the maximum age of metasedimentary rocks, which is younger than Middle Cambrian. The overlying Wechsel Phyllite Unit is younger than 450 Ma (Late Ordovician) and seems to have formed by denudation of the underlying Variegated Wechsel Gneiss Complex. We speculate on potential relationships of the continental arc-type magmatism of the Variegated Wechsel Gneiss Complex and potential oceanic lithosphere (Speik complex) of Prototethyan affinity, which is also preserved in the Austroalpine nappe complex. The abundant, nearly uniform 2.1 Ga- and ca. 2.5 Ma-age signature of detrital zircons in metasediments (paragneiss, quartzite) of the Variegated Wechsel Gneiss Complex calls for Lower Proterozoic continental crust in the nearby source showing the close relationship to northern Gondwana prominent in West Africa and Amazonia.

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The Schwarzhorn Amphibolite (Eastern Rätikon, Austria): an Early Cambrian intrusion in the Lower Austroalpine basement

Cited by 3 publications

References 29 publications

Kinematics and Age of Syn‐Intrusive Detachment Faulting in the Southern Alps: Evidence for Early Permian Crustal Extension and Implications for the Pangea A Versus B Controversy

Kinematics and Age of Syn‐Intrusive Detachment Faulting in the Southern Alps: Evidence for Early Permian Crustal Extension and Implications for the Pangea A Versus B Controversy

Pre-Alpine tectonic evolution of the Eastern Alps: From Prototethys to Paleotethys

The Wechsel Gneiss Complex of Eastern Alps: an Ediacaran to Cambrian continental arc and its Early Proterozoic hinterland

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