Abstract
The Strona-Ceneri Zone is located south of the Insubric line, where Alpine overprint is mainly brittle and of low grade or even absent. Apart from the unmetamorphic Permo-Carboniferous sediments and intrusiva the Strona-Ceneri Zone is an Ordovician gneiss complex composed of paragneisses, migmatites, peraluminous orthogneisses and banded amphibolites associated with meta-gabbros and meta-ultramafics. Despite of the individual characters of the other Ordovician gneiss terranes north of the Insubric line, most prominently the Aar Massif, the Gotthard, Silvretta and Ötztal nappes, they show analogous lithological formations and pre-Mesozoic structures indicating similar genetic processes. A revision of geological maps and new field observations in these gneiss terranes indicate characteristic spatial relationships of banded amphibolite formations with migmatites and orthogneisses. The contrasting chemistries of the peraluminous rocks (para- and orthogneisses) and the basaltic amphibolites with a lack of intermediate lithologies in between can be explained by the setting of peraluminous arc magmatism within a subduction–accretion complex. In this model the amphibolites represent primary basalts which ponded at the base of the subduction–accretion complex and delivered the heat for the production of peraluminous melts. Volume estimations indicate a “zone of intermingling” composed of immiscible basalts and peraluminous melts with a total thickness of several kilometers. In this “zone of intermingling” the protoliths of the banded amphibolite formations were generated. Steep strike-slip faults, which are important structures for the syn-magmatic cratonization of subduction–accretion complexes, provide pathways for the emplacement of magmas, migmatites and intermingled materials. This results in the formation of steeply oriented sheets of orthogneisses, deformed migmatites and banded amphibolite formations, respectively. Finally, the paper lists many other peri-Gondwanan regions with an early Paleozoic peraluminous arc magmatism, indicating a similar setting on a global scale.
Highlights
Albert Heim (1921, p. 65) stated that “The Alps, despite of the many magmatic rocks, are not a magmatic orogen.” the majority of magmatites is much older than the Alpine orogeny
Other than collisional orogens with subhorizontal nappes or continental arcs composed of complex spheroidal batholiths, cratonized subduction–accretion complexes create a steeply structured crust consisting of intercalated sheets of paragneisses, orthogneisses, migmatites and banded amphibolite formations (Zurbriggen 2015)
7 Conclusions Following conclusions can be made: 1. The orthogneisses, paragneisses, migmatites and amphibolites of the pre-Variscan basement units in the Alps indicate a common history during the Cenerian orogeny in early Paleozoic times
Summary
Albert Heim (1921, p. 65) stated that “The Alps, despite of the many magmatic rocks, are not a magmatic orogen.” the majority of magmatites is much older than the Alpine orogeny. 65) stated that “The Alps, despite of the many magmatic rocks, are not a magmatic orogen.”. The majority of magmatites is much older than the Alpine orogeny. They were generated either (i) in late Paleozoic related to the formation of Pangaea and subsequent Permian transtension, or (ii) during the Ordovician orogeny at the periphery of Gondwana (Bussien et al 2011; Zurbriggen 2015 and references therein). Von Raumer et al (2015) and Villaseca et al (2016), just to mention two of many more studies, developed comprehensive reconstructions of the early Paleozoic magmatic event, for which Zurbriggen (2017) has suggested the new term “Cenerian orogeny”.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
