Is there an Upper Devonian rift zone under the northern front of the Alps separating East and West Armorican crustal segments?

Finger, Friedrich; Riegler, Gudrun

doi:10.31577/geolcarp.73.3.1

Cited by 4 publications

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“…Like von Raumer et al ( 2013), we propose that, after a major rifting event in the Devonian (opening of the Palaeotethys), the CENO and CADO units detached from Gondwana and were subsequently juxtaposed via dextral strike-slip processes in the Carboniferous. Parts of the Carboniferous CENO/CADO suture zone are now hidden under the northern front of the Alps (Finger and Riegler, 2022). Of course, it should be noted that the Permian arrangement of the CENO-derived units was massively disturbed by Alpine tectonic events.…”

Section: Discussionmentioning

confidence: 99%

The role of the proto-Alpine Cenerian Orogen in the Avalonian- Cadomian belt

Finger

Riegler

2023

Austrian Journal of Earth Sciences

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The proto-Alpine Cenerian orogen (Ediacaran-Ordovician) and the Cadomian orogen (Ediacaran-Cambrian), remnants of which are exposed in the central European Variscides, should be defined as two distinct and spatially separated coastal orogens within the Avalonian-Cadomian belt. The Cadomian orogen originally lay in front of the Sahara metacraton. It underwent a change from an active to a passive margin setting during the Cambrian. The Cenerian orogen, represented by intra-Alpine rocks, was located farther east near the Arabian Nubian Shield, from where it inherited a characteristic Tonian/Stenian detrital zircon signal. Subduction persisted in the Cenerian Orogen until the Ordovician. The Cadomian orogen was akin to Andean type whereas the Cenerian orogen was more akin to Alaskan type. This paper explores why the two orogens have such different characteristics and tectonic evolutions despite their probable proximity in the Avalonian-Cadomian belt. One explanation could be that they were at nearly right-angles to each other due to a strong concave bending of the northern Gondwana margin ahead of the Arabian-Nubian Shield.

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Section: Discussionmentioning

confidence: 99%

The role of the proto-Alpine Cenerian Orogen in the Avalonian- Cadomian belt

Finger

Riegler

2023

Austrian Journal of Earth Sciences

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“…There is wide agreement today that the pre-Variscan intra-Alpine basement units are mainly derived from an eastern segment of the northern Gondwana margin. They may have resided either adjacent to South China (von Raumer et al 2013) or in front of the Arabian-Nubian Shield and the Sahara craton (Siegesmund et al 2021;Finger and Riegler 2022). Also, there is wide agreement that large parts of the northern Gondwana margin had an Andean-type character during the Cadomian orogeny (e.g., Nance et al 2008;von Raumer et al 2013).…”

Section: Comparison Of the Kutjevo Zone With The Strona-ceneri Zone A...mentioning

confidence: 99%

Tracing the cryptic Sardic (Ordovician) metamorphism across Alpine Europe: the Krndija region in the Slavonian Mountains, Croatia

Mayer

Zeh

Krenn

et al. 2023

Int J Earth Sci (Geol Rundsch)

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Results of a combined petrological, geochemical and geochronological study suggest that metasedimentary rock units in the Krndija region of the Slavonian Mountains, Croatia, were affected by at least three major tectonometamorphic imprints: during the Middle Ordovician (Sardic event), the early Carboniferous (Variscan event), and the Cretaceous (Alpine event). All three metamorphic phases are established by electron microprobe-based in-situ U–Th–Pb dating of monazite grains. The Sardic metamorphic event is additionally confirmed by a precise Lu–Hf garnet-whole-rock isochron age of 466.0 ± 2.3 Ma. Taken together, the data unveil a relatively large and well-preserved piece of the cryptic Sardic orogen in central Krndija, that we name the Kutjevo Zone. A Sardic subduction-related metamorphic event (ca. 540-580 ℃, 8–11 kbar) at ca. 466 Ma is manifested in the mineral paragenesis Ca-rich garnet plus rutile. A low degree of retrograde reequilibration suggests a subsequent fast exhumation. Low-Ca cores in some garnets and staurolite relics record a pre-HP metamorphic event that involves isobaric heating from 570 to 610 ℃ at ~ 7 kbar. We attribute this (so far undated) event to mid-crustal contact metamorphism caused by early Sardic magmatism. Southern parts of Krndija (the Gradište Zone) experienced an (additional?) clockwise PT evolution in Variscan times at ca. 350 Ma. Garnet formed with ilmenite during a PT increase from 580 ℃/5 kbar to 600 ℃/6 kbar and underwent later strong retrograde resorption. Slow Variscan exhumation resulted in andalusite formation at < 550 ℃/ < 3.8 kbar. Penetrative Alpine metamorphism was observed in low-grade phyllites in the north. The lithology and metamorphic history of the Kutjevo Zone is similar to what has been reported from the Sardic Strona-Ceneri Zone in the western Alps. Both areas expose metapelitic (metagreywacke) rocks with a pre-middle Ordovician formation age. These metasedimentary rocks are inter-layered with numerous small amphibolitic units as well as metagranitoids and were likely deposited along the active Gondwana margin, perhaps in a fore-arc position, prior to their subduction during the middle Ordovician. According to recent palaeogeographic reconstructions, both the Kutjevo Zone and the Strona-Ceneri Zone have once resided in an eastern sector of the northern Gondwana margin (i.e., in E-Armorica). We conclude that in the Middle Ordovician, important subduction activities took place in this E-Armorican segment of north Gondwana, which is today exposed in the Alps. The W-Armorican segment of north Gondwana (now exposed in the French, German, and Czech Variscides) had probably already mutated from a (Cadomian) subduction setting to an extensional (transtensional–transpressional) setting by the late Cambrian.

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Cadomian to Cenerian accretionary orogenic processes in the Alpine basement: the detrital zircon archive

Siegesmund

Oriolo

Broge

et al. 2023

Int J Earth Sci (Geol Rundsch)

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New whole-rock geochemical and detrital zircon U–Pb and Lu–Hf data of metasedimentary sequences of the Silvretta Nappe, Orobic Alps, Strona-Ceneri Zone, Gotthard Massif and Venediger Nappe are presented. These units seem to share a common early to middle Paleozoic geological record, which has alternatively been interpreted as the result of intraplate or orogenic processes. Detrital zircon data mainly indicate late Ediacaran to early Ordovician maximum sedimentation ages for the studied sequences, suggesting that they were intimately related to Cadomian and Cenerian orogenic processes along the northwestern Gondwana margin. The common presence of late Ediacaran to Cambrian Cadomian ages associated with variable subchondritic to suprachondritic Lu–Hf compositions points to recycling processes of Cadomian sequences, further supported by geochemical data indicating a relatively low to moderate maturity of sedimentary protoliths. The occurrence of Cenerian arc-related intrusions in Austroalpine and South Alpine basement unit points to an arc/back-arc position in the early Paleozoic Cenerian orogen, except for the Strona-Ceneri Zone, which was likely located closer to the forearc region, as indicated by the presence of high-pressure metamorphism. Younger sequences, such as the Landeck Quartz-phyllite, document post-Cenerian sedimentation, whereas those of the Venediger Nappe more likely record the early stages of Variscan subduction, as indicated by Devonian maximum deposition ages.

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Is there an Upper Devonian rift zone under the northern front of the Alps separating East and West Armorican crustal segments?

Cited by 4 publications

References 0 publications

The role of the proto-Alpine Cenerian Orogen in the Avalonian- Cadomian belt

The role of the proto-Alpine Cenerian Orogen in the Avalonian- Cadomian belt

Tracing the cryptic Sardic (Ordovician) metamorphism across Alpine Europe: the Krndija region in the Slavonian Mountains, Croatia

Cadomian to Cenerian accretionary orogenic processes in the Alpine basement: the detrital zircon archive

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