Ediacaran to Cambrian oceanic rocks of the Gondwana margin and their tectonic interpretation

Raumer, Jürgen F. von; Stampfli, Gérard M.; Arenas, Ricardo; Martı́nez, Sonia Sánchez

doi:10.1007/s00531-015-1142-x

Cited by 132 publications

(70 citation statements)

References 95 publications

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“…A distinct arc/rift change of its magmatic evolution is marked from 550-530 Ma volcanic arc basalts to 530-520 eclogitised gabbroic and tonalitic melts intruding a continental margin magmatic arc (Von Raumer and Stampfli 2008;Von Raumer et al 2015).…”

Section: Cadomian Arc-related Events In West Gondwanamentioning

confidence: 99%

Cadomian volcanosedimentary complexes across the Ediacaran–Cambrian transition of the Eastern Pyrenees, southwestern Europe

Padel

Álvaro

Casas

et al. 2017

Int J Earth Sci (Geol Rundsch)

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International audienceThe volcanism hosted by the Ediacaran–Terreneuvian Canaveilles Group of the Eastern Pyrenees displays two distinct geochemical affinities: (1) metabasites of the Nyer and Olette formations reflect the emplacement of a tholeiitic magmatism linked to extensional conditions, whereas (2) subsequent felsic and calc-alkaline magmatic rocks marking the top of the Olette Formation and forming the overlying Fabert and Finestrelles members represent Cadomian magmatic events. Based on U–Pb zircon dating constraints, palaeotopographic relationships linked to onlap geometries and distance from vent sources, three volcanosedimentary edifices can be distinguished, the so-called Tregurà (ca. 565–552 Ma), Cap de Creus (ca. 558 Ma) and Coll d’Ares (ca. 542–532 Ma) edifices. The top of their palaeoreliefs recorded locally the nucleation of centres of microbial carbonate productivity (Puig Sec Member) linked to synsedimentary tilting and karstification. Throughout West Gondwana, the presence of carbonate production across the Ediacaran–Cambrian transition is exclusively located in back-arc settings (Central-Iberian Zone) and areas far from the Cadomian subduction trench and devoid of significant terrigenous input, such as those reported in the Eastern Pyrenees and the neighbouring Montagne Noire

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Section: Cadomian Arc-related Events In West Gondwanamentioning

confidence: 99%

Cadomian volcanosedimentary complexes across the Ediacaran–Cambrian transition of the Eastern Pyrenees, southwestern Europe

Padel

Álvaro

Casas

et al. 2017

Int J Earth Sci (Geol Rundsch)

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“…The metabasites correspond to former hydrothermally altered enriched mid-ocean ridge basalts (E-MORB), interlayered with pelitic micaschists (Bernard-Griffiths et al 1986;Bosse et al 2002;El Korh et al 2009. Because of the lack of ultrabasic and gabbroic rocks, the high-pressure rocks were interpreted as remnants of the uppermost part of an oceanic lithosphere or of basaltic lavas, emplaced during the Cambro-Ordovican rifting widely recognised along the northern Gondwana margin (El Korh et al 2012;von Raumer et al 2015). The Cambro-Ordovician magmatism in the southern Armorican Massif is thought to result from the intra-continental back-arc basin rifting following the closure of the ProtoRheic ocean, as recognised in the allochthonous domain of the Variscan belt (von Raumer et al 2015).…”

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

“…Because of the lack of ultrabasic and gabbroic rocks, the high-pressure rocks were interpreted as remnants of the uppermost part of an oceanic lithosphere or of basaltic lavas, emplaced during the Cambro-Ordovican rifting widely recognised along the northern Gondwana margin (El Korh et al 2012;von Raumer et al 2015). The Cambro-Ordovician magmatism in the southern Armorican Massif is thought to result from the intra-continental back-arc basin rifting following the closure of the ProtoRheic ocean, as recognised in the allochthonous domain of the Variscan belt (von Raumer et al 2015). The metabasalts and metasediments were sheared off and imbricated in an accretionary prism during the Variscan subduction (El Korh et al 2012).…”

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

Iron isotope fractionation in subduction-related high-pressure metabasites (Ile de Groix, France)

Korh

Luais

Deloule

et al. 2017

Contrib Mineral Petrol

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1during metamorphism: newly-formed Fe-rich minerals allowed preserving bulk rock Fe compositions during metamorphic reactions and hampered any Fe isotope fractionation. Greenschists have δ 56 Fe values (+0.17 ± 0.01 to +0.27 ± 0.02‰) similar to high-pressure rocks. Hence, metasomatism related to fluids derived from the subducted hydrothermally altered metabasites might only have a limited effect on mantle Fe isotope composition under subsolidus conditions, owing to the large stability of Fe-rich minerals and low mobility of Fe. Subsequent melting of the heavy-Fe metabasites at deeper levels is expected to generate mantle Fe isotope heterogeneities.Keywords Fe isotopes · Metabasites · Subduction · HP-LT metamorphism · Blueschists · Eclogites · Greenschists · Basaltic protoliths IntroductionHigh-pressure/low-temperature (HP-LT) rocks are remnants of ancient subduction zones. They provide information on geochemical processes and deep fluid-rock interactions occurring at present-day active convergent margins. Fluid infiltration during high-and lowtemperature hydrothermal alteration of the oceanic crust at mid-ocean ridges and on the seafloor is responsible for the hydration of basic rocks and serpentinisation of the lithospheric mantle. During subduction, the hydrothermally altered oceanic crust dehydrates continuously and releases large amounts of H 2 O at a relatively shallow level in the subduction zone (50-80 km) (Schmidt and Poli 1998;Rüpke et al. 2004). Deserpentinisation of the lithospheric mantle occurs at deeper levels (100-200 km), where fluids are expected to be the source of arc melting (Ulmer and Abstract Characterisation of mass transfer during subduction is fundamental to understand the origin of compositional heterogeneities in the upper mantle. Fe isotopes were measured in high-pressure/low-temperature metabasites (blueschists, eclogites and retrograde greenschists) from the Ile de Groix (France), a Variscan high-pressure terrane, to determine if the subducted oceanic crust contributes to mantle Fe isotope heterogeneities. The metabasites have δ 56 Fe values of +0.16 to +0.33‰, which are heavier than typical values of MORB and OIB, indicating that their basaltic protolith derives from a heavy-Fe mantle source. The δ 56 Fe correlates well with Y/Nb and (La/Sm) PM ratios, which commonly fractionate during magmatic processes, highlighting variations in the magmatic protolith composition. In addition, the shift of δ 56 Fe by +0.06 to 0.10‰ compared to basalts may reflect hydrothermal alteration prior to subduction. The δ 56 Fe decrease from blueschists (+0.19 ± 0.03 to +0.33 ± 0.01‰) to eclogites (+0.16 ± 0.02 to +0.18 ± 0.03‰) reflects small variations in the protolith composition, rather than Fe fractionation

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“…Although the Pyrite belt is not specifically discussed in this strongly juxtaposed assemblage (Pereira et al 2012), the attribution of part of this assemblage to the Rhenohercynian type of evolution at the Laurussian border should not be disregarded (see discussion above). Menor-Salván et al (2010) indicate well the complication of the general plate-tectonic situation, where the closure of the Rheic Ocean between the Hanseatic terrane and Ossa Morena-type microcontinents , the supposed detachment of the Rheic slab (von Raumer et al 2015) and the subsequent subduction reversal , would accelerate an orographic evolution, and a strong mobilization of thermal circulation.…”

Section: The Devonian Plate-tectonic Environment-a Discussionmentioning

confidence: 99%

The north-subducting Rheic Ocean during the Devonian: consequences for the Rhenohercynian ore sites

Raumer

Nesbor

Stampfli

2016

Int J Earth Sci (Geol Rundsch)

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activated Early Devonian growth faults. Hydrothermal brines equilibrated with the basement and overlying Middle-Upper Devonian detrital deposits forming the SHMS deposits in the southern part of the Pyrite Belt, in the Rhenish Massif and in the Harz areas. Volcanic-hosted massive sulfide deposits (VHMS) formed in the more eastern localities of the Rhenohercynian domain. In contrast, since the Tournaisian period of ore formation, dominant pull-apart triggered magmatic emplacement of acidic rocks, and their metasomatic replacement in the apical zones of felsic domes and sediments in the northern part of the Iberian Pyrite belt, thus changing the general conditions of ore precipitation. This two-step evolution is thought to be controlled by syn-to post-tectonic phases in the Variscan framework, specifically by the transition of geotectonic setting dominated by crustal extension to a one characterized by the subduction of the supposed northern slab of the Rheic Ocean preceding the general Late Variscan crustal shortening and oroclinal bending.

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Ediacaran to Cambrian oceanic rocks of the Gondwana margin and their tectonic interpretation

Abstract: Ordovician age in the Alpine realm is explained by the accretion of exotic China-derived basements and their collision with the Gondwana margin during the opening of the Rheic Ocean.

Cited by 132 publications

References 95 publications

Cadomian volcanosedimentary complexes across the Ediacaran–Cambrian transition of the Eastern Pyrenees, southwestern Europe

Cadomian volcanosedimentary complexes across the Ediacaran–Cambrian transition of the Eastern Pyrenees, southwestern Europe

Iron isotope fractionation in subduction-related high-pressure metabasites (Ile de Groix, France)

The north-subducting Rheic Ocean during the Devonian: consequences for the Rhenohercynian ore sites

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