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[Display omitted] • Arc evolution in SW Iberia suggests subduction erosion and recycling from 645 to 540 Ma. • Geochronology, geochemistry and Sr-Nd sources show cyclical changes of arc magmatism. • High tectonic erosion rates lead crustal Sr-Nd signature and adakitic magmatism. In the peri -Gondwanan Ediacaran arc section outcropping in the SW of the Iberian Massif (Mérida region), changes in the subduction angle and subduction rate, variable participation of highly modified mantle sources together with the role of old crustal material and juvenile mafic rocks driven by the incoming slab, occur with a recognizable cyclicality and can be traced according to the geochronology, geochemistry and isotopic sources of the magmatic bodies. Our results support the initial existence of a mantle wedge highly modified due to percolation of significant volumes of variably old crustal materials, whose isotopic sources are almost identical to those found in the oldest known metasedimentary sequence described in SW Iberian Massif, the Serie Negra Group. Old crustal sources, analogous to those of this series were introduced to high depths by common subduction an also probably by significant subduction erosion. During the oldest period recorded in the study arc section, between c. 602 and c. 550 Ma, subduction episodes that involve high rates of crustal material along with an eventual incorporation of mafic and ultramafic materials from the incoming oceanic plate, favoured by low subduction angles, lead to the generation of more silicic magmas with adakitic geochemical affinity and isotopic signature (Nd-Sr) with crustal tendency. However, an increase in the subduction angle and change to a roll-back stage dated at c. 540 Ma, caused significant decrease in the access of cortical material to the subduction channel, favouring generation of typical calc-alkaline magmas derived from the modified mantle wedge, which is also consistent with more juvenile Nd-Sr ratios. The correlation found between the magmatic events and the involved tectonic processes suggests that subduction erosion mechanisms have been very likely underestimated as active dynamic processes along the peri -Gondwana margin during at least Neoproterozoic to Early Cambrian times. [ABSTRACT FROM AUTHOR]

The Ossa-Morena Zone (OMZ) has a complex geological history including both Cadomian and Variscan orogenic events. Therefore, the OMZ plays an important role in understanding the geodynamic evolution of Iberia. However, the P–T–t evolution of the OMZ is poorly documented. Here, we combine structural and metamorphic analyses with new geochronological data and geochemical analyses of mafic bodies in Ediacaran metasediments (in Iberia known as Série Negra) to constrain the geodynamic evolution of the OMZ. In the studied mafic rocks, two metamorphic stages were obtained by phase equilibria modelling: (1) a high-pressure/low-temperature event of 1.0 ± 0.1 GPa and 470–510 °C, and (2) a medium-pressure/higher-temperature event of 0.6 ± 0.2 GPa and 550–600 °C. The increase in metamorphic temperature is attributed to the intrusion of the Beja Igneous Complex (around 350 Ma) and/or the Évora Massif (around 318 Ma). New U–Pb dating on zircons from the mafic rocks with tholeiitic affinity yields an age between 815 and 790 Ma. If the zircons crystallised from the tholeiitic magma, their age would set a minimum age for the pre-Cadomian basement. The ca. 800 Ma protolith age of HP-LT tholeiitic dykes with a different metamorphic history than the host Série Negra lead us to conclude that: (1) the HP-LT mafic rocks and HP-LT marbles with dykes were included in the Ediacaran metasediments as olistoliths; (2) the blueschist metamorphism is older than 550 Ma (between ca. 790 Ma and ca. 550 Ma, e.g., Cadomian). [ABSTRACT FROM AUTHOR]

Detrital zircon age spectra of Ediacaran paragneiss from the Rheic suture between the Rhenohercynian Zone and Saxothuringian Zone suggest that they originated from different parts of peri-Gondwana. The paragneiss from the Northern Phyllite Belt displays an age spectrum of detrital zircons with a high amount of Neoproterozoic (82%) and Mesoproterozoic zircons (11%) typical for Amazonian provenance, whereas the spectrum from the metagreywacke of the Odenwald (Mid-German Crystalline Zone) shows a Mesoproterozoic age gap which is correlated with the West African Craton. The metagreywacke of the Odenwald contains 20% Paleoproterozoic and 32% Archean zircons, whereas the paragneiss of the Northern Phyllite Belt (Wartenstein Crystalline) contains only 6% Paleoproterozoic and no Archean zircons. The paleoposition of the basement of Northern Phyllite Belt was proximal to the Avalonian magmatic arc of the London–Brabant high. The Armorican metagreywacke of the Odenwald occupied a distal position to a Neoproterozoic magmatic arc, probably in a back-arc basin related to the West African Craton. Such a U–Pb age spectrum of detrital zircons together with a Mesoproterozoic age gap is typical for sediments of Armorica in Europe during the Ediacaran to Carboniferous. Neoproterozoic igneous rocks extruded at 566 ± 2 Ma forming a volcano-clastic sequence of the Cadomian magmatic arc which is the wall rock of the Silurian to Carboniferous plutons of the entire West Odenwald. This is the first occurrence of an extensive Cadomian crystalline basement in the Mid-German Crystalline Zone. Metagranite dykes crosscut the foliation of the Cadomian para- and orthogneiss at 542 ± 3 Ma. The deformation and migmatization of the Cadomian basement are bracketed between 566 and 542 Ma. A similar late Cadomian event is known from the Bohemian Massif and the Armorican Massif. Large Cadomian plutons with an age around 540 Ma, like that of the northern Odenwald, are common for Armorica. Silurian to Devonian granitoids (434 ± 4 Ma, 411 ± 5 Ma) are witness to an active margin along the northern boundary of Armorica. The Cadomian basement of the Odenwald together with the Palaeozoic granitoids is overprinted by a high-grade metamorphism at 384 ± 4 Ma (U–Pb on zircon) and cooled down below ca. 500 °C at 370 Ma (K–Ar ages of amphibole; U–Pb on titanite). Such a combination of late Cadomian and early Variscan ages could be correlated with the Münchberger Nappe, the Tepla–Barrandian Unit, Central Armorican Domain and the Massif Central. [ABSTRACT FROM AUTHOR]