Following more than a decade during which the reality of Pannotia was widely accepted, the existence of this Ediacaran supercontinent has come into question. This is due largely to advancing geochronology, which suggests that the supposed landmass had begun to break up well before it was fully assembled. Paleomagnetic data from this time interval have been used to both support and refute the existence of Pannotia, but are notoriously equivocal, and proxy signals of Ediacaran-Cambrian supercontinent assembly and breakup, although collectively compelling, can be individually challenged. Efforts to detect the mantle legacy expected of supercontinent amalgamation, however, are more compelling, and support large-scale mantle upwelling in the wake of Pannotia assembly. So, irrespective of whether Pannotia was a supercontinent or not, its assembly appears to have influenced global mantle convection patterns in a manner consistent with one. In the context of the supercontinent cycle, the question of Pannotia’s existence is of fundamental importance since it is central to the nature, duration and evolution of the cycle, it dictates the cycle’s geodynamic pathway from the breakup of Rodinia to the assembly of Pangea and, more crucially, it queries whether a full-blown supercontinent is needed to drive the cycle from one iteration to the next.

The Variscan belt of western Europe is characterized by the deformation of an anomalously wide continental passive margin, located in northern Gondwana, that acted as the lower plate during the upper Devonian – Carboniferous Variscan collision. Another feature in this collisional belt are the unrooted “allochthonous complexes” with lower crust and mantle rocks associated with dismembered ophiolite-like rocks, classically interpreted as sutures of putative oceanic realms (Rheic and/or Paleo Tethys oceans).

Many models have been built in the past decades to explain the architecture of the Variscan belt, generally using oversimplified geometries for the passive margin. When continents break apart, the lithosphere is thinned by stretching and “necking” through time. In rifted margins, the lower and upper continental crust become coupled and embrittled, causing major faults (i.e. extensional detachments) to propagate into mantle depths, and leading to mantle uplift. This process, “hyperextension”, is increasingly documented worldwide in recent passive margins and it may also be accompanied by magmatic activity derived from the decompression of the lowermost crustal components or even the mantle.

Two episodes of partial melting in lower crustal and/or mantle rocks can be identified during the long-lived evolution of the northern Gondwana passive margin, during Ordovician and lower Devonian, and can be associated with the margin stretching linked to ridge subduction. Inversion of a complex hyperextended margin depicting key magmatic features may explain most of the characteristics that can be observed nowadays in the West European Variscan Belt, including the unrooted nature of the complexes.

During Ediacaran to earliest Cambrian times, the Cadomian Orogen was formed on the periphery of the Gondwana supercontinent. The orogenic belt was structured in the geotectonic style of the recent western Pacific region. Cadomian arcs and marginal basins aged at c. 570-538 Ma were linked to an intense recycling (remelting) of crustal units of the West African and the Sub-Sahara cratons. The existence of an Upper Ediacaran glacial period at c. 566-560 Ma places the origin of the Cadomian orogen in high latitudes of the southern hemisphere. Due detrital zircon populations from Cambrian strata the Cadomian orogen shared a part of its geotectonic history with East Avalonia. Because of the split-off of Avalonia from Gondwana mainland the Rheic ocean became opened. Provenance studies point to a docking of East Avalonia onto southern Baltica at c. 430 Ma and to a closure of the Rheic Ocean at c. 430-420 Ma. In the aftermath, the re-opening of a narrow Rhenish Seaway happened in mid-Devonian time. Deposits formed on the Rheno-Hercynian margin display sedimentary supply from southern Baltica, while most East Avalonian sources were buried and not available for erosion. Siliciclastic shelf deposits of Saxo-Thuringia were derived from Cadomia and its West African hinterland. As a result of the closure of the Rhenish Seaway the old suture of the Rheic Ocean was overprinted. Pangea´s internal suture is complex and became formed by closure of two oceanic basins and thus, forms a “cryptic” structure.

The geochemistry of sedimentary sequences allows the recognition of patterns and shifts in geodynamic settings. On active margins, the contribution of these sequences to arc magmatism through processes such as subduction erosion is being actively investigated. Thick sequences were sedimented along the Gondwana margin between the Ediacaran and Cambrian times. These preserve the evolution of their sources, which are closely related to the activity of arc systems and nearby continental areas. In the Variscan Belt, the SW Iberian Massif (Ossa-Morena Complex) preserves a section of an arc whose evolution is followed through the characterisation of subduction-related magmatism and the coeval metasedimentary record, during a time interval spanning almost 100 Ma. This study reveals that arc magmatism was linked to synorogenic sedimentation in a complex and poorly explored way. In this sense, arc recycling is shown by the isotopic (Nd) equivalence between the sedimentary series and the mafic magmatism related with subduction onset (pre- to 602 Ma) preserved in this section. Early magmatic pulses of arc building (c. 602-550 Ma) are characterised by their adakitic signature related to the melting of a significant volume of slab-induced sediments, probably favoured by subduction erosion. Meanwhile, during late stages (c. 540-534 Ma), magmatism evolved towards greater mantle input associated with the progressive variation of the slab angle. This study provides a model for the petrogenetic and geodynamic evolution of the arc from the Ediacaran to the early Cambrian times, improving the accuracy of future paleogeographic reconstructions.