Early Paleozoic accretionary orogens along the Western Gondwana margin

The birth of the Alps: Ediacaran to Paleozoic accretionary processes and crustal growth along the northern Gondwana margin

“…630-590 Ma, representing a large contribution of Late Cryogenian to Early Ediacaran magmatic sources (Table 2, Supplementary Material 4). The most likely source seem thus to be widespread Pan-African magmatism along the northern Gondwana shelf (e.g., Meinhold et al 2011;Garfunkel 2015), most likely in the eastern segment (Siegesmund et al 2018;Stephan et al 2019a, b;Oriolo et al 2021), thus accounting for Neoarchean to Paleoproterozoic basement contribution of the Saharan Metacraton (Abdelsalam et al 2002;Liégeois et al 2013). The paleogeographic position at the eastern segment of the Gondwanan shelf is further supported by the characteristic Late Stenian to Early Tonian peak (ca.…”

“…550-540 Ma (Figs. 10, 11;Peucat 1986;Zulauf et al 1999;Dörr et al 2002;Linnemann et al 2007Linnemann et al , 2014Garfunkel 2015;von Raumer et al 2015;Moghadam et al 2017Moghadam et al , 2019Dörr and Stein 2019;Oriolo et al 2021).…”

“…The Ediacaran to Paleozoic northern Gondwana margin is mostly represented by northern African and European basement realms, which essentially record intracontinental and marginal orogenic processes, respectively (e.g., Meinhold et al 2011Meinhold et al , 2013Stephan et al 2019a;Oriolo et al 2021). The Ediacaran to Cambrian evolution is intimately related to the last stages of the Pan-African Orogeny, leading to the final assembly of Gondwana, and the nearly coeval Cadomian Orogeny, associated with a retreating accretionary margin, back-arc basin development and a magmatic flare-up (Linnemann et al 2007(Linnemann et al , 2014Murphy et al 2013;Garfunkel 2015;von Raumer et al 2015;Moghadam et al 2017Moghadam et al , 2019Oriolo et al 2021). Further subduction and coeval retroarc extension triggered the opening of the Rheic Ocean by the Ordovician, leading to the separation of Avalonia from the Gondwana margin and favoring crustal reworking of Cadomian domains (Murphy et al 2006;Linnemann et al 2007;Nance et al 2010Nance et al , 2012Stephan et al 2019a;Oriolo et al 2021).…”

“…The Ediacaran to Cambrian evolution is intimately related to the last stages of the Pan-African Orogeny, leading to the final assembly of Gondwana, and the nearly coeval Cadomian Orogeny, associated with a retreating accretionary margin, back-arc basin development and a magmatic flare-up (Linnemann et al 2007(Linnemann et al , 2014Murphy et al 2013;Garfunkel 2015;von Raumer et al 2015;Moghadam et al 2017Moghadam et al , 2019Oriolo et al 2021). Further subduction and coeval retroarc extension triggered the opening of the Rheic Ocean by the Ordovician, leading to the separation of Avalonia from the Gondwana margin and favoring crustal reworking of Cadomian domains (Murphy et al 2006;Linnemann et al 2007;Nance et al 2010Nance et al , 2012Stephan et al 2019a;Oriolo et al 2021). Long-lasting extension in the back-arc region resulted in the opening of the Paleotethys Ocean in the Silurian-Devonian (Stampfli 2000;Stampfli et al 2002;Schulz et al 2008;von Raumer et al 2013), which in turn gave rise to the drift of Cadomian blocks forming the Hun superterrane (Stampfli 2000).…”

“…In the first place, it is unclear whether subduction was continuous or episodic. This is particularly relevant during the Ordovician opening of the Rheic Ocean, thus implying a rifted margin or, alternatively, a retreating accretionary orogen (e.g., Garfunkel 2015;Zurbriggen 2017;Stephan et al 2019a;Oriolo et al 2021). The nature and extension of Paleozoic oceanic basins (i.e., incipient back-arc basins vs extensive oceanic crust development) is also a critical point with deep implications for the paleogeography of Cadomian domains (e.g., Stampfli et al 2002;Kroner and Romer 2013;von Raumer et al 2013;Žák and Sláma 2018;Romer and Kroner 2019): did they remain attached to the northern Gondwana margin or were they drifted far away from the mainland?…”