A look at the 1.8-2.2 Ga zircon distribution as a paleogeographic and provenance indicator for peri-Gondwanan terranes

The Paleoproterozoic orogenies are among the most significant crustal growth events recorded in Western Gondwana, as depicted by their strong detrital zircon signature into the Gondwanan and peri-Gondwanan sediments. Indeed, the Neoproterozoic–Cambrian sediments of peri-Gondwanan terranes, particularly those in Iberia, Meguma, Avalonia, and Ganderia, display distinctive 2.2–1.8 Ga zircon distributions. In the Iberian Massif, the Galicia-Trás-os-Montes (upper allochthonous) and Ossa-Morena zones present distinctive 1.95–1.9 and 2.1–2.05 Ga peaks, whereas West Asturian-Leonese and Cantabrian zones show a prominent ~2.0 Ga peak. The Centro-Iberian Zone also has a curve centred at 2.0 Ga but of greater wavelength. In contrast, the Avalonian and Ganderia sediments show multiple peaks between ~1.6 and ~2.1 Ga, whereas Meguma has a distinctive ~2.05 Ga peak. These unique distributions are most likely paleogeographic indicators of the diachronic Paleoproterozoic orogenic events from the western blocks (Amazonian Craton) to the eastern blocks (Sahara Metacraton) of Gondwana. Indeed, in the Amazonian and the North African Precambrian regions, the magmatic-metamorphic Paleoproterozoic events are mainly constrained to: (1) ~2.0–1.6 Ga in the western Amazonian provinces, (2) ~2.2–2.0 Ga in the Transamazonian province, (3) ~2.2–2.0 Ga in the West African Craton, (4) ~2.1–1.9 Ga in the Trans-Sahara Belt, and (5) ~2.0 Ga in the Sahara Metacraton. Furthermore, North African sedimentary rocks show peaks within 2.1–2.05 Ga in the western block, while eastern blocks show peaks within 2.1–1.9 Ga, which are generally congruent with adjacent cratonic orogenic events. Indeed: (1) Anti-Atlas Tonian-middle Cambrian sedimentary rocks show prominent 2.1–2.05 Ga peaks, coincident with the 2.1–2.05 Ga event in West African Craton, (2) Trans-Sahara Belt Ordovician sedimentary rocks display ~1.75, ~1.9 and ~2.1 Ga peaks congruent with the ~1.9 Ga event present in the basement inlier of this belt, and (3) Sahara Metacraton Tonian sedimentary rocks present a ~2.0 Ga peak consistent with the main 2.0 Ga event in this metacraton. However, Sahara Metacraton Cambrian rocks show 1.85 and 2.05 Ga peaks, most likely suggesting provenance from Trans-Sahara Belt or that these orogenic events have not yet been adequately identified in this metacraton. The 2.2–1.8 Ga zircon distribution is, in some cases, a distinctive feature throughout the Palaeozoic. For example, the middle-upper Devonian sediments of the Iberian Pyrite Belt display a prominent ~2.1 Ga peak, similar to the West African Craton, Anti-Atlas and Meguma, which do not occur in any of the other Iberian zones