The detrital zircon Hf and O isotope signals recorded in Paleozoic Saxothuringian clastic rocks of Germany: insights into the Eburnean and Cadomian orogenies

Saxothuringian sandstones of the Armorican Terrane Assemblage reflect a dichotomous detrital zircon age provenance signal representing the Eburnean Orogeny on the West African Craton (2200–2000 Ma) and the Cadomian Orogeny of northern Gondwana (750–540 Ma). We present O isotope data on detrital zircons from the Saxothuringian Zone of southern Germany, and Saxothuringian nappes in the Rhenohercynian Zone, including the first zircon O isotope data on the Cadomian Orogen. Considering exclusively pre-Silurian zircon ages, we find that the “reworked Eburnean provenance” for detritus reflecting the 2000–1800 Ma interval on the West African Craton is a misnomer. There are no Eburnean source rocks with ages in this range. The Eburnean Orogen formed by collision of the West African Craton with Amazonian Guiana leading there to the Transamazonian Orogeny. Detrital zircon ages between 2000 and 1800 Ma in Saxothuringian sedimentary rocks were likely derived through polycyclic transfer from northeastern Amazonia. Around 25% of our detrital zircon δ18O data from Saxothuringian sandstones on the Eburnean and Cadomian orogens are mantle-like. 60% and 40% of εHf(t) signatures representing the Eburnean and Cadomian orogenies, respectively, are suprachondritic. Supracrustal processes and reworking of metasedimentary crust predominate in the Transamazonian and the upper plate Cadomian orogens. The distribution of εHf(t) and δ18O zircon data representing both is similar. Data on the Eburnean Orogen show a stronger mantle influence. This may indicate that the Transamazonian Orogen occupied the upper plate in the collision between the West African Craton and Amazonia. Graphical Abstract