Geochronology and isotopic geochemistry of Ediacaran high-K calc-alkaline felsic volcanism: An example of a Moroccan perigondwanan (Avalonian?) remnant in the El Jadida horst (Mazagonia)
Résumé
Reliable new U/Pb zircon data from volcanic felsic rocks outcropping in the El Jadida region (Moroccan Coastal block) were carried out on five samples. Concordant U/Pb zircon data yielded two main crystallization ages at about 605 Ma (described for the first time in this
area) and 580 Ma. These Neoproterozoic ages correspond to the Cadomian and/or to the end of the Pan-African orogenic cycle. The presence of inherited Mesoproterozoic zircons in the felsic magmatic rocks suggests that this older continental crust belonged to the Eastern Avalonia terrane, where sources of the same age are already known. Furthermore, isotopic Sm/Nd analyses were carried out on the same rocks and the results suggested that the source of the studied volcanic rocks has a TDM model age between 1.59 and 1.86 Ga, which may correspond to Paleo-Mesoproterozoic crustal components. The low values of ɛNd, together with the absence of magmatic mafic microgranular enclaves in the studied rocks, preclude any involvement of the mantle in the genesis of the El Jadida felsic rocks. 2018), we interpret the El Jadida Ediacaran high-K calc-alkaline magmatism hors (Mazagonia) as an example of a Moroccan perigondwanan (Avalonian?) remnant.