U–Pb zircon ages (SHRIMP) for Cadomian and Early Ordovician magmatism in the Eastern Pyrenees: New insights into the pre-Variscan evolution of the northern Gondwana margin

Abstract

New geochronological data from low- to medium-grade metamorphic areas of the Eastern Pyrenees (Canigó, Roc de Frausa and Cap de Creus massifs) confirm the presence of two significant pre-Variscan igneous events: Ediacaran–Early Cambrian and Early Ordovician. The Ediacaran–Early Cambrian (580–540 Ma) magmatism is characterized by metavolcanic plagioclasic gneisses (metatuffs) coeval with sedimentation and by sheets of granitic orthogneisses emplaced in the lower part of the metasedimentary series. In the Canigó and Roc de Frausa massifs, the metatuffs are spatially associated with metabasites. Both lithologies occur as massive layers of lava flows, discontinuous lense-shaped, subvolcanic, gabbroic bodies or volcanoclastic tuffs interbedded in the lower and middle part of the pre-Upper Ordovician metasedimentary succession. This magmatism is bimodal and has a tholeiitic and calc-alkaline affinity. The granitic orthogneisses represent thick laminar intrusions of subaluminous and aluminous composition. Early Ordovician (475–460 Ma) magmatism is represented by laccoliths of aluminous granitic orthogneisses emplaced in the middle part of the pre-Upper Ordovician succession. These geochronological data reveal the existence of an Ediacaran metasedimentary sequence and Cadomian magmatism in the Pyrenees and allow their correlation along the Eastern Pyrenean massifs. The data also show ages ranging from Neoproterozoic to Early Ordovician of the large bodies of granitic orthogneisses that intruded into the series at different levels. Both events represent the final stages of the Cadomian orogeny and its transition to the Variscan cycle in the Eastern Pyrenees. A Cambrian rifting event linking both cycles has not been identified in the Pyrenees to date. Our findings provide a better fit for the pre-Variscan sequences of the Pyrenees with those of the Iberian Massif and allow their comparison with other pre-Variscan massifs in Europe.