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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

Castiñeiras García, Pedro and Navidad Fernández de la Cruz, Marina and Liesa Torre Marín, Montserrat and Carreras, Jordi and Casas Tuset, Josep María (2008) 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. Tectonophysics, 461 . pp. 228-239. ISSN 0040-1951

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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.


Item Type:Article
Uncontrolled Keywords:Pre-Variscan; Cadomian; Ordovician magmatism; SHRIMP Geochronology; U–Pb zircon dating; Eastern Pyrenees
Subjects:Sciences > Geology > Petrology
ID Code:14021
Deposited On:05 Dec 2011 12:39
Last Modified:05 Dec 2011 12:39

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