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727554.pdf (7.53 MB)

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2022

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cc-by-sa (c) Pujol Solà, Núria et al., 2022
Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/191734

Cadomian metabasites of the Eastern Pyrenees revisited

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https://doi.org/10.1344/GeologicaActa2022.20.17

Resum

This study presents a new geochemical, petrological, and geochronological U-Pb dataset from Ediacaran metabasites of the Canigó and Cap de Creus massifs, Eastern Pyrenees. The rocks are composed of calcic amphibole + plagioclase + chlorite + epidote ± quartz plus titanite + apatite + ilmenite ± biotite ± rutile as accessory phases and show relict igneous textures. Peak pressure-temperature determinations share common conditions, ranging 452-482ºC and 5.2-7.7kbar. These intermediate P-T conditions suggest Barrovian-type metamorphism, most likely related to a collisional setting. The metabasites correspond to evolved basaltic rocks (Mg#<0.55) with moderate TiO2 content (up to 2.08wt.%) and relatively low Cr (43-416ppm). The rocks are moderately enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) (average (La/Lu)n of 2.7) and the N-MORB normalized multi-element patterns show negative slopes, with prominent negative Nb anomalies ((Nb/La)NMORB=0.33-0.78). These variations are akin to island arc tholeiites generated in back-arc basins and to other metabasites described in the Eastern Pyrenees with a putative Ediacaran age, and they differ from the Ordovician tholeiitic metabasites from the Canigó massif, which derived from a contaminated E-MORB source. The positive ƐNd(T) values (0.82-3.05) of the studied metabasites preclude a notable contribution from an older continental crust. U-Pb dating (LA-ICP-MS) of one chlorite-rich schist sample in contact with the metabasites from the Canigó massif yielded a main peak at ca. 632Ma. We argue that the Cadomian metabasites from the Pyrenees formed during back-arc extension in the continental margin of Gondwana and were later affected by (probably early Variscan) medium-P metamorphism before the HT-LP metamorphism classically described in the Pyrenees.

Matèries

Geoquímica, Geocronologia, Petrologia, Pirineus

Matèries (anglès)

Geochemistry, Geochronology, Petrology, Pyrenees

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Articles publicats en revistes (Dinàmica de la Terra i l'Oceà)

Citació

PUJOL SOLÀ, Núria, et al. Cadomian metabasites of the Eastern Pyrenees revisited. Geologica Acta. 2022. Vol. 20, num. 1-26. ISSN 1695-6133. [consulted: 3 of August of 2026]. Available at: https://hdl.handle.net/2445/191734

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