Tales from xenoliths: the link between the Papôa Volcanic Breccia and the Berlengas Archipelago (West Portugal): geodynamic implications

• Published in: Journal of Iberian Geology
• Main Authors: Rosa, Ana Rita, Cachapuz, P., Santos, Telmo M. Bento Dos, Pereira, Inês, Solá, A. Rita, Carvalho, D., Romão, José, Valverde-Vaquero, Pablo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2024
• Subjects: Crustal xenoliths; Magmatism; Mesozoic; Lusitanian Basin; Variscan orogeny; Peniche; Portugal; North Atlantic
• Online Access: http://hdl.handle.net/10400.9/4270; https://doi.org/10.1007/s41513-023-00218-6

ABSTRACT: The Papoa Volcanic Breccia (Peniche, West Portugal) is a Mesozoic pyroclastic deposit that includes numerous igneous and metamorphic xenoliths belonging to the Variscan basement of the Lusitanian Basin, in which this unit outcrops. These rocks correspond mostly to syenogranites and diatexites affected by intense pyrometamorphism and, despite their strong secondary alteration by weathering, they still preserve several original petrographic features that are traceable to the lithologies that comprise the Berlengas Archipelago, located 15 km offshore the Peniche coast. New geochemical and mineral chemistry data now indicate a genetic relationship between these basement xenoliths and the Late Devonian migmatites outcropping in the Farilhoes Anatectic Complex. Such evidence strongly suggests the physical continuity of these high-grade metamorphic terrains at least to the Peniche region, thus constraining the nature and composition of the crustal block beneath the sedimentary sequences of the Lusitanian Basin in the studied location. In addition, in situ LA-ICP-MS U-Pb dating of rutile formed during the pyrometamorphic event endured by the xenoliths provided an age of 92.3 +/- 1.4 Ma for the Papoa volcanic eruption, placing this occurrence within the third magmatic cycle related to the opening and spreading of the North Atlantic Ocean in the West Iberian Margin. RESUMEN: La Brecha Volcanica de Papoa (Peniche, Oeste de Portugal) es un deposito piroclastico de edad mesozoica que se encuentra en la Cuenca Lusitanica y que presenta numerosos xenolitos igneos y metamorficos procedentes del basamento Varisco de esa cuenca. Estas rocas corresponden en su mayoria a sienogranitos y diatexitas que estan afectadas por un intenso pirometamorfismo y que, a pesar de su fuerte alteracion secundaria debida a meteorizacion, conservan caracteristicas petrograficas originales que permiten asimilarlas a las litologias que componen el Archipielago de Berlengas, ubicado a 15 km de la costa de Peniche. Nuevos datos geoquimicos y ...