Magmatismo Neoproterozoico calcoalcalino en el Antiforme del Narcea (N de España)

Abstract

4 sequence of acid to basic igneous rocks is exposed within Neoproterozoic sediments of the Narcea Antiform (N of the Iberian Variscan Belt). Volcanic and volcanoclastic rocks, classically known as 'porphyroids', are rhyolites to andesites in composition. Cranodioritic to quartz-dioritic or gabbroic rocks are intrusive into the metasedimentary sequence and the volcanic rocks. Finally, hypabissal basaltic dykes are found cross cutting both the extrusive and intrusive rocks. The best outcrops of igneous rocks occur along the Tineo-Cilldn area forming, near Tineo, a continuous sequence ca. 350 m thick of volcanic-volcanoclastic units and basaltic dykes. Original igneous textures are preserved where deformational processes barely affected the sequence, whereas secondary mineral assemblages - spilitized rocks - reflect hydrothermal and/or metasomatic processes. Whole rock composition of the igneous rocks has a calc-alkaline affinity and reflects a crustally contaminated mantle signature