Cadomian arc recycling along the northern Gondwana margin: Source-inherited composition of Miaolingian rift-related rhyolitic rocks (Ossa-Morena Zone, SW Iberia)

Rhyolites and rhyolitic tuffs of the Freixo-Seg ' ovia Volcanic-Sedimentary Complex of the Cambrian of the Ossa-Morena Zone (Variscan belt, SW Iberia) were analyzed for petrography, major and trace element geochemistry, Sm-Nd isotopes and U-Pb zircon geochronology in order to deduce magma sources. New U-Pb zircon age data indicate that Freixo-Seg ' ovia rhyolitic rocks, previously assigned to the Terreneuvian, formed during the Miao-lingian (ca. 509-505 Ma). These rhyolitic rocks exhibit calc-alkaline signature, LREE enrichment, nearly flat HREE patterns, negative Eu, Nb and Ti anomalies, and are chemically similar to the bulk continental crust. Freixo-Seg ' ovia rhyolitic rocks have negative to slightly positive epsilon Nd(T) values (-2.8; 0.5) resulting in TDM model ages (1.0-1.3 Ga) that overlap the range defined by Terreneuvian Malcocinado andesites, formed in the tran-sition of the Cadomian (West-African) arc to continental rifting in northern Gondwana margin. Based on the Sm-Nd isotopic data, the Freixo-Seg ' ovia rhyolitic rocks may have resulted from of partial melting of andesitic crust. The presence of Ediacaran-age zircon in the Freixo-Seg ' ovia rhyolitic rocks indicates inheritance from the Cadomian arc. Inherited zircon grains with West African affinity were probably transferred into the rhyolitic magma from an older igneous source formed in the Cadomian arc. Based on their major and trace element composition, combined with isotopic and geochronological data, the Freixo-Seg ' ovia rhyolitic rocks record recycling of arc crust during a Late Cambrian rifting event along the northern Gondwana margin. The transition from Cadomian accretion to peri-Gondwana break-up leading to the opening of the Rheic Ocean is also known in other parts of the Variscan belt.

Automated summary

Rhyolites and rhyolitic tuffs from the Freixo-Seg'oVia complex in the Ossa-Morena Zone of the Variscan belt were studied to determine their magma sources. The results show that these rhyolitic rocks formed during the Late Cambrian and were derived from partial melting of andesitic crust. The presence of Ediacaran-age zircon indicates inheritance from the Cadomian arc. The major and trace element composition, isotopic and geochronological data suggest that these rocks record the recycling of arc crust during a late Cambrian rifting event along the northern Gondwana margin.