Mid-Ordovician U-Pb ages of porphyroids in the Peloritan Mountains (NE Sicily): paleogeographic implications for the evolution of the Alboran microplate

Petrographic, geochemical and geochronological work on a metavolcanic suite interbedded in ametapelitic sequence of the Palaeozoic basement in the Peloritan Mountains (Sicily) is used to contribute to abetter understanding of the pre-Variscan geodynamic evolution of the former Alboran microplate. Major andtrace element data show that the volcanic suite consists of two main groups: an Intermediate Unit of andesitesand dacites with volcanic arc affinity and a Felsic Porphyroid Unit of rhyolites with peraluminouscomposition. Isotope dilution thermal ionization mass spectrometry U–Pb analyses for single- and multigrainzircon fractions from four samples of the felsic porphyroids yield results that are tightly clustered on or nearconcordia giving Caradoc ages in the range of 456–452 Ma. The consistent morphological characteristics andoscillatory zoning of the zircons indicate single-stage magmatic crystallization. Xenocrystic zircon grains withages of 1150 and 2015 Ma indicate that these rocks were developed upon a cratonic basement with Grenvillianand Transamazonian components, hence supporting a peri-Gondwanan origin. From the combined evidencewe conclude that this portion of the Alboran microplate formed as a Mid-Ordovician volcanic arc in a sectorof the peri-Gondwanan terranes that was affected by a tectonothermal Caradoc event.