Zircon Compositions of Lower Mesozoic Redbeds of the Tethyan Margins, West-Central Mediterranean Area

Abstract

Typologic study and chemistry of zircon populations from Middle Triassic-Lower Liassic arenitic continental redbeds of the Internal Domains successions of the Mediterranean chains, from the Gibraltar Arc to the Calabria-Peloritani Arc, allow assessment of whether this type of study may be used to obtain more comprehensive inferences on the sedimentary evolution of ancient clastic rocks. Calabria-Peloritani Arc zircons are primarily euhedral, with subordinate rounded and subrounded grains. Rifian Maghrebides samples contain abundant euhedral zircons, with minor rounded and ovoid zircons. Betic Cordillera zircons are rounded or subrounded, with minor euhedral elongate grains; rounded zircons of these samples cannot be typologically classified. Electron-microprobe analyses (Si, Zr, Hf, P, and HREE) indicate homogeneous compositions, suggestive of common source areas characterized by granitoid rocks, whereas typology suggests the existence of two distinct groups. The first group includes arenites from the Calabria-Peloritani Arc and the Rifian Maghrebides. The second group includes arenites from the Betic Cordillera. Differences between the two zircon groups may be related to recycling effects, in agreement with a geochemical study of Triassic to lowermost Jurassic mudrock redbeds. Recycling likely was more significant for the Betic Cordillera samples. These results suggest that zircon typology and mudrock geochemistry can be useful tools for provenance, especially in complex sedimentary contexts where arenite-mudrock couplets occur.