Chemical compositions of tourmaline from the Inch Conglomerate Formation, Dingle Peninsula, SW Ireland and their implication in provenance analysis

The Inch Conglomerate Formation within the Old Red Sandstone (ORS) successi on on the Dingle Peninsula contains metamorphic clasts that were derived lo cally from a basement high, thrust up along the Dingle Bay Lineament during Middle Devonian time. Tourmaline occurs in three types of clasts in the In ch Conglomerate: quartz-tourmaline veins, banded tourmalinites, and tourmal ine pegmatites. Chemical compositions and zoning trends of the tourmalines are very similar to those of tourmalines from SE Ireland, but are different from the north Connemara tourmalines. Together with petrological and geoph ysical evidence, we conclude that the metamorphic basement block that under lies the Dingle Basin has an affinity to the pre-Caledonian basement lithol ogies of SE Ireland rather than to the Connemara metamorphic complex.