Turbidite provenance in the Lower Palaeozoic Manx Group, Isle of Man: implications for the tectonic setting of Eastern Avalonia

The provenance of turbidites from the predominantly Arenig-aged Manx Group has been constrained using petrographical and geochemical techniques. Petro graphical analysis of sandstones reveals that mono- and poly-crystalline qu artz grains of cratonic origin are dominant. Major. trace and rare earth el ement concentrations in both sandstones and mudstones complement the petrog raphical data indicating that the source of the sediments consisted of quar tzose basement and mature sedimentary rocks. There is little evidence of a juvenile volcanic input but a minor palaeovolcanic component of active cont inental margin affinity is present. There are indications of a more immatur e character in the oldest units but, on the whole, geochemical data from th e Manx Group suggest an overall passive margin setting. These results sugge st that Eastern Avalonia was attached to Gondwana during deposition of the Manx Group and that Iapetus oceanic crust did not subduct beneath the regio n before the end of the Arenig.