A 1,800-million-year-old Proterozoic gneiss terrane in Islay with implications for the crustal structure and evolution of Britain

A basement gneiss terrane is exposed in the western part of Islay, an island south of Mull in Scotland. This gneiss terrane has been inferred previously1–5 to be part of the Lewisian complex (that is, Archean in age), although no direct radiometric information is available. Bentley et al.6 questioned the Lewisian age for the basement and suggested that the Islay terrane is allochthonous. In this study we employ four different isotope techniques …