TIMING OF PEAK METAMORPHISM AND DEFORMATION ALONG THE APPALACHIAN MARGIN OF LAURENTIA IN NEWFOUNDLAND - SILURIAN, NOT ORDOVICIAN

U/Pb and Ar/Ar isotopic age data from the Corner Brook Lake region of the eastern Appalachian Humber zone in western Newfoundland indicate t hat regional deformation and peak amphibolite-facies metamorphism are Early Silurian. A lower limit on deformation is provided by a U/Pb zir con age of 434 +2/-3 Ma for a pegmatite that is affected by the region al foliation and is interpreted to be syntectonic. Monazite and rutile from a garnet-kyanite-staurolite schist, which records peak-metamorph ic conditions and in which porphyroblasts have overgrown the regional foliation, gave U/Pb ages of 430 +/-2 Ma and 437 +/-6 Ma, respectively . Ar/Ar cooling ages for hornblende from amphibolites and muscovite fr om psammitic and pelitic schists range from 430 to 420 Ma. A Silurian age for deformation and metamorphism of the Laurentian margin is coinc ident with the timing of similar events along the Newfoundland Gondwan a margin and suggests that the Silurian was a period of major continen t-continent collision.