GEOLOGICAL DEVELOPMENT OF EASTERN HUMBER AND WESTERN DUNNAGE ZONES - CORNER-BROOK - GLOVER-ISLAND REGION, NEWFOUNDLAND

The Corner Brook-Glover Island region records the development of the i nternal domain of the Humber Zone and its relationship to the adjoinin g external domain and Dunnage Zone. The region preserves both the Laur entian margin basement-cover contact and the siliciclastic-carbonate t ransition within the cover sequence. Precambrian Grenville basement of the Corner Brook Lake Complex is the oldest lithostratigraphic unit a nd yielded a U/Pb zircon age of 1510 +/- 6 Ma. Three main lithostratig raphic assemblages overlie basement: silicic and mafic igneous rocks o f the Lady Slipper Pluton which yielded a U/Pb zircon age of 555(-5)(3) Ma; siliciclastic lithologies which include the South Brook and Sum merside formations; and carbonate-dominated sequences with elastic inc ursions which include the Port au Port, St. George, and Table Head gro ups, and the Breeches Pond, Irishtown, and Pinchgut formations. Dunnag e Zone units include plutonic ultramafic to mafic rocks of the Grand L ake Complex, dated by U/Pb zircon from trondhjemite at 490 +/- 4 Ma, v olcanic and epiclastic rocks of the Glover Island Formation, and the M atthews Brook Serpentinite, the latter restricted to fault slivers wit hin the Humber Zone sequence. The deformed Glover Island Granodiorite intrudes the Dunnage Zone rocks on Glover Island and is dated by U/Pb zircon and titanite at 440 +/- 2 Ma. Little deformed Carboniferous sed imentary rocks unconformably overlie both Humber Zone and Dunnage Zone rock units. Timing of regional deformation and peak amphibolite-facie s metamorphism in the eastern Humber Zone is constrained by isotopic d ata to the Early Silurian. In the Dunnage Zone, shear zones and foliat ion development both pre- and postdate the age of the Glover Island Gr anodiorite, with the later possibly temporally equivalent to deformati on in the Humber Zone. Final juxtaposition of the two zones occurred d uring Carboniferous movement of the Cabot Fault.