Ophiolite emplacement along the Baie Verte-Brompton Line at Glover Island, western Newfoundland

Knapp, Douglas Alan (1982) Ophiolite emplacement along the Baie Verte-Brompton Line at Glover Island, western Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The Glover Island Area of western Newfoundland spans the Humber-Dunnage Zone Boundary at the northern end of the Appalachian Orogen. Here a deformed ophiolitic pluton separates schists and gneisses (west) from mafic volcanic rocks (east). To the west, quartzo-feldspathic gneisses of the Cobble Cove Gneiss are structurally overlain by the Keystone Schist. To the east, the ophiolitic Grand Lake Complex is structurally juxtaposed against the Keystone Schist and unconformably overlain by volcanic rocks of the Glover Group. Farther east the Glover Group is unconformably overlain by the Corner Pond Formation and to the south, volcanic rocks and dykes of the Otter Neck Group are unconformably overlain by the Red Point Formation. -- The Cobble Cove Gneiss consists of granodioritic gneiss and metasomatized mafic dykes. It is followed eastward by metamorphosed greywackes, quartzites, conglomerates and mafic volcanics of the Keystone Schist. Intruded by mafic dykes and trondhjemite, cumulate ultramafic and mafic rocks of the Grand Lake Complex are structurally juxtaposed against the Keystone Schist. The Glover Group unconformably overlies the Grand Lake Complex and is divided into a lower metasedimentary unit termed the Kettle Pond Formation which contains abundant clasts derived from the underlying ophiolite, and an upper metavolcanic unit termed the Tuckamore Formation. Pillow basalts and mafic tuffs of the Tuckamore Formation are similar to low-K tholeiites. The Otter Neck Group consists of tholeiitic sheeted dykes and aquagene tuffs intruded by porphyries geochemically comparable to the Tuckamore Formation. It is unconformably overlain by metasediments of the Red Point Formation which are correlated with the Corner Pond Formation. Arenig conodants have been recovered from a newly discovered fossil locality within the Corner Pond Formation. -- The Cobble Cove Gneiss is interpreted as Grenvillian basement overlain by a Paleozoic metaclastic cover represented by the Keystone Schist. The Grand Lake Complex and Otter Neck Group are interpreted to represent Iapetus Ocean crust obducted during Taconic Ordgenesis. Exhumation during ophiolite obduction led to the formation of unconformities upon which the Glover Group, Red Point Formation and Corner Pond Formation were deposited. Similarities in lithology and structural sequence between Glover Island and Baie Verte indicate that the Baie Verte-Brompton Line is continuous between these two localities.

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