HR: 0800h
AN: T51A-0300    [Abstracts]
TI: Arc – arc collisional tectonics within the Central Mobile Belt of the Newfoundland Appalachians
AU: * Zagorevski, A
EM: azagorev@nrcan.gc.ca
AF: Geological Survey of Canada, 601 Booth St., Ottawa, On K1A0E8, Canada
AU: Rogers, N
EM: nrogers@nrcan.gc.ca
AF: Geological Survey of Canada, 601 Booth St., Ottawa, On K1A0E8, Canada
AU: van Staal, C R
EM: cvanstaa@nrcan.gc.ca
AF: Geological Survey of Canada, 625 Robson Street, Vacouver, BC V6B5J3, Canada
AU: McNicoll, V J
EM: vmcnicol@nrcan.gc.ca
AF: Geological Survey of Canada, 601 Booth St., Ottawa, On K1A0E8, Canada
AU: Valverde-Vaquero, P
AF: Instituto Geológico y Minero de Espaρa, La Calera 1, Tres Cantos, Madrid, 28760, Spain
AB: The Central Mobile Belt of Newfoundland Appalachians records the Ordovician arc – arc collision between the peri-Laurentian Red Indian Lake Arc of the Annieopsquotch accretionary tract (c. 480–460 Ma), and the peri- Gondwanan Victoria – Popelogan Arc (c. 473–453 Ma), which marks the closure of the Cambro-Ordovician Iapetus Ocean. Although the arc systems are in part coeval, they are distinguishable by the preservation of distinct structural histories and stratigraphies, unique basement characteristics as demonstrated by lead isotopic values of volcanic massive sulphide deposits and faunal differences. A modern analogue of such an arc - arc collision is observed in the Molucca and Solomon seas of the southwest Pacific. From such modern analogues it is evident that the Victoria – Popelogan Arc occupied a lower-plate setting during collision. This tectonic setting is demonstrated by subsidence of the Victoria – Popelogan Arc similar to the collision induced subsidence that is developed on the Australian active margin and Halmahera arcs of the Southwest Pacific. The timing of Victoria – Popelogan Arc subsidence is constrained by three age dates that form the last vestiges of arc volcanism (457 ± 2; 456.8 ± 3.1; 457 ± 3.6 Ma). These volcanic rocks are immediately overlain by Caradocian black shale of the Point Leamington Formation that marks the base of the Badger Group and the initiation of a successor basin. Caradocian black shale is noticeably absent from the top of the Red Indian Lake Arc with this time interval instead represented by a sub-Silurian unconformity, formed in response to collisional uplift. Emergence of the peri- Laurentian margin is demonstrated by detritus from it preserved in the Badger Group, which as it stratigraphically overlies the peri-Gondwanan Victoria – Popelogan Arc, requires that Iapetus was closed by this time. Following this collision, subduction stepped back into the outboard Tetagouche – Exploits back-arc basin. Whereas correlative tracts representing Ordovician arc – arc collision occur elsewhere within the Northern Appalachians and British Caledonides, none of them have as well preserved evidence as in Newfoundland.
DE: 1100 GEOCHRONOLOGY
DE: 5475 Tectonics (8149)
DE: 8178 Tectonics and magmatism
DE: 8185 Volcanic arcs
SC: Tectonophysics [T]
MN: 2007 Fall Meeting