Paper No. 8
Presentation Time: 4:15 PM
EARLY ORDOVICIAN ARC CONTINENT COLLISION AND SYN- TO POST-COLLISIONAL VOLCANISM IN THE NEWFOUNDLAND APPALACHIANS, BAIE VERTE PENINSULA
On Baie Verte Peninsula (NL), Early Ordovician ophiolites and volcanic cover provide insight into juvenile island arc formation and syn-collisional submarine volcanism. In the east, the Betts Cove ophiolite complex comprises ultramafic cumulates, layered and massive 489 Ma gabbro and cogenetic, sheeted boninite dykes and overlying pillowed lavas (Bedard et al. 2000). Rare, thin felsic rocks occur within the lower lavas and underlying dykes. Overlying island arc tholeiitic pillow basalts are interbedded with intermediate TiO2 boninites, host VMS mineralization, and represent the upper part of a juvenile arc complex. In south-central Baie Verte, pillowed boninites and thin, felsic tuffs and flows are overlain by the 487Ma Rambler rhyolite and its attendant VMS mineralization. To the north, the Point Rousse ophiolite comprises mantle peridotite, layered ultramafic and mafic boninitic cumulates, 489 Ma trondhjemite, and overlying sheeted boninitic and island arc tholeiitic dykes and lavas. The Advocate Complex to the west is separated from the continental margin by the Baie Verte Line, and comprises a tectonically thinned and eroded sequence of mantle harzburgite overlain by layered cumulates, boninitic dykes and erosional remnants of boninitic and island arc tholeiitic lavas. The overlying ophiolite cover was deposited between 476 and 467 Ma. In the west, it comprises a proximal, <479 Ma ophiolite- and platform-derived conglomerate overlain by 476 Ma rhyolite, iron formation, and tholeiitic, pillowed basalts and tuffs. In the east, the conglomerates thins and gives way to basinal-facies iron formation, mafic tuffs, pillowed tholeiitic basalts, calc-alkaline basalt and 470 Ma felsic tuff, volcanic turbidites, and 467 Ma rhyolite and tholeiitic basalts. Ophiolite obduction was accompanied by erosion, deposition of conglomerates (479-476 Ma), followed by trench migration, episodic arc volcanism (470 Ma) and arc rift-related tholeiitic volcanism.