NEW CONSTRAINTS ON THE GEOLOGY OF BAIE VERTE PENINSULA, NEWFOUNDLAND: PART 1-TECTONOSTRATIGRAPHY OF OPHIOLITES AND THEIR VOLCANIC COVER

The tectonostratigraphy and geochronology of ophiolite and volcanic cover on Baie Verte Peninsula (Newfoundland Appalachians) provides valuable insight into the history of the Laurentian continental margin. The Betts Cove ophiolite comprises 489 Ma mafic/ultramafic cumulates, gabbro, sheeted dykes and pillowed boninites. Overlying these are plag-phyric island arc tholeiitic basalts that host VMS mineralization, and locally, ophiolite-derived conglomerates. Local tilting was followed by deposition of the Snooks Arm Gp. including jasper cherts and conglomerate, intermediate volcaniclastics, tholeiitic (OIB) basalts, and cpx-megaphyric intermediate breccia and felsic tuff. Green volcanogenic turbidites are overlain by tholeiitic basalt, graptolitic black shale, rhyolite (467 Ma) and basalt. The Pacquet Harbour Gp. comprises pillowed boninites overlain by island arc tholeiitic basalt and felsic volcanic rocks dated at 487 Ma (with 1- 2.6 Ga inheritance) that host major VMS deposits. Overlying these are red chert lenses, volcaniclastic rocks, plag-phyric, tholeiitic (OIB) basalts, felsic tuffs and volcanogenic turbidites. The Pointe Rousse Complex includes serpentinized harzburgite, ultramafic/mafic cumulates, gabbro, sheeted dykes and pillowed boninite. The overlying cover includes jasper iron formation, intermediate volcaniclastic rocks, cpx-megaphyric intermediate breccia, tholeiitic basalts (OIB) and gabbro dated at 482 Ma. The Advocate Complex comprises harzburgite, ultramafic/mafic cumulates and sheeted dykes. The overlying Flatwater Pond Gp. includes ophiolite-derived conglomerate and megabreccia with ophiolite-and platform-derived detritus, overlain by plag-phyric pillow basalts, cpx-megaphyric andesite tuff, and felsic volcanic rocks dated at 476 Ma (with 1 Ga and 2.6 Ga inheritance). We propose that a sheet of 489-487 Ma suprasubduction zone ophiolite and overlying juvenile island arc crust was obducted onto the Humber continental margin. Proximal megabreccia and distal ophiolite-derived flysch are the erosional products derived from the leading edge of this thrust sheet. Renewed back arc volcanism between 482 and 467 Ma resulted in the eruption of juvenile, mantle-derived mafic lavas and crustally contaminated felsic volcanic rocks.