Sinistral displacement of the Pearya Terrane along the Canadian Arctic margin

W McClelland; S Malone; W von Gosen; K Piepjohn; A Laeufer

Structural and geochronologic observations from the Pearya Terrane, northern Ellesmere Island, provide insight into the origin of the Canadian Arctic margin. The composite terrane records amalgamation of various fragments between 475 and 460 Ma and was accreted via sinistral transpression to the northern margin of Laurentia by 425 Ma (Trettin et al., 1991). New U-Pb SHRIMP-RG (USGS/Stanford) data from igneous rocks of the Pearya Terrane help refine magmatic components of the composite terrane to include Neoproterozoic arc plutons (ca 960-970 Ma), a Cambrian syenite-monzodiorite complex (Ward Hunt Pluton: 539 + or - 4 Ma), Ordovician arc magmatism (Ayles Fiord Pluton: 475 + or - 3 Ma; Cape Richards Pluton: 464 + or - 3 Ma) and Devonian-Carboniferous magmatism (Petersen Bay plutonic complex: 332 + or - 2 Ma). Samples from the Ordovician Taconite River Formation provide unimodal peaks characteristic of arc settings with LA-ICPMS (Arizona LaserChron Center) detrital zircon U/Pb ages ranging from 440 to 480 Ma. The Pearya Terrane is cut by the Pearya shear zone, a major ductile structure defined by a thick zone of sub-vertical mylonites that consistently display a sinistral sense of shear. Mylonites exposed at Cape Columbia are cross-cut by leucocratic pegmatite dikes that give a U-Pb zircon age of 453 + or - 3.5 Ma. Quartz and feldspar deformation textures coupled with the orientation of a studied dike are consistent with emplacement during late sinistral deformation. Displacement on the Pearya shear zone at or prior to 450 Ma is interpreted to record translation of the Pearya Terrane toward or along the north Laurentian margin, outboard of the Franklinian Basin, in the early stages of the Baltica-Laurentia Caledonian collision. The Pearya shear zone merges with or is truncated by the Petersen Bay fault, a complex northwest-southeast contractional structure that marks a segment of the Ellesmerian boundary between the Pearya Terrane and Franklinian Basin. Major structures within the Pearya Terrane and at its margin are overprinted by post-Ellesmerian brittle deformation that records both sinistral and dextral displacement. The timing of this reactivation is poorly constrained but the effects of modifying the original Pearya Terrane-Franklinian Basin boundary are pronounced. The long standing correlation of the Pearya Terrane with Svalbard can be expanded to included parts of the Arctic Alaska, Farewell, and Alexander Terranes. Development of a major strike-slip boundary along the Canadian Arctic margin in the early Paleozoic with continued reactivation through the Tertiary is consistent with models arguing for large scale translation of Cordilleran terranes from the Arctic realm followed by translation of terranes during the Mesozoic opening of the Canada Basin.

Sinistral displacement of the Pearya Terrane along the Canadian Arctic margin

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