Abstract The Cordilleran orogen of western Canada and Alaska records tectonic processes than span over 1.8 billion years, from assembly of the Laurentian cratonic core of Ancestral North America in the Precambrian to sea-floor spreading, subduction, and geometrically linked transform faulting along the modern continental margin. The evolution of tectonic regimes, from Proterozoic intracratonic basin subsidence and Paleozoic rifting to construction of Mesozoic and younger intraoceanic and continent-margin arcs, has led to diverse metallogenetic styles. The northern Cordillera consists of four large-scale paleogeographic realms. The Ancestral North American (Laurentian) realm comprises 2.3 to 1.8 Ga cratonic basement, Paleoproterozoic through Triassic cover successions, and younger synorogenic clastic deposits. Terranes of the peri-Laurentian realm, although allochthonous, have a northwestern Laurentian heritage. They include continental fragments, arcs, accompanying accretionary complexes, and back-arc marginal ocean basins that developed off western (present coordinates) Ancestral North America, in a setting similar to the modern western Pacific basin. Terranes of the Arctic-northeastern Pacific realm include the following: pre-Devonian pericratonic and arc fragments that originated near the Baltican and Siberian margins of the Arctic basin and Late Devonian to early Jurassic arc, back-arc, and accretionary terranes that developed during transport into and within the northeastern paleo-Pacific basin. Some Arctic realm terranes may have impinged on the outer peri-Laurentian margin in the Devonian. However, main-stage accretion of the two realms to each other and to the Laurentian margin began in mid-Jurassic time and continued through the Cretaceous. Terranes of the Coastal realm occupy the western edge of the present continent; they include later Mesozoic to Cenozoic accretionary prisms and seamounts that were scraped off of Pacific oceanic plates during subduction beneath the margin of North America. Each realm carries its own metallogenetic signature. Proterozoic basins of Ancestral North America host polymetallic SEDEX, Cu-Au-U-Co-enriched breccias, MVT, and sedimentary copper deposits. Paleozoic syngenetic sulfides occur in continental rift and arc settings in Ancestral North America, the peri-Laurentian terranes, and in two of the older pericratonic Arctic terranes, Arctic Alaska, and Alexander. The early Mesozoic peri-Laurentian arcs of Stikinia and Quesnellia host prolific porphyry Cu-Au and Cu-Mo and related precious metal-enriched deposits. Superimposed postaccretionary magmatic arcs and compressional and extensional tectonic regimes have also given rise to important mineral deposit suites, particularly gold, but also porphyries. Very young (5 Ma) porphyry Cu deposits in northwestern Vancouver Island and sea-floor hotspring deposits along the modern Juan de Fuca Ridge off the southwest coast of British Columbia show that Cordilleran metallogeny continues.

Abstract Exotic terranes of inferred Arctic affinity form an outer belt within the North American Cordillera extending from Alaska to northern California. The geological history, fossil and detrital zircon data for these terranes show strong correlations and linkages among them, and many features in common with the northern Caledonides, the Timanide orogen and the Urals. They probably occupied an intermediate position between Baltica, Laurentia and Siberia, in proximity to the northern Caledonides in Early Palaeozoic time. Westward dispersion of these terranes is interpreted to result from development of a Scotia-style subduction system between Laurentia–Baltica and Siberia in Mid-Palaeozoic time – the NW Passage – following closure of the Iapetus ocean. Diachronous orogenic activity from Late Silurian in Arctic Canada to Early Devonian in north Yukon and Alaska records passage of some of these terranes. Westward propagation of a narrow subduction zone coupled with a global change in plate motion, linked to closure of the Rheic Ocean are proposed to have led to initiation of subduction along the western margin of Laurentia. This is recorded by the Late Devonian initiation of arc magmatism along western Laurentia, and the Late Devonian–Early Mississippian Antler orogeny in the western US and Ellesmerian orogeny in the Canadian Arctic.

Abstract Palaeozoic to early Mesozoic terranes of the North American Cordillera mostly originated from three distinct regions in Palaeozoic time: the western peri-Laurentian margin, western (Asian) Panthalassa, and the northern Caledonides–Siberia. A review of geological history, fossil and provenance data for the Caledonian–Siberian terranes suggests that they probably occupied an intermediate position between northern Baltica, northeastern Laurentia and Siberia, in proximity to the northern Caledonides, in early Palaeozoic time. Dispersion of these terranes and their westward incursion into eastern Panthalassa are interpreted to result from development of a Caribbean- or Scotia-style subduction system between northern Laurentia and Siberia in mid-Palaeozoic time, termed here the Northwest Passage. Westward propagation of a narrow subduction zone coupled with a global change in plate motion, related to the collision of Gondwana with Laurentia–Baltica, are proposed to have led to initiation of subduction along the western passive margin of Laurentia and development of the peri-Laurentian terranes as a set of rifted continental fragments, superimposed arcs and marginal ocean basin(s) in mid- to late Palaeozoic time. Diachronous orogenic activity from Late Silurian in Arctic Canada, to Early Devonian in north Yukon and adjacent Alaska, Middle Devonian in southeastern British Columbia, and Late Devonian–Early Mississippian in the western USA records progressive development of the Northwest Passage and southward propagation of subduction along western Laurentia.