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Mafic volcanic and clastic strata of the Middle Triassic Joe Mountain Formation, east of Lake Laberge, Yukon, represent a juvenile volcanic arc sequence. Mafic volcanic rocks of the Upper Triassic Lewes River Group were formed in the spatial and temporal continuity of Joe Mountain volcanism. Carbonate sedimentation took place in shallow oceanic subbasins adjacent to the arc from the Carnian to Rhaetian; these subbasins were separated by physiographic boundaries inherent to the arc, resulting in lateral stratigraphic variations. Polymictic conglomerate and turbiditic sequences of the Lower-Middle Jurassic Laberge Group unconformably overlie Triassic rocks. Two north-northwest strike-slip faults, the Laurier Creek and the Goddard, control the distribution of units. Joe Mountain Formation rocks are characterized by an east-west structural trend, whereas the Upper Triassic and Jurassic sequences are characterized by north-northwest trending tight folds and thrust faults. At least five post-accretion igneous suites intrude or overlie older stratigraphy, including the Late Cretaceous Open Creek volcanic complex.

The Joe Mountain area of the Yukon contains Middle Triassic to Upper Triassic volcanic, sedimentary and intrusive rocks of the Stikine Terrane. The Ladinian (~237 to 228 Ma) rocks of the Joe Mountain Formation of Stikinia are divided into four units, including: 1) a lowermost mafic-ultramafic complex (mTJM4); 2) a lower basalt-flow-dominated unit (mTJM3); 3) a volcaniclastic- and sedimentary-rockdominated unit; and 4) and uppermost unit of black pillow basalts and volcaniclastic rocks (mTJM4). In the Joe Mountain Formation there is a general increase in the abundance of volcaniclastic and sedimentary material, and a decrease in flow material, away from Joe Mountain suggesting that Joe Mountain is a volcanic centre. Hematite-magnetite iron formation was discovered in 2004 interlayered with unit mTJM3 basalts. These iron formations have anomalous metal concentrations, but more importantly, have hydrothermal geochemical signatures (e.g., high Fe/Al ratios) similar to volcanogenic massive sulphide-associated iron formations globally.

Paleozoic rocks of the Pelly Mountains, central Yukon, preserve greater than 150 m.y. of sedimentation, magmatism and base-metal mineralization. To identify secular trends in regional tectonics and metallogeny, a multi-year project on the stratigraphy of the Pelly Mountains in the Quiet Lake (105F) and Finlayson Lake (105G) map areas was initiated. Field studies during summer 2015 focused on two stratigraphic intervals: (1) mafic volcanic, volcaniclastic and clastic rock successions assigned to the Cambrian-Ordovician Cloutier and Groundhog formations (Kechika group); and (2) felsic volcanic, volcaniclastic and clastic rock successions assigned to the Devonian-Mississippian Black Slate and Felsic Volcanic formations (Seagull group). Cambrian-Ordovician strata were deposited in a marine environment characterized by episodic mafic volcanism and extensional tectonism. Devonian-Mississippian strata record the transition from an extensional turbidite basin to a metalliferous volcanic rift basin, and resemble key rock assemblages of the Selwyn basin (Earn Group) and Yukon-Tanana terrane (Grass Lakes and Wolverine Lake groups).

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The central Pelly Mountains in southeastern Yukon Territory consist of imbricate thrust sheets, which have undergone syn and post-thrusting deformation and metamorphism. The local geology is further complicated by intrusion of Upper Cretaceous batholiths, and by strike-slip faulting related to the Tintina Fault, a major northwest-trending transcurrent fault of uppermost Cretaceous or early Tertiary age. This faulting disrupts the northeast edge of the study area. Upper Devonian and Mississippian strata are present in at least two of the thrust sheets, but the Mississippian volcanic rocks occur in only one of them. The volcanic rocks consist of volcaniclastic material with minor interbedded flows, and were deposited in a submarine environment. Several coeval and cogenetic syenite and trachyte domes and small stocks are the remains of vent areas. Although the volcanic rocks are all highly altered and show evidence of widespread chemical mobility, trace element data indicate that the rocks are meta-luminous trachytes, most closely resembling peralkaline volcanics generated in extensional environments. This suggestion of a predominantly extensional tectonic setting in mid-Mississippian time in the Pelly Mountains is consistent with recent tectonic syntheses for the area. Stratabound and stratiform massive base metal sulphide deposits that occur within the Mississippian volcanic sequence are similar in many respects to the Kuroko-type volcanogenic massive sulphide deposits of Japan. The Pelly Mountains deposits, however, are among the first known occurrences in the world of Kuroko-type mineralization in a rift environment. A copy of this thesis is available at the EMR library – QE195 M67 1979. This thesis is available online at http://hdl.handle.net/2429/22257.

A lithologic succession is recognized in tectonites of the eastern Teslin suture zone in south-central Yukon. Metagraywacke and quartzite, marble, mafic metavolcanics, and interbedded metagraywacke and argillite outcrop on both limbs of an upright northwest-trending syncline at Little Salmon Lake. A body of equigranular granodiorite intrudes the basal stratigraphic units. The granodiorite and its host sediments were penetratively deformed during top-to-the-SW shearing and greenschist facies metamorphism. The granodiorite gives a Devono-Mississippian U-Pb zircon age (353 +1.3/-1.4 Ma) which is interpreted as the minimum age of crystallization. This provides a minimum depositional age for these suture zone protoliths. Based on the sedimentary succession and the age constraints, the eastern suture zone protoliths show a clear genetic link to other pericratonic terranes in the northern Cordillera.

The tectonic evolution of the Whitehorse trough in central Yukon is largely preserved by the Early to Middle Jurassic Laberge Group, an ~3000-m thick succession of synorogenic clastic strata that unconformably overlies arc and arc marginal rocks of the Lewes River Group. A two-year project was initiated to test a Sinemurian to Toarcian transgression of basal Laberge Group strata westward across the Whitehorse trough and examine the regional relationships between the timing of Jurassic exhumation, sedimentation, and terrane accretion in the northern Canadian Cordillera. Field studies in 2017 targeted basal Laberge Group strata at seven locations in central Yukon. At each field locality, basal Laberge Group strata are known or inferred to unconformably overlie the Povoas formation and multiple units of the Aksala formation. Pre-Early Jurassic unconformities may indicate variable basin topography due to the complex internal stratigraphy of the Lewes River Group, or that regional exhumation and erosion affected the Whitehorse trough prior to Laberge Group sedimentation.

New fieldwork investigating the provenance and stratigraphic setting of Triassic sedimentary rocks in the northern Cordillera focused on previously documented, but largely unstudied, exposures overlying the Yukon-Tanana, Slide Mountain and Cassiar terranes. We report on the lithologies observed and samples collected from the Sheldon Lake, Quiet Lake and Glenlyon map areas of Yukon, and McDame map area of northern British Columbia. Our research goal is to characterize sediment source regions in the Triassic and constrain early Mesozoic basin development in the northern Cordillera. We interpret the Triassic sedimentary evolution in Yukon and northern British Columbia to be intimately tied to collision of the Yukon-Tanana terrane with the ancient Pacific margin by closing of the Slide Mountain ocean. Our new samples collected from Middle to Late Triassic strata will further constrain that collisional event and add to the database that consists mainly of Early to Middle Triassic miogeoclinal rocks.

The Cache Creek (CCT) and Slide Mountain terranes (SMT), including the Seventymile Terrane in Alaska of the Northern Cordillera consist of oceanic assemblages that have been tectonically emplaced. The CCT has been enclosed by a series of arc terranes, whereas the SMT has been thrust onto pericratonic North America. Detailed studies of ultramafic rocks in CCT, SMT, Livengood Terrane and the Kluane metamorphic assemblage across Yukon, Alaska and British Columbia were conducted at nine site locations. The most common type of ultramafic rock present at these localities is serpentinized harzburgite. The ultramafic rocks from the CCT and SMT have been interpreted as the lower layers from dismembered ophiolite complexes. Samples collected from the CCT are consistently harzburgite, whereas samples from the SMT are both mantle-derived harzburgite and lherzolite. The variety of ultramafic rock present in the SMT suggests they were generated within contrasting geological settings.