The volcano-sedimentary rocks of the Semenof block of central Yukon have not been closely studied in the past. Recent bedrock mapping in the southern Semenof Hills highlights the presence of possibly two exceptionally well preserved, undeformed and unmetamorphosed volcanosedimentary sequences of Late Paleozoic age. The main sequence is composed, from bottom to top, of (1) 2- to 3-km-thick thinly bedded fragmental volcanic rocks interbedded with few limy intervals, (2) thick massive plagioclase- and clinopyroxene-phyric basaltic lava fl ows with clastic intervals, and (3) a 1- to 3-km-thick volcanic conglomerate. The other sequence, of lesser extent, consists of (1) a thin quartz-porphyritic felsic volcanic unit, less than 50 m thick, (2) 2- to 3-km of massive to pillowed fine-grained basaltic lavas, and (3) 100 m of fossiliferous Upper Carboniferous limestone. These two sequences sit in faulted contact on ~2 km of a deformed clastic sequence of unknown affinity.

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for a copy of this paper please contact the Yukon Geological Survey; geology@gov.yk.ca.

Mainly schitose clastic strata of the northern Selwyn basin underlie Lansing map area. These strata form rounded mountains, although jagged ridgelines occur in the thermal metamorphic aureoles surrounding six Cretaceous granitic plutons. Major faults occupy some broad northwest-trending valleys: two of these extend eastward as the Hess and Macmillan faults (Abbott and Turner, 1990) in the Macmillan Pass area; another appears to contine westward as the Robert Service Thrust Fault. Argentiferous galena veins were intermittently mined from the east edge of the map area from 1976 to 1985; whereas the stratiform base metal and disseminated gold potential of these rocks have been investigated during the 1990s.

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).

In 2008 Exploration Syndicate Inc. contracted Geotech Inc. to fly a regional-scale ZTEM survey covering a 25,000 km2 area (1 km line spacing) in the Selwyn basin. The survey footprint straddles the Canol Road in east-central Yukon and overlaps into the western Northwest Territories. In March 2013 Yukon Geological Survey purchased the survey data, and in May we received approval to distribute the data publicly. As no interpretation was included with the purchase of the data, Condor Consulting Inc. offered to process the data and generate maps, gridded data, and a report. Condor undertook the work at no charge, and their contribution to the project is gratefully acknowledged. This Miscellaneous Report comprises a number of parts: - original survey report produced by Geotech Ltd. describing the data acquisition and processing parameters; - raw survey data acquired from Exploration Syndicate Inc.; - a report summarizing the processing and interpretation undertaken by Condor Consulting; - a series of maps in pdf and tiff formats; and - gridded data. File sizes are large. If you experience problems downloading any of the products or would like to obtain the raw data, Geotech data, Multiplots, or any of the other files please contact us at geology@gov.yk.ca. The project was funded by the Canadian Northern Economic Development Agency (CanNor) through their Strategic Investments in Northern Economic Development program.

At present, little metal speciation information exists for most parts of the Yukon. The current database of knowledge is largely based on research from southern stream environments which tend to be warmer than Yukon streams. This presents a challenge for regulators and practitioners interpreting data from northern systems using guidance that is developed and defined by southern baseline data and effects. This study was designed using a preliminary approach to assist in filling the current information gap. The Selwyn Basin in the Yukon has natural elevated concentrations of metals including arsenic, mercury and selenium (EDI 2008, Gartner Lee 2007). Water quality studies that have been conducted within the Selwyn Basin have not considered the importance of metal speciation and changes in mobility and exposure to aquatic organisms inhabiting lotic watercourses likely impacted by both naturally elevated and anthropogenic (mining related) metal input sources. The objective of this project was to increase the understanding of metal speciation in relation to surface water and sediment metal concentrations within the Selwyn Basin at six discrete lotic watercourse sites over two seasons.

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 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.