Discovery of the volcanic-associated massive sulphide (VMS) Kudz Ze Kayah (KZK) deposit in 1994, closelyfollowed by the discovery of the Wolverine VMS deposit, resulted in a period of intense exploration activity in Yukon. This led to the discovery of additional VMS mineralization that includes GP4F, Ice and significant new reserves at Fyre Lake. Numerous VMS prospects were identified. The Fyre Lake, KZK, GP4F, Wolverine, and Ice VMS deposits are hosted by the Yukon-Tanana Terrane (YTT) in the Finlayson Lake district of southeastern Yukon. The Fyre Lake deposit (8 200 000 tonnes of 2.1% Cu and 0.73 g/t Au) is stratigraphically lowest and occurs in mafic metavolcanic rocks of the Devonian to Mississippian Grass Lakes succession. The KZK and GP4F deposits (13 000 000 tonnes of 5.5% Zn, 1% Cu, 1.3% Pb, 125 g/t Ag and 1.2 g/t Au and 1 500 000 tonnes of 6.4% Zn, 3.1% Pb, 0.1% Cu, 89.7 g/t Ag and 2.0 g/t Au, respectively) are within the Devonian to Mississippian succession but lie stratigraphically above Fyre Lake in felsic metavolcanic rocks. The Wolverine deposit (6 237 000 tonnes of 12.66% Zn, 1.33% Cu, 1.55% Pb, 370.9 g/t Ag and 1.76 g/t Au) is hosted by Carboniferous rhyolitic metavolcanic rocks and carbonaceous argillite of the Wolverine succession. The Ice deposit (4 561 863 tonnes of 1.48% Cu ) occurs highest in the stratigraphy and is hosted within late Palaeozoic mafic metavolcanic and associated metasedimentary rocks of the Campbell Range succession. The YTT underlies a large part of Yukon, east-central Alaska and parts of British Columbia. VMS mineralization occurs within rocks of the YTT in the Dawson and Glenlyon areas of Yukon, in the Teslin-Rancheria area in Yukon and adjacent British Columbia, and in several areas within Alaska, as well as in the Finlayson Lake area of the Yukon. In the Dawson area, which lays adjacent to the massive-sulphide-rich Finlayson Lake district (before approximately 425 km of right lateral movement on the Tintina Fault), VMS prospects are hosted in Late Devonian to mid-Mississippian Nasina Assemblage and Permian Klondike Schist. In the Glenlyon area, massive sulphide mineralization and chert horizons occur within a belt of rocks that is at least 20 km long. In the Teslin-Rancheria area and adjacent northern British Columbia, several VMS prospects have been identified. The Alaskan VMS occurrences are in the Delta, Bonnifield and Trident Glacier districts. Exploration during this period was not confined to the YTT but extended into rocks of the North American miogeocline that are coeval, and possibly correlative, with Devono-Mississippian strata of the YTT. This led to the discovery of additional resources at the Marg and Wolf VMS deposits. The Marg deposit (5 527 002 tonnes of 1.76% Cu, 2.46% Pb, 4.60% Zn, 62.7 g/t Ag and 1.0 g/t Au) occurs in the Selwyn Basin within a Devonian to Mississippian sequence of carbonaceous siliceous phyllite, quartz-muscovite and quartz-chlorite phyllite and massive quartzite. These strata also host the Jane prospect. The Wolf deposit (4.1 million tonnes of 6.2% Zn, 1.8% Pb and 84 g/t Ag) occurs in the Pelly-Cassiar Platform within the Devono-Mississippian Pelly Mountains volcanic belt and is hosted by felsic metavolcanic and associated metasedimentary rocks. Numerous other VMS prospects, including MM, occur throughout the length of this 80-km-long volcanic belt. The newly defined VMS deposits are comparable in size to the average Canadian VMS deposit indicating the discoveries are significant. Mineralization in the YTT occurs in Late Devonian to Permian strata thus there are several prospective horizons and the potential for additional discoveries is significant.

Upper Devonian and Lower Mississippian metavolcanic rocks of Yukon-Tanana Terrane in southern Finlayson Lake and Frances Lake map areas occur in three thrust sheets, locally modified by a Cretaceous normal fault. The lower thrust sheet, the Big Campbell sheet, comprises the Upper Devonian to Lower Mississippian metavolcanic stratigraphy that hosts the main volcanichosted massive sulphide (VHMS) deposits of the district. Metavolcanic rocks in the middle thrust sheet, the Money Creek sheet, include the Upper Devonian Waters Creek and Early Mississippian Tuchitua River formations. The former comprises primarily felsic metavolcanic rocks and carbonaceous phyllite and is extensively intruded by sheets of comagmatic porphyry. The latter comprises primarily intermediate metavolcanic, volcaniclastic and epiclastic rocks. The upper thrust sheet, the Cleaver Lake sheet, is in part made up of Late Devonian calc-alkaline basalt and rhyolite, the Cleaver Lake formation, and comagmatic felsic to ultramafic plutonic rocks. Of these, the Waters Creek formation and the formations in the Big Campbell sheet have the highest potential to host VHMS deposits.

The Marg (Cu-Zn-Pb-Au-Ag) volcanogenic massive sulphide deposit is hosted within metasedimentary and metavolcanic rocks of the Devonian-Mississippian Earn Group and Mississippian Keno Hill Quartzite. These rocks form part of the Selwyn Basin, an off-shelf sequence that developed at the continental margin prior to Cordilleran deformation and accretion. Geological mapping and re-analysis of drill core was completed to re-assess the deposit and property-scale economic potential. The Marg deposit is deformed by at least three generations of structures that developed during Late Jurassic to Early Cretaceous time and are geometrically correlative with regional-scale structures such as the Robert Service Thrust and the Tombstone strain zone. The Marg deposit occurs within a southeasterly plunging, complex fold structure, a significant part of which has been removed by erosion. Discovery of additional stratigraphy comparable to the Marg sequence and new sulphide occurrences within the claims underscores both property and regional exploration potential. The presence of probable rift-related volcanism and mineralization within the Selwyn Basin, and the similarities of this mineralization to that within 'suspect' terranes, has implications for both regional tectonics and exploration.

The Wolverine polymetallic volcanic-hosted massive sulphide deposit occurs in a highly deformed but coherent stratigraphic succession of early Mississippian to early Permian metavolcanic and metasedimentary rocks of the Yukon-Tanana Terrane. The deposit is part of the emerging Finlayson Lake volcanic-hosted massive sulphide district and contains a geological resource of 6,237,000 tonnes grading 12.66% zinc, 1.33% copper, 1.55% lead, 370.9 g/t silver and 1.76 g/t gold. Local stratigraphy consists of four major units including (from oldest to youngest): (1) quartz-and feldspar-phyric volcaniclastic, carbonaceous sedimentary and porphyritic intrusive rocks; (2) interbedded argillite, aphyric rhyolite and magnetite-carbonate-pyrite exhalite; (3) fragmental rhyolite; and (4) interbedded carbonaceous argillite, greywacke, basalt and rhyolite. The mineralization consists of pyrite and sphalerite, with lesser pyrrhotite, chalcopyrite, galena, tetrahedrite-tennantite and arsenopyrite. Mineralization occurs as massive stratiform, massive replacement and sulphide stringer veins. Sulphides are typically massive, fine-grained, layered and locally brecciated. Styles of hydrothermal alteration identified in the host rocks include proximal silicification and more distal chloritization, sericitization and, in places, carbonatization. Future research will be focussed on identifying the salient physico-chemical controls on the mineralization process and their implications for volcanic-hosted massive sulphide exploration in the district and elsewhere.

In 1978, a drillhole discovery of a barite associated massive sulphide was made on the SUE claims by Conwest Exploration in central Yukon. This report presents geochemical data from some drill core of the massive sulphide.

A sequence of Permo-Triassic rocks within a 260 square kilometre part of the Kluane Ranges, southwestern Yukon, consists of Lower Permian volcaniclastic and sedimentary rocks, disconformably overlain by upper Triassic amygdaloidal volcanic rocks. Mafic to ultramafic rocks occur within the upper part of the Permian section and in the Triassic flows. Folding and faulting of this sequence is intense. The ultramafic rocks are peridotite-dunite complexes in the form of sills. Some gabbroic bodies have intruded along sill boundaries, but most are separate sills or dykes. Nowhere have they been found cutting rocks younger than the upper Triassic volcanics. Ni-Cu mineralization is spatially associated with the gabbros and peridotites. Dunite portions of ultramafic complexes are barren. Sulphide minerals include pyrrhotite, pentlandite and chalcopyrite, locally with pyrite, sphalerite and galena. Occurrences are classified as follows:: 1. Massive to stringer within country rock adjacent to gabbro intruding peridotite. 2. Massive to heavily disseminated at the country rock contact of gabbro intruding peridotite. 3. A) Heavily disseminated to nearly massive within gabbro intruding peridotite. B) Disseminated within separate gabbroic bodies. 4. Very weakly disseminated within peridotite. The mineralized gabbro-ultramafic intrusions are spatially related to the Triassic volcanic flows. The mafic and ultramafic rocks, their Ni-Cu deposits, and volcanic flows are believed to be related genetically. This report is accompanied by five geological maps as follows:: 1) Arch Creek (1::4760 scale; NTS 115 G/5 northeast); 2) Wellgreen area (1::4800 scale; NTS 115 G/5 northeast); 3) Linda Creek (1::2380 scale; NTS 115 G/6 northwest); 4) White River (1::4760 scale; NTS 115 F/15 northeast); and 5) Quill Creek (1::80 000; 115 G/5,6 north and 115 G/11,12 south).

not_specified

The upper Sixtymile River area is located approximately 128 km west of Dawson City, Yukon. Lithology in this area consists of Precambrian to Paleozoic metamorphic rocks, Paleozoic ultramafic rocks, Middle Jurassic pegmatitic and aplitic dikes, Upper Cretaceous porphyritic dikes and volcanic rocks with intercalated sedimentary rocks, Quaternary alkaline basaltic dikes and Quaternary alluvial sediments. Precious metal occurrences in these volcanic rocks are divided into two types, based on differences in local distribution, petrology and wall rock alteration: a gold-bearing pyrite-arsenopyrite type and a silver-bearing galena-sphalerite type. Both types are characterized by four stages of mineralization.

The Yukon-Tanana Terrane (YTT) in the Finlayson Lake region (FLR), southeastern Yukon, Canada is host to five volcanic-hosted massive sulphide (VHMS) deposits (total -34 Mt) that have been discovered since the mid-1990's. In this thesis, field, lithogeochemical and Nd isotopic data are presented for felsic and mafic igneous rocks in the FLR to understand the tectonic setting, style of magmatism, and their relationships to VHMS mineralization. All rocks in the FLR were built upon a continental (or continent-derived) substrate of pre-Mississippian (>365 Ma) age. The Fire Lake unit (FLU) reflects Devonian-Mississippian (-365-360 Ma) arc and back-arc magmatism built upon a composite basement of oceanic and continental (or continent-derived) crust above an east-dipping subduction zone. Models proposed herein for the magmatic and tectonic evolution of FLU include: 1) arc magmatism punctuated by back-arc basin generation; 2) ridge propagation into an evolving arc with subsequent evolution to back-arc magmatism; and/or 3) ridge-subduction (slab-window) with eventual back-arc basin magmatism. The Kudz Ze Kayah (KZK) unit overlies the FLU and consists predominantly of crustally derived Devonian-Mississippian (-360-356 Ma) felsic volcanic and high-level subvolcanic rocks and variably carbonaceous sedimentary rocks; the latter are crosscut and overlain by alkalic mafic rocks. The high field strength element (HFSE)-enriched (A-type) felsic rocks and alkalic mafic rocks in the KZK unit are inferred to represent magmatism within an ensialic back-arc basin upon evolved crust. The Wolverine succession (WS) unconformably overlies the KZK unit and consists of a lower succession of felsic volcanic and subvolcanic rocks with carbonaceous sedimentary rocks; the upper portion of the succession, above the Wolverine VHMS deposit, consists predominantly of aphyric rhyolitic rocks that are overlain basalt flows. Felsic rocks ofthe WS are broadly similar to those in the KZK unit and represent ensialic back-arc basin magmatism. However, the succession is younger (-356-346 Ma), and post-dates a period of uplift, deformation, and erosion prior to commencement of back-arc magmatism. Back-arc spreading eventually evolved to true seafloor spreading within the WS. Massive sulphide deposits in the FLR are preferentially associated with rocks indicative of high temperature magmatism (e.g., boninites, A-type felsic rocks) and extensional tectonic activity (e.g., back-arc rifting and spreading).