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 McMillan deposit contains 1.1 million tonnes grading 8.3% Zn, 4.1% Pb and 62 g/t Ag in a manto-like replacement deposit in the Proterozoic/Lower Cambrian Hyland Group at the sheared contact between carbonate rocks and underlying shale. A smaller deposit to the south contains a further 0.4 million tonnes grading 9.3% Pb, 1.7% Zn and 214 g/t Ag. These deposits appear to lie in the footwall of a southward-dipping thrust fault which extends eastward toward the Hyland Gold property.

Recent discoveries of at least two types of volcanogenic massive sulphide (VMS) deposits hosted in varying terranes have greatly expanded the mineral potential of the Yukon Territory. Kuroko style deposits at Kudz Ze Kayah and Wolverine are hosted by an Early Mississippian felsic metavolcanic and carbonaceous sedimentary package within the Yukon-Tanana Terrane in the Finlayson Lake area. The massive sulphide lenses at Wolverine have spectacular grades and constitute a geological resources, as of November 1996, of 5,311,000 tonnes with 1.81 g/t Au, 359.1 g/t Ag, 1.41% Cu, 1.53% Pb and 12.96% Zn. New discoveries at the Fyre Lake and Ice properties continue to expand the volcanic hosted massive sulphide potential of the Finlayson Lake area. Fyre Lake is a copper-cobalt-gold Besshi-type deposit hosted by chlorite schist. Towards the end of the season DDH 65 at Fyre Lake intersected 31.3 m of 2.29% Cu, 0.53 gpt Au and 0.07% Co. The enigmatic, ""Cyprus-type"", Ice occurrence has copper-cobalt mineralization in mafic volcanic rocks that are interpreted to belong to the Slide Mountain Terrane. The last hole of the season, DDH IC96-34 intersected 20.56 m of massive pyrite, chalcopyrite and bornite with grades of 5.2% Cu, 0.6 gpt Au, 25 gpt Ag and 0.6% Co. Prior to discovery of Ice, volcanic hosted massive sulphide mineralization was unknown in the Slide Mountain Terrane in the Yukon. The Yukon-Tanana and Slide Mountain Terranes are not restricted to the Finlayson Lake area but cover a considerable portion of the Yukon Territory. West of Dawson the Yukon-Tanana Terrane contains several exhalite occurrences in the Devono-Missisippian Nasina Assemblage and the Permian Klondike Schist. Devono-Mississippian strata in the Yukon-Tanana Terrane may correlate with similar aged units in the Pelly-Cassiar Platform and Selwyn Basin where there are several massive sulphide occurrences. The Marg Deposit occurs at the northern edge of the Selwyn Basin; the MM, Bnob and Chzerpnough properties are hosted by extension related, pyritic, brecciated, felsic metavolcanic rocks within the Pelly-Cassiar Platform. The Yukon-Tanana Terrane extends westward into the Delta District of Alaska where there are at least 26 stratiform and replacement massive sulphide deposits and occurrences. Strata potentially correlative with the Yukon-Tanana Terrane hosts several volcanogenic massive sulphide deposits and occurrences in northern British Columbia.

The Mel deposit consists of a concordant, folded lens of barite and coarse recrystallized galena and sphalerite at the contact between Cambro-Ordovician limestone and shaly limestone. Based on diamond drilling since 1972, the deposit contains geological reserves of 6,200,000 tons grading 6.77% Zn, 1.92% Pb and 49.6% barite to a depth of 457 m. The mineralization is open to depth and the higher grade part of the deposit lies below 305 m.

The Brown-McDade deposit was the first vein system discovered in the Mount Nansen camp and has produced approximately 34,000 ounces (1058 kg) of gold and 131,000 ounces (4,075 kg) of silver from 225,000 metric tonnes of ore since production began in November, 1996. Production rates have varied since the mill start-up but the carbon-in-leach (CIL) plant is currently operating near capacity at 700 metric tonnes per day. Mining at the Brown-McDade open pit has exposed two separate and distinct deposit types. The first type is gold-silver vein mineralization hosted by a massive feldspar porphyry dyke. These fine-grained quartz-sulphide veins and vein breccia are enclosed by silicified and/or intensely clay-altered brecciated feldspar porphyry. The feldspar porphyry dyke has intruded along an igneous-metamorphic contact that has been mined over a strike length of 50 m in the southern portion of the pit. The second deposit type that occurs at the north end of the pit consists of a siliceous, sulphide-rich breccia in a pipe-like structure hosted by metamorphosed carbonate and clastic rocks of the Nasina Assemblage. The pipe is elongate in plan with a high-grade core approximately 15 m wide and 25 m long surrounded by a low-grade envelope consisting of quartz-sulphide stringers in a silicified breccia. The deposits are separated by a northeast-striking fault which truncates and offsets the main vein-dyke mineralization. The ore is composed of fine-grained quartz and sulphides in narrow veins or as matrix to a breccia of silicified and pyritized wall rock fragments. Unoxidized ore contains dark grey silica and pyrite, arsenopyrite, sphalerite, galena, sulphosalts, bornite, stibnite and chalcopyrite. Gold is genetically related to the pyrite phase of the mineralization and occurs as 5 to 50 micron-sized inclusions in pyrite grains. Oxidation of sulphide minerals extends to depths of up to 70 m and a large portion of the gold grains have been exposed by oxidation of the sulphides and post-depositional cataclastic fractures in the pyrite. The silver mineralogy is not as well understood but appears to be related to the base metal sulphide mineralization.

Sphalerite and tetrahedrite occur with arsenopyrite and minor chalcopyrite and galena in a tabular, fault-bounded body which cuts granitic rocks of the Cassiar batholith. Diamond drilling between 1986 and 1988 outlined a deposit 1100 m long and 50-100 m wide containing geological reserves of 12.3 million tonnes grading 6.17% Zn and 26 g/t Ag. These reserves are amenable to open pit mining and the deposit is open to depth.

The Vangorda deposit is a small (7.1 million tonne), SEDEX-type, Pb-Zn-Ag (barite) massive sulphide ore body, in the Anvil District, Yukon, Canada. The deposit is currently being open pit mined at aprroximately 13,000 tonnes per day by Curragh Inc. This paper illustrates the macroscopic deformational style of the Vangorda deposit. The deposit is deformed by four significant and one minor phase of deformation. Though there is a very good correlation in macroscopic structural style between the host phyllites and the sulphides, the Vangorda deposit has mesoscale textures that reflect extensive shearing of the orebody, especially in the baritic and pyrrhotitic massive sulphides. The orientation and location of features such as faults, joints, and various foliations provide important information that can be used to help predict and assess pit wall stability, potential problems with water, location of road access to the active mining area, and to predict loading pattern and charge of blasts. Furthermore, an enhanced understanding of the location and orientation of folds and faults, and which are major and which minor, are of importance in grade control during mining.

The AurMac property, located 35 km north of Mayo in central Yukon, includes two metasedimentary rock-hosted gold deposits: the 6158 koz Au Powerline deposit and the 845 koz Au Airstrip deposit. Mineralization at the Powerline and Airstrip deposits is characterized by gold in sheeted quartz veins and mineralized skarn horizons, respectively. The AurMac deposits straddle the Robert Service thrust fault whereby the Powerline deposit is hosted in the Late Proterozoic to Cambrian Hyland Group hanging wall, and the Airstrip deposit is hosted in the Mississippian Sourdough Hill Member of the Keno Hill Quartzite footwall. Host rocks comprise siliciclastic metasedimentary rocks, variably calc-silicate–altered calcareous metasedimentary rocks and magmatic rocks. Magmatic rocks in the Powerline zone consist of foliated mafic horizons that are geochemically similar to Cambro-Ordovician magmatic rocks found in Hyland Group metasedimentary rocks in the McQuesten, Mayo, Clark Lakes and Hart River map areas. In the Airstrip zone, magmatic rocks include a steeply south-dipping, unfoliated, aplite dike. Evidence for intrusion-related gold mineralization at AurMac includes sheeted vein and skarn mineralization similar to the intrusionhosted, intrusion-related gold deposits at Dublin Gulch, as well as the presence of metamorphic porphyroblast assemblages that suggest contact metamorphism. These findings suggest potential for further discovery of mineralized intrusion-hosted zones on the AurMac property and sedimenthosted, intrusion-related gold deposits elsewhere in the region.

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).

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