Much of west-central Yukon escaped glaciation and is underlain by leached and oxidized, deeply weathered bedrock. Background and anomalous metal values in these soils are presumed to be lower than normal and therefore increase the challenge of interpreting soil geochemical surveys. It is suspected that the geochemical contrast between background and anomalous values can be maximized by sampling a particular soil horizon or analysing a specific size fraction. One hundred and sixteen samples were collected from soil profiles at ten sites above four porphyry-style mineral deposits - Antoniuk, Revenue, Nucleus and Casino in the Dawson Range of the Yukon-Tanana Terrane. B-horizon soils are locally clay-rich, thin and poorly developed. C-horizon soils are unconsolidated and very coarse grained. Bedrock samples from each site were crushed and analysed for comparison. All samples were analysed using the Au plus 32 (FA-AA and ICP) package which is a popular and economical method currently employed in most exploration programs. The results are generally consistent within the few samples taken at each deposit, but vary considerably overall, and probably reflect the variable physio-chemical conditions between the deposits. Gold and copper are emphasized in the evaluation of the data, but gold data from the fine-grained fraction are incomplete due to insufficient material from the generally coarse-grained soils. Although statistical accuracy cannot be confirmed with such a small sample set, the following trends are recognized: - the highest gold values typically occur in the lowest soil horizon (C2) and in the -200 mesh fraction; - the highest copper values were found in both the -35+80 and -200 mesh fractions (deposit dependent) but were consistently richer in the C2 horizon; - metal values are commonly depleted in the highest B-horizon (B1), particularly in the +35-80 fraction; - metal values are most commonly enriched in the B2 and C2 horizons; - metal depletion is most pronounced in the -35+80 fraction; - there is a strong positive correlation between gold, copper and molybdenum; - in addition, As, Bi, P, and to a lesser extent, Sb and Sr have a strong positive correlation with gold, As, Sb, Sr and to a lesser extent Ba and Pb have a strong positive correlation with copper.

Cambrian (?) schist and phyllite of the Anvil Range, Yukon, host three large stratabound lead-zinc deposits: Faro, Vangorda, and Swim. Because geological exploration is limited by a thick cover of glacial overburden, geochemical techniques were tested in the area. These include bedrock sampling for primary halos and geochemical marker horizons, and glacial overburden sampling for secondary dispersion patterns. Multi-element geochemistry of bedrock indicates that the schist and phyllite are not distinctive in one or any combination of the trace elements analyzed. However, some younger rocks are enhanced in various elements: amphibolite in Ni, Cr, Co, and Cu; rhyolite in Pb and Sn; and granite in Sn. Despite presence of glacial overburden, the trace element content of bedrock is reflected in soils. Soils overlying magnetic greenstones are enriched in Ni and Cu, whereas soils overlying granite are slightly enriched in Sn content. Detailed bedrock, overburden and soil sampling at the Faro deposit reveals that primary Pb, Zn, Mo, and Ba halos exist about the ore zone. Mo parallels the visible alteration envelope, but Pb and Zn extend into the hanging wall and the footwall. Ba extends into the hanging wall but is not detected in the footwall. Secondary dispersion patterns are primarily related to the proximity of the Faro ore zone and type of parent material sampled. Till deposits have higher background and threshold values for Cu, Pb, and Zn than those of glaciofluvial deposits. Bath Pb and Zn distributions in overburden delineate the Faro #2 ore body; Zn extends to surface whereas Pb, in some cases, does not. This is a reflection of the type of overburden sampled. In general, Zn is the more consistent indicator of ore. The Zn anomaly is primarily hydromorphic in origin, cxZn having higher anomalous/threshold contrast than total Zn (11.1 for cxZn vs 4.8 for total Zn). The nature of the Pb anomaly is not understood. This thesis is available online at https://open.library.ubc.ca/cIRcle/collections/ubctheses/831/items/1.0302661. A copy of this thesis is available at the EMR library – TN27.Y8 M677.

Quantitative mineralogy, U-Pb geochronology of zircon and monazite, 40Ar/39Ar geochronology of muscovite and sericite, and Pb isotopes from galena in veins and feldspar in plutons provide insight into the age of metamorphism, mineralization, intrusion emplacement and the sources of metals at the Plateau South (MINFILE 105N 034, 035, 036) occurrences in central Yukon. Orogenic mineralization and metamorphism is ca. 110 Ma to 100 Ma, and possibly as old as ca. 130 Ma. Following deformation and regional metamorphism, two biotite-muscovite plutons, the Russell stock and Armstrong pluton, were emplaced at 95.39 ± 0.03 Ma and 95.51 ± 0.03 Ma, respectively. These plutons are here reassigned to the Tungsten suite based on mineralogy, chemistry and age. Coeval with these plutons are contact metamorphism and possibly intrusion-related mineralization. Lead isotopic data from galena cluster into two groups: Group 1 is enriched in thorogenic Pb with 206Pb/204Pb values between 18.31 and 18.14, 207Pb/204Pb between 15.62 and 15.55 and 208Pb/204Pb between 38.77 and 38.30. Group 2 is isotopically evolved with 206Pb/204Pb values between 19.13 nd 18.91, 207Pb/204Pb between 15.78 and 15.63 and 208Pb/204Pb between 39.24 and 39.07. We suggest that late Early Cretaceous mineralization is related to large-scale orogenic fluids that tapped primitive (deep?) metal sources and early Late Cretaceous mineralization, coeval with local intrusions, sourced isotopically distinct metals from the intrusions. Alternatively, all mineralization could relate to Early Cretaceous orogenic fluids but with heterogeneous, locally derived metal sources and thermal resetting of Ar ages near the intrusions.

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

New mineral discoveries in the Dawson Range have been heavily supported by soil geochemistry. The use of soil augers to penetrate through loess-rich units and into locally derived weathered bedrock has been important in the successful application of this technique. To assist the mineral exploration industry, we characterized the surficial geology, soils and permafrost of the northern Dawson Range. Mapping indicated that widespread loess is present in the study area and the thickest deposits are located in basins on the south side of the Dawson Range near the Donjek and White rivers. A mantle of weathered bedrock covers virtually the entire landscape. The texture of fluvial deposits is affected by stream order and base level changes along the Yukon River. By understanding the effects of slope, aspect, elevation and permafrost processes on surficial materials, a landscape model can be developed that will facilitate geochemical exploration and mineral development in the region.

The RAM zinc-lead-silver property in southwest Yukon Territory (105 D/4) is on the contact between metamorphic rocks of the Yukon Crystalline Terrane and foliated granitic rocks of the Coast Plutonic Complex. Both are intruded by an Eocene granitic stock. The metamorphic rocks, predominantly biotite-quartz pelitic schists, with amphibolite, marble, graphitic phyllite and foliated metagranite, may be partly Precambrian and are modified by metamorphism. Foliated granodiorite to quartz diorite of the Coast Plutonic Complex intrudes the metamorphic rocks. Rb-Sr analyses of two of these granitic rocks give a possible whole rock date for foliated granite of 143 Ma (initial 87Sr/86 Sr ratio of 0.7068), and a maximum age of 200 Ma, while K-Ar dating of hornblende and biotite separates from a granodiorite gives 106 ±4 Ma and 53.7 ±1.9 Ma, respectively. An Eocene, porphyritic microgranite stock (Rb-Sr whole rock date:: 43 Ma with assumed initial 87Sr/86Sr ratio of 0.705) discordantly crosscuts the older rocks on the property, and has probably reset the biotite K-Ar date in the granodiorite. Mineralization on the property includes small skarns (maximum size 15m x 6 m) with disseminated sphalerite and galena, in metasedimentary rocks of the Yukon Crystalline Terrane, near the Eocene stock. Assay of grab samples from the showings average 53.8 gm/t silver, 4.35% zinc, and 2.20% lead.

This report releases whole-rock geochemical assay results of 102 samples collected by the Geological Survey of Canada (GSC) and Yukon Geological Survey (YGS) from four Carlin-type gold zones (Conrad, Sunrise, Osiris and Anubis) in the Nadaleen Trend, Yukon.

This is a product of the Gold and base metals–southeastern Yukon (Selwyn basin) project funded jointly by the Geo-mapping for Energy and Minerals (GEM) program of Natural Resources Canada, and the Yukon Geological Survey (Government of Yukon).

Kalzas, in central Yukon, is a porphyry-style stockwork and sheeted-vein wolframite deposit. Alteration includes a potassic core, a quartz-tourmaline-sericite zone and an outer quartz-sericite-pyrite zone, the latter in excess of 2 km in diameter. Wolframite is confined to the inner two zones, in an oval area 1500 m by 800 m. The wolframite is disseminated within the quartz-tourmaline stockwork and also occurs as coarse crystals in sheeted veins. Mineralization occurs within Neoproterozoic to Early Cambrian Hyland Group quartzites and phyllites, which are likely intruded at depth by a pluton, possibly of the Cretaceous Tombstone Suite. From 1981 to 1984, Union Carbide carried out mapping, soil and rock geochemistry, an airborne magnetometer survey, road building, trenching and drilling of two diamond drill holes. Results from Copper Ridge's 2001 sample program range from 0.3% WO3 to 0.5% WO3 over widths up to 70 m. They demonstrate the potential to define a signifi cant resource of surface-mineable tungsten mineralization at a grade of 0.4% WO3 or better. Drilling is required to confirm grade continuity at depth and along strike.