Meta-sandstone, siltstone and phyllite, with marble and intermediate-to-felsic tuffaceous horizons, host the Munson (TBMB) and Mod zinc-lead occurrences, about 7 km southwest of the Dan and Crescent properties. These host rocks are part of the Late Devonian Dorsey assemblage. Complexities resulting from isoclinal folding and faulting inhibit direct correlation of strata from one ridge exposure to another. The strata are overlain by dark meta-siltstone of the mid-Mississippian Swift River succession. Although faulted, the lack of a strong lithologic contrast between the units suggests only minor dislocation. Pre-Jurassic and Cretaceous granites and a diorite sill intrude the Dorsey rocks. Chloritic tuffaceous layers host showings of pyrrhotite, chalcopyrite and sphalerite; carbonate pods contain sphalerite + galena ± pyrrhotite; and quartz-feldspar meta-tuff layers are pyritic. U-Pb zircon age results for leucosome from a nearby exposure of lower Dorsey rocks indicate an approximate crystallization age of 373 Ma, and about 358 Ma for a granitic dyke in the upper Dorsey assemblage, bracketing the age of deposition of this Yukon-Tanana Terrane assemblage.

not_specified

The TBMB claim group, 4 km southwest of the Dan occurrence in the upper Swift River area of stratiform zinc occurrences, reveals the nature of the host rocks and style of folding. A train of east-southeast-trending, east-northeast-verging, km-scale F1 overturned anticlines and synclines dominates the area. These folds clearly control the distribution of low metamorphic grade tectonites (in map and vertical cross-sections) and a structural model allows definition of general stratigraphy of the TBMB and BOUND claim areas. A lower, an intermediate, and an upper unit of siliciclastic metasedimentary rocks are separated by two intervening units of base-metal -sulphide-bearing strata (acid to intermediate metavolcanic rock and marble, respectively). Based upon the repetitive F1 folds (possibly associated with thrust faults) and the similarity of rock types in the TBMB and Dan areas, the authors propose a structural linkage between them.

not_specified

Marble, calc-silicate rock and pelitic layers of the Ram Creek assemblage surrounding the Dan Zn (± Cu-Pb-Ag) occurrence display ample evidence of a monocyclic structural evolution with three main events of progressive deformation (D1-D3). These events developed a tightly folded package of west-northwest-trending tectonites. Primary planar structures (S0) generally lie sub-parallel to two tectonic foliations (S1 and S2), which dip shallowly to steeply southwest. Inter-foliation slip (D3) resulted in a transverse, sub-vertical foliation (S3) that dips generally shallowly to moderately north. Cross-sections based on new mapping and fold analysis indicate that similar folds containing stratabound zinc-sulphide mineralization should be present south of the Dan occurrence, as part of regional north-northeast-verging folds or a thrust-fault-repeated succession.

During the 2000 field season, a project was initiated to study the geology, geochemistry and alteration characteristics of high-level subvolcanic porphyritic intrusions associated with the Wolverine volcanic-hosted massive sulphide deposit in the Finlayson Lake district, Yukon. Subvolcanic porphyritic intrusions within the Wolverine deposit are located approximately 10-20 m beneath exhalative sulphide bodies or iron-formation in four zones (Wolverine/Lynx, Fisher, Sable and Puck). Most intrusions are K-feldspar porphyritic (Fisher and Wolverine/Lynx Zones); however, a few are quartz and K-feldspar porphyritic (Puck and Sable zones). Feldspar-porphyritic intrusions consist of euhedral to subhedral grains of K-feldspar in a grey fine-grained matrix. Quartz-feldspar porphyritic intrusions contain slightly smaller feldspar crystals and blue to black glassy quartz eyes set in a fine-grained matrix. Most of the intrusions have non-peperitic upper margins with carbonaceous argillite (Wolverine/Lynx, Fisher, Puck). Some of the quartz- feldspar porphyritic intrusions are in contact with fine-grained volcaniclastic rocks along their upper margins (Sable); both types of intrusions have lower contacts with fine-grained volcaniclastic sedimentary rocks. These intrusions are, for the most part, unaltered and have only minor sericite-silica ±chlorite ±pyrite alteration and small mm-to cm-scale veinlets of quartz-sericite ±chlorite ±pyrite ± sphalerite. This suggests a pre-to syn-mineralization timing for the emplacement of the intrusions. The contribution of these intrusions to the heat and metal budget of the Wolverine deposit is the focus of ongoing research.

Magmatism in the Nahanni region, which defines the eastern extent of the Tintina Gold Province, is generally associated with tungsten mineralization and/or gold-copper-antimony-bismuth-lead-zinc metal occurrences. Intrusions are subalkaline, granitic to granodioritic, and contain several types of textural variations and highly evolved phases. The intrusions range from large composite batholiths to small stocks with associated felsic dykes and veins. Initial U-Pb and Ar-Ar geochronology reveals ages of 97.5-95 Ma with short (0.5-1.5 m.y.) cooling periods, although the intrusion associated with the Cantung tungsten-skarn orebody cooled over a relatively long period (3 m.y.). Magmatism in the area has been interpreted as crustally derived, however, the rare earth element primitive-mantlenormalized profile revealed negative niobium, tantalum and titanium anomalies suggesting an arctype setting. Furthermore, the granites lack volumetrically significant, primary peraluminous mineralogies characteristic of S-type granites.

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

Paleomagnetic results are presented for 154 specimens from 16 sites in the Late Cretaceous Seymour Creek stock, a small granodioritic intrusion emplaced into Paleozoic gneisses and schists of the Yukon-Tanana Terrane (YTT), west-central Yukon. Stepwise demagnetization of the specimens revealed steep characteristic remanent magnetization directions in 2 normal- and 14 reversed-polarity sites with a mean direction of declination D=65.0°, inclination I =-83.6° (alpha 95 = 4.3°, k =73.8). Geological relations suggest that the stock has not been tilted since its emplacement at 68.5 ± 0.2 Ma. The paleopole for the Seymour Creek stock at 55.2°N, 202.5°E (dp =8.3°, dm=8.5°), plots south of the North American apparent polar wander path. This suggests that the YTT has experienced a net 79° ± 36° counter-clockwise rotation, and a nonsignificant 2.4° ± 7.5° anti-poleward translation relative to North America since 68.5 Ma. This result does not agree with the previously reported large poleward translation and minimal rotation estimated for the YTT from paleomagnetism of the coeval Carmacks Group volcanic rocks.

Auriferous sheeted quartz veins and silicified shear zones occur along the margins and within adjacent hornfels zones of mid-Cretaceous Tombstone intrusions near the head of Clear Creek in the central Yukon. The lodes are the source for more than 120,000 ounces of downstream placer gold production. These lodes contain variable amounts pyrrhotite, pyrite, and arsenopyrite, with less abundant scheelite - alkali-feldspar, muscovite, biotite and tourmaline are common gangue phases. Grab samples of mineralization often contain gold grades in excess of 1 ounce per ton. Gold-to-silver ratios vary most commonly from 1:1 to 5:1. Gold-rich quartz veins cut all stocks, adjacent hornfels and associated lamprophyre dykes commonly contain greater than 1% arsenic. Bismuth, and less consistently tungsten and stibnite, characterize many of the most highly mineralized veins within and surrounding the stocks. Quartz veins along the intrusive-metasedimentary rock contact around the Pukelman stock are also enriched in lead and silver. R-mode factor analysis of multi-element geochemical data for 111 gold- and sulphide-bearing rock samples indicates that there are two geochemically distinct metal suites in the Clear Creek occurrences. The first is characterized by As-Au-Bi ± Sb, Te ore-related mineral association, which is typical of many intrusion-related deposits in the Tombstone gold belt. Less consistently, anomalous concentrations of Ag, Co, Cu, Fe, and Mo occur within these auriferous rocks. The second metal factor is defined by Ag-Bi-Pb ± As, Au and Te. It characterizes metalliferous vein samples that have uncommonly low Au: Ag ratios and may represent a second hydrothermal episode. Tungsten shows little consistent correlation with the metalliferous veins in either element suite.