Structural settings and geochemistry of the Cynthia gold prospect, Tintina Gold Belt, Hess River area (105O/6), Yukon
공공데이터포털
The Cynthia property overlies a large (greater than 2x2 km) area of gold mineralization related to a Cretaceous Tombstone Suite quartz monzonite intrusive body. The mineralization is controlled by two district-scale fault zones and is especially intensive in the area of their intersection, located above and adjacent to the intrusive body. These larger structures host abundant gold-bearing massive and drusy quartz and chalcedony veins, zones of intense stockwork and strong brecciation, as well as numerous mineralized felsic dykes. The gold grades within the mineralized structures are commonly in the range of 200 ppb to 2.0-3.0 g/t Au, with higher (up to 16 g/t Au) values attributed to the fault intersection area. Multi-staged gold mineralization found in the quartz veins, stockwork and altered dykes is associated with sulphide minerals (mainly pyrite and arsenopyrite) and elevated As, Bi and Ag values. A later mineralizing episode produced sulphide mineral-bearing chalcedony and drusy quartz veins, with gold concentrations accompanied by elevated Sb, Hg, Ag and Pb values, indicating the affi nity of epithermal style gold mineralization. The property is considered to represent a bulk-tonnage exploration target, with potential of the structures to host a major gold deposit. During the 2002 exploration program, the prospect has been advanced to a drill-ready stage.
Geochronologic and Pb-isotopic constraints on gold mineralization at the Plateau South property (Yukon MINFILE 105N 034, 035, 036), central Yukon
공공데이터포털
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.
New mapping around the Slab iron oxide-copper-gold occurrence, Wernecke Mountains (parts of NTS 106C/13, 106D/16, 106E/1 and 106F/4), Yukon
공공데이터포털
Bedrock underlying the Slab iron oxide-copper-gold occurrence consists of fine-grained sedimentary rocks and schist of the Fairchild Lake Group (oldest unit of the Early Proterozoic Wernecke Supergroup), intermediate to mafic Slab volcanics, dioritic Bonnet Plume River Intrusions, and Early Proterozoic Wernecke Breccia that crosscuts all other units. The Wernecke Breccia was divided into two units: Type 1 and Type 2. Type 1 is limited in extent and consists of sedimentary and locally abundant massive magnetite clasts in a carbonate-magnetite matrix. Type 2 cuts Type 1 and comprises sedimentary clasts in a micro-breccia matrix. Iron oxide-copper-gold mineralization is associated with Wernecke Breccia. It occurs disseminated in quartz-carbonate veins cutting metasomatized sedimentary rocks, as sulphide veins that cut Type 1 breccia, as sulphide clasts in Type 2 breccia, as well as disseminated in the matrix of Type 2 breccia, and finally as sulphide veinlets crosscutting Type 2 breccia.
The Scheelite Dome gold project, central Yukon
공공데이터포털
La Teko Resources Ltd. acquired the Scheelite Dome gold property from Kennecott Canada Exploration Inc. in 1998. Kennecott had explored the central Yukon property since 1994. The strongly deformed Yusezyu Formation of the Upper Proterozoic-Lower Cambrian Hyland Group underlies the property and is intruded by unfoliated mid-Cretaceous granitic stocks, dykes and sills of the Tombstone Plutonic Suite (TPS). Vein-type (both metasediment- and granite-hosted), skarn and replacement mineralization on the property is associated with the TPS intrusives. Mapping, trenching and drilling by Kennecott identified numerous structurally controlled metasediment-hosted zones of mineralization within an east-west 3.5 km by 1.4 km > 40 ppb, gold soil anomaly. In 1997, a 13 hole 1052 m reverse circulation drill program tested the gold soil anomaly with the two best holes returning weighted averages of 0.48 g/t gold over 29 m (RC97-4) and 0.41 g/t gold over 61 m (RC97-11). In 1998, a seven hole 1268 m diamond drill program by La Teko tested targets defined using a combination of soil and rock gold anomalies, geological structures and chargeability and resistivity anomalies. Results included intersections of 1.04 g/t gold over 14.9 m, 1.07 g/t gold over 12.1 m, and 3.67 g/t gold over 7.7 m.
Geology and geochemistry of the Clear Creek gold occurrences, Tombstone gold belt, central Yukon Territory
공공데이터포털
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.
Preliminary observations from four reduced intrusion-related gold deposits, Selwyn basin, Yukon
공공데이터포털
Host rocks, veins and alteration in reduced intrusion-related gold (RIRG) deposits display similar features and distribution across the Tombstone gold belt (TGB). The primary intrusive rocks hosting gold at these deposits are felsic to intermediate, silica-saturated, alkalic to calcic, metaluminous to weakly peraluminous magnesian (calc-alkaline) granodiorite, quartz-monzonite, monzonite and syenite. Preliminary field and petrographic observations suggest that distribution of veins, vein textures, and their correlative vein selvedge alteration assemblages show similar distribution patterns to porphyry deposit models on a more spatially restricted but observable (drill core) scale. At each of the deposits examined on four properties, sulphide-poor (3–5% sulphide minerals) quartz veins were commonly observed proximal to the causative intrusion, whereas sulphide-rich (>10% sulphide minerals) veins tend to be more distal, though are commonly observed using the same fluid pathways as earlier veins. Early sulphide-poor quartz veins commonly exhibit potassic and locally sodic alteration in vein selvedges, whereas sulphide-rich veins typically coincide with phyllic (sericitic) alteration. Sinuous veins with diffuse boundaries suggest emplacement within a higher temperature ductile regime closer to the centre of the mineralizing intrusion, whereas sharp, straight-sided quartz sulphide-rich veins are more typical and emplaced within a moderate temperature brittle regime in the intrusion carapace and hornfelsed country rocks.