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A study of rare barium minerals from the Yukon Territory has resulted in the discovery of at least one and possibly five new species. The present investigation is concerned with one of these, a barium-calcium-iron-alumino-silicate, which is tentatively classed as an inosilicate and named keeleite. The optical and physical properties, a chemical analysis, and the calculation of its formula are presented. The mineral has also been successfully synthesized. An X-ray study of some supergene and alteration products present in the rocks revealed the presence of an interesting mixture of barium-calcium carbonate salts, similar to those obtained as laboratory products. A paragenesis Is also presented. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The map area is a four miles by ten miles strip that extends westward from the summit of Potato Hills. The centre of the map area lies about thirty miles north of Mayo, Y.T. Exposure is poor in many parts of the area, because of the thick Pleistocene cover. The rocks in the area are quartzites of the precambrian Yukon Group. Quartzite is generally micaceous and contains interbedded phyllite. Regional metamorphism (greenschist facies) has affected these rocks. An early bedding plane foliation has been modified by two distinct phases of folding. A granodiorite stock with related sills of similar composition has intruded the metamorphic assemblage and a five hundred feet wide thermal metamorphic aureole that contains corundum has been developed in the metasedimentary rocks around the stock. East trending and later north trending faults have disrupted the rocks. Mineralization in the area is of various types. Silver-lead-antimony veins occur in the west. A preliminary study of their mineralogy shows them to contain jamesonite, galena, sphalerite, chalcopyrite, pyrite, arsenopyrite, tetrahedrite and boulangerite in a gangue of siderite and dolomite. Secondary minerals include bindheimite or stetefeldite, anglesite, goethite, scorodite, covellite and chalcosite. Two stages of Pleistocene ice advance have modified the topography. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Macmillan Pass area is underlain by Hadrynian to Middle Devonian fine grained sedimentary strata and volcanic rocks of Selwyn Basin. Widespread occurrences of Upper Devonian debris flows and turbidites record uplift and erosion of older rocks to the west or northwest. Deposition of overlying, locally derived coarse clastic assemblages are related to subsequent formation of a graben-like, fault-bounded trough in the study area. Continued slow subsidence of the down dropped basin is reflected by anomalously large thicknesses of an overlying siliceous black shale unit. Upper Devonian strata are unconformably overlain by Mississippian(?) peri-tidal or shallow water clastic sedimentary rocks which record a gradual, northward sea level transgression. Paleozoic and older rocks are intruded by Cretaceous granitic bodies. Stratiform barite-lead-zinc mineralization on the Tom claims is contained in two tabular zones separated by a fault. Both zones occur at the transition between Upper Devonian locally derived coarse clastic rocks and overlying basinal shales. The two mineralized bodies together contain nine million tons of ore grade material averaging 8.6% Pb, 8.4% Zn and 2.8 oz/ton Ag, based on initial development work. The Tom West Zone, studied in detail, consists of seven stratiform mineral horizons, each with distinctly different characteristics. Ore textures vary from massive quantities of poorly bedded galena, sphalerite and pyrite to finely laminated barite and cherty argil lite with disseminated sulphide minerals. A mineralized and altered breccia body underlies the stratiform massive sulphide mineralization. Time-stratigraphic reconstructions of a cross-section through the Tom West Zone, with accompanying mineralogical and assay data, predicate a multi-stage genetic model. Each mineralizing event is time related to localized tectonic activity which resulted in the formation of depressions on the seafloor. Ore forming constituents were carried by geothermal fluids, ascending along cross-stratal permeability provided by deep-seated faults and venting to the seafloor through the breccia body. Exhalative fluids were initially relatively high temperature, cooling gradually through the life of the geothermal system. Observed metal and mineralogical zonation within the stratiform mineralization reflects these processes. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Unknown

Casino porphyry copper-molybdenum deposit ia in the Dawson Range, midway between Dawson City and Whitehorse, Y.T. Mid-Cretaceous granitic rocks of the Klotassin batholith form the backbone of the Dawson Range and have intruded the Yukon Hetamorphic Complex of Paleozoic or earlier age. A 70 m.y. old volcanic unit, the Casino complex, intruded the Klotassin batholith, and is cogenetic with Casino deposit. Hear the deposit extrusive volcanic rocks are unknown but formation of a subvolcanic plug of feldspar porphyry was followed by an explosive event that formed a steeply plunging, conical breccia pipe. This permeable pipe, about 2,000 ft. (670m.) by 1,200 ft. (400m.) at the surface localized hydrothermal fluids that formed large concentrically zoned alteration patterns during upward and outward percolation. A potassic alteration facies core, about 1,500 ft. (500m.) in diameter, is centered approximately on the breccia pipe, and is characterized by secondary magnetite, biotite and potassium feldspar. This core is surrounded by phyllic (quartz, sericite, sulphide) alteration that extends about 1,000 ft. (330m.) into adjacent rocks of the Klotassin batholith. Chalcopyrite and molybdenite are concentrated in the phyllic zone along the potassic alteration side of a pyrite halo. Peripheral, weakly developed zones of argillic (clay-carbonate minerals) and propylitic (chlorite) alterations are present. This characteristic location of economically significant minerals within a zonal distribution of alteration minerals provides an important exploration guide for porphyry-type deposits in the area. Breccia formation and hydrotherrnal zoning appear interrelated and probably result from escape of metal-bearing saline solutions from "wet" magmas derived from an underlying Benioff zone associated with subduction of an oceanic plate. Supergene enrichment, preserved because the area is unglaciated, probably occurred mainly in the Paleogene and resulted in an increase in the grade of copper by an average factor of 1.7 through precipitation of chalcocite in a subhorizontal enriched zone. Copper added to this zone was extracted from up to 500 ft. (l70a.) of overlying capping rock. Controls for enrichment processes include grade of original hypogene copper, favourable breccia occurrence and alteration, and presence of pyrite. A plate-tectonic model relates the genesis of Upper Cretaceous to Tertiary porphyry-type deposits to the evolution of the western and central Canadian Cordillera. Existence of two Benioff zones is assumed from definition of two distinct younging trends of intrusive centres. The first Benioff zone, initiated west of the Queen Charlotte Islands near the Middle Triassic, continued activity until the early Tertiary when 50 m.y. old granitic rocks and associated porphyry deposits near the eastern boundary of the Coast Crystalline Belt were formed. The second Benioff zone, initiated near the earliest-Cretaceous, extended under the western margin of the North America plate and produced stocks and associated porphyry deposits that become younger from west to east across the Intennontane Belt. Intrusive activity associated with both Benioff zones ceased at about the same time, 50 m.y. ago, implying that they became imbricated. As a result, the North America plate overrode the Insular plate. Doubling of these plates is reflected in the late Mesozoic and Tertiary uplift and erosion of the Coast Crystalline Belt. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Brown McDade Mine is a recent gold-silver discovery in the Yukon Territory, halfway between Whitehorse and Dawson. It lies in the area unglaciated during the Pleistocene Period. Diamond drilling and stripping in 1946 indicated commercial values across a width of 10 feet and over a length of 1000 ft. The geologic structure is that of a Late Tertiary, dyke-like body of quartz feldspar porphyry cutting quartz diorite of Jurassic or later age. This body has a Northwest strike and dips steeply west. The ore zone lies in the porphyry and is believed genetically related to it. The mineralization consists of a cherry-like fine grained blue quartz, with disseminated sulphides comprising less than 5% of the mass. Metallic minerals are pyrite, arsenopyrite, and sphalerite, with lesser amounts of galena, chalcopyrite, tetrahedrite, stibnite, bournonite, jamesonite and gold. The gold is associated with the pyrite in fine particles, the majority less than 150 microns in size. The gold-silver ratio is about one to ten. Sericitization and carbonatization are the chief forms of hydrothermal alteration, while considerable limonite, and around the ore zone, jarosite, have been produced by weathering. On the basis of comparisons with known deposits, the Brown McDade is considered to belong to the deeper epithermal type. It should continue to reasonable depths although the ore shoots are likely to be erratic. The area south of the main ore zone, underlain by schistose rocks will probably be unfavorable for the occurrence of ore. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

In March of 1987, the Geologic Survey of Canada conducted a major seismic refraction experiment in the Mackenzie Delta-Southern Beaufort Sea-Northern Yukon area. This study involves the analysis of a portion of the resulting data set. A 2D velocity profile through the Richardson Mountains of the northern Yukon has been constructed using raytracing to model the travel-times and amplitudes. The line is approximately 320 km long, running from a shotpointon the Eagle Plains in the south to one 50 km offshore in Mackenzie Bay to the north, with an average receiver spacing of 3.5 km. An additional shotpoint is located at Shingle Point, on the shore of Mackenzie Bay. A series of four sedimentary basins separated by major structural highs produces a complex basement structure. Two distinct upper crustal layers were modelled, a 5.95 km/s layer overlying a 6.3 km/s layer, as well as a lower crustal layer with a velocity of 7.25 km/s. Crustal velocity gradients are low (≤ 0.005 s⁻¹). The 6.3 km/s layer pinches out beneath the Beaufort-Mackenzie Basin in the north, accompanied by a thinning of the lower crust from a thickness of 20 km in the south to less than 10 km beneath MB. This results in the crust as a whole thinning from a thickness of 50 km under the Richardson Mountains to only 40 km under the Beaufort-Mackenzie Basin. The velocity of the upper mantle is 7.95 km/s. The modelling of shear wave arrivals indicate Poisson's ratios of 0.23 ±0.02 in the upper crust and 0.25 + 0.02 in the lower crust. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Tertiary Mt. Skukum gold - silver epithermal vein deposit occurs 65 km southwest of Whitehorse in the Yukon Territory. Veins are hosted by a sequence of nearly flat-lying Eocene Skukum Group andesitic volcanic rocks of the Mt. Skukum Volcanic Complex, part of the Sloko Volcanic Province which unconformably overlies these intrusive complexes as well as metamorphic rocks of the Yukon Group. Major known mineralized zones occur within a regional halo of propylitic alteration centered on a fault-bounded graben within Main Cirque in the southwestern corner of the Mt. Skukum Volcanic Complex. Each zone consists of steeply-dipping quartz-carbonate-sericite veins associated with major faults and rhyolite dykes which bound blocks of the graben. Precious metals occur as electrum and native silver as fine grains averaging 15 to 20 microns and locaIly exceeding 1 mm across, in veins containing only trace amounts of sulphides. Fluid inclusions indicate that vein minerals were deposited from hydrothermal fluids averaging 313°C with an average salinity of 0.7 weight percent NaCl equivalent. Primary inclusions show that depositional fluids existed under two pressure regimes; one close to hydrostatic, the other approaching lithostatic. Both reflect depths of deposition of about 470 m below paleosurface. Variable fluid pressures reflecting similar depths of deposition combined with variable liquid to vapour ratios in primary inclusions as well as abundant textural evidence of hydrothermal brecciation indicate that boiling was common during mineralization. Oxygen and carbon isotope composition of minerals in the deposit and surrounding wall rocks indicate that depositional fluids were meteoric in origin with no contribution from magmatic sources. Large depletions in 0¹⁸ content of andesitic rocks in the deposit area indicate a minimum water rock ratio over the life of the deposit of 0.81:1. Precious metals at the Mt. Skukum deposit were emplaced at relatively low temperature in a near surface environment by a circulating, meteoric water dominated, hydrothermal system driven by a heat source associated with the rhyolite dykes. Gold, leached from andesitic volcanic rocks and metamorphic and granitic rocks was precipitated with quartz and carbonate in permeable conduits such as fault zones, and breccia bodies. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Clinton Creek asbestos deposit is situated at 77 kilometres northwest of Dawson City on Clinton Creek in Yukon Territory. Yukon Metamorphic Complex of Ordovician to Devonian age (470 Ma, Rb-Sr date) covers most of the Clinton Creek area. The most prominent metamorphism of the area occurred in Permian time (245 to 278 Ma, K-Ar dates). Based on intensity and style of deformation of ultramafic bodies and country rocks it is suggested that the ultramafic rocks were emplaced probably during the Permian period. Tintina fault is a weak zone along which the alpine ultramafic bodies of Clinton Creek and probably some of the others along and close to the Tintina Trench were tectonically emplaced. These were later folded and metamorphosed with the country rocks. During latest Cretaceous-earliest Tertiary time (64.9 Ma, K-Ar date) the area was intruded by acid intrusive rocks. The youngest undeformed and fresh basalt is probably of Selkirk volcanics equivalent. Three prominent phases of deformation were delineated. Probably the oldest and most complex phase occurred during the Permian, along with the initial movement of the Tintina fault. Small, tight, isoclinal folds are characteristics of this phase. The structural trend (300* to 315') is roughly parallel to the direction of the Tintina Trench. Due to later deformations changes in direction of fold axes of this phase (190* to 350") is common. The second phase of deformation gave rise to large recumbent folds with trends varying from 270" to 290' with southerly vergence. Third phase of deformation gave rise to antiform structure of regional scale. The Porcupine and Snow Shoe ultramafic bodies are mined for chrysotiile asbestos. A few other ultramafic bodies contain appreciable amount of chrysotile-fibre but not of adequate quantity to be mined. Most of the ultramafic bodies are sheared or massive, and are devoid of known chrysotile-fibre. In general, if serpentinization is less than 75 percent there is no chance of commercial mineralization. Fairly intense fractures are essential to provider adequate openings for chrysotile-fibre formation in ore grade concentrations. Chrysotile-fibre bearing serpentinized ultramafic masses within argillite unit or at the contact of argillite and other units seem to carry ore grade or substantial amount of chrysotile-fibre. Evidence of Clinton Creek asbestos deposit mainly supports formation of chrysotile-fibre as fracture filling. Although evidence of fracture filling rather than replacement seems convincing and exists on a wide scale, a few evidence indicates replacement characteristics on minor scale. The main phase of mineralization is believed to occur at the end of Cretaceous when acid intrusive rocks intruded the vicinity of the Clinton Creek area. These intrusions could have provided warm aqueous solution to react with the existing serpentine along fractures. This resulted deposition of chrysotile-fibre in an essentially closed system. Analysis of isotopic dates of the Yukon Crystalline Plateau shows a distinct grouping of igneous activity at mid Cretaceous and latest Cretaceous time. Some isotopic dates of igneous and metamorphic rocks ranging from 135 to 230 Ma show a distinct younging trend away from the Tintina Trench. The trend suggests that the date at the Tintina Trench is about 200 Ma, and 2'50 kilometres perpendicular distance from the trench is 150 Ma. The apparent horizontal rate of isotherm migration is about 0.5 cm/yr. However, more data is required to confirm the speculation that the Tintina Trench represents an extinct geosuture and vanished ocean. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Devonian and Early Carboniferous marine clastic rocks of the Earn Group host several economically important stratiform massive sulphide and bedded barite deposits. Due to the chaotic sedimentation, considerable regional metamorphic overprint and, relative inaccessibility, little was known about the stratigraphy, the Late Devonian conodont fauna, or the age of the stratiform mineral deposits within the Earn Group. Conodont microfossils, however, are an excellent fauna for an Earn Group biostratigraphy program because of their ability to withstand both temperatures in excess of 400° C, and significant physical stress. With standard laboratory techniques conodonts were readily extracted from fine grain calcareous elastics and carbonate lenses within the Earn Group. The conodonts are described from three specific areas where the Earn Group is known to host stratiform barite and barite-lead-zinc mineral deposits: Macmillan Pass, Midway, and Gataga. As the majority of conodonts were diverse and well preserved platform elements of the genus Palmatolepis, the taxonomic studies focused on this genus; other genera including Ancyrodella, Icriodus, Klapperina, Mesotaxis, and Polygnathus were examined as part of the biostratigraphic/taxonomic studies. Previous to this study the widespread stratiform mineralization was dated as only Late Devonian. The conodont taxonomy and biostratigraphy in the Earn Group provide age constraints for duration and formation of the stratiform mineralization. The ability to tightly constrain the age of the stratiform mineralization adds to the knowledge of Earn Group deposition, the paleogeography of the Selwyn and Kechika Basins, and has implications for stratiform mineral exploration strategies in the Earn Group. On the basis of conodont faunal ages barite mineralization at MACMILLAN PASS apparently occurs as three different levels: 1) CATHY property - Eifelian to early Frasnian; 2) PETE, JEFF, GARY, and GHMS properties - middle to late Frasnian; 3) TEA property -Early Carboniferous. In addition, barite-lead-zinc mineralization at TOM and JASON properties likely occurs during middle to late Frasnian. In the GATAGA area barite and barite-lead-zinc mineralization have been recognized at several temporally distinct levels in the early to middle Famennian: 1) Lower rhomboidea Zone; 2) Lower marginifera Zone; 3) Upper marginifera Zone. Several other mineralized horizons are loosely constrained within the same interval. Within the MIDWAY area the stratiform barite mineralization at the EWEN and PERRY properties is of Early Carboniferous, Tournaisian age, and correlates broadly with the TEA barite in the Macmillan Pass area. In summary, events that produced stratiform barite-lead-zinc and barite mineralization in the Selwyn and Kechika Basins were not coeval. The Late Givetian and early Frasnian barite mineralization took place in the Macmillan Pass and southernmost Gataga areas. During the middle Frasnian barite and barite-lead zinc mineralization events occurred at Macmillan Pass. Several episodes of barite and/or barite-lead-zinc mineralization occurred in the Gataga area during the middle Famennian. The youngest barite mineralization events in the Earn Group took place in the Early Carboniferous, Tournaisian time at Macmillan Pass and Midway. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate