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MARG DEPOSIT Page Index
Property and Ownership
The property is situated within sub-alpine to alpine terrain within the Patterson Range with elevations varying from 600 metres to 1,900 metres. The majority of the project is covered with a thin veneer of talus or colluvium. Overall, outcrop exposure averages less than 10%, although some slopes within cirque headwalls approach 70% exposure.
Geology and Mineralization Three major fault structures control the geometry of the major stratigraphic units. The northern-most fault, the Dawson Thrust, separates offshelf rocks of the Selwyn Basin from shelf rocks of the Wernecke Supergroup. The Tombstone Thrust imbricates rocks of the Keno Hill Quartzite and the Earn Group, host of the Marg deposit. The southern-most fault, the Robert Service Thrust, carries rocks of the Hyland Group onto Earn Group and Keno Hill Quartzite. The Wernecke Supergroup and other associated shelf rocks are not present in the vicinity of the Marg property. All of the rock units have been deformed by at least two and locally three, phases of deformation. The structures are generally composed of varying degrees of ductile and brittle deformation, compatible with the lower to middle greenschist facies metamorphic grade of the region and vary depending upon proximity to the thrust faults. The first phase of deformation is characterized by north to northeast vergent, overturned, isoclinal folds whose axial surface parallels the south-dipping, regional-scale thrust faults. These folds, and related thrust faults, define the major south-dipping aspect of the thrust panel, with the majority of fold axes and associated linear features plunging to the southeast. Refolding of first phase structures locally produces a penetrative rodding and mineral lineation plunging to the southeast and a second axial planar cleavage. A later phase of deformation consists of upright, open to tight, southwest vergent folds. These third phase folds have axial planes with steep northeasterly dips and fold axes that plunge to the south-southeast.
Mineralization is concentrated within the southern and central limbs in the western part of the Marg deposit, but becomes progressively concentrated in the northern or lower fold nose to the east and down plunge. This transition from upper to lower fold limbs indicates that the original strike of the deposit was at a shallow angle to the fold structure. Sulphide minerals consist of pyrite, sphalerite, chalcopyrite, galena, tetrahedrite and arsenopyrite in a gangue of quartz, ferroan carbonate, muscovite and rare barite. Magnetite is notable absent. Sulphide sheets are massive to semi-massive with sharp or less commonly gradiational interlayered contacts. Alteration haloes of pervasive muscovite and carbonate are moderately developed and most conspicuous within the volcanic rocks. Black chlorite occurs locally, most notably near the up-dip footwall of the upper sheet. Alteration is accompanied by enrichment in base metals as well as mercury, molybdenum, arsenic, silver, nickel, barium and manganese. Sulphide mineralization is commonly overlain or underlain by silica, ferroan carbonate and more rarely, barite layers of possible exhalative origin. Exhalative horizons range from three to 300 centimetres thick and are most prominent in the central to eastern part of the deposit, commonly marking the structurally inferred location of the sulphide horizon where sulphide mineralization is minimal or absent. Interpreted exhalites are highly anomalous in base and precious metals as well as the indicator elements. Previous Exploration In 1982, the area was re-staked by the ZX joint venture between SMD Mining Company Ltd. (now Cameco), Chevron Minerals Ltd. and Enterprise Exploration Ltd. (an Australian exploration subsidiary of Rio Tinto). An exploration program carried out included hand trenching in geochemically anomalous areas in search of sedimentary exhalative-style lead-zinc mineralization. Enterprise Exploration abandoned their interest in the property and their portion of the project was optioned to All-North Resources Ltd.
In 1987, NDU Resources Ltd. ("NDU") purchased All-North's interest in the Marg property and Chevron converted its 25% working interest to a 5% net profits interest, resulting in a joint venture of the Marg property between NDU and Cameco. The NDU/Cameco joint venture explored the Marg property in two phases. The 1988 work program included claim staking, geological, geochemical and geophysical surveys plus 6,038 metres of diamond drilling in 33 holes, which defined extensive volcanogenic mineralization. Work also included construction of a 380 metre long airstrip, an airphoto survey, preliminary exploration of the Jane zone and initiation of a baseline environmental program. In 1989, the NDU/Cameco joint venture continued to explore the property and purchased Chevron's 5% net profits interest in proportion to existing ownership. Diamond drilling on the Marg zone consisted of 1,819 metres in five holes and work on the Jane zone included grid geological, geochemical and geophysical surveys. Reconnaissance geochemical sampling was also completed over much of the property and further water samples were collected for environmental monitoring. Work continued in 1990, with an additional nine holes, totalling 4,120 metres, completed on the Marg zone as well as hand trenching and sampling being carried out on the Jane zone. Baseline environmental monitoring surveys initiated in 1988 were continued and the resource estimate was updated. In 1996, NDU re-activated work on the Marg property that consisted of 8,518 metres of diamond drilling in 29 holes and additional work was carried out on the Jane zone. Environmental monitoring water sample sites were re-established and sampled. At this time, NDU commissioned Franzen to prepare an assessment of the mineral reserve of the Marg property. This report set out a resource of 5.5 million tonnes with an average grade of 1.76% copper, 2.46% lead, 4.60% zinc, 62.7 grams of silver per tonne and 0.98 grams of gold per tonne. UKHM acquired NDU in 1997, thereby obtaining the majority interest in the Marg property. UKHM completed additional diamond drilling consisting of seven holes totalling 2,540 metres, and nearly completed a winter road from the town of Keno to the project. In 1998, UKHM lost its interest in the Marg property through the company's default on a promissory note and the project was acquired by Atna in 1999. Atna and Cameco completed an agreement and formed a joint venture to further explore the property. A limited amount of work was carried out under this joint venture. To learn more about the Marg Deposit and its structure and mineralization, please read the Holbek Report. (PDF 4.2MB)
Click the map to download a larger view. (PDF 256 KB) |
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