Base Metals

Base Metals

Polymetallic black shale

Polymetallic black shales are stratabound ores, predominantly sulphides, occurring in organic-rich marine shale sequences that are enriched in zinc, nickel, molybdenum, precious metals, platinum-group elements, and rare earth elements, among others. Polymetallic black shales occur in northern, northeastern, and southwestern Alberta. Examples of polymetallic black-shales elsewhere are the Devonian Nick nickel-zinc deposit in the Yukon, the Cambrian Huangjiawan deposit in southeastern China, and the Paleoproterozoic Talvivaara deposit in Finland.

The Buckton polymetallic black shale deposit in northeastern Alberta was discovered in 1997 and intensively explored between 2008 and 2012, with estimated inferred resources as of 2013 of 4.4 billion tonnes and indicated resources of 271 million tonnes with recoverable molybdenum, nickel, uranium, vanadium, zinc, cobalt, copper, lithium, rare earth elements, yttrium, thorium, and scandium. The deposit is hosted by the Cretaceous White Speckled Shale Formation on the eastern flanks of the Birch Mountains in northeastern Alberta.

Stratabound polymetallic mineralization occurs in basal black shale of the Mississippian Exshaw Formation in southwestern Alberta, locally interbedded with a thin bentonite horizon. Black shale near the top of the Triassic Sulphur Mountain Formation in the Athabasca River–Smoky River region contains local horizons of massive pyrite and is underlain by phosphate-rich sediments. Anomalous base metal content also occurs in black shale of both the Jurassic Fernie Group in western Alberta and Cretaceous Loon River Formation in northwestern Alberta.

Black shale polymetallic mineralization is currently thought to be syngenetic, with metals precipitated under anoxic (sulphate-reducing) conditions from seawater and/or hydrothermal fluid from submarine vents.

Polymetallic Shale

Birch Mountains - polymetallic black shale

Sediment-hosted copper

Sediment-hosted copper occurrences in Alberta are stratabound ores (predominantly silver-bearing chalcocite, chalcopyrite, and bornite) accompanied by iron sulphides, occurring as disseminations in shallow marine epicontinental sandstone and siltstone. Sulphide occurrences and anomalous copper-silver concentrations were reported between the late 1960s and mid-1970s in the Grinnell Formation of the Mesoproterozoic Purcell Group in Alberta’s southern Mountains and Foothills. Several quartz arenite beds were described as mineralized, with thicknesses up to 7 feet, but mostly less than half a foot.

Sediment Copper

Sediment-hosted lead-zinc

Sediment-hosted lead-zinc occurrences in Alberta are stratabound deposits (predominantly sphalerite, galena, and iron sulphides) occurring in sandstone, siltstone and black shales. Sulphide occurrences and anomalous lead and zinc concentrations were reported back in late 1960s and early 1970s in the Sheppard Formation of the Mesoproterozoic Purcell Group in Alberta’s southern Mountains and Foothills. Geochemical anomalies were also identified in siltstone and shale of the Triassic Spray River Group, in shale of the Jurassic Fernie Group, and siltstone and sandstone of the Paleocene Paskapoo Formation along the Central Mountains and Foothills.

Carbonate-hosted lead-zinc

Carbonate-hosted lead-zinc occurrences in Alberta consist of stratabound mineralization (predominantly galena and iron sulphides) occurring as disseminations, open-space fillings in carbonate breccia, or as replacement of either breccia fragments or wall rock, principally in dolomite. Lead and zinc mineralization occurs in Cambrian and Devonian dolomite outcrops in Alberta’s central Mountains and Foothills (Baker Creek, Eldon, Spray Lake, and Oldman River occurrences) and in subsurface from central to northeastern Alberta, but can be at excessive depths. The only known surface zinc occurrences in Devonian dolomite on the plains include the Whitemud Falls on the Clearwater River in northern Alberta, Wood Buffalo National Park and the Vermilion Chutes on the Peace River in northeastern Alberta.

Carbonate Zinc

Oldman Riversite, west–central Alberta

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Oolitic ironstone

Iron deposits occur as oolitic and pisolitic ironstone of the Bad Heart Formation sandstone of the Smoky Group in the Clear Hills area in northwestern Alberta. The iron occurrences in the Clear Hills were initially discovered in 1924, sporadically studied since the early 1960s, and more intensively explored and evaluated since 2008. The Rambling Creek–North Whitemud River iron deposit of the Clear Hills property is an advanced project with a 2012 indicated resource of 558 Mt at 33.3% Fe and 0.20% vanadium pentoxide

Oolitic ironstone

The Rambling Creek–North Whitemud River deposit (also known as Clear Hills deposit) is bedded, flat lying, has a maximum thickness of 15 m, and extends northwest and southeast of Rambling Creek for several kilometres. The ironstone is composed of ooliths, siderite and clastic material in a siliciclastic matrix with ferruginous cement. The ooids consist of concentric layers of goethite, nontronite and amorphous phosphate that form on cores of quartz, goethite, amorphous phosphate and ooid fragments.

The Clear Hills deposit is classified as a Minette-type iron formation. Geological evidence suggests that oolitic ironstones grew in a shallow-water marine transgressive environment, close to shorelines and deltas. Ironstones have been interpreted either as a result of diagenesis or, alternatively, as growth assisted by iron-rich exhalative fluids circulating along reactivated faults.

Rambling River – Oolitic ironstone

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