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Tiger |
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Yukon Territory, Canada |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Tiger carbonate-hosted gold deposit, located 98 km NE of Mayo in east central Yukon Territory, in northwestern Canada (#Location: 64° 11' 25"N, 134° 28' 19"W).
The deposit lies within a band of regional-scale thrust and high angle reverse faults that imbricate rocks of Selwyn Basin and Mackenzie Platform in central Yukon. The Selwyn Basin stratigraphy comprises regionally metamorphosed, basinal sediments of Neoproterozoic to Palaeozoic age, whilst the Mackenzie Platform is composed of dominantly shallow water carbonate and clastic sedimentary rocks that were deposited from Mid-Proterozoic to Paaleozoic times. Both sequences were deposited on the western margin of ancestral North America.
Thrust faulting was active during Jurassic to Cretaceous times (160 to 130 Ma) when the area underwent compressional orogenesis related to large-scale plate convergence to the west. In Late Cretaceous time (94-90 Ma), of the Tombstone Suite of intermediate to felsic plutons were emplaced. A further compressional orogenic event at ~65 Ma accompanied emplacement of felsic intrusions assigned to the McQuesten Suite.
The Tombstone, Dawson and Robert Service, and a number of lesser thrust faults deformed the stratigraphy along the trend in which the Tiger deposit lies. All of these structures are northeast vergent and predate emplacement of the Tombstone Suite intrusions. The thrust package that contains the Tiger deposit lies immediately to the north of the boundary between the Selwyn Basin and the Mackenzie Platform and includes units belonging to both tectonic entities.
The thrust package hosting the Tiger deposit is composed of unmetamorphosed Silurian-Devonian carbonate rocks, predominantly of the Mackenzie Platform, 7 km NE of the Dawson thrust, which broadly marks the northeast boundary of the Selwyn Basin. This thrust package is limited to the south by the Dawson Thrust, and to the north by the Kathleen Lakes Fault. The stratigraphic units within this suite occur as open folds that are aligned parallel to the thrusts, plunging gently to the SE, with several high angle faults parallelling the general structural trend inferred in the vicinity. These latter faults are interpreted to have been conduits for mineralising fluids.
Mineralisation at the Tiger deposit is hosted by carbonates of the regionally extensive Bouvette Formation, which comprises bedded limestones intercalated with locally extensive basalt flows and airfall tuffs, all of which dip to the NE. Locally it consists of lime mudstone to skeletal wackestone with minor skeletal floatstone and rudstone. Primary fossil assemblages include crinoid ossicles, rugose corals, bryzoans, stromatoporoids, and the tabulate corals suggesting a Silurian age (Moore et al., 1952).
The Rackla pluton, a two-mica granite, intrudes Bouvette Formation stratigraphy ~3 km ESE of the Tiger deposit, manifested as a subcropping stock. Small aplitic and pegmatitic dykes and sills also occur ~2 km east of the Tiger deposit with 40Ar/39Ar muscovite ages of 62.3±0.7, 62.4±1.8, and 59.1±2 Ma ages (Kingston et al., 2010). No intrusive rocks have been found within the immediate Tiger deposit at surface or in drill core.
The Tiger Deposit is a stratabound, structurally-controlled gold deposit that trends northwest, dips moderately northeast and is characterised by replacement of host karst limestone by iron carbonate minerals. It is 800 m long, 100 to 200 m wide, and up to 96 m thick. Mineralisation occurs within a zone of small-scale folding and shearing, which is developed in and adjacent to a regionally extensive corridor of highly strained rocks that are interpreted to possibly reflecting a deep seated fault zone. The mineralised system is defined by a series of stacked and folded limestone horizons intercalated with locally extensive mafic flows and volcaniclastic units.
Gold occurs as both primary sulphide and oxide mineralisation. Sulphide mineralisation is accompanied by, and developed within, limestone that is replaced by ferruginous dolomite and iron carbonate minerals. The sulphide assemblage consist of disseminated to banded pyrite, with subordinate arsenopyrite and pyrrhotite, and minor bismuthinite and sphalerite. Small amounts of disseminated scheelite are also observed. The main sulphide minerals exhibit at least three stages of mineralisation.
Oxide mineralization is totally devoid of sulphide minerals and ranges from very competent, weakly porous limonitic mud to rubbly porous limonitic grit. The oxides appear to be texturally amorphous in most intersections, although they occasionally exhibits residual colour banding that are interpreted to represent relict sulphide textures. Complete oxidation extends to a depth of up to 250 m. The best oxide grades and deepest oxidation occur where north-striking extensional faults intersect the regional northwest-striking structure.
NI 43-101 compliant Mineral Resources are (ATAC Resources Limited website, 2016):
Oxide + sulphide resources, at 0.30 g/t Au cut-off
Indicated resources - 7.15 Mt @ 2.21 g/t Au,
Inferred resources - 8.28 Mt @ 1.09 g/t Au.
Oxide resources alone, at 1.60 g/t Au cut-off
Indicated resources - 2.47 Mt @ 4.25 g/t Au,
Inferred resources - 0.18 Mt @ 3.00 g/t Au.
This summary is drawn from Theissen et al., 2016, and "Kappes, D., Giroux, G.H., Hafez, S.A., McIntyre, R.L. and Carlson, G., 2014 - Preliminary Economic Assessment (PEA) on the Tiger Gold Project, Yukon Territory, Canada; an NI 43-101 Technical Report prepared for ATAC Resources Ltd. by Kappes, Cassiday & Associates, Nevada, USA, 277p."
The most recent source geological information used to prepare this decription was dated: 2016.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Tiger
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Thiessen, E.J., Gleeson, S.A., Bennett, V. and Creaser, R.A. 2016 - The Tiger Deposit: A Carbonate-Hosted, Magmatic-Hydrothermal Gold Deposit, Central Yukon, Canada: in Econ. Geol. v.111 pp. 421-446
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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