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Buttle Lake District - Myra Falls, H-W, Lynx, Battle, the Gap |
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British Columbia, Canada |
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Cu Zn Pb Ag
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Super Porphyry Cu and Au
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The Buttle Lake District containing the Myra Falls, H-W, Lynx, Battle and the Gap deposits is located in a provincial park in central Vancouver Island, British Columbia, ~90 km by road from the port of Campbell River, and 200 km NW of Victoria in British Columbia, Canada.
Mineralisation is present as a series of massive sulphide bodies hosted by Permian felsic volcanics. The hosts are the Price and Myra Formations of the Sicker Group, the oldest known unit of the Wrangellia Terrane in western Canada. The Sicker group is exposed in three fault bounded uplifts on the island. The deposits of the Buttle Lake district are restricted to one of these uplifts.
The Price Formation is comprises more than 300 m of massive to pillowed basaltic andesite flows, volcanic breccias, interflow clastic sediments and turbidites. It underlies the Myra Formation which is a complex sequence of mafic to rhyolitic volcaniclastics with lesser flows infilling a north-west trending basin. The Myra Formation consists of 10 lithostratigraphic units, the six lower of which host the known mineral occurrences, as follows:
H-W Horizon - a 15 to 200 m thick unit of mainly felsic flows and volcaniclastics, including seven members which comprise - massive sulphide lenses, argillite-chert, H-W mafic sills, pumiceous lapilli tuff, rhyolite tuff, upper zone massive sulphide lenses and a felsic flow dome complex. Ore deposits inlude the H-W Main lens, H-W North lens, and the Battle Main zone which all occur at the base of the horizon. The Upper zone massive sulphide lenses occur both within and at the top of the rhyolitic tuff, and include the H-W Upper zone, the Ridge West and Battle Upper lenses.
Hangingwall Andesite - up to 100 m of basaltic andesite flows and shallow sills (that also locally intrude the H-W horizon) and flow breccias.
Ore clast breccia - an up to 90 m thick series of debris flows composed of feldspar porphyritic andesite, amygdaloidal mafic dacite, quartz feldspar porphyritic rhyolite, massive sulphides, fine rhyolitic tuff, chert and argillite. It is characterised by massive sulphide clasts and olistoliths of pyrite mineralised rhyolite up to 50x15 m.
Lower mixed volcaniclastics - up to 90 m thick, dominated by andesite with lesser dacite and contains bedded and coarse clastics deposits.
Upper dacite - 5E andesite - the Upper dacite comprises up to 60 m of re-sedimented hyaloclastite, pillow breccia and sub-aqueous pyroclastics and intermediate flows, while the 5E andesite is as much as 250 m thick of pillowed basaltic andesite flows and flow breccias.
The Lynx-Myra-Price horizon which is up to 60 m thick and consists of massive to bedded, fine to coarse quartz-feldspar crystal tuff, quartz-feldspar crystal and pumiceous rhyolite lapilli tuff and lesser chert. Massive sulphides occur at two levels within this horizon, some being located at the base where they are underlain by schistose sericite-quartz-pyrite feeder zones within the 5E andesite, while others are at the top of rhyolitic tuffs without obvious feeder zones and are composed of banded sphalerite, barite, pyrite, chalcopyrite, galena and tennantite.
Reserves in 1991 (AME, 1992) were: 11.2 Mt @ 4% Zn, 0.3% Pb, 2% Cu, 34 g/t Ag.
Production from 1966 - 1992 (Godwin & Robinson, 1996) totalled 13.8 Mt @ 1.9% Cu, 5.6% Zn, 0.6% Pb, 2.2 g/t Au, 64 g/t Ag.
This production was derived as follows: 7.5 Mt from H-W, 5.3 Mt from Lynx and 1.0 Mt from the Myra mine.
Geological reserves at the end of 1992 (Godwin & Robinson, 1996) totalled:
12.5 Mt, including the newly discovered deposits Battle (2.0 Mt) and the Gap (0.6 Mt).
Resources at December, 2012 (Nyrstar, NV reserve release) were:
Measured + Indicated Resources - 6.70 Mt @ 6.18% Zn, 0.60% Pb, 1.17% Cu, 56.57 g/t Ag, 1.78 g/t Au;
Inferred Resources - 2.90 Mt @ 7.39% Zn, 0.94% Pb, 0.84% Cu, 111.53 g/t Ag, 1.78 g/t Au;
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1996.
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.
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Selected References:
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Godwin C I, Robinson M, Juras S J 1996 - Galena Lead isotopes, Buttle Lake Mining Camp, Vancouver Island, British Columbia, Canada: in Econ. Geol. v91 pp 549-562
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Jones J J, Gemmell J B and Davidson G J, 2006 - Petrographic, Geochemical, and Fluid Inclusion Evidence for the Origin of Siliceous Cap Rocks Above Volcanic-Hosted Massive Sulfide Deposits at Myra Falls, Vancouver Island, British Columbia, Canada: in Econ. Geol. v101 pp 555-584
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Jones S, Berry R and Sinclair B, 2006 - Multiple deformation episodes at Myra Falls volcanic-hosted massive sulfide camp, central Vancouver Island, British Columbia, Canada: in Can. J. Earth Sci. v43 pp 1711-1732
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Jones S, Herrmann W and Gemmell J B 2005 - Short Wavelength Infrared Spectral Characteristics of the HW Horizon: Implications for Exploration in the Myra Falls Volcanic-Hosted Massive Sulfide Camp, Vancouver Island, British Columbia, Canada: in Econ. Geol. v100 pp 273-294
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McNulty, B.A., Gemmell, J.B., Davidson, G. and Fox, N., 2023 - Integrated stratigraphy, lithofacies, and U-Pb geochronology of the Myra Falls VHMS deposits, British Columbia, Canada: implications for episodic volcanism and ore deposit formation: in Mineralium Deposita v.58, pp. 307-335.
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Robinson M, Godwin C I, Stanley C R 1996 - Geology, lithogeochemistry, and alteration of the Battle Volcanogenic Massive Sulfide Zone, Buttle Lake Mining Camp, Vancouver Island, British Columbia: in Econ. Geol. v 91 pp 527-548
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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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