An AMF-PGC International Study Tour
Developed & Managed by Porter GeoConsultancy
Zinc '98
Zinc Deposits of Europe & North America
16th July to 17th August, 1998 - In Three Separate Modules
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DESCRIPTIONS of ORE DEPOSITS

[Flin Flon, Manitoba]
Image: Section of the Flin Flon Complex, Manitoba, Canada.   
This tour, which was developed, organised and managed by Mike Porter of Porter GeoConsultancy Pty Ltd (PGC), on behalf of the Australian Mineral Foundation Inc. (AMF), included:

Module 3 - North American Volcanic-Hosted Deposits, Fri 7 to Mon 17 Aug, 1998 For information on the remainder of the tour, see the Deposit Descriptions for Module 1 and Module 2

MODULE 3 - NORTH AMERICAN VOLCANIC HOSTED DEPOSITS

This module included briefings by, and field reconnaissances with local experts at a number of localities and most of the districts visited.  The aim was to provide a context to the deposits visited, and an overview of the tectonics, geology and metallogeny of the surrounding region.  The deposits visited included:

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Flin Flon

The Flin Flon and adjacent camps in Manitoba, Canada embraces a group of massive sulphide copper-zinc orebodies hosted by a Lower to Middle Proterozoic volcanogenic sequence within the 1850 Ma Trans-Hudson Mobile Belt.  These include:

  • Flin Flon with 62.5 Mt @ 4.1% Zn, 2.2% Cu, 41 g/t Ag, 2.64 g/t Au.
  • Ruttan - 48 Mt @ 1.24% Zn, 1.22% Cu, 12 g/t Ag, 0.48 g/t Au.
  • Trout Lake - 10.3 Mt @ 5.6% Zn, 1.8% Cu, 17 g/t Ag, 1.75 g/t Au.
  • Chisel Lake ? 8.4 Mt @ 10.5% Zn, 0.5% Cu, 1.4% Pb, 46 g/t Ag, 2.4 g/t Au.
  • Stall Lake - 6.4 Mt @ 0.5% Zn, 4.4% Cu, 12 g/t Ag, 1.4 g/t Au.
  • Callinan - 3.5 Mt @ 3.6% Zn, 1.4% Cu, 23 g/t Ag, 2.1 g/t Au.
  • Osborne - 2.8 Mt @ 1.5% Zn, 3.1% Cu, 4 g/t Ag, 0.27 g/t Au.
  • Anderson - 2.5 Mt @ 0.1% Zn, 3.4% Cu, 7 g/t Ag, 0.62 g/t Au.
  • Schist Lake - 1.8 Mt @ 7.3% Zn, 4.3% Cu, 37 g/t Ag, 1.3 g/t Au; etc. 

The mineralisation is associated with felsic volcanics within a tholeiite assemblage, at major stratigraphic and compositional breaks within the sequence.  Most of the massive sulphide deposits are underlain by coarse mafic, intermediate or felsic volcaniclastic rocks.  At Flin Flon, the massive sulphides are emplaced within a rhyolite flow complex, and underlain by a transgressive chloritic alteration zone within the footwall basalt breccia.  The massive sulphides are in turn overlain by more than 3 km of basalt to andesites.  The orebodies at Flin Flon comprised 6 individual lenses of massive and disseminated ore, averaging 270 m long, 21 m thick and 760 m down plunge.  These were distributed over a strike length of 1600 m.  All of these mines are owned and operated by Hudson Bay Mining & Smelting Co Ltd.

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Kidd Creek

The Kidd Creek Mine is in the Timmins-Porcupine district, and is hosted by a suite of Archaean felsic volcanics of the Abitibi Greenstone Belt.  The orebody is located near the top of a locally thickened rhyolite unit which is composed of massive flows and volcaniclastic debris.  The rhyolite is underlain by carbonate altered ultramafics, and is overlain by a thick sequence of mafic flows and associated intrusives.  The ore is composed of stringer and massive banded and brecciated pyrite, sphalerite and galena associated with carbonaceous rocks.  The massive and breccia, and the stringer ore respectively, form two adjoining, parallel, elongate flattened cylindrical bodies.  The massive sulphide lens is generally 100 long, to a maximum of 400 m and around 30 m thick, with a down plunge extent of near 3000 m.  The stringer zone has similar dimensions, and is found in the immediate footwall of the massive and brecciated sulphides.  The main alteration is sericitisation, silicification and chloritisation.  Reserves + production total more than 139 Mt @ 6.5% Zn, 2.3% Cu, 0.4% Pb, 89 g/t Ag.  The mine is operated by Falconbridge Ltd.

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Bouchard-Hébert (Mobrun)

The Bouchard-Hébert mine, previously known as Mobrun, comprises two gold rich poly-metallic complexes of conformable massive sulphides hosted in Archaean felsic volcanics of the Abitibi Belt, some 30 km to the north-east of Rouyn-Noranda.  The host volcanics of the Main Complex are mostly massive, brecciated and tuffaceous rhyolites.  It consists of five separate en echelon orebodies.  The 1100 Complex, which is 250 m south-east of, and stratigraphically 100 to 200 m lower than the Main Complex, comprises four separate, closely spaced lenses, hosted by tholeiitic rhyolites, with one andesitic interval.  Within 100 m of the Main ore lenses in particular, the host sequence has been silicified and sericitised, with local chloritic zones in the upper footwall, reflected by mass gains of FeO+MgO and gains in K2O.  Prior to mining, economic reserves stood at 10.4 Mt @ 5.1% Zn, 1.5 g/t Au, 0.77% Cu, 37 g/t Ag in the 1100 Complex and 0.95 Mt @ 2.4% Zn, 2.2 g/t Au, 0.8% Cu, 30 g/t Ag.  The Main Complex had potential reserves of 28 Mt, and the Main Complex 3.4 Mt.  The Main Complex sulphides are 90% pyrite, 5% sphalerite, 2% chalcopyrite with minor galena, digenite and pyrrhotite.  The mine owner is Cambior Inc.

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Brunswick #12

The Brunswick #12 and the #6 mine and Heath Steele orebodies are hosted by an Ordovician sequence of metamorphosed volcano-sedimentary rocks.  The hosts are underlain by a Cambro-Ordovician sequence of quartz-wacke and shaly phyllite, while the host unit comprises quartz-feldspar augen schist, quartz-eye schist, crystal tuff and sericite-chlorite schist.  The immediate footwall rocks are chloritic phyllites with thin bands of chert and sulphides.  The massive sulphides comprise  1) a massive pyrite zone containing minor amounts of sphalerite and galena, and variable chalcopyrite, magnetite and pyrrhotite;  2) massive banded pyrite-sphalerite-galena with minor chalcopyrite and pyrrhotite; and  3) massive pyrite with minor sphalerite, galena and chalcopyrite.  The sulphides are overlain by iron formation, which can be dominated by oxide, silicate or carbonate minerals.  The geometry, grade and thickness of the Brunswick deposits have been heavily influenced by structure, with the ore being attenuated on the limbs of, and concentrated in the axial zone of, isoclinal F1 sheath folds where they are intersected by tight F2 folds.  The ore and iron formation predates the oldest folding, although it is regarded that the attainment of ore grade and economic thickness is a result of the structural modification.  Reserves plus production amount to 161 Mt @ 8.83% Zn, 3.55% Pb, 0.31% Cu, 99 g/t Ag,  plus  25 Mt @ 1.1% Cu.  The mine is operated by Noranda Inc.

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Crandon

The Crandon deposit lies within the eastern-most of three districts of Lower Proterozoic base metal and gold bearing massive sulphide deposits in northern Wisconsin.  These districts are located within the 1860 to 1820 Ma Penokean Mobile Belt which defines the southern margin of the Archaean Superior Province.  All are located, within felsic centres on the flanks of the core of a major 280 km long, east-west trending Lower Proterozoic volcanic complex.  Crandon is contained within a sequence of andesitic to dacitic pyroclastics, flows and chemical sediments that dip sub-vertically.  The footwall is a thick sequence of andesitic tuffs, overlain by volcanic breccias.  The massive sulphide mineralisation is up to 100 m thick and is composed of pyrite and sphalerite with minor chalcopyrite, galena, quartz, chlorite, sericite and dolomite.  Stringer vein mineralisation is found in the footwall breccias and cutting the massive sulphides.  Alteration comprises silicification, sericitisation, pyritisation and minor chloritisation, within the tabular volcanic breccia zone in the immediate footwall.  Reserves are 61 Mt @ 5.6% Zn, 1.1% Cu, 0.5% Pb, 37 g/t Ag, 1 g/t Au.  The property, which was discovered in 1975, has had serious environmental objection and is not expected to come into production until at least 1999.  The project is operated by Nicolet Minerals Co, a subsidiary of Rio Algom Limited.

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For more information contact:   T M (Mike) Porter, of Porter GeoConsultancy   (mike.porter@portergeo.com.au)

This tour was designed, developed, organised, managed and escorted by
T M (Mike) Porter of Porter GeoConsultancy Pty Ltd.

Porter GeoConsultancy Pty Ltd
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LINDEN PARK, 5065
South Australia
Telephone: +61 8 8379 7397
Mobile: +61 422 791 776



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