DESCRIPTIONS of ORE DEPOSITS
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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
- Flin Flon, Manitoba, Canada.
- Kidd Creek, Ontario, Canada.
- Bouchard-Hébert, Quebec, Canada.
- Brunswick #12>, New Brunswick, Canada.
- Crandon, Wisconsin, USA.
3 - NORTH AMERICAN VOLCANIC HOSTED DEPOSITS
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:
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:
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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.
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
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.
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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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
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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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#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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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
This tour was designed, developed, organised, managed and escorted by
T M (Mike) Porter of Porter GeoConsultancy Pty Ltd.
Porter GeoConsultancy Pty Ltd|
6 Beatty Street
LINDEN PARK, 5065
Telephone: +61 8 8379 7397
Mobile: +61 422 791 776