KAU Volcanogenic & Gold Rich Volcanogenic Massive Sulphide Deposits Report & PPT

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Report and presentation about Volcanic massive sulphides from 2 Articles Frist about Volcanic massive sulphides and the next article Volcanic massive sulphides rich gold. please cover all points and add figures and photos specially for presentation.VOLCANOGENIC MASSIVE SULPHIDE DEPOSITS
ALAN G. GALLEY1, MARK D. HANNINGTON2, AND IAN R. JONASSON1
1. Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8
2. Department of Earth Sciences, University of Ottawa, Marion Hall, 140 Louis Pasteur,Ottawa, Ontario K1N 6N5
Corresponding author’s email: agalley@nrcan.gc.ca
Abstract
Volcanogenic massive sulphide (VMS) deposits, also known as volcanic-associated, volcanic-hosted, and volcanosedimentary-hosted massive sulphide deposits, are major sources of Zn, Cu, Pb, Ag, and Au, and significant sources for
Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga, and Ge. They typically occur as lenses of polymetallic massive sulphide that form
at or near the seafloor in submarine volcanic environments, and are classified according to base metal content, gold content, or host-rock lithology. There are close to 350 known VMS deposits in Canada and over 800 known worldwide.
Historically, they account for 27% of Canada’s Cu production, 49% of its Zn, 20% of its Pb, 40% of its Ag, and 3% of
its Au. They are discovered in submarine volcanic terranes that range in age from 3.4 Ga to actively forming deposits
in modern seafloor environments. The most common feature among all types of VMS deposits is that they are formed
in extensional tectonic settings, including both oceanic seafloor spreading and arc environments. Most ancient VMS
deposits that are still preserved in the geological record formed mainly in oceanic and continental nascent-arc, riftedarc, and back-arc settings. Primitive bimodal mafic volcanic-dominated oceanic rifted arc and bimodal felsic-dominated
siliciclastic continental back-arc terranes contain some of the world’s most economically important VMS districts.
Most, but not all, significant VMS mining districts are defined by deposit clusters formed within rifts or calderas. Their
clustering is further attributed to a common heat source that triggers large-scale subseafloor fluid convection systems.
These subvolcanic intrusions may also supply metals to the VMS hydrothermal systems through magmatic devolatilization. As a result of large-scale fluid flow, VMS mining districts are commonly characterized by extensive semi-conformable zones of hydrothermal alteration that intensifies into zones of discordant alteration in the immediate footwall
and hanging wall of individual deposits. VMS camps can be further characterized by the presence of thin, but areally
extensive, units of ferruginous chemical sediment formed from exhalation of fluids and distribution of hydrothermal
particulates.
Résumé
Les gîtes de sulfures massifs volcanogènes (SMV) sont connus sous diverses appellations parmi lesquelles on peut
mentionner les gîtes de sulfures massifs associés à des roches volcaniques, encaissés dans des roches volcaniques ou
logés dans des assemblages volcano-sédimentaires. Ils constituent des sources considérables de Zn, Cu, Pb, Ag et Au,
ainsi que des sources importantes de Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga et Ge. Ils consistent généralement en lentilles
de sulfures massifs polymétalliques formées dans des milieux volcaniques sous-marins, au sein ou à proximité du fond
océanique, et sont classés d’après leur contenu en métaux communs ou en or ou selon la lithologie des roches encaissantes. Près de 350 gîtes SMV ont été découverts au Canada et plus de 800, de par le monde. Dans l’histoire de la production minière du Canada, 27 % du cuivre, 49 % du zinc, 20 % du plomb, 40 % de l’argent et 3 % de l’or ont été
extraits de gisements SMV. On trouve de tels gîtes aussi bien dans des terrains volcaniques sous-marins datant de 3,4
Ga que dans les fonds océaniques actuels où de nouveaux gîtes sont en cours de formation. La caractéristique la plus
commune à tous les gîtes de SMV tient à leur formation dans des milieux tectoniques de distension, parmi lesquels on
peut mentionner les fonds océaniques en expansion et les arcs. La plupart des anciens gîtes SMV conservés dans les
archives géologiques se sont formés dans des milieux océaniques et continentaux d’arc naissant, d’arc de divergence
et d’arrière-arc. Quelques-uns des districts à gisements SMV les plus importants dans le monde sur le plan économique
se trouvent dans des terrains océaniques primitifs d’arc de divergence caractérisés par un volcanisme bimodal à dominante mafique, de même que dans des terrains continentaux d’arrière arc caractérisés par un volcanisme bimodal à dominante felsique et la présence de matériaux silicoclastiques. La plupart des principaux districts miniers à gisements SMV
consistent en amas de gisements formés dans des rifts ou des caldeiras. Leur regroupement est attribuable à l’existence
d’une source de chaleur commune qui donne naissance à de vastes réseaux de convection de fluides sous le plancher
océanique. Les intrusions subvolcaniques qui produisent cette chaleur peuvent aussi fournir des métaux aux réseaux
hydrothermaux des gîtes SMV par le biais d’un dégagement magmatique de matières volatiles. En raison de l’écoulement de fluides sur une grande étendue, les districts miniers à gisements SMV se caractérisent souvent par la présence
de vastes zones semi-concordantes d’altération hydrothermale, qui gagnent en intensité pour devenir des zones d’altération discordantes, dans l’éponte inférieure et l’éponte supérieure immédiates des gisements. Ces districts se distinguent
aussi par la présence d’unités minces mais étendues de sédiments chimiques ferrugineux qui résultent de l’exhalaison
et de la diffusion de particules hydrothermales.
Definition
Volcanogenic massive sulphide (VMS) deposits are also
known as volcanic-associated, volcanic-hosted, and volcano-sedimentary-hosted massive sulphide deposits. They
typically occur as lenses of polymetallic massive sulphide
that form at or near the seafloor in submarine volcanic environments. They form from metal-enriched fluids associated
with seafloor hydrothermal convection. Their immediate
host rocks can be either volcanic or sedimentary. VMS
deposits are major sources of Zn, Cu, Pb, Ag, and Au, and
significant sources for Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga,
and Ge. Some also contain significant amounts of As, Sb,
and Hg. Historically, they account for 27% of Canada’s Cu
production, 49% of its Zn, 20% of its Pb, 40% of its Ag, and
Galley, A.G., Hannington, M.D., and Jonasson, I.R., 2007, Volcanogenic massive sulphide deposits, in Goodfellow, W.D., ed., Mineral Deposits of Canada:
A Synthesis of Major Deposit-Types, District Metallogeny, the Evolution of Geological Provinces, and Exploration Methods: Geological Association of
Canada, Mineral Deposits Division, Special Publication No. 5, p. 141-161.
A.G. Galley, M.D. Hannington, and I.R. Jonasson
COLLAPSED AREA
BLACK SMOKER COMPLEX
ANHYDRITE CONE
WHITE SMOKERS
DEBRIS APRON &
METALLIFEROUS SEDIMENT
SULFIDE TALUS
ANHYDRITE
SEALED
ZONE
PYRITE
Zn-RICH MARGINAL
FACIES
QUARTZ
GRADATIONAL CONTACT
SILICIFIED, PYRITIC STOCKWORK
APPROX. LIMIT OF
DEMAGNETIZED ZONE
CHLORITIZED ± HEMATIZED BASALT
ALTERATION PIPE
FIGURE 1. Schematic diagram of the modern TAG sulphide deposit on the Mid-Atlantic Ridge. This represents a classic cross-section of a VMS deposit, with concordant semi-massive to massive sulphide lens underlain by a discordant stockwork vein system and associated alteration halo, or “pipe”. From Hannington et al.
(1998).
Cu
Cu
World VMS
103 tonnes per 1% area
(Modified from
Franklin, 1996)
1-100
100-1000
Zn-Pb-Cu
1000-10 000
n
-Z
>10 000
Zn-Cu
Pb-Zn
Pb
Zn
VMS deposits
SEDEX deposits
Cu
Cu
Canadian VMS
n
-Z
Cu
142
100 M
Cu
3% of its Au. Because of their polymetallic content, VMS deposits
continue to be one of the most
desirable deposit types for security
against fluctuating prices of different metals.
VMS deposits form at, or near,
the seafloor through the focused
discharge of hot, metal-rich
hydrothermal fluids. For this reason, VMS deposits are classified
under the general heading of
“exhalative” deposits, which
includes sedimentary exhalative
(SEDEX) and sedimentary nickel
deposits (Eckstrand et al., 1995).
Most VMS deposits have two components (Fig. 1). There is typically
a mound-shaped to tabular,
stratabound body composed principally of massive (>40%) sulphide,
quartz and subordinate phyllosilicates, and iron oxide minerals and
altered silicate wall-rock. These
stratabound bodies are typically
underlain by discordant to semiconcordant stockwork veins and
disseminated sulphides. The stockwork vein systems, or “pipes”, are
enveloped in distinctive alteration
halos, which may extend into the
hanging-wall strata above the VMS
deposit.
VMS deposits are grouped
according to base metal content,
gold content, and host-rock lithology (Figs. 2, 3, 4). The base metal
classification used by Franklin et
al. (1981) and refined by Large
(1992) and Franklin et al. (2005) is
perhaps the most common. VMS
deposits are divided into Cu-Zn,
Zn-Cu, and Zn-Pb-Cu groups
according to their contained ratios
of these three metals (Fig. 2). The
Cu-Zn and Zn-Cu categories for
Canadian deposits were further
refined by Morton and Franklin
(1987) into Noranda and Mattabi
types, respectively, by including
the character of their host rocks
(mafic vs. felsic, effusive vs. volcaniclastic) and characteristic alteration mineral assemblages (chlorite-sericite dominated vs. sericitequartz ± carbonate-rich). The ZnPb-Cu category was added by
Large (1992) in order to more fully
represent the VMS deposits of
Australia (Fig. 2). Poulsen and
Hannington (1995) created a sim-
Zn-Pb-Cu
Zn-Cu
Pb-Zn
Pb
SEDEX deposits
Zn
VMS deposits
FIGURE 2. Base metal classification scheme of worldwide and Canadian VMS deposits as defined by Franklin
et al. (1981) and modified by Large (1992) to include the Zn-Pb-Cu class. The preponderance of Cu-Zn and
Zn-Cu VMS deposits in Canada is due to the abundance of Precambrian primitive oceanic arc settings.
Worldwide, there is a larger proportion of felsic-hosted, more Pb-rich continental rift and continent margin
arc settings.
Volcanogenic Massive Sulphide Deposits
ple bimodal definition of “normal” versus “Au-rich” VMS
deposits (Fig. 3). This originally was intended to identify
deposits that are transitional between VMS and epithermal
deposits (e.g. Sillitoe et al., 1996) (Fig. 4). Further research
has indicated a more complex spectrum of conditions for the
generation of Au-rich VMS related to water depth, oxidation
state, the temperature of the metal-depositing fluids, and
possible magmatic contributions (e.g. Hannington et al.,
1999a). In the classification of Poulsen and Hannington
(1995) Au-rich VMS deposits are arbitrarily defined as those
in which the abundance of Au in ppm is numerically greater
than the combined base metals (Zn+Cu+Pb in wt.%, Fig. 3).
A third classification system that is gaining acceptance is a
five-fold grouping first suggested by Barrie and Hannington
(1999), and later modified by Franklin et al. (2005). This
system classifies VMS deposits by their host lithologies
(Fig. 4), which includes all strata within a host succession
defining a distinctive time-stratigraphic event (Franklin et
al., 2005). These five different groups are bimodal-mafic,
mafic-backarc, pelitic-mafic, bimodal-felsic, and felsic-siliciclastic. To this is added a sixth group of hybrid bimodal
felsic, which represent a cross between VMS and shallowwater epithermal mineralization (Fig. 4). These lithologic
groupings generally correlate with different submarine tectonic settings. There order here reflects a change from the
most primitive VMS environments, represented by ophiolite
settings, through oceanic rifted arc, evolved rifted arcs, continental back-arc to sedimented back-arc.
Geographical Distribution
There are close to 850 known VMS deposits worldwide
with geological reserves of over 200,000 t. They are located
in submarine volcanic terranes that range in age from the 3.4
Ga Archean Pilbara Block, Australia, to actively forming
deposits in modern seafloor spreading and oceanic arc terranes (Fig. 5, Table 1). VMS-epithermal hybrids are also
forming today in volcanically active shallow submarine
(Manus Basin) and lacustrine environments. VMS deposits
are recognized on every major continent except Antarctica,
although Zn-Pb-Cu deposits are forming in the Bransfield
Strait adjacent to the Antarctic Peninsula (Peterson et al.,
2004). Cu and Au have been produced from Tertiary-age
deposits hosted in ophiolites around the eastern
Mediterranean and Oman for over 5000 years. Prior to 2002,
VMS deposits are estimated to have supplied over 5 billion
tonnes of sulphide ore (Franklin and Hannington, 2002).
This includes at least 22% of the world’s Zn production, 6%
of the world’s Cu, 9.7% of the world’s Pb, 8.7% of its Ag,
and 2.2% of its Au (Singer, 1995).
Over 350 deposits and major VMS occurrences containing geological reserves of more than 200,000 tonnes are
known in Canada, of which only 13 are producing mines as
of 2006 (Fig. 6, Table 2). Of these, Louvicourt, BouchardHébert, Selbaie, and Konuto have been closed. VMS
deposits are known to occur in every province and territory
except Alberta and Prince Edward Island. The largest number of deposits is in Quebec (33%), followed in descending
order by Manitoba (15%), Newfoundland (12%), British
Columbia (10%), Ontario (9%), and New Brunswick (9%).
The deposits in New Brunswick have had the highest aggre-
Gold (ppm)
AURIFEROUS
MT MORGAN
BOUSQUET NO 2
HORNE
BOLIDEN
RAMBLER CONS
LA RONDE
ESKAY CREEK
Cu+Zn+Pb (%)
FLIN FLON Silver (ppm)
FIGURE 3. Classification of VMS deposits based on their relative base metal
(Cu+Zn+Pb) versus precious metal (Au, Ag) contents. Some of Canada’s
better known auriferous deposits (underlined) are compared to international
examples. Despite having produced 170 t of Au, the Flin Flon deposit is not
considered an auriferous VMS deposit under this classification. Modified
from Hannington et al. (1999c).
gate metal value (Cu+Zn+Pb), followed by Quebec and then
Ontario (Fig. 7).
Grade and Tonnage
The over 800 VMS deposits worldwide range in size from
200,000 tonnes to supergiant deposits containing more than
150 million tonnes (Franklin et al., 2005) (Table 3). Among
the largest is Rio Tino, Spain’s portion of the Iberian Pyrite
Belt (IPB), with contained ore in excess of 1.535 Bt. The
richest supergiant produced to date is Neves Corvo on the
Portuguese side of the IPB, with ore in excess of 270 Mt,
with 8.8 Mt of contained metal. At the average metal prices
to date for 2006 (Cu=$1.75/lb, Zn=$1.25/lb, Ag=$6.00/oz),
this orebody was originally worth in the order of 26 billion
dollars (US). Other large districts are the Urals and Rudny
Altai of Russia and Kazakhstan with over 70 Mt of contained
metals each (Fig. 5). Canada has two supergiant VMS
deposits (Windy Craggy and Brunswick No. 12) and two
giant VMS deposits (Kidd Creek, and Horne), which are
defined as being in the upper 1% of the world’s VMS
deposits with respect to total original reserves (Fig. 10A). In
Canada, the largest VMS mining district is Bathurst, New
Brunswick, which contained over 320 Mt of geological
resource of massive sulphide containing 30 Mt of combined
Zn, Cu, and Pb (Figs. 6, 10A). The 128 Mt Brunswick No.
12 deposit alone contained 16.4 Mt of metal (Table 2). This
is followed by the 138.7 Mt Kidd Creek deposit containing
12.6 Mt of metal. The largest known Canadian VMS deposit
is the 297 Mt Windy Craggy deposit, but it contains only 4.1
Mt of Cu, Co, and Au. The 50 Mt Horne deposit contains 2.2
Mt of Zn+Cu+Pb, along with over 330 t of Au, making it
also a world-class gold deposit (Fig. 10B). The 98 Mt
LaRonde VMS deposit contains 258 Mt of gold, and because
of its high Au/base metal ratio (Au ppm/Zn+Cu+Pb% = 1.9)
it is classified by its owner as a gold deposit rather than a
VMS deposit.
Determining the mean and median metal concentrations
for Canadian VMS deposits is difficult due to missing or
143
A.G. Galley, M.D. Hannington, and I.R. Jonasson
BACK-ARC
MAFIC
100 m
Canadian grade
and tonnage
Average 1.3 Mt
Median 2.3Mt
3.2% Cu
1.9% Zn
0.0% Pb
15 g/t Ag
2.5 g/t Au
Chlorite-sericite alteration
+ jasper infilling
Pillowed mafic
flows
Banded jasperchert-sulphide
Sphalerite-chalcoppyrite
-rich margin
Pyrite-quartz breccia
Massive pyrite
Flows or volcaniclastic strata
BIMODAL-MAFIC
Lobe-hyaloclastite
rhyolite
Pillowed mafic
flows
Pyrite-quartz in situ breccia
Sericite-chlorite
Quartz-pyrite stockwork
Quartz-chlorite
Chlorite-pyrite stockwork
Chlorite-sulphide
Massive magnetitepyrrhotite-chalcopyrite
Pyrrhotite-pyritechalcopyrite stockwork
BIMODAL-FELSIC
100 m
Felsic flow complex
Pyrite-sphalerite-galena
tetrahedrite-Ag-Au
Barite (Au)
Chlorite-sericite
Pyrite-sphalerite-galena
Carbonate/
gypsum
Quartz-chlorite
Chalcopyritepyrite veins
Massive
Sericite-quartz Detrital
Pyrite-sphalerite-chalcopyrite
Chalcopyrite-pyrrhotite-pyrite
Argillite-shale
Alkaline basalt
Felsic epiclastic
Basement sediments
Iron formation facies
Hematite
Magnetite
Carbonate
Manganese-iron
200 m
Felsic
lava
dome
Quartz-sericieAl silicate
(advanced argillic)
Sericite-quartz-pyrite
(argillic)
Carbonaceous shale
Chlorite-pyrrhotite-pyrite
-chalcopyrte-(Au)
Massive fine-grained and
layered pyrite
Siliceous stockwork
Layered pyrite-sphaleritegalena-Ag-Au (transitional ore)
500 m
Massive pyrrhotite-pyritechalcopyrite-(Au)
Infilling and
Realgar-cinnabar-stibnite
replacement
Arsenopyrite-stibnitetetrahedrite-Pb sulphosalts
Quartz-pyrite-arsenopyritesphalerite-galena-tetrahedrite veins
Laminated argillite
and shale
Canadian grade
and tonnage
Felsic volcaniclastic
and epiclastic
Sulphidic tuffite/exhalite
Massive pyrite-sphalerite
-chalcopyrite
Massive pyritepyrrhotite-chalcopyrite
Felsic
clastic
FELSICSILICICLASTIC
Average 9.2 Mt
Median 64.4 Mt
0.98% Cu
4.7% Zn
2.0% Pb
53 g/t Ag
0.93 g/t Au
200 m
HYBRID
BIMODAL-FELSIC
Shale/argillite
Canadian grade
and tonnage
Average 5.5 Mt
Median 14.2 Mt
1.3% Cu
6.1% Zn
1.8% Pb
123 g/t Ag
2.2 g/t Au
Canadian grade
and tonnage
Average 6.3 Mt
Median 113.9 Mt
1.7% Cu
5.1% Zn
0.6% Pb
45 g/t Ag
1.4 g/t Au
PELITICMAFIC
Canadian grade
and tonnage
Average 34.3 Mt
Median 148 Mt
Basalt sill/flow
Laminated argillite
and shale
Pyrrhotite-pyrite-magnetite
transition zone
Pyrrhotite-pyrite-chalcopyrite zone
Pyrrhotite-chalcopyrite-pyritesphalerite stockwork zone
200 m
1.6% Cu
2.6% Zn
0.36% Pb
29 g/t Ag
1300°C)
Crust
Felsic melts
Mantle
Mafic melt
FIGURE 13. VMS environments are characterized by tectonic extension at
various scales (open arrows). Extension resulted in crustal thinning, mantle
depressurization, and the generation of basaltic melts. Depending on crustal
thickness and density, these mafic melts ponded at the base of the crust,
resulting in partial melting and generation of granitoid melts. These anhydrous, high-temperature melts quickly rose to a subseafloor environment
(350°C) hydrothermal systems, from
which may have precipitated Cu, Cu-Zn, and Zn-Cu- (Pb)
VMS deposits with variable Au and Ag contents. Areally
extensive, 1 to 5 m thick, Fe-rich “exhalites” (iron formations) may mark the most prospective VMS horizons (Spry
et al., 2000; Peter, 2003) (Fig. 18A). These exhalite deposits
consist of a combination of fine volcaniclastic material,
chert, and carbonates. They formed during the immature
and/or waning stages of regional hydrothermal activity when
shallowly circulating seawater stripped Fe, Si, and some
base metals at 900°C) felsic volcanic
environments favourable for VMS formation. The presence
of synvolcanic dyke swarms and exhalite horizons are
indicative of areas of high paleo-heat flow.
In continental back-arc, bimodal siliciclastic-dominated
settings aeromagnetic surveys can be used to identify aerially extensive iron formations to target hydrothermally
active paleo-seafloor horizons. Variations in the mineralogy
of the iron formations and varying element ratios can serve
as vectors toward high-temperature hydrothermal centres.
Volumetrically minor sill-dyke complexes also may identify
higher temperature hydrothermal centres.
In upper greenschist-amphibolite metamorphic terranes,
distinctive, coarse-grained mineral suites commonly define
VMS alteration zones. These include chloritoid, garnet, staurolite, kyanite, andalusite, phlogopite, and gahnite. More
aluminous mineral assemblages commonly occur closer to a
high-temperature alteration pipe. Metamorphic mineral
chemistry, such as Fe/Zn ratio of staurolite, is also a vector
to ore. These largely refractory minerals have a high survival
rate in surficial sediments, and can be used through heavy
mineral separation as further exploration guides in till-covered areas.
Mineralogy and chemistry can be used to identify largescale hydrothermal alteration systems in which clusters of
VMS deposits may form. Broad zones of semiconformable
alteration will show increases in Ca-Si (epidotization-silicification), Ca-Si-Fe (actinolite-clinozoisite-magnetite), Na
(spilitization), or K-Mg (mixed chlorite-sericite±Kfeldspar). Proximal alteration associated with discordant sulphide-silicate stockwork vein systems includes chloritequartz-sulphide- or sericite-quartz-pyrite±aluminosilicaterich assemblages and is typically strongly depleted in Na and
Ca due to high-temperature feldspar destruction. In addition
to geochemical analysis, X-ray diffraction, PIMA, and oxygen isotope analysis can assist in vectoring towards higher
temperature, proximal alteration zones and associated VMS
mineralization. Although PIMA has been used most effectively on alteration systems that contain minerals with a high
reflective index, there has been some success in identifying
greenschist-facies minerals within Precambrian VMS
hydrothermal systems (Thompson et al., 1999)
Knowledge Gaps
Researchers have gathered an impressive amount of
knowledge over the last ten years with respect to how, and
where, VMS deposits form within various geodynamic
regimes. This is due to a combination of studies of modern
seafloor environments and detailed and regional-scale studies of ancient VMS environments. These studies have
allowed us to place VMS depositional environments within
the context of diverse supra-subduction settings that can be
identified in deformed and metamorphosed terranes through
lithostratigraphic facies evaluation and lithogeochemical
analyses. Prospective settings for subseafloor hydrothermal
systems can now be determined through identification of
synvolcanic intrusions that trigger the systems, geochemical
variations in altered rocks and chemical sedimentary horizons, and the use of mineralogy, geochemistry, and isotope
geology. The fundamental ingredient for the efficient use of
158
these tools is an appropriate level of understanding of the
architecture of the volcanic terranes. Mapping at 1:20 thousand scale and complementary geochronological studies of
the Flin Flon, Snow Lake, Leaf Rapids, and Bathurst mining
camps were key to understanding the evolution of the various VMS-hosting arc assemblages and at what period of
time in this evolution the deposits formed. Detailed lithostratigraphic mapping was essential in unraveling deformation histories and understanding the structural repetitions of
prospective ore horizons. At larger scales, we still need a better understanding of the longevity of hydrothermal systems
and the character and scale of fluid flow into both volcanic
and sedimentary hanging-wall strata. We also need a better
understanding of how to prospect for VMS environments
through thick drift cover using novel heavy mineral analysis
and selective leach methods. Successful exploration under
cover requires improved understanding of the processes of
secondary and tertiary remobilization of metals and trace
elements from a VMS deposit and its associated alteration
system.
Some Areas of High Mineral Potential in Canada
The recognition of new classes of high-sulphidation and
shallow-water VMS deposits and their genetic association
with differentiated magmatic suites in both calc-alkaline and
alkaline volcanic arcs opens up new terranes and volcanic
environments to exploration that were previously considered
non-prospective for VMS. These environments include arc
fronts and successor magmatic arcs in addition to primitive
rifted-arc and back-arc terranes. Calc-alkaline to alkaline terranes, such as the Triassic Nicola Group and the Lower
Jurassic Hazelton Group in British Columbia, should be
revisited for atypical VMS deposits. Evolved parts of
Archean greenstone terranes, in particular >2.8 Ga terranes
in which there was involvement of early sialic crust, should
also be considered in this context, e.g. Frotet-Troilus
Domain, Grand Nord, North Caribou, and western Slave
subprovinces.
Incipient rift environments of the Paleoproterozoic TransHudson Orogen: The presence of large volumes of iron formation and associated VMS mineralization in the Labrador
Trough is evidence of extensive hydrothermal systems generated in these 2.1 to 2.0 Ga rift systems on both margins of
the orogen. Why did these not develop large VMS deposits
as in other Fe-formation-rich environments (e.g.
Manitouwadge)?
Intrusions associated with Ni-Cu-PGE mineralization represent large volumes of magma, commonly emplaced at
shallow crustal levels as part of volcano-plutonic complexes.
If emplaced in a subaqueous environment, these terranes
should be highly prospective for mafic siliciclastic or maficdominated VMS deposits. These may include the submarine
volcanic stratigraphy above the Fox River and Bird River
sills in Manitoba and possibly the Bad Vermilion
anorthositic complex in southwestern Ontario.
Intra-continental back-arc environments have been recognized as highly prospective for VMS deposits. Where are the
continental back-arc environments in the Superior, Slave,
and Grenville provinces? Have we explored enough in the
>2.8 or
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Description Report and presentation about Volcanic massive sulphides from 2 Articles Frist about Volcanic massive sulphides and the next article Volcanic massive sulphides rich gold. please cover all points and add figures and photos specially for presentation.VOLCANOGENIC MASSIVE SULPHIDE DEPOSITS ALAN G. GALLEY1, MARK D. HANNINGTON2, AND IAN R. JONASSON1 1. Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8 2. Department of Earth Sciences, University of Ottawa, Marion Hall, 140 Louis Pasteur,Ottawa, Ontario K1N 6N5 Corresponding author’s email: agalley@nrcan.gc.ca Abstract Volcanogenic massive sulphide (VMS) deposits, also known as volcanic-associated, volcanic-hosted, and volcanosedimentary-hosted massive sulphide deposits, are major sources of Zn, Cu, Pb, Ag, and Au, and significant sources for Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga, and Ge. They typically occur as lenses of polymetallic massive sulphide that form at or near the seafloor in submarine volcanic environments, and are classified according to base metal content, gold content, or host-rock lithology. There are close to 350 known VMS deposits in Canada and over 800 known worldwide. Historically, they account for 27% of Canada’s Cu production, 49% of its Zn, 20% of its Pb, 40% of its Ag, and 3% of its Au. They are discovered in submarine volcanic terranes that range in age from 3.4 Ga to actively forming deposits in modern seafloor environments. The most common feature among all types of VMS deposits is that they are formed in extensional tectonic settings, including both oceanic seafloor spreading and arc environments. Most ancient VMS deposits that are still preserved in the geological record formed mainly in oceanic and continental nascent-arc, riftedarc, and back-arc settings. Primitive bimodal mafic volcanic-dominated oceanic rifted arc and bimodal felsic-dominated siliciclastic continental back-arc terranes contain some of the world’s most economically important VMS districts. Most, but not all, significant VMS mining districts are defined by deposit clusters formed within rifts or calderas. Their clustering is further attributed to a common heat source that triggers large-scale subseafloor fluid convection systems. These subvolcanic intrusions may also supply metals to the VMS hydrothermal systems through magmatic devolatilization. As a result of large-scale fluid flow, VMS mining districts are commonly characterized by extensive semi-conformable zones of hydrothermal alteration that intensifies into zones of discordant alteration in the immediate footwall and hanging wall of individual deposits. VMS camps can be further characterized by the presence of thin, but areally extensive, units of ferruginous chemical sediment formed from exhalation of fluids and distribution of hydrothermal particulates. Résumé Les gîtes de sulfures massifs volcanogènes (SMV) sont connus sous diverses appellations parmi lesquelles on peut mentionner les gîtes de sulfures massifs associés à des roches volcaniques, encaissés dans des roches volcaniques ou logés dans des assemblages volcano-sédimentaires. Ils constituent des sources considérables de Zn, Cu, Pb, Ag et Au, ainsi que des sources importantes de Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga et Ge. Ils consistent généralement en lentilles de sulfures massifs polymétalliques formées dans des milieux volcaniques sous-marins, au sein ou à proximité du fond océanique, et sont classés d’après leur contenu en métaux communs ou en or ou selon la lithologie des roches encaissantes. Près de 350 gîtes SMV ont été découverts au Canada et plus de 800, de par le monde. Dans l’histoire de la production minière du Canada, 27 % du cuivre, 49 % du zinc, 20 % du plomb, 40 % de l’argent et 3 % de l’or ont été extraits de gisements SMV. On trouve de tels gîtes aussi bien dans des terrains volcaniques sous-marins datant de 3,4 Ga que dans les fonds océaniques actuels où de nouveaux gîtes sont en cours de formation. La caractéristique la plus commune à tous les gîtes de SMV tient à leur formation dans des milieux tectoniques de distension, parmi lesquels on peut mentionner les fonds océaniques en expansion et les arcs. La plupart des anciens gîtes SMV conservés dans les archives géologiques se sont formés dans des milieux océaniques et continentaux d’arc naissant, d’arc de divergence et d’arrière-arc. Quelques-uns des districts à gisements SMV les plus importants dans le monde sur le plan économique se trouvent dans des terrains océaniques primitifs d’arc de divergence caractérisés par un volcanisme bimodal à dominante mafique, de même que dans des terrains continentaux d’arrière arc caractérisés par un volcanisme bimodal à dominante felsique et la présence de matériaux silicoclastiques. La plupart des principaux districts miniers à gisements SMV consistent en amas de gisements formés dans des rifts ou des caldeiras. Leur regroupement est attribuable à l’existence d’une source de chaleur commune qui donne naissance à de vastes réseaux de convection de fluides sous le plancher océanique. Les intrusions subvolcaniques qui produisent cette chaleur peuvent aussi fournir des métaux aux réseaux hydrothermaux des gîtes SMV par le biais d’un dégagement magmatique de matières volatiles. En raison de l’écoulement de fluides sur une grande étendue, les districts miniers à gisements SMV se caractérisent souvent par la présence de vastes zones semi-concordantes d’altération hydrothermale, qui gagnent en intensité pour devenir des zones d’altération discordantes, dans l’éponte inférieure et l’éponte supérieure immédiates des gisements. Ces districts se distinguent aussi par la présence d’unités minces mais étendues de sédiments chimiques ferrugineux qui résultent de l’exhalaison et de la diffusion de particules hydrothermales. Definition Volcanogenic massive sulphide (VMS) deposits are also known as volcanic-associated, volcanic-hosted, and volcano-sedimentary-hosted massive sulphide deposits. They typically occur as lenses of polymetallic massive sulphide that form at or near the seafloor in submarine volcanic environments. They form from metal-enriched fluids associated with seafloor hydrothermal convection. Their immediate host rocks can be either volcanic or sedimentary. VMS deposits are major sources of Zn, Cu, Pb, Ag, and Au, and significant sources for Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga, and Ge. Some also contain significant amounts of As, Sb, and Hg. Historically, they account for 27% of Canada’s Cu production, 49% of its Zn, 20% of its Pb, 40% of its Ag, and Galley, A.G., Hannington, M.D., and Jonasson, I.R., 2007, Volcanogenic massive sulphide deposits, in Goodfellow, W.D., ed., Mineral Deposits of Canada: A Synthesis of Major Deposit-Types, District Metallogeny, the Evolution of Geological Provinces, and Exploration Methods: Geological Association of Canada, Mineral Deposits Division, Special Publication No. 5, p. 141-161. A.G. Galley, M.D. Hannington, and I.R. Jonasson COLLAPSED AREA BLACK SMOKER COMPLEX ANHYDRITE CONE WHITE SMOKERS DEBRIS APRON & METALLIFEROUS SEDIMENT SULFIDE TALUS ANHYDRITE SEALED ZONE PYRITE Zn-RICH MARGINAL FACIES QUARTZ GRADATIONAL CONTACT SILICIFIED, PYRITIC STOCKWORK APPROX. LIMIT OF DEMAGNETIZED ZONE CHLORITIZED ± HEMATIZED BASALT ALTERATION PIPE FIGURE 1. Schematic diagram of the modern TAG sulphide deposit on the Mid-Atlantic Ridge. This represents a classic cross-section of a VMS deposit, with concordant semi-massive to massive sulphide lens underlain by a discordant stockwork vein system and associated alteration halo, or “pipe”. From Hannington et al. (1998). Cu Cu World VMS 103 tonnes per 1% area (Modified from Franklin, 1996) 1-100 100-1000 Zn-Pb-Cu 1000-10 000 n -Z >10 000 Zn-Cu Pb-Zn Pb Zn VMS deposits SEDEX deposits Cu Cu Canadian VMS n -Z Cu 142 100 M Cu 3% of its Au. Because of their polymetallic content, VMS deposits continue to be one of the most desirable deposit types for security against fluctuating prices of different metals. VMS deposits form at, or near, the seafloor through the focused discharge of hot, metal-rich hydrothermal fluids. For this reason, VMS deposits are classified under the general heading of “exhalative” deposits, which includes sedimentary exhalative (SEDEX) and sedimentary nickel deposits (Eckstrand et al., 1995). Most VMS deposits have two components (Fig. 1). There is typically a mound-shaped to tabular, stratabound body composed principally of massive (>40%) sulphide, quartz and subordinate phyllosilicates, and iron oxide minerals and altered silicate wall-rock. These stratabound bodies are typically underlain by discordant to semiconcordant stockwork veins and disseminated sulphides. The stockwork vein systems, or “pipes”, are enveloped in distinctive alteration halos, which may extend into the hanging-wall strata above the VMS deposit. VMS deposits are grouped according to base metal content, gold content, and host-rock lithology (Figs. 2, 3, 4). The base metal classification used by Franklin et al. (1981) and refined by Large (1992) and Franklin et al. (2005) is perhaps the most common. VMS deposits are divided into Cu-Zn, Zn-Cu, and Zn-Pb-Cu groups according to their contained ratios of these three metals (Fig. 2). The Cu-Zn and Zn-Cu categories for Canadian deposits were further refined by Morton and Franklin (1987) into Noranda and Mattabi types, respectively, by including the character of their host rocks (mafic vs. felsic, effusive vs. volcaniclastic) and characteristic alteration mineral assemblages (chlorite-sericite dominated vs. sericitequartz ± carbonate-rich). The ZnPb-Cu category was added by Large (1992) in order to more fully represent the VMS deposits of Australia (Fig. 2). Poulsen and Hannington (1995) created a sim- Zn-Pb-Cu Zn-Cu Pb-Zn Pb SEDEX deposits Zn VMS deposits FIGURE 2. Base metal classification scheme of worldwide and Canadian VMS deposits as defined by Franklin et al. (1981) and modified by Large (1992) to include the Zn-Pb-Cu class. The preponderance of Cu-Zn and Zn-Cu VMS deposits in Canada is due to the abundance of Precambrian primitive oceanic arc settings. Worldwide, there is a larger proportion of felsic-hosted, more Pb-rich continental rift and continent margin arc settings. Volcanogenic Massive Sulphide Deposits ple bimodal definition of “normal” versus “Au-rich” VMS deposits (Fig. 3). This originally was intended to identify deposits that are transitional between VMS and epithermal deposits (e.g. Sillitoe et al., 1996) (Fig. 4). Further research has indicated a more complex spectrum of conditions for the generation of Au-rich VMS related to water depth, oxidation state, the temperature of the metal-depositing fluids, and possible magmatic contributions (e.g. Hannington et al., 1999a). In the classification of Poulsen and Hannington (1995) Au-rich VMS deposits are arbitrarily defined as those in which the abundance of Au in ppm is numerically greater than the combined base metals (Zn+Cu+Pb in wt.%, Fig. 3). A third classification system that is gaining acceptance is a five-fold grouping first suggested by Barrie and Hannington (1999), and later modified by Franklin et al. (2005). This system classifies VMS deposits by their host lithologies (Fig. 4), which includes all strata within a host succession defining a distinctive time-stratigraphic event (Franklin et al., 2005). These five different groups are bimodal-mafic, mafic-backarc, pelitic-mafic, bimodal-felsic, and felsic-siliciclastic. To this is added a sixth group of hybrid bimodal felsic, which represent a cross between VMS and shallowwater epithermal mineralization (Fig. 4). These lithologic groupings generally correlate with different submarine tectonic settings. There order here reflects a change from the most primitive VMS environments, represented by ophiolite settings, through oceanic rifted arc, evolved rifted arcs, continental back-arc to sedimented back-arc. Geographical Distribution There are close to 850 known VMS deposits worldwide with geological reserves of over 200,000 t. They are located in submarine volcanic terranes that range in age from the 3.4 Ga Archean Pilbara Block, Australia, to actively forming deposits in modern seafloor spreading and oceanic arc terranes (Fig. 5, Table 1). VMS-epithermal hybrids are also forming today in volcanically active shallow submarine (Manus Basin) and lacustrine environments. VMS deposits are recognized on every major continent except Antarctica, although Zn-Pb-Cu deposits are forming in the Bransfield Strait adjacent to the Antarctic Peninsula (Peterson et al., 2004). Cu and Au have been produced from Tertiary-age deposits hosted in ophiolites around the eastern Mediterranean and Oman for over 5000 years. Prior to 2002, VMS deposits are estimated to have supplied over 5 billion tonnes of sulphide ore (Franklin and Hannington, 2002). This includes at least 22% of the world’s Zn production, 6% of the world’s Cu, 9.7% of the world’s Pb, 8.7% of its Ag, and 2.2% of its Au (Singer, 1995). Over 350 deposits and major VMS occurrences containing geological reserves of more than 200,000 tonnes are known in Canada, of which only 13 are producing mines as of 2006 (Fig. 6, Table 2). Of these, Louvicourt, BouchardHébert, Selbaie, and Konuto have been closed. VMS deposits are known to occur in every province and territory except Alberta and Prince Edward Island. The largest number of deposits is in Quebec (33%), followed in descending order by Manitoba (15%), Newfoundland (12%), British Columbia (10%), Ontario (9%), and New Brunswick (9%). The deposits in New Brunswick have had the highest aggre- Gold (ppm) AURIFEROUS MT MORGAN BOUSQUET NO 2 HORNE BOLIDEN RAMBLER CONS LA RONDE ESKAY CREEK Cu+Zn+Pb (%) FLIN FLON Silver (ppm) FIGURE 3. Classification of VMS deposits based on their relative base metal (Cu+Zn+Pb) versus precious metal (Au, Ag) contents. Some of Canada’s better known auriferous deposits (underlined) are compared to international examples. Despite having produced 170 t of Au, the Flin Flon deposit is not considered an auriferous VMS deposit under this classification. Modified from Hannington et al. (1999c). gate metal value (Cu+Zn+Pb), followed by Quebec and then Ontario (Fig. 7). Grade and Tonnage The over 800 VMS deposits worldwide range in size from 200,000 tonnes to supergiant deposits containing more than 150 million tonnes (Franklin et al., 2005) (Table 3). Among the largest is Rio Tino, Spain’s portion of the Iberian Pyrite Belt (IPB), with contained ore in excess of 1.535 Bt. The richest supergiant produced to date is Neves Corvo on the Portuguese side of the IPB, with ore in excess of 270 Mt, with 8.8 Mt of contained metal. At the average metal prices to date for 2006 (Cu=$1.75/lb, Zn=$1.25/lb, Ag=$6.00/oz), this orebody was originally worth in the order of 26 billion dollars (US). Other large districts are the Urals and Rudny Altai of Russia and Kazakhstan with over 70 Mt of contained metals each (Fig. 5). Canada has two supergiant VMS deposits (Windy Craggy and Brunswick No. 12) and two giant VMS deposits (Kidd Creek, and Horne), which are defined as being in the upper 1% of the world’s VMS deposits with respect to total original reserves (Fig. 10A). In Canada, the largest VMS mining district is Bathurst, New Brunswick, which contained over 320 Mt of geological resource of massive sulphide containing 30 Mt of combined Zn, Cu, and Pb (Figs. 6, 10A). The 128 Mt Brunswick No. 12 deposit alone contained 16.4 Mt of metal (Table 2). This is followed by the 138.7 Mt Kidd Creek deposit containing 12.6 Mt of metal. The largest known Canadian VMS deposit is the 297 Mt Windy Craggy deposit, but it contains only 4.1 Mt of Cu, Co, and Au. The 50 Mt Horne deposit contains 2.2 Mt of Zn+Cu+Pb, along with over 330 t of Au, making it also a world-class gold deposit (Fig. 10B). The 98 Mt LaRonde VMS deposit contains 258 Mt of gold, and because of its high Au/base metal ratio (Au ppm/Zn+Cu+Pb% = 1.9) it is classified by its owner as a gold deposit rather than a VMS deposit. Determining the mean and median metal concentrations for Canadian VMS deposits is difficult due to missing or 143 A.G. Galley, M.D. Hannington, and I.R. Jonasson BACK-ARC MAFIC 100 m Canadian grade and tonnage Average 1.3 Mt Median 2.3Mt 3.2% Cu 1.9% Zn 0.0% Pb 15 g/t Ag 2.5 g/t Au Chlorite-sericite alteration + jasper infilling Pillowed mafic flows Banded jasperchert-sulphide Sphalerite-chalcoppyrite -rich margin Pyrite-quartz breccia Massive pyrite Flows or volcaniclastic strata BIMODAL-MAFIC Lobe-hyaloclastite rhyolite Pillowed mafic flows Pyrite-quartz in situ breccia Sericite-chlorite Quartz-pyrite stockwork Quartz-chlorite Chlorite-pyrite stockwork Chlorite-sulphide Massive magnetitepyrrhotite-chalcopyrite Pyrrhotite-pyritechalcopyrite stockwork BIMODAL-FELSIC 100 m Felsic flow complex Pyrite-sphalerite-galena tetrahedrite-Ag-Au Barite (Au) Chlorite-sericite Pyrite-sphalerite-galena Carbonate/ gypsum Quartz-chlorite Chalcopyritepyrite veins Massive Sericite-quartz Detrital Pyrite-sphalerite-chalcopyrite Chalcopyrite-pyrrhotite-pyrite Argillite-shale Alkaline basalt Felsic epiclastic Basement sediments Iron formation facies Hematite Magnetite Carbonate Manganese-iron 200 m Felsic lava dome Quartz-sericieAl silicate (advanced argillic) Sericite-quartz-pyrite (argillic) Carbonaceous shale Chlorite-pyrrhotite-pyrite -chalcopyrte-(Au) Massive fine-grained and layered pyrite Siliceous stockwork Layered pyrite-sphaleritegalena-Ag-Au (transitional ore) 500 m Massive pyrrhotite-pyritechalcopyrite-(Au) Infilling and Realgar-cinnabar-stibnite replacement Arsenopyrite-stibnitetetrahedrite-Pb sulphosalts Quartz-pyrite-arsenopyritesphalerite-galena-tetrahedrite veins Laminated argillite and shale Canadian grade and tonnage Felsic volcaniclastic and epiclastic Sulphidic tuffite/exhalite Massive pyrite-sphalerite -chalcopyrite Massive pyritepyrrhotite-chalcopyrite Felsic clastic FELSICSILICICLASTIC Average 9.2 Mt Median 64.4 Mt 0.98% Cu 4.7% Zn 2.0% Pb 53 g/t Ag 0.93 g/t Au 200 m HYBRID BIMODAL-FELSIC Shale/argillite Canadian grade and tonnage Average 5.5 Mt Median 14.2 Mt 1.3% Cu 6.1% Zn 1.8% Pb 123 g/t Ag 2.2 g/t Au Canadian grade and tonnage Average 6.3 Mt Median 113.9 Mt 1.7% Cu 5.1% Zn 0.6% Pb 45 g/t Ag 1.4 g/t Au PELITICMAFIC Canadian grade and tonnage Average 34.3 Mt Median 148 Mt Basalt sill/flow Laminated argillite and shale Pyrrhotite-pyrite-magnetite transition zone Pyrrhotite-pyrite-chalcopyrite zone Pyrrhotite-chalcopyrite-pyritesphalerite stockwork zone 200 m 1.6% Cu 2.6% Zn 0.36% Pb 29 g/t Ag 1300°C) Crust Felsic melts Mantle Mafic melt FIGURE 13. VMS environments are characterized by tectonic extension at various scales (open arrows). Extension resulted in crustal thinning, mantle depressurization, and the generation of basaltic melts. Depending on crustal thickness and density, these mafic melts ponded at the base of the crust, resulting in partial melting and generation of granitoid melts. These anhydrous, high-temperature melts quickly rose to a subseafloor environment (350°C) hydrothermal systems, from which may have precipitated Cu, Cu-Zn, and Zn-Cu- (Pb) VMS deposits with variable Au and Ag contents. Areally extensive, 1 to 5 m thick, Fe-rich “exhalites” (iron formations) may mark the most prospective VMS horizons (Spry et al., 2000; Peter, 2003) (Fig. 18A). These exhalite deposits consist of a combination of fine volcaniclastic material, chert, and carbonates. They formed during the immature and/or waning stages of regional hydrothermal activity when shallowly circulating seawater stripped Fe, Si, and some base metals at 900°C) felsic volcanic environments favourable for VMS formation. The presence of synvolcanic dyke swarms and exhalite horizons are indicative of areas of high paleo-heat flow. In continental back-arc, bimodal siliciclastic-dominated settings aeromagnetic surveys can be used to identify aerially extensive iron formations to target hydrothermally active paleo-seafloor horizons. Variations in the mineralogy of the iron formations and varying element ratios can serve as vectors toward high-temperature hydrothermal centres. Volumetrically minor sill-dyke complexes also may identify higher temperature hydrothermal centres. In upper greenschist-amphibolite metamorphic terranes, distinctive, coarse-grained mineral suites commonly define VMS alteration zones. These include chloritoid, garnet, staurolite, kyanite, andalusite, phlogopite, and gahnite. More aluminous mineral assemblages commonly occur closer to a high-temperature alteration pipe. Metamorphic mineral chemistry, such as Fe/Zn ratio of staurolite, is also a vector to ore. These largely refractory minerals have a high survival rate in surficial sediments, and can be used through heavy mineral separation as further exploration guides in till-covered areas. Mineralogy and chemistry can be used to identify largescale hydrothermal alteration systems in which clusters of VMS deposits may form. Broad zones of semiconformable alteration will show increases in Ca-Si (epidotization-silicification), Ca-Si-Fe (actinolite-clinozoisite-magnetite), Na (spilitization), or K-Mg (mixed chlorite-sericite±Kfeldspar). Proximal alteration associated with discordant sulphide-silicate stockwork vein systems includes chloritequartz-sulphide- or sericite-quartz-pyrite±aluminosilicaterich assemblages and is typically strongly depleted in Na and Ca due to high-temperature feldspar destruction. In addition to geochemical analysis, X-ray diffraction, PIMA, and oxygen isotope analysis can assist in vectoring towards higher temperature, proximal alteration zones and associated VMS mineralization. Although PIMA has been used most effectively on alteration systems that contain minerals with a high reflective index, there has been some success in identifying greenschist-facies minerals within Precambrian VMS hydrothermal systems (Thompson et al., 1999) Knowledge Gaps Researchers have gathered an impressive amount of knowledge over the last ten years with respect to how, and where, VMS deposits form within various geodynamic regimes. This is due to a combination of studies of modern seafloor environments and detailed and regional-scale studies of ancient VMS environments. These studies have allowed us to place VMS depositional environments within the context of diverse supra-subduction settings that can be identified in deformed and metamorphosed terranes through lithostratigraphic facies evaluation and lithogeochemical analyses. Prospective settings for subseafloor hydrothermal systems can now be determined through identification of synvolcanic intrusions that trigger the systems, geochemical variations in altered rocks and chemical sedimentary horizons, and the use of mineralogy, geochemistry, and isotope geology. The fundamental ingredient for the efficient use of 158 these tools is an appropriate level of understanding of the architecture of the volcanic terranes. Mapping at 1:20 thousand scale and complementary geochronological studies of the Flin Flon, Snow Lake, Leaf Rapids, and Bathurst mining camps were key to understanding the evolution of the various VMS-hosting arc assemblages and at what period of time in this evolution the deposits formed. Detailed lithostratigraphic mapping was essential in unraveling deformation histories and understanding the structural repetitions of prospective ore horizons. At larger scales, we still need a better understanding of the longevity of hydrothermal systems and the character and scale of fluid flow into both volcanic and sedimentary hanging-wall strata. We also need a better understanding of how to prospect for VMS environments through thick drift cover using novel heavy mineral analysis and selective leach methods. Successful exploration under cover requires improved understanding of the processes of secondary and tertiary remobilization of metals and trace elements from a VMS deposit and its associated alteration system. Some Areas of High Mineral Potential in Canada The recognition of new classes of high-sulphidation and shallow-water VMS deposits and their genetic association with differentiated magmatic suites in both calc-alkaline and alkaline volcanic arcs opens up new terranes and volcanic environments to exploration that were previously considered non-prospective for VMS. These environments include arc fronts and successor magmatic arcs in addition to primitive rifted-arc and back-arc terranes. Calc-alkaline to alkaline terranes, such as the Triassic Nicola Group and the Lower Jurassic Hazelton Group in British Columbia, should be revisited for atypical VMS deposits. Evolved parts of Archean greenstone terranes, in particular >2.8 Ga terranes in which there was involvement of early sialic crust, should also be considered in this context, e.g. Frotet-Troilus Domain, Grand Nord, North Caribou, and western Slave subprovinces. Incipient rift environments of the Paleoproterozoic TransHudson Orogen: The presence of large volumes of iron formation and associated VMS mineralization in the Labrador Trough is evidence of extensive hydrothermal systems generated in these 2.1 to 2.0 Ga rift systems on both margins of the orogen. Why did these not develop large VMS deposits as in other Fe-formation-rich environments (e.g. Manitouwadge)? Intrusions associated with Ni-Cu-PGE mineralization represent large volumes of magma, commonly emplaced at shallow crustal levels as part of volcano-plutonic complexes. If emplaced in a subaqueous environment, these terranes should be highly prospective for mafic siliciclastic or maficdominated VMS deposits. These may include the submarine volcanic stratigraphy above the Fox River and Bird River sills in Manitoba and possibly the Bad Vermilion anorthositic complex in southwestern Ontario. Intra-continental back-arc environments have been recognized as highly prospective for VMS deposits. Where are the continental back-arc environments in the Superior, Slave, and Grenville provinces? Have we explored enough in the >2.8 or Purchase answer to see full attachment

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