Mineral resources of the northeastern Superior Province in Québec’s Far North :
A frontier region wide open to exploration
Alain Leclair* (Géologie Québec)
5700, 4th Avenue Ouest, A-210, Charlesbourg, Québec G1H 6R1, [email protected]
Daniel Bandyayera, Alain Berclaz, Anne-Marie Cadieux, Jean David, Charles Gosselin,
Jean-Yves Labbé, Pierre Lacoste, Youcef Larbi, Louis Madore, Martin Parent,
Kamal N.M. Sharma, Martin Simard (Géologie Québec)
At the dawn of the 21st century the globalization of mineral exploration continues to generate marked
interest for the exploration of new and mostly uncharted territories with promising mineral potential. The
undiscovered mineral resources from such territories represent a significant amount of Canada’s ultimate
mineral wealth. Many important discoveries of large mineral deposits remain to be realized in some
remote, but prospective, areas of the Canadian Shield. Consequently, the growth of Canada’s mining
industry hinges on the acquisition of new geoscientific data from these areas and the development of new
models that will serve to guide exploration activities.
In the Far North of Québec lies an immense and poorly explored territory covering about 300,000 km2 roughly 20% of the total surface area of the province. It encompasses the northeasternmost part of the
Superior Province, representing the largest under-explored frontier region of the Archean crust in the
Canadian Shield, with significant potential for gold, base metals and diamond deposits. Recent
exploratory investigations indicate that the northeastern Superior Province is characterized by relatively
magnetic granitoid-charnockitic intrusive complexes that correspond to broad positive aeromagnetic
anomalies, but also contains supracrustal remnants with well-preserved volcano-sedimentary sequences
enclosed in magnetically low troughs. These investigations, combined with geochemical anomalies from
a regional lake sediments survey performed in 1997, suggest the presence of a variety of geological
environments most likely to yield large metalliferous deposits. In 1998, Géologie Québec (Ministère des
Ressources naturelles du Québec) initiated the Far North Mapping Program (Leclair et al., 1998) which
stands for the most ambitious 1:250,000-scale mapping initiative ever undertaken in North America. This
multi-year program (1998-2003) is aimed at establishing the geological and structural framework of the
northeastern Superior Province and at providing guidelines for mineral exploration activities. Regional
mapping to date in seven regions reveals the presence of many new mineralized zones in previously
unknown geological domains that may provide favorable sites for the formation of economically viable
deposits, such as gold in iron formations and shear zones, Cu-Zn-Au massive sulphides in volcanic
sequences, Ni-Cu-PGE in ultramafic rocks, diamonds in kimberlites-lamproites, and uranium.
Archean rocks of the northeastern Superior Province have been subdivided into several lithotectonic
domains on the basis of their lithological, structural and aeromagnetic characteristics (Percival et al.,
1992). These domains resemble the subprovinces of the southern Superior Province in scale and diversity
(Card and Poulsen, 1998). However, a revision of this lithotectonic subdivision will become necessary as
new information is acquired. The domains are lithologically heterogeneous, characterized by northnorthwest-trending units consisting predominantly of granitoid rocks with abundant enclaves of
supracrustal rocks. The plutonic rocks, including charnockitic-type plutons, consist of variably-deformed
tonalite, granodiorite, granite, diatexite, gabbro, anorthosite, peridotite and pyroxenite. The supracrustal
rocks include mainly basalt, andesite, greywacke, tuff, silicate-, sulphide- and oxide-facies iron
formations, and lesser rhyolite, pelite, conglomerat, komatiite and marble. All of these rocks are
metamorphosed from upper greenschist to granulite facies and occur in polydeformed belts varying from
1 to 10 km in width and 10 to 100 km in length (Leclair et al., 1999). The mapping initiative of the last 2
years has led to the discovery of more than 20 new volcano-sedimentary belts (Figure 1), thus raising the
current total to about 35 belts distributed among all the domains investigated, even in those previously
72°
74°
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61°
lac
Klotz
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60°
lac
Payne
59°
59°
lac
Chavigny
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lac
MINTO
nto
Mi
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BIENVILLE
ASHUANIPI
LA GRANDE
OPINACA
OPATICA
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lac
GuillaumeDelisle
lac
à
l'Eau-Claire
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Bienville
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Figure 1: Simplified geology of the northeastern Superior Province and location of
volcano-sedimentary belts based on recent geological mapping.
70°
55°
69°
Mineral resources of the northeastern Superior Province in Québec’s Far North :
A frontier region wide open to exploration
known to be strictly plutonic or charnockitic in character (Labbé et al., 1999). The supracrustal sequences
and plutonic suites that have been characterized, so far, reflect a varied and complex record of deposition,
magmatism and tectonism that span the interval from ca. 2.87 Ga to ca. 2.63 Ga. The oldest elements
preserved are remnants of a Mesoarchean (3.1-2.9 Ga) protocraton that was reworked by the Neoarchean
tectono-magmatic processes, and for which evidence is most commonly indicated by the presence of
inherited zircons. The ages of volcanic sequences seem to correspond to three main magmatic episodes
which are constrained at ca. 2.86 Ga, ca. 2.78 Ga and ca. 2.71 Ga. The formation of migmatite-diatexite
and the emplacement of widespread crust-derived granitic-charnockitic plutonic suites in the interval of
ca. 2.74-2.68 Ga record an important episode of recycling of lithologies and amphibolite- to granulitefacies regional metamorphism. On the other hand, younger ages ranging from 2.68 to 2.63 Ga reflect
isotopic resetting, renewed magmatism, protracted metamorphism accompanying deformation, and
possibly late hydrothermal activity.
The volcano-sedimentary belts of the northeastern Superior Province have geological setting comparable
to some mineral-rich greenstone belts in the southern Superior Province, and like those in most other
Archean terrains, are the prime targets for gold and base metal exploration. In recent years, many new
mineral occurrences have been discovered in several volcano-sedimentary belts of the northeastern
Superior Province (Labbé et al., 1998). 1) Gold-bearing occurrences in association with silicate- and
oxide-facies iron formations have been found in the Dupire, Duvert, Kogaluc, Qalluviartuuq and Payne
belts. Anomalous gold values spatially related to zones of intense ductile and brittle deformation have
also been recorded in several volcano-sedimentary belts. For instance, brittle-ductile shear zones
containing quartz-sericite-chlorite schists derived from shearing of felsic-mafic volcanic and sedimentary
rocks, such as those in the Tasiataq belt, are known to represent important structural sites for the
precipitation of gold and uranium. 2) Volcanic-associated massive sulphide Cu-Zn-Au occurrences have
been identified in the Qalluviartuuq, Payne and Duquet belts. At these localities, mafic volcanic units
underlying rhyolitic rocks contain chlorite-garnet-cordierite-anthophyllite alteration zones that are
associated with meter-thick veins of massive sulphides. The same lithological association and type of
alteration have also been observed in the Tasiallujjuaq belt. 3) Ni and Cu occurrences associated with
ultramafic rocks of volcanic and/or intrusive origin have been discovered in the Vénus and Charras belts,
respectively. Several ultramafic units with high-potential for Ni mineralization have also been observed
within volcano-sedimentary sequences of the Moyer and Papijjusaq belts. At present, it appears that some
mineralized zones have undergone processes such as partial melting, remobilization and possibly
desulphidation. However, it has not yet been clearly established whether all the mineralized zones were
overprinted by or formed under conditions of amphibolite and granulite facies metamorphism.
Archean cratons have long been recognized to concentrate economic diamondiferous kimberlites and
lamproites. The Superior Province, which forms the core of the North American continent, is the world’s
largest contiguous archean craton. To date, five distinct kimberlite fields, totalling 48 pipes, have been
discovered in the Superior craton. This is quite small when compared to the 250 pipes reported from the
Slave archean craton, and thus it is conceivable that the Superior craton quite likely hosts more
kimberlites. Although no kimberlite, sensu stricto, have yet been discovered in the northeastern Superior,
the presence of unmetamorphosed ultramafic-mafic lamprophyres, their carbonatized equivalents and
even carbonatite dykes, which are located along major lineaments or large-scale brittle fault zones,
indicates a potential for diamondiferous kimberlites. Using the results from the Far North Mapping
Program, four areas of interest have been defined as targets for diamond exploration in the northeastern
Superior Province (Moorhead et al., 2000).
Mineral resources of the northeastern Superior Province in Québec’s Far North :
A frontier region wide open to exploration
The Superior Province contains some 450 important mineral deposits, which account for a significant
amount of Canada’s total production in gold, copper, zinc, silver, nickel and iron (Card and Poulsen,
1998). These deposits are concentrated in granite-greenstone terrains of the southern and western Superior
Province, but are virtually absent from the northeastern Superior Province. The Far North Mapping
Program in the northeastern Superior Province is opening this under-prospected region to exploration
plays, and therefore expanding the domestic mineral resource base. The ongoing acquisition of new
geoscientific information through systematic 1:250,000-scale geological mapping, combined with the data
from the lake bottom geochemical survey, is leading to the identification of new potential targets for
exploration which may result in interesting discoveries. The start-up of the geological survey had an
immediate impact on exploration activities in this Québec’s frontier region, with many new mining
exploration permits being issued in the last three years. The final objective of the program is to complete
the geological mapping of the rest of the northeastern Superior Province over the next three years, and to
present a comprehensive synthesis of its geology and mineral resources potential.
References
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