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Abstract |
The Slave craton of the northwestern Canadian Shield is one of the most distinct and oldest building blocks of North American cratonic lithosphere. It hosts Earth's oldest intact rocks, the Acasta gneisses. These ancient gneisses are embedded in a large Mesoarchean to Hadean basement complex that underlies the west-central parts of the craton. Itself poorly mineralized, the basement complex is overlain by Neoarchean supracrustal sequences, and heavily intruded and cannibalized by plutonic suites ranging in age from 2720-2670 Ma synvolcanic plutons to 2590-2580 Ma late-orogenic batholithic granites. Supracrustal sequences, collectively known as the Yellowknife Supergroup, are represented by an early cover sequence comprising quartzite and banded iron formation (ca. 2800 Ma), a thick dominantly tholeiitic greenstone sequence (ca. 2700 Ma), younger arc-like sequences (ca. 2690-2610 Ma), extensive turbidite blankets (ca. 2680-2620 Ma), and finally syn-orogenic conglomerates deposited at ca. 2600 Ma or shortly thereafter. The early cover sequence and the overlying tholeiites represent subaerial exposure and then volcanic-dominated rifting of the basement. Arc-like sequences formed in part on top of the attenuated basement and in progressively widening, juvenile, back-arc-like basins and contain some of Canada's largest undeveloped volcanogenic massive sulphide deposits. After 2680 Ma, much of the Slave craton became overlain by the Burwash Basin, one of the largest and best-preserved Archean turbidite basins in the world, comparable in size and setting to the Japan Sea. During orogenesis, supracrustal sequences were telescoped, thickened, and multiply folded between ca. 2650 Ma and 2580 Ma, with a peak in crustal anatexis between 2590-2580 Ma (the "granite bloom"). Numerous orogenic gold deposits formed throughout the Slave craton, either as shear- or vein-hosted deposits in deformed greenstones or within the chemical traps provided by banded iron formations in the turbidites. Proterozoic rift-related magmatic suites and arcs around the margins of the craton host a variety of mineral deposits, and several hundred Phanerozoic kimberlites support Canada's first diamond mines.
Introduction |
The Archean Slave craton (Fig. 1,Fig. 2; Padgham and Fyson,1992; Bleeker and Davis, 1999a) is a major building block of the Canadian Shield. It is one of ca. 35 Archean cratons preserved around the world (Bleeker, 2003). Its amalgamation with the Rae craton, starting at ca. 2 Ga, initiated the climactic growth of Laurentia (Hoffman, 1988, 1989) from 2.0 to 1.8 Ga, probably within the broader context of the formation of Earth's first modern supercontinent, Nuna. Much of the Slave craton is old and within the context of the Laurentian collage it can be regarded, for all practical purposes, as an exotic fragment of crust relative toother well-known cratons in Laurentia such as the Superior, Nain, and Rae (Bleeker, 2003, 2004).
As a mere fragment of ancient crust, surrounded by Paleoproterozoic rifted margins, it originated from the break-up of a much larger late Archean landmass-perhaps a speculative late Archean supercontinent Kenorland (Williams et al., 1991) or, perhaps more likely, a smaller landmass referred to as the supercraton Sclavia (Bleeker, 2003). The late Archean and earliest Proterozoic development of Slave crust should thus be viewed in the context of this larger supercraton (Sclavia),even though the shape and size of this supercraton are currently unknown. The salient point is that cratons like the Slave only preserve parts of the much larger tectonic systems in which they were generated.
In agreement with this conceptual view, latest Archean events are remarkably homogeneous across the Slave craton and may be used, together with pre-breakup Proterozoic mafic dyke swarms, to help identify neighbouring fragments of Sclavia from among the 35 extant cratons. One such Slave craton-wide event is a voluminous "granitebloom" between ca. 2590-2580 Ma (Davis and Bleeker, 1999). This singular event in the craton's evolution transferred, irreversibly, a significant fraction of heat-producing elements and lower crustal fluids to the upper crust, thus allowing cooling and stiffening of the lower crust and setting the stage for cratonization and long-term preservation (Bleeker,2002).
Predating these latest events, the Slave crust preserves a complex and spatially heterogeneous record of crustal growth spanning nearly 1.5 billion years (Bleeker and Davis, 1999a, b and references therein; Sircombe et al., 2001; Ketchum et al., 2004). The present paper briefly summarizes this crustal growth history and the overall geological evolution of the Slave craton, while highlighting significant metallogenic events preserved within the craton. Significant ore deposits and occurrences are listed in Table 1 and will be discussed in terms of their overall setting within the geology of the craton.
Ancient Basement Complex |
Much of the central and western parts of the craton are underlain by ancient and largely crystalline basement - the Central Slave Basement Complex (Figs. 2, 3, and 4; see Bleeker et al., 1999a, b; Ketchum and Bleeker, 2001; Ketchum et al., 2004). Along the Acasta River, this basement complex consists of polymetamorphic gneisses of tonalitic to gabbroic composition (e.g., Fig.5a) that yield protolith ages up to ca. 4.03 Ga (Bowring et al., 1989; Stern and Bleeker, 1998; Bowring and Williams, 1999). Although essentially a chance discovery (M. St.-Onge, pers. comm., 2000; Bowring et al., 1989), no other rocks of this age have yet been found. Apart from a central core with sporadic ages >3.5 Ga (Acasta to Point Lake), the Central Slave Basement Complex is mostly younger with important age modes, from detrital and protolith U-Pb zircon ages, around 3400 Ma, 3150 Ma, 2950 Ma and 2826 Ma (Fig. 4b; e.g., Sircombe et al., 2001; see Bleeker and Davis, 1999b for a compilation of basement ages).
Interestingly, complementary data from the mantle suggest that at least part of the lithospheric mantle below the central part of the craton may be of similar antiquity (Aulbach et al., 2004). Although a crude age zonation can be recognized in the basement complex (Ketchum and Bleeker, 2001), no easily interpretable tectonic pattern has yet emerged. Pre-2.9 Ga supracrustal rocks have been found at the base of some greenstone belts (e.g., Ketchum et al., 2004) but form only a small component.
Mineralization
There are few if any known mineral occurrences of note within the Mesoarchean (or older) crystalline basement complex, a statistic that is generally mirrored by other ancient gneisscomplexes in cratons around the world. To a first degree, thispoor endowment probably correlates with the virtual lack ofsupracrustal rocks within such complexes.
Indirectly, however, the presence of the ancient basement complex may have exerted controls on several classes of younger mineral deposits:
Seafloor hydrothermal deposits or occurrences within Neoarchean bimodal rift volcanic rocks that overlie faulted basement, for instance the basal greenstones of the Yellowknife and Courageous Lake belts.
Late Archean evolved granites and their associated pegmatite swarms, some of which are enriched in rare elements (Sn, Ta, Li). Such enrichment typically correlates with multiple cycles of crustal fractionation.
Diamondiferous kimberlites in the Lac de Gras region (Fig. 6), which appear to have ascended through the edge of the basement complex and its ancient lithosphere (Fig. 2b).
The association of diamondiferous kimberlites with
"low-geotherm" Archean cratons and their mantle keels
is well known ("Clifford's rule"). Whether
Mesoarchean or older crustal rocks are particularly favourable
within the context of Archean cratons is not clearly established,
but appears a question worth testing against a global database.
The distribution of economic diamond deposits in the Slave craton
(Fig. 2) helps to bring this question intofocus.
The Cover Sequence |
The contiguous nature of the basement complex, by at least 2.9 Ga, is indicated by a thin but widespread ca. 2.9-2.8 Ga cover sequence of quartzite and banded iron formation (Fig. 7; see also Fig. 5b), the Central Slave Cover Group (Bleeker et al., 1999a). This sequence, which is locally intruded by ultramafic sills (Fig. 7), marks the onset of the Neoarchean cycle of supracrustal development (Bleeker et al., 1999a).
The supermature and commonly fuchsitic quartzites that are characteristic of this sequence mark the emergence and erosional unroofing of the basement complex in what was probably an aggressive, CO2-rich, Archean atmosphere. Abundant detrital chromite may suggest contemporaneous komatiitic volcanism. Similar fuchsitic quartzite sequences occur in many other cratons worldwide, particularly between ca. 3.1 Ga and 2.8 Ga. After 2.4 Ga, mature quartzites are rarely fuchsitic, indicating a lesser role for detrital chromite (and komatiites) in the post-Archean world.
Mineralization
The Central Slave Cover Group hosts some of the more prominent banded iron formations (BIF) of the Slave craton, although most are thin (1-10 m) and variable in composition along strike, changing from oxide iron formation into silicate-rich varieties or merely ferruginous chert. Locally, however, folding has thickened the highly magnetic BIF into substantial thicknesses (e.g., at Amacher Lake, on the eastern flank of the Sleepy Dragon Complex), resulting in some of the highest amplitude total field magnetic anomalies in the Slave craton. Overall, the BIFs appear of low economic value, although some may possibly host epigenetic gold mineralization and may be under explored for this commodity. However, most iron formation-hosted gold mineralization appears to be associated with BIFs hosted in low to medium-grade turbidite packages.
Fuchsitic quartzites below the iron formations (Fig. 7, photo C) are enriched in detrital minerals, including highly stable heavy minerals such as chromite, zircon, and rutile. Individual, dark, detrital chromite grains are a characteristic feature of these otherwise white to grey quartzites (Bleeker et al., 1999a). Commonly, these chromite grains have undergone variable reaction towards bright green fuchsitic mica during metamorphism and deformation. In a few localities, chromites are concentrated in seams of "black sand", but clearly such concentrations are too small to be of economic interest. If road access were available, some of the green-white quartzite would make attractive building or decorative stone. In Greenland, India, and Australia, similar quartzites are often quarried for this purpose. Elsewhere in the world, quartzites similar to these contain paleoplacer deposits of gold and/or uranium. An initial survey of such potential in the Slave craton was carried out by Roscoe (1990).
Ultramafic sills (or flows?) intruded the cover sequence
in several places, and locally contain seems of magmatic chromite
(Covello et al., 1988). Economic concentrations have not been
found. In one remote locality, on the south shore of Desteffany
Lake, the author found sulphide concentrations adjacent to
ultramafic rocks within the cover sequence. Overall, the volume
of komatiitic rocks is limited, not only at this stratigraphic
interval but throughout the Slave craton.
Ca. 2.73-2.70 Ga Tholeiitic Volcanism |
Wherever the thin cover sequence is recognized, it is overlain by a thick and extensive sequence of tholeiitic basalts, with minor komatiite and rhyolite tuff intercalations (Figs. 7, 8). In the Yellowknife greenstone belt, this basalt-dominated volcanic sequence (Fig. 8) is known as the Kam Group (Helmstaedt and Padgham, 1986; Bleeker et al., 1999a). Possible correlative basalt successions (Fig. 9) are known across the basement domain, as far east as the Courageous Lake belt, and at least as far north as around the Exmouth antiform in the Acasta area. This basalt sequence typically consists of several hundred meters to several kilometres of pillowed and massive flows, with thin felsic horizons, and intruded by numerous dykes and sills of several generations (Fig. 8).
Well-dated components of this basalt-dominated sequence yield ages from >2738 Ma to 2697 Ma (Isachsen and Bowring, 1997; Davis et al., 2004; and unpublished data). In Yellowknife, the top of the sequence is represented by voluminous basaltic flows and intercalated felsic volcanic rocks of the Yellowknife Bay Formation, dated at ca. 2700 Ma (Fig. 8). In support of the overall regional correlation, similar ca. 2700 Ma ages have been obtained from Courageous Lake and Acasta areas. Stratigraphy, dense dyke swarms, and isotopic data link the basalt sequence to the basement (Henderson, 1985; Bleeker et al., 1999a, b; Bleeker, 2002, and references therein; Northrup et al., 1999; Cousens, 2000).
If the broad regional correlation of these basalts is valid, the magnitude of volcanism approaches LIP (large igneous province) proportions (areal distribution >100,000 km2, typical thickness 1-6 km). The widespread basaltic volcanism probably accompanied protracted rifting of the basement complex, possibly assisted by mantle plume activity. The stratigraphy in Yellowknife is compatible with such a rifting interpretation. At the top of the Kam Group, bimodal volcanic rocks of the Yellowknife Bay Formation become progressively more intercalated with volcaniclastic sediments, before final intrusion by thick tholeiitic sills. One of these sills, the Kam Point gabbro sill, has a preliminary baddeleyite age of ca. 2697 Ma (Fig. 8).
Mineralization
A volcanically active rift environment, characterized by bimodal volcanism and minor aprons of volcaniclastic sedimentary rocks, is a highly favourable environment for seafloor hydrothermal activity and the formation of volcanogenic massive sulphide deposits. Indeed numerous showings of sulphidic horizons occur throughout the basalt-dominated greenstone belts of the west-central Slave.
Of particular interest are intercalated felsic volcanic flows and/or sills, which are direct indicators of proximity to a differentiated magmatic center, and thus a long-lived subvolcanic heat source. The Bell Lake quartz-porphyritic tonalite sill (Fig. 5c) and the rhyolitic Townsite Formation, dated at 2713Õ2 Ma and ca. 2709 Ma, respectively (Davis et al., 2004), are examples of such proximal felsic volcanic rocks in the Yellowknife greenstone belt. Hydrothermal alteration and minor sulphide mineralization is known from the Yellowknife Belt (e.g., the Homer Lake showing, and horizons northeast of Bell Lake), but to date no significant deposits have been found. Similarly, despite at least a first wave of exploration across the other basaltic greenstone belts of the west-central Slave craton, the author is not aware of any major discoveries.
From a mantle perspective, it seems inconceivable that events
associated with the voluminous basaltic volcanism recorded across
the ancient basement terrain did not involve thinning or at least
modification of the lithospheric mantle below the Central Slave
Basement Complex. Large-scale melting was probably triggered by
adiabatic rise of asthenospheric mantle. Perhaps, then, the ca.
2.7 Ga basaltic volcanism may have contributed to the highly
depleted mantle compositions underlying the core of the
craton.
Post-2.70 Ga Volcanism |
Following ca. 2.7 Ga basaltic volcanism and rifting, most areas in the Slave craton show a transition to calc-alkaline volcanism characterized by abundant felsic and intermediate volcanic rocks, calc-alkaline basaltic rocks, and intercalated volcaniclastic sedimentary rocks (Fig. 9). In nearly all areas, these arc-like rocks are stratigraphically overlain by turbiditic sedimentary rocks (Fig. 9). Ages for the arc-like volcanic rocks are typically in the range of 2690-2660 Ma.
The arc-like volcanic rocks are geochemically juvenile (e.g, Davis and Hegner, 1992). They dominate the eastern part of the craton, where they lack any apparent association with older basement, its cover, and/or the basalt-dominated rift sequence. These observations have led to models in which the eastern Slave represents an exotic juvenile arc (the "Hackett River arc") that collided with the basement domain in the west (e.g., Kusky, 1989, 1990). However, similar arc-like rocks, with identical ages, stratigraphically overlie the basement domain and its cover in the west-central parts of the craton (Fig. 9a), where they can be tied to the basement and bimodal rift volcanic rocks by means of unconformities, cross-cutting feeder dykes, and subvolcanic intrusions (Fig. 10).
It thus appears that, if these rocks were generated in an arc-like setting, this arc was constructed marginal to and on top of the highly extended continental crust of the Central Slave Basement Complex. This suggests a marginal to continental arc setting. The arc was actively extending and evolved into a back-arc basin that was ultimately filled with turbiditic sediments (Figs. 9, 10). The geochemistry of the volcanic rocks and the associated subvolcanic plutons, although juvenile, typically shows strong arc-like signatures (light rare earth and large-ion lithophile element enrichment, Nb depletion) compatible with enriched sources in a supra-subduction zone setting.
Mineralization
The ca. 2687-2660 Ma time interval and the arc-like volcanic sequences are highly favourable for volcanogenic massive sulphide (VMS) mineralization. Nearly all known massive sulphide deposits, including Izok Lake, the Hackett River deposits, and the Sunrise deposit (Fig. 5e; see Fig. 2 for locations) of the southern Slave craton belong to this group. An exception is the High Lake deposit, which is associated with older, ca. 2705 Ma, bimodal volcanic rocks.
Nearly all the VMS deposits of this group occur associated
with proximal felsic volcanic rocks at or near the transition to
overlying turbiditic metasedimentary rocks. This transition is
characterized by rhyodacite to rhyolite complexes, volcaniclastic
sediment aprons, thin sulphidic chert horizons and, in some
localities, banded iron formations. Carbonate rocks
(calc-arenites) are associated with some of the felsic complexes
(Fig. 5d). This typical stratigraphic evolution, from shallow
water or emergent felsic volcanic complexes to deep-water
turbidite sedimentation, suggests active extension and tectonic
subsidence of the arc environment, most likely in an overall
back-arc setting (Fig. 10). Such an environment of active
faulting, active volcanism, thinning lithosphere, and high heat
flow, has long been recognized as a classic environment for VMS
deposits. Izok Lake and the Hackett River deposits represent some
of Canada's largest undeveloped volcanogenic massive
sulphide deposits that will be economic as soon as road and coast
access is available.
Ca. 2.68-2.66 Ga Sedimentation |
Starting at ca. 2680 Ma, a broad turbidite basin-the Burwash Basin-developed across much of the craton and progressively buried the volcanic substrate (e.g., Ferguson et al., 2005). A persistence of volcanic intercalations up-section and late mafic sill complexes suggest a volcanically active extensional setting, perhaps best compared with modern back-arcs. The minimum size of this basin was ca. 400x800 km (Fig. 11a), comparable to that of the Japan Sea, and making it the largest and possibly best-preserved Archean turbidite basin in the world. Like the Japan Sea, the Burwash Basin was largely ensialic, in agreement with inferences by early workers (e.g., Henderson, 1985).
The Burwash Basin fill consists largely of immature greywackes and mudstones, deposited below wave base, and may locally be up to 10 km thick. Intercalated tuff layers have been dated at ca. 2661 Ma (e.g., Bleeker and Villeneuve, 1995). Across the Slave craton, the greywacke turbidites have been given different formational names: the classical Burwash Formation in the Yellowknife Domain; the Contwoyto Formation in central and northern Slave, identical in essentially all aspects to the Burwash Formation further south, except for the presence of intercalated iron formations; the Itchen Formation, a more mud-rich facies in the north-central Slave; and the Beechey Lake Group in the northeastern Slave.
Many of the turbidite beds, particularly those of the Burwash and Contwoyto Formation, are sand dominated with only thin silt to mud sections at the top of the graded beds. In the Yellowknife Domain, thick amalgamated sand beds (2-10 m) are not unusual (Fig. 5f). Petrography, detrital zircons, and geochemical analysis indicate that the greywacke detritus consists of a mixture of mafic and felsic volcanic rocks and uplifted plutonic infrastructure, with only minor input from ancient basement rocks. The main axis of the basin and subsequent structural trends appear to have been northeast-southwest (Fig. 11), distinctly across the north-south isotopic boundaries that track the nature of deep basement (see also Padgham, 1992). This interpretation is based on the following observations:
Identical Burwash Formation turbidites extend from near Yellowknife (the type area) to the northeastern Slave (Figs. 9, 10, 11a).
Banded iron formations in the turbidites are restricted to the northwest half of the craton, suggesting a northeast-southwest facies boundary or tectonic trend across the basin (Fig. 11a).
Earliest folds in the turbidites, which formed between 2650-2630 Ma, have northeasterly trends after qualitative "unfolding" of younger fold generations. Early folds appear to form a systematic northeast-southwest trending fold belt (Fig. 11b).
The earliest plutonic suite that intrudes folded Burwash strata, the ca. 2630 Ma Defeat Suite, appears to form a northeast-southwest-trending magmatic belt across the southeastern half of the craton (Fig. 11c).
With more and better U-Pb zircon ages, a tentative "volcanic line" of 2661 Ma felsic volcanic complexes, coeval with turbidite sedimentation, has begun to emerge (Bleeker and Davis, in preparation). This volcanic line also trends northeast-southwest and may represent the first recognition of a linear arc system.
Mineralization
The immature greywackes and mudstones of the Burwash Basin contain few primary mineral deposits other than banded iron formations (Fig. 5g). The latter occur intercalated in greywackes scattered across a broad swath in the northwestern part of the craton (Fig. 11c), from the Goose Lake and George Lake areas to the Point Lake area, and from there to the southwestern Slave. Many are highly magnetic. Although of scientific interest for the understanding of facies boundaries, basin evolution, and geochemistry, they are uneconomic in terms of their ferrous metal content.
The principal type of economic mineralization within Burwash Formation metaturbidites is epigenetic gold mineralization hosted by the intercalated banded iron formations. The most important example of this deposit type is the Lupin deposit on the southern shores of Contwoyto Lake, which has been a significant gold producer from 1982 to 2003, yielding 3-4 million ounces of Au (Normin, 2005). Other examples, e.g. George Lake and Goose Lake, occur throughout the northern Slave craton and may become economic with elevated gold prices and better access.
The general model for these deposits is that the host iron formations formed chemical traps for gold-bearing H2O-CO2 fluids during metamorphism and deformation. Destabilization of the Au-carrying sulphur complexes, due to interaction with reduced Fe-rich host rocks, led to alteration and gold deposition, either in veins or in fluid-altered and sulphidized zones of the iron formations. The structural timing of these epigenetic deposits is generally syn- to late-kinematic and syn- to late-metamorphic, i.e. consistent with maximum fluid production deeper in the telescoped structural-metamorphic pile. The most likely source for the fluids, and the gold, is metamorphic devolatilization of a voluminous, immature sediment pile and its volcanic substrate. Sporadic iron formations provide accidental traps to the migrating fluids, with discrete structures locally playing a role in increased focusing of fluid flow.
Similar processes also led to gold-bearing quartz veins within
metaturbidites (e.g., laminated veins along sheared bedding
planes, saddle reefs), but without a specific focusing mechanism
these occurrences and deposits tend to be of small size, although
locally of high grade. Examples are the Ptarmigan and Discovery
mines in proximity to Yellowknife (Fig. 2).
Ca. 2.65-2.63 Ga Closure Of The Burwash Basin |
Turbidite sedimentation in the Burwash Basin came to an end sometime before 2650 Ma, the age of the oldest recorded granitoid pluton intruding Burwash strata (Point Lake area; W. Mueller, pers. comm.). Subsequent tectonic events record the closure and folding of the Burwash Basin (D1) prior to 2634 Ma (see F1 fold belt in Fig. 11b). The latter age constraint is provided by early plutons of the Defeat Suite, a distinct and possibly subduction-related magmatic suite across the southern (and southeastern) Slave craton (Fig. 11c).
Closure of the highly extended, but largely ensialic back-arc basin allowed considerable shortening and mobility but with a structural style dominated, at least at high structural levels, by fairly systematic, mostly upright, northeast-southwest trending fold trains. At deeper levels, e.g. along the basement-cover interface, the fold trains must have been detached allowing differential shortening of the basement and cover.
The folded Burwash strata do not represent an outboard accretionary prism (which would require a trench setting rather than the more likely back-arc setting), and there is no evidence for a discrete "Contwoyto terrane" (cf. Kusky, 1989). The northeast-southwest structural grain of the F1 fold belt is also recognized in the lithospheric mantle (Grütter et al., 1999). Shallow subduction (either from the SE or NW?) may have emplaced distinct mantle slabs (Davis et al., 2003). These processes terminated with docking of an outboard terrane (e.g., Fig. 10), either in the southeast or the northwest; but this terrane is not preserved, however, within the exposed Slave craton. Crustal thickening led to uplift and erosional exhumation of folded Burwash strata and the unroofing of Defeat Suite plutons. Detrital zircons of Defeat Suite age are recorded in younger sedimentary packages (e.g., Fig. 9f).
Mineralization
Folding, incipient crustal thickening, and the onset of regional metamorphism, together with Defeat Suite plutonism, must have initiated devolatilization reactions and metamorphic fluid flow. These events thus likely kick-started the development of epigenetic gold mineralization, but were followed by much more intense metamorphic events ca. 20-30 million years later, during D2.
Arc-generation and subduction processes almost certainly
modified the mantle lithosphere below the Slave craton, possibly
creating the starting conditions for what is now a thick
diamondiferous mantle root (e.g., Davis et al., 2003).
Interestingly, trends of similar mantle domains, based on
indicator mineral chemistry, appear to parallel the
northeast-southwest trends of the Burwash Basin and D1 folding
(Grütter et al., 1999).
Post-2.63 Ga Turbidites |
Along the northwestern margin of the craton, younger turbidites containing ca. 2630 Ma detrital zircons (Figs. 9e, f and 11d; Sircombe and Bleeker, unpublished SHRIMP data; Pehrsson and Villeneuve, 1999) record a migration of tectonic activity to the northwest. Deposition was coeval with uplift and erosional unroofing of Defeat plutons and tightly folded Burwash Formation strata. Shortly following their deposition, these younger turbidites were shortened and intruded by ca. 2616-2608 Ma tonalite-granodiorite plutons of the Concession Suite.
In the multiply folded, metamorphosed, and intermittently exposed terrain of the western Slave craton, it has proven difficult to distinguish these younger turbiditic greywackes from Burwash Basin turbidites. There is no sharply defined demarcation line that separates the two turbidite packages and recognition of the younger sequence relies largely on the absence of Defeat Suite-age plutons and the presence of <2640 Ma detrital zircons. Preliminary work suggests that the younger turbidite sequence contains abundant intercalated iron formations, mostly of silicate facies, those of the Damoti Lake area representing one of the more significant examples. Many of the iron formations are "lean", comprising background turbiditic greywacke variably enriched in metamorphic garnet, other Fe-rich silicates, and/or disseminated sulphides.
A distinct, post-Burwash Basin, greywacke and/or volcaniclastic sediment package, associated with felsic volcanic rocks and subvolcanic intrusions, and dated at approximately 2716-2712 Ma, occurs along the tightly folded synclinal core of the High Lake greenstone belt of the northern Slave craton (Henderson et al., 2000; see Figs. 9d and 11d). This package is of significance in that it is one of the few examples of a preserved volcano-sedimentary carapace to one of the major plutonic suites, i.e. the coeval Concession Suite.
Mineralization
Types of mineralization within the younger (turbiditic)
greywacke packages are similar to those in folded Burwash Basin
strata. A principal example of epigenetic gold mineralization is
that hosted by silicate facies iron formation in the Damoti Lake
area. Similar iron formations occur all along the southwestern
edge of the Slave craton, from the Emile River area in the north
to the Russel Lake area in the south, and have been moderately
explored for gold and base metals. Scattered gold mineralization
also occurs in numerous "lean" iron formations
throughout the western Slave, e.g. the Wheeler and Germaine Lake
areas ("W" in Fig. 11d). The stratigraphic status of
the lean iron formations and their host turbidites in the
Wheeler-Germaine Lake areas is currently unresolved.
2.60-2.58 Ma, Final Orogenesis |
Starting at ca. 2600 Ma, the entire craton was affected by cross-folding and significant further shortening (D2), characterized by broadly north-south structural trends, and probably in response to final collision along a distant active margin of Sclavia. Moderate overthickening of the crust led to HT-LP metamorphism, widespread anatexis, the appearance of S-type granites, and a hot and weak lower crust. These processes culminated in ca. 2590 Ma extension and the regional "granite bloom". The intrusion of carbonatites (Villeneuve and Relf, 1998) and involvement of other mantle-derived melts indicate a role for mantle processes (delamination ?). Overall timing relationships are summarized in Figures 12a and b.
While peak temperatures were attained in the lower crust, large basement-cored domes were amplified by buoyancy driven deformation (Fig. 3); lower crustal devolatilization reactions mobilized gold-bearing fluids; and syn-orogenic clastic basins formed and were immediately infolded into tight synclines (Bleeker, 2002). At least one of these syn-orogenic clastic basins may have formed as late as ca. 2580 Ma (Sircombe and Bleeker, unpublished SHRIMP data; see detrital zircon age spectra in Fig. 12b). Late strike-slip faulting overprinted and truncated the synclinally infolded clastic basins. The lower crust cooled (Bethune et al., 1999), finally coupled with the mantle, and the Slave (within Sclavia) became a craton.
Mineralization
Strong penetrative regional deformation, culminating between 2600 Ma and 2590 Ma, as determined from syn-kinematic granite sheets (Davis and Bleeker, 1999), represents the most obvious deformation throughout most of the Slave craton. It must have driven moderate to significant crustal thickening and led to the main thermal peak of regional metamorphism in most areas. This D2 deformation and the associated metamorphism were the main driver for epigenetic gold mineralization throughout the Slave craton. In the Yellowknife greenstone belt, it led to formation of the ca. 15 million ounce Con-Giant Au deposit, along a complex system of mostly reverse shear zones. As is typical for this class of deposits, the Con-Giant system occurs mostly within moderate to strongly deformed basaltic rocks, in proximity to a regional stratigraphic break, the Yellowknife River Fault Zone. An asymmetric synclinal panel of syn-orogenic conglomerates (the Jackson Lake Formation) occurs along this fault zone. Identical relationships are observed in several other major Archean gold camps, most notably Timmins, Kirkland Lake, and Kalgoorlie. The critical control common to all these camps is localization of Au mineralization within significant bends of the regional fault zones; these bends were most likely dilational during emplacement of the gold-bearing quartz veins.
Although numerous other volcanic-hosted gold vein systems are known from the Slave craton, some of which were briefly in production in the past, only one other major camp has emerged in recent years. This camp occurs in the Hope Bay belt, on the Coronation Gulf coast of the Slave craton, and consists of a string of deposits (Boston, Doris, Madrid) that are being readied for production. Elsewhere, despite significant past exploration, overall potential for this class of deposits remains excellent. Several greenstone belts throughout the Slave craton have very similar structural-stratigraphic characteristics to that of the Yellowknife belt, including a thick, folded turbidite pile adjacent to a basaltic greenstone belt, a regional deformation zone, and a young conglomerate package. Best examples are the Point Lake and Arcadia Bay areas.
Another class of mineral deposits related to final orogenesis
is that of rare-element enriched granitoids, particularly highly
evolved anatectic granites and their pegmatites. Tin
(cassiterite) and Li (spodumene) were briefly mined from such
pegmatites in the Yellowknife Domain, but other pegmatite fields
are known throughout the Slave craton. From a global metallogeny
point of view, these occurrences are of interest as they
typically correlate with ancient, multiply recycled, felsic
crust.
Cratonization And Beyond |
The youngest significant granite plutons of the Slave craton are ca. 2585-2580 Ma. Only a few pegmatites are known to be significantly younger. Between ca. 2590 Ma and 2580 Ma, an enormous volume of granite was generated throughout much of the Slave craton. This "granite bloom", driven by moderate tectonic overthickening (D1-D2) and high intrinsic heat production, irreversibly transferred a significant fraction of heat-producing elements and lower crustal fluids (and Au) to the upper crust. In the lower crust, it must have involved large-scale migration of anatectic granitoid magmas, significant horizontal channel flow of partially molten rocks, development of a horizontal layering, and flattening of the Moho discontinuity into a stable density configuration. Collectively, these processes allowed the lower crust to cool and stiffen, over several tens of millions of years. U-Pb geochronology of lower crustal xenoliths shows that high-grade metamorphic reactions and zircon growth continued to about 2510 Ma at depth (Davis et al, 2003b). Finally, sufficient cooling allowed the crust to mechanically couple with the mantle (Bleeker, 2002). The end product was cratonic crust of high relative strength.
Following cratonization, there is a ca. 300 million time interval for which there are few recorded events within the Slave craton (Fig. 12b). Ca. 2.45 Ga magmatism, known from many other cratons around the world (e.g., Heaman, 1997), so far appears to be absent from the Slave craton.
At 2230 Ma, the northeast-trending Malley mafic dyke swarm, transecting the central Slave craton, provides the first evidence for mantle-driven magmatism and attempted rifting events. Involving at least ten different dyke swarms and associated extension events, the Slave craton finally broke out of its ancestral Sclavia supercraton between 2200 Ma and 2000 Ma. Details remain sketchy. Almost certainly, the eastern margin of the Slave craton, now involved in and overridden by the Thelon orogen, became established as a passive margin well before the western margin. The latter is referred to as the so-called Coronation margin and later became involved in Wopmay orogen (e.g., Hoffman, 1980; Bowring and Grotzinger, 1992; Hildebrand and Bowring, 1999). Once liberated out of the confines of its ancestral supercraton, the Slave continental microplate must have experienced a drift phase as an independent craton, before being progressively incorporated into the growing Laurentian collage and the supercontinent of Nuna.
Paleoproterozoic amalgamation processes varied along the margins of the Slave craton. In the east, the Slave acted as a lower plate, being overridden by the west-vergent Thelon orogen. In the south, along the shores and islands of Great Slave Lake, deformation was mainly transpressional along a long-lived transform boundary. In the west, at least two arc terranes (Hottah and the Great Bear Magmatic Zone) were involved, followed by oblique folding and late-stage, dextral, strike-slip deformation along the Wopmay Fault Zone. Development of the Great Bear arc, between about 1880 Ma and 1840 Ma, likely involved subduction of Paleoproterozoic lithosphere below the western Slave craton (e.g., Bostock, 1998).
Post-dating the assembly of Laurentia and Nuna, the Slave craton, particularly along its margins, became partially buried beneath intra-continental Proterozoic basins. At ca. 1269-1267 Ma, the craton was partly uplifted and intruded by the giant Mackenzie dyke swarm, radiating from a plume center west of Victoria Island (Barager et al., 1996; LeCheminant and Heaman, 1989). This is the last major event affecting the core of the craton, although some younger mafic magmatic events affect its edges (e.g. the ca. 780 Ma Hottah sheets). Since that time, Slave crust has been "bobbing" gently up and down, with interior seas expanding and receding across the craton. Ordovician and Cretaceous sedimentary rocks and fossils are known as wall rock fragments in some of the central Slave kimberlites.
Despite the relative stability at the surface, melting
events were triggered in the subcontinental mantle lithosphere,
leaving their traces as clusters of kimberlites across the
craton. From the several hundreds of kimberlites now known across
the craton, the following ages have been recorded: Cambrian,
Siluro-Ordovician, Permian, Jurassic, Cretacous, and finally
Eocene (e.g., Heaman et al., 2003). It are Eocene (ca. 55-50 Ma)
kimberlite pipes of the Lac de Gras area in the central Slave
craton that now support two highly profitable diamond mines,
Ekati and Diavik. Several other diamond mines are in various
stages of development. In just over a decade, diamonds have
become the most profitable commodity within this ancient
craton.
Summary |
The Slave craton is a relatively small Archean craton with a geological knowledge base that is relatively mature. However, the following major questions remain:
To many of these first-order questions, we currently have only rudimentary answers. More sophisticated answers will require more complete and more refined data sets. In particular, a greatly expanded geochronological database, both in quantity and precision, in conjunction with targeted field work across the craton and its marginal belts, would quickly advance the state of knowledge.
In terms of mineral potential, much of the craton and
all significant greenstone belts have seen at least a first wave
of exploration for major commodities. These investigations
quickly discovered a number of large VMS deposits (e.g., Izok
Lake), which await road access for economic production. Gold
potential remains high, particularly in more remote greenstone
belts that may not have seen the required level of drill testing.
In this respect, the Point Lake greenstone belt and its extension
further north appears attractive as it has all the major
attributes of a world-class gold camp.
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Tables |
Deposit type & name | Fig. 2 (#) |
Principal commodity |
Status | Host rocks | Age | Geological environment | Deposit size | Metal ratios | Other | Comments | Latitude | Longitude | NTS Sheet | Refs. |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Diamonds in kimberlites: | ||||||||||||||
Ekati | 26 | Gem diamonds | Producing mine, several kimberlite pipes | Kimberlite pipes, Eocene | 52-56 Ma | Lac de Gras area, central Slave craton, Lac de Gras structural basin | 64.7167 | -110.6064 | 076D10 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Diavik | 27 | Gem diamonds | Producing mine | Kimberlite pipes, Eocene; mostly volcaniclastic facies kimberlite | 52-56 Ma | Lac de Gras area, central Slave craton, Lac de Gras structural basin | 64.4997 | -110.2372 | 076D08 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Jericho | 28 | Gem diamonds | Permitting stage | Kimberlite pipes, Jurassic | 173 Ma | Contwoyto Lake, north-central Slave craton | Heaman et al., 2002; Heaman et al., 2003 and references therein | |||||||
Snap Lake | 29 | Gem diamonds | Producing mine | Kimberlite dykes, Siluro-Ordovician | 523-535 Ma | South-central Slave craton, Central Slave Basement Complex | 63.5925 | -110.7281 | 075M10 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Kennady Lake (Gahcho Kue) | 30 | Gem diamonds | Advanced exploration | Kimberlite pipes, Cambrian | 542 Ma | Southeastern Slave craton | 63.4358 | -109.2100 | 075N06 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Proterozoic hydrothermal Cu-Au (IOCG): | ||||||||||||||
Lou Lake, NICO | 23 | Cu, Au, Co, Bi | Feasibility | Disseminated and vein-type mineralization, calc-alkaline intrusion related | ca. 1860 Ma | Southern Great Bear Magmatic Zone | ca. 42 Mtonnes | 63.5483 | -116.7586 | Goad et al., 2000; Ghandhi et al., 2001 | ||||
Sue-Diane | 24 | Cu, Au, Ag, U, Fe | Advanced exploration | Volcanic-hosted, calc-alkaline suite | ca. 1860 Ma | Southern Great Bear Magmatic Zone | ca. 17 Mtonnes | 63.7586 | -116.9128 | Goad et al., 2000; Ghandhi et al., 2002 | ||||
Proterozoic alkaline intrusion-related rare-element deposits: | ||||||||||||||
Thor Lake | 22 | Ta, Nb, Be | Advanced exloration | Blatchford Lake intrusive complex | ca. 2180-2175 Ma | Anorogenic (rift-related?) intrusion along southern margin | 62.1161 | -112.5969 | 085I02 | Normin, 2005 | ||||
Proterozoic mafic intrusion-related deposits: | ||||||||||||||
Muskox Intrusion | 25 | Platinum group elements | Advanced exploration | Layered mafic intrusion, lopolithic dyke | 1269 Ma | Proximal to Mackanzie event plume center | ||||||||
Booth River Complex | V, PGEs? | Exploration? | Large layered intrusion | 2026 Ma | North-central Slave craton, overlain by Kilihigok Basin | 66.8394 | -109.0731 | 076K14 | Normin, 2005 | |||||
Late Archean rare-element enriched granites and pegmatitites: | ||||||||||||||
Hidden Lake, Prosperous Lake | 20 | Li, Be | Exploration trenches | Late stage pegmatite dykes, probably Prosperous Suite related | ca. 2595 Ma | Yellowknife Domain, southwestern Slave craton | 62.3081 | -112.8036 | 085I07 | Normin, 2005 | ||||
Upper Ross Lake (Peg Tantalum) | 21 | Be, Ta, Nb, Sn | Producer during WWII | Late stage granites and pegmatites, Redout Suite | ca. 2592 Ma | Yellowknife Domain, southwestern Slave craton | 62.7442 | -113.1083 | 085I11 | Normin, 2005 | ||||
Gold in turbidite-hosted BIF: | ||||||||||||||
Lupin | 16 | Au-Ag | Past producer (1982-2003); c&m | Iron formations hosted by Contwoyto Formation turbidites | ca. 2665-2660 Ma | Contwoyto Lake area, north-central Slave craton | 65.7647 | -111.2250 | Normin, 2005 | |||||
George Lake | 17 | Au | Advanced exploration | Silicate (oxide) BIFs in low-grade metaturbidites (Beechey Lake Group) | 2680-2660 Ma | Northeastern Slave craton, George Lake synclinorium | 65.9258 | -107.4764 | 076G13&14 | Normin, 2005 | ||||
Goose Lake | 18 | Au | Advanced exploration | Silicate (oxide) BIFs in low-grade metaturbidites (Beechey Lake Group) | 2680-2660 Ma | Northeastern Slave craton, George Lake synclinorium | 65.5439 | -106.4278 | 076G09 | Normin, 2005 | ||||
Damoti Lake | 19 | Au, Ag | Advanced exploration | Silicate facies BIFs in Damoti Lake assemblage turbidites | ca. 2620 Ma | Indin Lake belt, western Slave craton | 64.1383 | -115.1136 | 086B03 | Normin, 2005 | ||||
Wheeler (Germaine) Lake area | Au, Ag | Exploration | Lean silicate BIFs in metaturbidites (Burwash Formation??) | ca. 2660 Ma?? | Southwestern Slave craton, west of Yellowknife Domain | |||||||||
Vein-hosted gold in folded turbidites: | ||||||||||||||
Discovery Mine | 11 | Au | Past producer (1949-1969) | Quartz veins in folded turbidites | ca. 2650-2600 Ma | Yellowknife Domain, folded turbidites of the Burwash Formation | 63.1883 | -113.8972 | 085P04 | Normin, 2005 | ||||
Ptarmigan Mine | 10 | Au, Ag | Past producer; c&m | Quartz veins in folded turbidites | ca. 2650-2600 Ma | Yellowknife Domain, folded turbidites of the Burwash Formation | 62.5192 | -114.1972 | 085J09 | Normin, 2005 | ||||
Shear and vein-hosted gold in volcanic rocks: | ||||||||||||||
Giant Yellowknife | 9 | Au, Ag | Past producer; c&m | Sheared and altered mafic volcanics | ca. 2600-2580 Ma | Yellowknife greenstone belt | 62.4989 | -114.3628 | 085J08&09 | Normin, 2005 | ||||
Con Mine | 8 | Au, Ag | Past producer; c&m | Sheared and altered mafic volcanics | ca. 2600-2580 Ma | Yellowknife greenstone belt | 62.4333 | -114.3681 | 085J08 | Normin, 2005 | ||||
Ormsby Zone | Au | Advanced exploration | Quartz veins and alteration in an amphibolite panel; rare pillow structures | Yellowknife Domain | 63.1722 | -113.9253 | 085P04 | Normin, 2005 | ||||||
Nicholas Lake | Au, Ag | Advanced exploration | Veined and altered granodiorite | Yellowknife Domain | 63.2472 | -113.7617 | 085P04 | Normin, 2005 | ||||||
Tundra Gold Mine | 12 | Au, Ag | Past producer; abandoned | Quartz veins along contact between felsic volcanics and Burwash Formation turbidites | Courageous Lake greenstone belt | 64.0400 | -111.1744 | 076D03 | Normin, 2005 | |||||
Tundra-Fat | Au | Advanced exploration | Sheared and altered felsic volcaniclastic rocks | Courageous Lake greenstone belt | 64.1178 | -111.2706 | 076D03 | Normin, 2005 | ||||||
Salmita | Au, Ag | Past producer; abandoned | Veins in mafic volcanic package | Courageous Lake greenstone belt | 64.0750 | -111.2411 | 076D03 | Normin, 2005 | ||||||
Arcadia | 14 | Au, Ag | Exploration, some zones drilled | Volcanic rocks and tonalite | Anialik River greenstone belt, Coronation Gulf | 67.6869 | -111.3400 | 076M11 | Normin, 2005 | |||||
Hope Bay: Boston, Madrid, Doris | 15 | Au, Ag | Starting production | Sheared and altered mafic volcanics | Hope Bay greenstone belt | 67.6494 | -106.3881 | 076O09 | Normin, 2005 | |||||
Colomac | 13 | Au, Ag | Past producer; c&m | Sheared and altered porphyries? | Indin Lake greenstone belt | 64.3975 | -115.0856 | 086B06 | Normin, 2005 | |||||
Kim | Au | Advanced exploration | Sheared and altered mafic volcanics | 64.3167 | -115.2706 | 086B06 | Normin, 2005 | |||||||
Volcanogenic massive sulphide deposits in arc-like volcanics: | Tonnage | Cu:Zn:Pb | Ag (ppm) | |||||||||||
Izok Lake | 1 | Cu, Zn, Pb, Ag | Waiting for road access | Felsic volcanic complex | ca. 2684 Ma | Northern Point Lake greenstone belt | 10,800,000 | 15:77:8 | 66 | 65.6311 | -112.7989 | 086H10 | Normin, 2005; Padgham, 1992 | |
Gondor | 2 | Zn, Ag, Cu, Pb, Au | Advanced exploration | Felsic and intermediate volcaniclastic rocks | Central volcanic belt | 7,500,000 | 6:87:7 | 45 | average for 3 drill holes | 65.5628 | -111.7969 | Normin, 2005; Padgham, 1993 | ||
Yava | 3 | Zn, Cu, Ag, Pb, Au | Drilled | Felsic and intermediate volcaniclastic rocks | ca. 2680 Ma | Hackett River greenstone belt | 1-2,000,000 | 12:75:13 | 103 | 65.6044 | -107.9383 | 076G12 | Normin, 2005; Padgham, 1994 | |
Musk | 4 | Zn, Pb, Cu, Ag, Au | Advanced exploration | Felsic volcanic rocks | ca. 2680 Ma | Hackett River greenstone belt | 300,000 | 10:79:11 | 343 | 65.3231 | -107.6208 | 076G05 | Normin, 2005; Padgham, 1995 | |
Hackett River, A Zone | Zn, Pb, Cu, Ag, Au | Advanced exploration | Felsic volcanic rocks | ca. 2680 Ma | Hackett River greenstone belt | 5,000,000 | 2:84:14 | 280 | 65.9172 | -108.3631 | 076F16 | Normin, 2005; Padgham, 1996 | ||
Hackett River, Boot | Cu, Zn, Pb, Ag | ca. 2680 Ma | Hackett River greenstone belt | 5,000,000 | 4:82:14 | 176 | Normin, 2005; Padgham, 1997 | |||||||
Hackett River, Cleaver | Cu, Zn, Pb, Ag | ca. 2680 Ma | Hackett River greenstone belt | 4,000,000 | 5:83:12 | 160 | Normin, 2005; Padgham, 1998 | |||||||
Hackett River, Stringer Zone | Cu, Zn, Pb, Ag | ca. 2680 Ma | Hackett River greenstone belt | 4,000,000 | 20:45:35 | 291 | low grade | Normin, 2005; Padgham, 1999 | ||||||
High Lake, Ab | 5 | Cu, Zn, Ag | Advanced exploration | Felsic volcanics | ca. 2705 Ma | High Lake greenstone belt | 2,400,000 | 83:17:0 | 67.3814 | -110.8500 | 076M07 | Normin, 2005; Padgham, 2000 | ||
High Lake, D-Zone | 5 | Zn, Cu, Ag, Pb, Au | Advanced exploration | ca. 2705 Ma | High Lake greenstone belt | 2,800,000 | 35:62:3 | 33 | 67.3758 | -110.8436 | 076M07 | Normin, 2005; Padgham, 2001 | ||
High Lake, W-Zone | 5 | Cu, Zn, Pb, Ag | Advanced exploration | ca. 2705 Ma | High Lake greenstone belt | Normin, 2005; Padgham, 2002 | ||||||||
Sunrise | 6 | Zn, Pb, Ag, Cu, Au | Advanced exploration | Felsic volcanic complex near volcanic-sedimentary interface | ca. 2670 Ma | Beaulieu River greenstone belt | 2,057,000 | 1:67:32 | 367 | probable | 62.9000 | -112.3794 | 085I16 | Normin, 2005; Padgham, 2003 |
Bear | Zn, Pb, Ag, Cu, Au | Advanced exploration | Beaulieu River greenstone belt | 809,700 | 1:72:27 | 218 | 29 holes | 62.8919 | -112.3931 | 085I16 | Normin, 2005; Padgham, 2004 | |||
Boot Lake | Cu, Zn, Pb, Ag | 67.1025 | -110.8983 | 076M02 | Normin, 2005; Padgham, 2004 | |||||||||
Creek Zone Mat | Cu, Zn, Pb, Ag | Normin, 2005; Padgham, 2005 | ||||||||||||
Deb | Cu, Zn, Pb, Ag | Advanced exploration | 1,118,000 | 24:75:1 | 20 | drilling | 64.0017 | -111.2325 | 075M14 & 076D03 | Normin, 2005; Padgham, 2006 | ||||
East Cleaver Lake | Cu, Zn, Pb, Ag | Normin, 2005; Padgham, 2007 | ||||||||||||
Hood #10 | Cu, Zn, Pb, Ag | 20:80:1 | 30 | Normin, 2005; Padgham, 2008 | ||||||||||
Hood #10 | Cu, Zn, Pb, Ag | 150,000 | 59:41:0 | low grade | Normin, 2005; Padgham, 2009 | |||||||||
Hood #41 | Cu, Zn, Pb, Ag | 300,000 | 27:73:0 | 16 | Normin, 2005; Padgham, 2010 | |||||||||
Kennedy Lake (BB+Lk+Cuzone) | Zn, Pb, Ag, Cu | Advanced exploration | 63.0322 | -110.9483 | 075M02 | Normin, 2005; Padgham, 2011 | ||||||||
Kennedy, 1. zone | Cu, Zn, Pb, Ag | 70,000 | 0:86:14 | 150 | trenches | Normin, 2005; Padgham, 2012 | ||||||||
Kennedy, BB zone | Cu, Zn, Pb, Ag | 150,000 | 100:0:0 | ? | drilling | Normin, 2005; Padgham, 2013 | ||||||||
Kennedy, Cu zone | Cu, Zn, Pb, Ag | 970,000 | 0:93:7 | 102 | drilling | Normin, 2005; Padgham, 2014 | ||||||||
Lark | Cu, Zn, Pb, Ag | 4:89:7 | ? | 2 drill holes | Normin, 2005; Padgham, 2015 | |||||||||
Lark | Cu, Zn, Pb, Ag | 5:81:10 | ? | Normin, 2005; Padgham, 2016 | ||||||||||
Len | Cu, Zn, Pb, Ag | 0:32:68 | 54 | 2 drill holes | Normin, 2005; Padgham, 2017 | |||||||||
Len | Cu, Zn, Pb, Ag | 0:34:66 | 42 | trenches | Normin, 2005; Padgham, 2018 | |||||||||
Susu Lake | Cu, Zn, Pb, Ag | 142,500 | 100:0:0 | ? | 9 holes | Normin, 2005; Padgham, 2019 | ||||||||
Turnback, OK | Cu, Zn, Pb, Ag | 0:62:38 | 395 | Normin, 2005; Padgham, 2020 | ||||||||||
Turnback, XL | Cu, Zn, Pb, Ag | 12:72:16 | 157 | 25 holes | Normin, 2005; Padgham, 2021 | |||||||||
Volcanogenic sulphides in bimodal rift volcanics of Kam Group type: | ||||||||||||||
Homer Lake 1 | 7 | Ag, Zn, Pb, Au, Cu | Showings, trenches; drilled | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Yellowknife greenstone belt | 3:32:65 | 84 | only VMS in Yellowknife belt | 62.6544 | -114.2994 | 085J09 | Normin, 2005; Padgham, 2020 | |
Homer Lake 2 | Ag, Zn, Pb, Au, Cu | Showings, trenches | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Yellowknife greenstone belt | 2:55:43 | 45 | only VMS in Yellowknife belt | Normin, 2005; Padgham, 2021 | |||||
Bell Lake | Cu, Zn | Showings | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Yellowknife greenstone belt | |||||||||
Courageous Lake | Cu, Zn | Showings | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Courageous Lake greenstone belt | |||||||||
Point Lake | Cu, Zn | Showings | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Point Lake greenstone belt | |||||||||
Banded iron formations: | ||||||||||||||
Dwyer Lake | Fe; epigenetic Au? | Prospective for Au? | Banded iron formations at the top of the Central Slave Cover Group | ca. 2826 Ma | At base of Yellowknife greenstone belt | |||||||||
Patterson Lake | Fe; epigenetic Au? | Prospective for Au? | Banded iron formations at the top of the Central Slave Cover Group | 2850-2800 Ma | ||||||||||
Amacher | Fe; epigenetic Au? | Prospective for Au? | Banded iron formations at the top of the Central Slave Cover Group | 2850-2800 Ma | At base of Beaulieu greenstone belt | |||||||||
e.g., Point Lake; others | Fe; epigenetic Au? | Prospective for Au? | Minor banded iron formations within basalt-dominated volcanic packages | ca. 2720-2700 Ma | Minor iron formations within basalt-dominated volcanic packages | |||||||||
Contwoyto Formation | Fe; epigenetic Au | Prospective for Au? | Banded iron formations in turbidites | 2680-2660 Ma | Contwoyto Lake area, north-central Slave craton | |||||||||
Back River | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in turbidites | 2680-2660 Ma | Overlying the Back River volcanic complex and in turbitidites | |||||||||
George Lake | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in turbidites | 2680-2660 Ma | Northeastern Slave craton | |||||||||
Goose Lake | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in turbidites | 2680-2660 Ma | Northeastern Slave craton | |||||||||
Damoti Lake | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in Damoti Lake turbidites | 2625-2615 Ma | Indin Lake belt, western Slave craton | |||||||||
Mesoarchean paleo-placer Au, U, Cr: | ||||||||||||||
Dwyer Lake | Cr as detrital chromite | Curiosity | Supermature quartzites of the Central Slave Cover Group | >2853 Ma | Bleeker et al., 1999a | |||||||||
Other quartzites | Au, U paleo-placers? | Prospects? | Supermature quartzites of the Central Slave Cover Group | 2900-2800 Ma | Roscoe, 1990 | |||||||||
Mesoarchean basement-hosted deposits: | ||||||||||||||
No known deposits | Bleeker et al., 1999a,b |
Figures |
[Click on an image thumbnail to view a larger image, notice]
Appendix |
Deposit Type & Name |
# * |
Principal Commodity |
Status | Host rocks | Age | Geological Environment | Deposit Size | Metal Ratios | Other | Comments | Latitude | Longitude | NTS Sheet | References |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Diamonds in kimberlites: | ||||||||||||||
Ekati | 26 | Gem diamonds | Producing mine, several kimberlite pipes | Kimberlite pipes, Eocene | 52-56 Ma | Lac de Gras area, central Slave craton, Lac de Gras structural basin | 64.7167 | -110.6064 | 076D10 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Diavik | 27 | Gem diamonds | Producing mine | Kimberlite pipes, Eocene; mostly volcaniclastic facies kimberlite | 52-56 Ma | Lac de Gras area, central Slave craton, Lac de Gras structural basin | 64.4997 | -110.2372 | 076D08 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Jericho | 28 | Gem diamonds | Permitting stage | Kimberlite pipes, Jurassic | 173 Ma | Contwoyto Lake, north-central Slave craton | Heaman et al., 2002; Heaman et al., 2003 and references therein | |||||||
Snap Lake | 29 | Gem diamonds | Producing mine | Kimberlite dykes, Siluro-Ordovician | 523-535 Ma | South-central Slave craton, Central Slave Basement Complex | 63.5925 | -110.7281 | 075M10 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Kennady Lake (Gahcho Kue) | 30 | Gem diamonds | Advanced exploration | Kimberlite pipes, Cambrian | 542 Ma | Southeastern Slave craton | 63.4358 | -109.2100 | 075N06 | Normin, 2005; Heaman et al., 2003 and references therein | ||||
Proterozoic hydrothermal Cu-Au (IOCG): | ||||||||||||||
Lou Lake, NICO | 23 | Cu, Au, Co, Bi | Feasibility | Disseminated and vein-type mineralization, calc-alkaline intrusion related | ca. 1860 Ma | Southern Great Bear Magmatic Zone | ca. 42 Mtonnes | 63.5483 | -116.7586 | Goad et al., 2000; Ghandhi et al., 2001 | ||||
Sue-Diane | 24 | Cu, Au, Ag, U, Fe | Advanced exploration | Volcanic-hosted, calc-alkaline suite | ca. 1860 Ma | Southern Great Bear Magmatic Zone | ca. 17 Mtonnes | 63.7586 | -116.9128 | Goad et al., 2000; Ghandhi et al., 2002 | ||||
Proterozoic alkaline intrusion-related rare-element deposits: | ||||||||||||||
Thor Lake | 22 | Ta, Nb, Be | Advanced exloration | Blatchford Lake intrusive complex | ca. 2180-2175 Ma | Anorogenic (rift-related?) intrusion along southern margin | 62.1161 | -112.5969 | 085I02 | Normin, 2005 | ||||
Proterozoic mafic intrusion-related deposits: | ||||||||||||||
Muskox Intrusion | 25 | PGEs | Advanced exploration | Layered mafic intrusion, lopolithic dyke | 1269 Ma | Proximal to Mackanzie event plume center | ||||||||
Booth River Complex | V, PGEs? | Exploration? | Large layered intrusion | 2026 Ma | North-central Slave craton, overlain by Kilihigok Basin | 66.8394 | -109.0731 | 076K14 | Normin, 2005 | |||||
Late Archean rare-element enriched granites and pegmatitites: | ||||||||||||||
Hidden Lake, Prosperous Lake | 20 | Li, Be | Exploration trenches | Late stage pegmatite dykes, probably Prosperous Suite related | ca. 2595 Ma | Yellowknife Domain, southwestern Slave craton | 62.3081 | -112.8036 | 085I07 | Normin, 2005 | ||||
Upper Ross Lake (Peg Tantalum) | 21 | Be, Ta, Nb, Sn | Producer during WWII | Late stage granites and pegmatites, Redout Suite | ca. 2592 Ma | Yellowknife Domain, southwestern Slave craton | 62.7442 | -113.1083 | 085I11 | Normin, 2005 | ||||
Gold in turbidite-hosted BIF: | ||||||||||||||
Lupin | 16 | Au-Ag | Past producer (1982-2003); c&m | Iron formations hosted by Contwoyto Formation turbidites | ca. 2665-2660 Ma | Contwoyto Lake area, north-central Slave craton | 65.7647 | -111.2250 | Normin, 2005 | |||||
George Lake | 17 | Au | Advanced exploration | Silicate (oxide) BIFs in low-grade metaturbidites (Beechey Lake Group) | 2680-2660 Ma | Northeastern Slave craton, George Lake synclinorium | 65.9258 | -107.4764 | 076G13&14 | Normin, 2005 | ||||
Goose Lake | 18 | Au | Advanced exploration | Silicate (oxide) BIFs in low-grade metaturbidites (Beechey Lake Group) | 2680-2660 Ma | Northeastern Slave craton, George Lake synclinorium | 65.5439 | -106.4278 | 076G09 | Normin, 2005 | ||||
Damoti Lake | 19 | Au, Ag | Advanced exploration | Silicate facies BIFs in Damoti Lake assemblage turbidites | ca. 2620 Ma | Indin Lake belt, western Slave craton | 64.1383 | -115.1136 | 086B03 | Normin, 2005 | ||||
Wheeler (Germaine) Lake area | Au, Ag | Exploration | Lean silicate BIFs in metaturbidites (Burwash Formation??) | ca. 2660 Ma?? | Southwestern Slave craton, west of Yellowknife Domain | |||||||||
Vein-hosted gold in folded turbidites: | ||||||||||||||
Discovery Mine | 11 | Au | Past producer (1949-1969) | Quartz veins in folded turbidites | ca. 2650-2600 Ma | Yellowknife Domain, folded turbidites of the Burwash Formation | 63.1883 | -113.8972 | 085P04 | Normin, 2005 | ||||
Ptarmigan Mine | 10 | Au, Ag | Past producer; c&m | Quartz veins in folded turbidites | ca. 2650-2600 Ma | Yellowknife Domain, folded turbidites of the Burwash Formation | 62.5192 | -114.1972 | 085J09 | Normin, 2005 | ||||
Shear and vein-hosted gold in volcanic rocks: | ||||||||||||||
Giant Yellowknife | 9 | Au, Ag | Past producer; c&m | Sheared and altered mafic volcanics | ca. 2600-2580 Ma | Yellowknife greenstone belt | 62.4989 | -114.3628 | 085J08&09 | Normin, 2005 | ||||
Con Mine | 8 | Au, Ag | Past producer; c&m | Sheared and altered mafic volcanics | ca. 2600-2580 Ma | Yellowknife greenstone belt | 62.4333 | -114.3681 | 085J08 | Normin, 2005 | ||||
Ormsby Zone | Au | Advanced exploration | Quartz veins and alteration in an amphibolite panel; rare pillow structures | Yellowknife Domain | 63.1722 | -113.9253 | 085P04 | Normin, 2005 | ||||||
Nicholas Lake | Au, Ag | Advanced exploration | Veined and altered granodiorite | Yellowknife Domain | 63.2472 | -113.7617 | 085P04 | Normin, 2005 | ||||||
Tundra Gold Mine | 12 | Au, Ag | Past producer; abandoned | Quartz veins along contact between felsic volcanics and Burwash Formation turbidites | Courageous Lake greenstone belt | 64.0400 | -111.1744 | 076D03 | Normin, 2005 | |||||
Tundra-Fat | Au | Advanced exploration | Sheared and altered felsic volcaniclastic rocks | Courageous Lake greenstone belt | 64.1178 | -111.2706 | 076D03 | Normin, 2005 | ||||||
Salmita | Au, Ag | Past producer; abandoned | Veins in mafic volcanic package | Courageous Lake greenstone belt | 64.0750 | -111.2411 | 076D03 | Normin, 2005 | ||||||
Arcadia | 14 | Au, Ag | Exploration, some zones drilled | Volcanic rocks and tonalite | Anialik River greenstone belt, Coronation Gulf | 67.6869 | -111.3400 | 076M11 | Normin, 2005 | |||||
Hope Bay: Boston, Madrid, Doris | 15 | Au, Ag | Starting production | Sheared and altered mafic volcanics | Hope Bay greenstone belt | 67.6494 | -106.3881 | 076O09 | Normin, 2005 | |||||
Colomac | 13 | Au, Ag | Past producer; c&m | Sheared and altered porphyries? | Indin Lake greenstone belt | 64.3975 | -115.0856 | 086B06 | Normin, 2005 | |||||
Kim | Au | Advanced exploration | Sheared and altered mafic volcanics | 64.3167 | -115.2706 | 086B06 | Normin, 2005 | |||||||
Volcanogenic massive sulphide deposits in arc-like volcanics: | Tonnage | Cu:Zn:Pb | Ag (ppm) | |||||||||||
Izok Lake | 1 | Cu, Zn, Pb, Ag | Waiting for road access | Felsic volcanic complex | ca. 2684 Ma | Northern Point Lake greenstone belt | 10,800,000 | 15:77:8 | 66 | 65.6311 | -112.7989 | 086H10 | Normin, 2005; Padgham, 1992 | |
Gondor | 2 | Zn, Ag, Cu, Pb, Au | Advanced exploration | Felsic and intermediate volcaniclastic rocks | Central volcanic belt | 7,500,000 | 6:87:7 | 45 | average for 3 drill holes | 65.5628 | -111.7969 | Normin, 2005; Padgham, 1993 | ||
Yava | 3 | Zn, Cu, Ag, Pb, Au | Drilled | Felsic and intermediate volcaniclastic rocks | ca. 2680 Ma | Hackett River greenstone belt | 1-2,000,000 | 12:75:13 | 103 | 65.6044 | -107.9383 | 076G12 | Normin, 2005; Padgham, 1994 | |
Musk | 4 | Zn, Pb, Cu, Ag, Au | Advanced exploration | Felsic volcanic rocks | ca. 2680 Ma | Hackett River greenstone belt | 300,000 | 10:79:11 | 343 | 65.3231 | -107.6208 | 076G05 | Normin, 2005; Padgham, 1995 | |
Hackett River, A Zone | Zn, Pb, Cu, Ag, Au | Advanced exploration | Felsic volcanic rocks | ca. 2680 Ma | Hackett River greenstone belt | 5,000,000 | 2:84:14 | 280 | 65.9172 | -108.3631 | 076F16 | Normin, 2005; Padgham, 1996 | ||
Hackett River, Boot | Cu, Zn, Pb, Ag | ca. 2680 Ma | Hackett River greenstone belt | 5,000,000 | 4:82:14 | 176 | Normin, 2005; Padgham, 1997 | |||||||
Hackett River, Cleaver | Cu, Zn, Pb, Ag | ca. 2680 Ma | Hackett River greenstone belt | 4,000,000 | 5:83:12 | 160 | Normin, 2005; Padgham, 1998 | |||||||
Hackett River, Stringer Zone | Cu, Zn, Pb, Ag | ca. 2680 Ma | Hackett River greenstone belt | 4,000,000 | 20:45:35 | 291 | low grade | Normin, 2005; Padgham, 1999 | ||||||
High Lake, Ab | 5 | Cu, Zn, Ag | Advanced exploration | Felsic volcanics | ca. 2705 Ma | High Lake greenstone belt | 2,400,000 | 83:17:0 | 67.3814 | -110.8500 | 076M07 | Normin, 2005; Padgham, 2000 | ||
High Lake, D-Zone | 5 | Zn, Cu, Ag, Pb, Au | Advanced exploration | ca. 2705 Ma | High Lake greenstone belt | 2,800,000 | 35:62:3 | 33 | 67.3758 | -110.8436 | 076M07 | Normin, 2005; Padgham, 2001 | ||
High Lake, W-Zone | 5 | Cu, Zn, Pb, Ag | Advanced exploration | ca. 2705 Ma | High Lake greenstone belt | Normin, 2005; Padgham, 2002 | ||||||||
Sunrise | 6 | Zn, Pb, Ag, Cu, Au | Advanced exploration | Felsic volcanic complex near volcanic-sedimentary interface | ca. 2670 Ma | Beaulieu River greenstone belt | 2,057,000 | 1:67:32 | 367 | probable | 62.9000 | -112.3794 | 085I16 | Normin, 2005; Padgham, 2003 |
Bear | Zn, Pb, Ag, Cu, Au | Advanced exploration | Beaulieu River greenstone belt | 809,700 | 1:72:27 | 218 | 29 holes | 62.8919 | -112.3931 | 085I16 | Normin, 2005; Padgham, 2004 | |||
Boot Lake | Cu, Zn, Pb, Ag | 67.1025 | -110.8983 | 076M02 | Normin, 2005; Padgham, 2004 | |||||||||
Creek Zone Mat | Cu, Zn, Pb, Ag | Normin, 2005; Padgham, 2005 | ||||||||||||
Deb | Cu, Zn, Pb, Ag | Advanced exploration | 1,118,000 | 24:75:1 | 20 | drilling | 64.0017 | -111.2325 | 075M14 & 076D03 | Normin, 2005; Padgham, 2006 | ||||
East Cleaver Lake | Cu, Zn, Pb, Ag | Normin, 2005; Padgham, 2007 | ||||||||||||
Hood #10 | Cu, Zn, Pb, Ag | 20:80:1 | 30 | Normin, 2005; Padgham, 2008 | ||||||||||
Hood #10 | Cu, Zn, Pb, Ag | 150,000 | 59:41:0 | low grade | Normin, 2005; Padgham, 2009 | |||||||||
Hood #41 | Cu, Zn, Pb, Ag | 300,000 | 27:73:0 | 16 | Normin, 2005; Padgham, 2010 | |||||||||
Kennedy Lake (BB+Lk+Cuzone) | Zn, Pb, Ag, Cu | Advanced exploration | 63.0322 | -110.9483 | 075M02 | Normin, 2005; Padgham, 2011 | ||||||||
Kennedy, 1. zone | Cu, Zn, Pb, Ag | 70,000 | 0:86:14 | 150 | trenches | Normin, 2005; Padgham, 2012 | ||||||||
Kennedy, BB zone | Cu, Zn, Pb, Ag | 150,000 | 100:0:0 | ? | drilling | Normin, 2005; Padgham, 2013 | ||||||||
Kennedy, Cu zone | Cu, Zn, Pb, Ag | 970,000 | 0:93:7 | 102 | drilling | Normin, 2005; Padgham, 2014 | ||||||||
Lark | Cu, Zn, Pb, Ag | 4:89:7 | ? | 2 drill holes | Normin, 2005; Padgham, 2015 | |||||||||
Lark | Cu, Zn, Pb, Ag | 5:81:10 | ? | Normin, 2005; Padgham, 2016 | ||||||||||
Len | Cu, Zn, Pb, Ag | 0:32:68 | 54 | 2 drill holes | Normin, 2005; Padgham, 2017 | |||||||||
Len | Cu, Zn, Pb, Ag | 0:34:66 | 42 | trenches | Normin, 2005; Padgham, 2018 | |||||||||
Susu Lake | Cu, Zn, Pb, Ag | 142,500 | 100:0:0 | ? | 9 holes | Normin, 2005; Padgham, 2019 | ||||||||
Turnback, OK | Cu, Zn, Pb, Ag | 0:62:38 | 395 | Normin, 2005; Padgham, 2020 | ||||||||||
Turnback, XL | Cu, Zn, Pb, Ag | 12:72:16 | 157 | 25 holes | Normin, 2005; Padgham, 2021 | |||||||||
Volcanogenic sulphides in bimodal rift volcanics of Kam Group type: | ||||||||||||||
Homer Lake 1 | 7 | Ag, Zn, Pb, Au, Cu | Showings, trenches; drilled | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Yellowknife greenstone belt | 3:32:65 | 84 | only VMS in Yellowknife belt | 62.6544 | -114.2994 | 085J09 | Normin, 2005; Padgham, 2020 | |
Homer Lake 2 | Ag, Zn, Pb, Au, Cu | Showings, trenches | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Yellowknife greenstone belt | 2:55:43 | 45 | only VMS in Yellowknife belt | Normin, 2005; Padgham, 2021 | |||||
Bell Lake | Cu, Zn | Showings | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Yellowknife greenstone belt | |||||||||
Courageous Lake | Cu, Zn | Showings | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Courageous Lake greenstone belt | |||||||||
Point Lake | Cu, Zn | Showings | Weakly mineralized felsic rocks in bimodal rift succession | ca. 2720-2700 Ma | Point Lake greenstone belt | |||||||||
Banded iron formations: | ||||||||||||||
Dwyer Lake | Fe; epigenetic Au? | Prospective for Au? | Banded iron formations at the top of the Central Slave Cover Group | ca. 2826 Ma | At base of Yellowknife greenstone belt | |||||||||
Patterson Lake | Fe; epigenetic Au? | Prospective for Au? | Banded iron formations at the top of the Central Slave Cover Group | 2850-2800 Ma | ||||||||||
Amacher | Fe; epigenetic Au? | Prospective for Au? | Banded iron formations at the top of the Central Slave Cover Group | 2850-2800 Ma | At base of Beaulieu greenstone belt | |||||||||
e.g., Point Lake; others | Fe; epigenetic Au? | Prospective for Au? | Minor banded iron formations within basalt-dominated volcanic packages | ca. 2720-2700 Ma | Minor iron formations within basalt-dominated volcanic packages | |||||||||
Contwoyto Formation | Fe; epigenetic Au | Prospective for Au? | Banded iron formations in turbidites | 2680-2660 Ma | Contwoyto Lake area, north-central Slave craton | |||||||||
Back River | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in turbidites | 2680-2660 Ma | Overlying the Back River volcanic complex and in turbitidites | |||||||||
George Lake | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in turbidites | 2680-2660 Ma | Northeastern Slave craton | |||||||||
Goose Lake | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in turbidites | 2680-2660 Ma | Northeastern Slave craton | |||||||||
Damoti Lake | Fe; epigenetic Au | Advanced exploration for Au | Banded iron formations in Damoti Lake turbidites | 2625-2615 Ma | Indin Lake belt, western Slave craton | |||||||||
Mesoarchean paleo-placer Au, U, Cr: | ||||||||||||||
Dwyer Lake | Cr as detrital chromite | Curiosity | Supermature quartzites of the Central Slave Cover Group | >2853 Ma | Bleeker et al., 1999a | |||||||||
Other quartzites | Au, U paleo-placers? | Prospects? | Supermature quartzites of the Central Slave Cover Group | 2900-2800 Ma | Roscoe, 1990 | |||||||||
*#s refer to those in Figure 2. |
2006-04-18 |