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The Prairie Creek stratabound, vein and carbonate hosted zinc-lead-silver deposit is located in the Northwest Territories (NWT), Canada, near the Yukon border, and is 500 km west of Yellowknife, ~185 west of Fort Simpson, ~170 km NNW of Fort Liard and 340 km north of Fort Nelson in British Columbia (#Location: 61° 33' 16"N, 124° 47' 50"W).
Prairie Creek is located within, and towards the southern extremity of the arcuate Mackenzie Mountains Zinc District which extends for ~450 km from Gayna River in the NW to Prairie Creek in the south. The district straddles the transition from the Selwyn Basin to the Mackenzie Platform, but is mainly within the latter, and includes >230 Zn-Pb (±Cu, Ag, Ba, Sb, Ga) carbonate-hosted, vein and breccia style occurrences and deposits. It is up to 75 km wide and overlaps the Redstone Copper Belt from south of Coates Lake to north of Keele River and continues, parallel to the Plateau Thrust.
The original discovery of mineralisation at Prairie Creek was made by a local trapper in 1928 at the exposure of a mineralised vein exposed in the bank of Prairie Creek. Mr. In 1958 a limited mapping program was undertaken by Fort Reliance Minerals Limited. The claims lapsed in 1965, and were re-staked and subsequently conveyed to Cadillac Explorations Limited in 1966. Between 1966 and 1969, trenching was undertaken on a number of mineralised zones and underground exploration was commenced as follow-up to trench results in two zones, but only low metal values were encountered. In 1970 Penarroya Canada Limited optioned the title, extended the underground development in the Main Zone and carried out surface drilling, before withdrawing. In 1975, Noranda Exploration optioned the southern portion of the Property, drilled eight holes and subsequently exited in the same year. Cadillac Explorations continued to development of the Main Zone underground workings and in 1980 an independent feasibility study prompted a decision to put the Mine (then called Cadillac Mine) into production. Between 1980 and 1982, extensive mine development took place, including installation of a 1000 tpd mill and concentrator. In early 1982 the price of silver collapsed. Activities continued until May 1982 when they were suspended when Cadillac went into bankruptcy. Site maintenance was taken over by Procan, which acquired Cadillac’s interest from the receivers in 1984, before selling it to Nanisivik Mines Limited in 1991. In August 1991, Canadian Zinc Corporation(then San Andreas Resources Corporation), acquired a 60% interest in the Property from Nanisivik, and in 1993 purchased the remaining 40%. There has been no production from the deposit, despite trial mining having been carried out in 1982 that stockpiled ~10 000 tonnes of ore.
The regional geology is dominated by a Late Ordovician to Devonian stratigraphy, and in the Prairie Creek area was deposited within a palaeo-embayment of the westward thickening Selwyn Basin into the Mackenzie Platform to the east. This embayment is interpreted to have developed as a half-graben controlled by a north-trending fault with down-drop to the west. The Selwyn Basin succession is predominantly composed of deep-water clastic sediments, while the Mackenzie Platform is characterised by carbonate sequences.
Deposition in the Prairie Creek Embayment ended in Mid-Jurassic time when the eastward collision of an island-arc terrane to the west resulted in compression, imbrication and folding of the sedimentary succession and to the intrusion of widespread Cretaceous post-tectonic plutons in the western half of the Selwyn Basin. The resultant deformation varies with lithology, with thick, predominantly carbonate units, forming large structures whereas thinly bedded clastic units were formed repeated small folds and fault panels. Within the Prairie Creek Embayment there are three phases of deformation: i). regional north-south folding which is cut by steeply-dipping wrench faults; ii). these were subsequently reactivated as high-angle reverse faults; and iii). Late, shallow, north-trending thrust faults that predominate within the carbonate platform rocks. The current margins of the Prairie Creek Embayment are defined by the Tundra Thrust to the east and the Manetoe Thrust 20 km to the west. These structures juxtapose shallow-water shelf carbonate rocks against deeper-water basinal sedimentary rocks of the Embayment.
In the deposit area, north-south trending faulting and folding is apparent, with the deposit being developed on the western flank of the fault-bounded, doubly-plunging, Late Cretaceous to Eocene Laramide Prairie Creek anticline. The sequence in the deposit area reflects changes in patterns of sedimentation related to the inception, growth and filling of the Prairie Creek Embayment, and comprises, from the base:
Sunblood Platformal sequence, which includes shallow-water argillaceous limestone and dolomite of the Middle Ordovician Sunblood Formation, unconformably overlain by dolostones of the Whittaker Formation. West of Prairie Creek, the Sunblood Formation is conformably overlain by basinal shales of the Ordovician to Silurian Road River Formation.
Mount Kindle-Root River assemblage, which overlaps the platformal sequence and is composed of the Late Ordovician to Devonian sequence comprising the,
• Whittaker Formation, which unconformably overlies the Sunblood Formation and is, in turn, split into
i). Lower Whittaker - a Middle to Upper Ordovician dark-grey silty to sandy limestone, which in the deposit area is >50 m of chert nodule dolostone.
ii). Middle Whittaker - Middle to Upper Ordovician grey gritty dolostone with some sand size grit units with greenish, shaley partings.
iii). Upper Whittaker - an Upper Ordovician to Silurian suite of bedded to laminated, dark-grey fine-crystalline dolostone that is the host rock of stratabound mineralisation at Prairie Creek. It has been further subdivided into 7 units with gradational contacts:
- Massive Dolomite, 20 to 30 m of grey massive dolostone with minor chert nodules.
- Mottled Dolomite, 20 to 30 m of fine grained dolostone with spheroidal mottled texture and chert; hosting two of the stratabound sulphide deposits. Disseminated fine-grained pyrite is common. Hosts the stratabound mineralisation.
- Lower Chert Nodular Dolomite, 40 to 60 m of massive to poorly bedded, weakly bioclastic, fine- to medium- grained dolostone containing mid-grey to black chert nodules.
- Lower Spar, 9 to 24 m of massive bioclastic, mid-grey, fine grained dolostone with white spar-filled cavities. Bioclastic material (crinoids, brachiopods) is fine grained and comminuted.
- Upper Chert Nodular Dolomite, 55 to 100 m of dolostone similar to the Lower Chert Nodular Dolomite.
- Upper Spar, 11 to 25 m of bioclastic dolostone similar to the Lower Spar unit.
- Inter-bedded Chert-Dolomite, 50 to 55 m of well-bedded, black to mid-grey cherts interbedded with dolostone. Chert content decreases with depth. Algal mat-type structures and possible dolomitised anhydrite towards the base.
• Road River Formation, which at Prairie Creek is 230 to 280 m thick, is of Silurian to Devonian age and is composed of mid to dark grey graphitic argillaceous bioclastic dolostone (graptolites common, occasional crinoids and brachiopods). Marker horizon near base is a possible debris flow.
• Cadillac Formation, 300 to 350 m of grey, thinly banded siltstone / shale with minor debris flow.
• Root River Formation, which comprises Silurian light-grey, vuggy, micritic dolostone, and is interpreted to be the shallow-water section of the upper Cadillac Formation.
Prairie Creek assemblage, is of Silurian to Devonian age, and is variable in both lithology and thickness, reflecting the inception and growth of the Prairie Creek Embayment.
Funeral-Headless assemblage, marks the filling of the embayment and is composed of platformal shale, dolostone and limestone of Middle Devonian age.
In the Main deposit area, the Upper Whittaker Formation forms the core of the Prairie Creek antiform. It is composed of interbedded cherts and dolomites, and is overlain by the graphitic-shales/dolostones of the Road River Formation.
Base metal mineralised quartz veins are exposed on surface within a 16 km long, north to NNE-trending corridor in the southern half of the district. Vein showings were historically referred to as Zones 1 to 12. The Main Zone, which includes the Main Quartz Vein and other styles of mineralisation, is found in zones 1, 2, and 3 over a trend length of >2 km. Vein Zones 4 to 12 extend discontinuously for a further ~10 km to the south of the Main Zone. The Rico showing is located approximately 4 km north of the Main Zone.
Four styles of base metal mineralisation have been recognised: quartz vein, stockwork, stratabound and carbonate hosted, although no mineralisation of economic interest has been found in the latter.
Quartz veining, with the most extensively developed being the Main Quartz Vein - that dips at 65°E, with a strike length of at least 2.1 km, vertical extent of >600 m and thickness of from 0.1 to 5 m, averaging 2.7 m. This interval is part of mineralised trend that can be traced for ~10 km along the Prairie Creek Fault. Mineralisation comprises massive to disseminated galena and sphalerite with lesser pyrite and tennantite-tetrahedrite in a quartz-carbonate-dolomite matrix. The vein is best-developed in the more competent units of the Lower Road River and Whittaker Formations, and dissipates in the in the graphitic shales of the mid and upper Road River Formation. Offsets observed within this vein may represent a more complex en echelon structure rather than a simple vein.
Stockwork Mineralisation, which occur as a localised development of a series of 0.1 to 0.5 m thick, sub-vertical, massive sphalerite-galena-tennantite veins that are separated by <1 to >2 m of unaltered dolostone which sometimes contain thinner veins. They strike at ~40° to the Main Quartz Vein, and are interpreted to be splays from the latter.
Stratabound Mineralisation, which has been intermittently intersected over a strike length of ~3 km within the Mottled Dolomite unit of the Upper Whittaker Formation both in the main zone and to its south. It is associated with several of the known vein zones but occurs near the currently-known lower limits of veining. As such it has not been encountered at surface, only in drill holes. Mineralisation totally replaces the host without any significant alteration. It is generally fine-grained, banded to semi-massive and comprises massive fine-grained sphalerite, coarse-grained galena and disseminated to massive pyrite. Silver is in solid solution within both galena and sphalerite and the mineralisation is devoid of tennantite-tetrahedrite. It has very little Cu and ~50% of the galena, but has substantially more iron sulphide/pyrite compared to typical vein material. Fragments of this mineralisation style has been found in vein material.
Carbonate Hosted Mineralisation, occur discontinuously within coarse biohermal reefs of the Silurian Root River/Cadillac Formation that immediately overlies the Road River Formation. It comprises colloform rims of sphalerite, brassy pyrite-marcasite and minor galena, with or without later dolomite infilling. It occurs in a number of location distributed over a strike length of ~10 km, some 6 km NE of the Main Zone, and always at approximately the same stratigraphic horizon.
Published Mineral Resources at Prairie Creek, as at September 2015 (Canadian Zinc Corporation website, viewed Oct. 2018) were:
Main Quartz Vein - Measured + Indicated Resource 5.540 Mt @ 10.2% Zn, 11.6% Pb, 178 g/t Ag;
Inferred Resource 5.269 Mt @ 12.9% Zn, 8.7% Pb, 199 g/t Ag.
Stockwork - Measured + Indicated Resource 2.122 Mt @ 7.1% Zn, 3.6% Pb, 66 g/t Ag;
Inferred Resource 1.610 Mt @ 6.2% Zn, 4.6% Pb 70 g/t Ag.
Stratabound - Measured + Indicated Resource 1.042 Mt @ 10.8% Zn, 5.2% Pb, 54 g/t Ag;
Inferred Resource 0.17 Mt @ 11.2% Zn, 6.3% Pb, 60 g/t Ag.
Combined Resource - Measured + Indicated Resource 8.704 Mt @ 9.5% Zn, 8.9% Pb, 136 g/t Ag;
Inferred Resource 7.049 Mt @ 11.3% Zn, 7.7% Pb, 166 g/t Ag.
TOTAL Measured + Indicated + Inferred Resource 15.753 Mt @ 10.3% Zn, 8.4% Pb, 149 g/t Ag.
The information in this summary is largely drawn from Smith, H.A., Staples, L.P., Elfen, S., Mosher, G.Z., Wright, F. and Williams, D., 2005 - Prairie Creek Property Feasibility Study; An NI 43-101 Technical Report prepared by AMC Mining Consultants (Canada) Ltd. for Canadian Zinc Corp., 337p.
The most recent source geological information used to prepare this summary was dated: 2017.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Ootes, L., Gleeson, S.A., Turner, E., Rasmussen, K., Gordey, S., Falck, H., Martel., E. and Pierce, K., 2013 - Metallogenic Evolution of the Mackenzie and Eastern Selwyn Mountains of Canadas Northern Cordillera, Northwest Territories: A Compilation and Review: in Geoscience Canada, v.40, pp. 40-69, http://dx.doi.org/10.12789/geocanj.2013.40.005.|
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