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Hackett River, Bathurst Norsemines |
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Nunavut, Canada |
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Ag Zn Cu Au Pb
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Hackett River silver-zinc-copper deposits of 'Main A', East Cleaver and Bootlake are located 460 km north-east of Yellowknife (NWT), 240 km south-east of the High River deposit in Nunavut Territory, northern Canada (#Location: 65° 55' 02" N, 108° 21' 47"W).
The Hackett River deposits (also known as the Bathurst Norsemines occurrences) are located 100 km west of the Thelon Front in the northern part of the Slave craton in the northwestern Canadian Shield. Much of the central and western parts of the craton are underlain by a contiguous Paleo- to Mesoarchaean (4.03-2.9 Ga), largely crystalline basement complex, dominated by foliated to gneissic tonalites, diorites and granodiorites. These old rocks are overlain by Neoarchaean supracrustal sequences, and heavily intruded and reworked by plutonic suites ranging in age from 2.72 to 2.67 Ga synvolcanic plutons to 2.59 to -2.58 Ga late-orogenic batholithic granites.
The supracrustal sequences are collectively known as the Yellowknife Supergroup, and comprise: i). an early, around 2.8 Ga cover sequence comprising quartzite and banded iron formation, ii). a thick, dominantly tholeiitic greenstone sequence of approximately 2.7 Ga in age, iii). a younger 2.69 to 2.61 Ga arc-like sequences, iv). extensive 2.68 to 2.62 Ga turbidite blankets of the Burwash Basin, and v). syn-orogenic conglomerates deposited at approximately 2.6 Ga.
During subsequent orogenesis, the supracrustal sequences were telescoped, thickened, and multiply folded between around 2.65 and 2.58 Ga, with a peak in crustal anatexis between 2.59 and 2.58 Ga.
The Hackett River deposits are hosted within the 120 km long, north-west trending, Hackett River greenstone belt which is composed of a 2.69 to 2.61 Ga arc-like sequences which followed the 2.7 Ga basaltic volcanism and rifting within the Slave craton. The host sequence belongs to the Yellowknife Supergroup. During this time interval, most parts of the Slave craton showed a transition to such calc-alkaline volcanism characterised by abundant felsic and intermediate volcanic rocks, calc-alkaline basaltic rocks, and intercalated volcaniclastic sedimentary rocks. These volcanic arc sequences and the associated subvolcanic plutons, are interpreted to have formed in part on top of the attenuated basement and in progressively widening, juvenile, back-arc-like basins.
The Hackett River greenstone belt is overlain on its eastern margin and to the south-west by 2.68 to 2.62 Ga turbidite sequences, while to the west it is bounded by 2.68 and 2.58 Ga granitoids.
The mineral deposits generally occur within a mixed package of rhyolitic fragmentals, epiclastics and chemical and clastic sediments known as the 'Mineral Horizon' which is sandwiched between a thick footwall sequence of fragmental rhyolites and hangingwall clastic sediments.
Three main areas of mineralisation have been described:
i). the 'Main A' (or Central) area which includes the 'A', Jo and Jo South zones. The 'A' and Jo deposits are situated at the same stratigraphic position and comprise conformable lenses of pyrite with lesser sphalerite, galena and chalcopyrite. Both are found above discordant, zoned alteration pipe-like stringer zones of chalcopyrite, pyrrhotite, pyrite and magnetite. Alteration takes the form of an assemblage of sericite-quartz-(sillimanite-cordierite) developed along inferred hydrothermal fluid channelways, interspersed with patchy anthophyllite-cordierite-biotite-garnet-quartz-(sillimanite-sericite). Both zones fall within a relatively broad envelope of spotted sillimanite-biotite-garnet-quartz-(cordierite-sericite) rock. The Jo South zone is at a lower stratigraphic level and comprises a series of veins and disseminations of pyrite, sphalerite, chalcopyrite and galena;
ii). the Boot Lake area, 2 km from 'Main A' is within a thinner development of the 'Mineral Horizon', with a less complex internal stratigraphy. Sulphides occur in small lenses and as continuous layers of pyrite, both containing variable amounts of pyrrhotite, sphalerite, galena and chalcopyrite; and
iii). the East Cleaver area, 6 km from 'Main A' area, is also situated within the 'Mineral Horizon', and is a single, reasonably homogeneous sulphide body composed of pyrite, sphalerite and galena. It has been deformed by folding and shearing and is now highly contorted, occupying the nose of an overturned anticline. The sulphide body is underlain by a pipe-like stringer and alteration zone similar to those under the 'A' and Jo deposits.
Published resource figures (Sabina Silver, 2006) were:
Indicated resource - 47 Mt @ 134 g/t Ag, 4.67% Zn, 0.32% Cu, 0.68% Pb, 0.27 g/t Au at a 5 g/t Ag cutoff;
Inferred resource - 12.4 Mt @ 127 g/t Ag, 3.77% Zn, 0.27% Cu, 0.52% Pb, 0.27 g/t Au at a 5 g/t Ag cutoff;
Indicated resource - 10.2 Mt @ 187 g/t Ag, 8.68% Zn, 0.29% Cu, 1.258% Pb, 0.31 g/t Au at a 15 g/t Ag cutoff;
Inferred resource - 1.05 Mt @ 169 g/t Ag, 7.75% Zn, 0.27% Cu, 0.94% Pb, 0.25 g/t Au at a 15 g/t Ag cutoff
These resources are split between the main areas as follows: 'Main A' (30%), East Cleaver (30%) and Bootlake (50%).
The most recent source geological information used to prepare this decription was dated: 2006.
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.
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