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Detour Lake |
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Quebec, Canada |
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Cu Zn Au Ag
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Detour Lake Archaean volcanic hosted massive sulphide deposit is located 100 km west of Mattagami in north-west Quebec, Canada.
The deposit was discovered in 1974 as a result of an airborne electromagnetic survey followed by ground geophysics and diamond drilling. Mineralisation occurs in two distinct zones, ~400 m apart. The eastern of these, the A-1 zone, was the first to be discovered and to be drilled in detail. In this zone, mineralisation consists of fracture fillings and disseminations of Zn-Cu-Ag sutphides with associated pyrite and quartz gangue. Economic concentrations of mineralisation mainly occur above the 150 m RL as an irregularly shaped zone up to 500 m in lateral extent, and grade in all directions, laterally and to depth, into sub-economic mineralisation. Steep fracturing and possible block faults are commonl in the host rocks of this zone, although they do not appear to have been subjected to shearing or folding to any signifiant extent. In the western B zone, the host rocks have been severely sheared and sulphide minerals appear to have been extensively re-mobilised. Most of the
economic mineralisation is now concentrated along a zone of intense shearing.
The deposit lies near the western extremity of the Chibougamau-Matagami zone, within the Abitibi Belt which consist of sequences
of volcanic and sedimentary rocks intruded by elongate granitic bodies. The sulphide mineralisation occurs within a section of dominantly pyroclastic,
intermediate-to-acid volcanic rocks which exhibit textural features indicative of their having been deposited in a predominantly sub-aerial environment. A massive, acid pyroclastic unit, the Welded Acid Tuff, is the dominant host to the deposit. It consists of quartz grains, dark chloritic fiamme and rounded to angular lapilli in a cryptocrystalline siliceous matrix. The quartz grains are angular to rounded and range from 0.1 to 2.0 mm across and constitute ~5 vol.% of the rock. The fiamme, typically comprise up 5 to 10 vol.% of the rock, and range from 1 to 5 cm in length, generally showing some degree of parallel elongation. The lapilli, which are angular to rounded fragments of acid volcanic rocks up to 1O mm in diameter, comprise ~5 vol.% of the rock. The Welded Acid Tuff is varies up to a maximum of ~100 m in thickness, and grades into dacitic tuffs at its base, whilst its upper contact is generally abrupt and has an undulating surface. This surface is overlain by an irregularly intergrading sequence of rhyolitic and dacitic tufts, volcanic breccias and agglomerates. The breccias and agglomerates contain many fragments of the Welded Acid Tuff and many of the tuff bands contain abundant lithofacies. A sill-like quartz porphyry body within the Welded Acid Tuff has been shown by petrographic studies to have originated as an ash-flow deposit.
Within the pyroclastic rocks above the Welded Acid Tuff, there are some bands of massive, stratabound pyrite that appear to pre-date, and to be genetically unrelated to, the Zn-Cu.Ag minerakisation. This suggests there were probably occasional periods of submergence during the evolution of the sequence. Silicification, sericitization and chloritization are the modes of alteration commonly observed in the host rocks.
The silicification occurs as quartz veining with associated pyrite and Zn-Cu sulphides in fractures; and, secondly, as stratabound silicified zones in the pyroclastic rocks above the Welded Acid Tuff. These silicified zones contain remnant textural features that identify pyroclastic protolith rocks set in a matrix of cherty siliceous material. Chloritic and sericitic alteration are ubiquitous throughout the host rocks although the intensity of both is extremely variable.
The host rocks of the A-1 zone are dissected by an extensive plexus of steep fractures and possible block faults. A granite intrusion occurs to the east of the deposit. Intrusion of this body has not imposed extensive alteration on the volcanic rocks, nor does it have any apparent genetic relationship to the mineralisation.
The main ore minerals are chalcopyrite and sphalerite, which mainly occur within the system of steep fractures which penetrate the host rocks where they are associated with pyrite, quartz and subordinate amounts of carbonate. Stringers and disseminations of the ore minerals also occur in the silicified zones within the pyroclastic rocks above the Welded Acid Tuff. The sulphide minerals occur as fine to medium-grained, interlocking aggregates with a variable proportion of the relative proportions of the sulphide species. However, in general, sphalerite is significant throughout the deposit whilst the most important concentrations of chalcopyrite are found in the central part of the mineralised zone. Silver minerals are not visible in drill core although argentite and native Ag have
been observed during the microscopic examination of ore concentrates.
Estimated resources in 1980 were:
A1 Zone hypogene mineralisation totalled 32.1 Mt @ 0.39% Cu, 2.3% Zn, 36 g/t Ag, 0.31g/t Au.
B Zone contained 3.07 Mt @ 4.49% Cu, 0.80% Zn, 39 g/t Ag, 1.2 g/t Au.
The ore occurred in a number of bodies. The A1 deposit was controlled by a series of fractures over a surface area some 400 m in diameter and to a depth of no more than 200 m. The ore was present as a series of laminated veins up to 40 cm thick with quartz, sphalerite, pyrite, chalcopyrite and Ca or Mg carbonate.
The B Zone was 800 m west of A1 and comprised a series of anastomosing quartz-sulphide veins up to 20 cm thick within elongated lenses of mineralisation.
For detail see the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1980.
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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Selected References:
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Sinclair I G L, Gasparrini E 1980 - Textural features and age of supergene mineralization in the Detour copper-zinc-silver deposit, Quebec: in Econ. Geol. v75 pp 470-477
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Sinclair, I.G.L., 1977 - Primary disperersion patterns associated with the Detour zinc-copper-silver deposit at Lac Brouillan, Province of Quebec, Canada: in J. of Geochemical Exploration v.8, pp. 139-151.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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