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Bouchard, Hébert, Mobrun |
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Quebec, Canada |
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Zn Au Cu Ag
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Super Porphyry Cu and Au
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The Bouchard-Hébert mine, previously known as Mobrun, is located some 30 km to the north-east of Rouyn-Noranda in Quebec, Canada, within the Abitibi greenstone belt of the Archaean Superior province.
It comprises two gold rich poly-metallic complexes of conformable massive sulphides hosted by interbedded mafic-to-felsic submarine volcanic rocks of the Archaean Blake River Group. The Blake River Group is the uppermost stratigraphic unit in the southern part of the Abitibi greenstone belt and within Quebec by tholeiitic flows of the Kinojevis Group. The lower part of the Blake River Group in the Noranda district is interpreted to represent a shield volcano, and the upper part a caldera complex. The Mobrun deposit occurs in the upper part of the stratigraphic succession about 7 km NW of the inferred caldera margin.
Both the Blake River and Kinojevis groups are folded into a large-scale structure, the Blake River synclinorium, which is bounded to the north by the Porcupine-Destor break and to the south by the Larder Lake-Cadillac break. Two main periods of deformation are evident in the area. Mobrun is located on the gently dipping upright limb of one of a number of large-scale NW-trending D1 folds found in the Noranda-Mobrun. Associated D1 faults typically occur as bedding-parallel zones of schistosity. The main D2 event produced east-trending folds and an associated domainal cleavage. The most intense D2 deformation is localised to the south, in proximity to the east-west-trending Larder Lake-Cadillac break where many of the demonstrably synvolcanic faults that control the location of VHMS mineralisation in the Noranda-Mobrun district were reactivated during subsequent deformation. Metamorphic grades range from prehnite-pumpellyite to greenschist facies, with local overprinting amphibolite-facies assemblages in contact-metamorphic aureoles of syn- to late-tectonic intrusions.
The Mobrun deposit is hosted by felsic, intermediate and mafic lava flows, and felsic and intermediate pyroclastic rocks, that strike at 110 to 120° and dip subvertically to the south. It comprises three massive-sulphide complexes: the 1100, Main and Satellite lens complexes.
The 1100 Complex, which is 250 m south-east of, and stratigraphically 100 to 200 m lower than the Main lens complex, is the statigraphically lowest, and comprises four separate, closely spaced lenses, designated A, B, C and D, hosted by tholeiitic rhyolites, with one andesitic interval. The B lens contains the bulk of the mineralisation, with a length of 300 m, maximum thickness of 50 m, and comes to within 360 m of the surface.
The Main lens complex comprises five separate en echelon lenses, mostly hosted by massive, brecciated and tuffaceous rhyolites. It has a lateral extent of 350 m and is developed over a preserved vertical interval of ~200 m (the upper part of the orebody has been removed by erosion), with a maximum thickness of 40 m in the core, tapering towards the margins for an average of 15 m.
The Satellite lens complex comprises three small massive-sulphide bodies representing three parts of one originally continuous lens offset by northeast-striking faults. The largest of these averages 3 m in thickness.
Sericitisation is reported in the hanging wall of the 1100 lens complex, and chloritisation in the footwall. In the footwall of the Main lens complex, pervasive silicification and sericitisation of rhyolite breccia is crosscut by a small zone of copper-rich stockwork mineralisation accompanied by strong chloritisation and sericitisation. The hanging wall is sericitised, silicified and chloritised. The footwall of the Satellite lenses has been subjected to strong copper mineralisation and chloritisation. This alteration persists for up to 100 m or more from the Main lens complex in particular, and is reflected by mass gains of FeO+MgO and gains in K2O. In addition, carbonate alteration has been recognised in footwall rocks of the 1100 lens complex.
The Main Complex sulphides are 90% pyrite, 5% sphalerite, 2% chalcopyrite with minor galena, digenite and pyrrhotite.
Reserve, resources and production in 1991 (Larocque et al., 1993) were:
Main lens complex - resource, 3.374 Mt @ 0.61% Cu, 2.08% Zn, 24.65 g/t Ag, 1.73 g/t Au,
reserve, 1.356 Mt @ 0.70% Cu, 2.51% Zn, 27.67 g/t Ag, 2.27 g/t Au,
production, 1.674 Mt @ 0.84% Cu, 2.36% Zn, 29.54 g/t Ag, 2.45 g/t Au
1100 lens complex - resource, 16.959 Mt @ 0.79% Cu, 3.69% Zn, 33.04 g/t Ag, 1.19 g/t Au,
reserve, 7.572 Mt @ 0.84% Cu, 5.87% Zn, 42.5 g/t Ag, 1.75 g/t Au,
Satellite lens - proven reserve, 1989 (Larocque et al., 1995), 0.179 Mt @ 1.20% Cu, 2.41% Zn, 42.27 g/t Ag, 4.98 g/t Au
See the main Noranda record for more background on the setting.
The mine closed permantly in 2005.
The most recent source geological information used to prepare this decription was dated: 1995.
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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Barrett T J, Cattalani S, Hoy L, Riopel J, Lafleur P J 1992 - Massive sulfide deposits of the Noranda area, Quebec. IV. The Mobrun mine: in Can. J. Earth Sci. v29 pp 1349-1374
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Kerr D J, Gibson H L 1993 - A comparison of the Horne volcanogenic massive Sulfide deposit and intracauldron deposits of the mine sequence, Noranda, Quebec: in Econ. Geol. v88 pp 1419-1442
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Larocque A C L, Hodgson C J 1993 - Gold distribution in the Mobrun volcanic-associated massive Sulfide deposit, Noranda, Quebec: a preliminary evaluation of the role of metamorphic remobilization: in Econ. Geol. v88 pp 1443-1459
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Larocque A C L, Hodgson C J, Lafleur P J 1993 - Gold distribution in the Mobrun volcanic-associated massive sulfide deposit, Noranda, Quebec: A preliminary evaluation of the role of metamorphic remobilization: in Econ. Geol. v88 pp 1443-1459
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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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