Geology of the Deux Orignaux Lake Area, West of Chapais, Abitibi Subprovince, Eeyou Istchee James Bay, Quebec, Canada

In Essence

A new 1:50,000 scale geological map of the Deux Orignaux Lake area (Abitibi Subprovince) was produced following a survey carried out in the summers of 2012 and 2013. The Keller and Dusault prospective zones correspond to regional deformation corridors associated with fertile syenites. They include the Grizzly, Gladstone, Queenimich and Guettard-Nord mineralized zones, characterized by gold-bearing quartz-carbonate veins (up to 34.17 g/t Au; Hashimoto, 1980; Leblanc, 2008). The ankeritized quartz diorites of the Sunset prospective zone in the Travailleur Nord Stream area host gold-bearing quartz-pyrite-chalcopyrite veins, and those of the Golden Moose Gold mineralized zone have returned up to 8.8 g/t Au (Allard, 2011). The Berey-Bordure prospective zone, which includes the mineralized zones at La Trêve 1 (347 ppb Au, 3554 ppb Pt, 9304 ppb Pd, 12,945 ppb PGE, 13,060 ppm Cu, 693 ppm Co and 7518 ppm Ni; Beauregard and Gaudreault, 2000) and La Trêve 4 (1.17 g/t Pt+Pd+Au and 0.63% Cu+Ni+Co over 6.95 m in chip samples; Banas, 2003) highlight the potential for Ni-Cu-PGE mineralization along the edge of the Berey Massif. The Mildred-Est prospective zone refers to the volcanic rocks in the same area, which contain numerous chert-pyrite ± pyrrhotite ± chalcopyrite exhalite lenses prospective for exhalative sulphide mineralization.

Methodology

The area was mapped using the established method for surveys in forest areas served by a network of secondary roads. The geological mapping was carried out by a team of one geologist, one geologist-in-training and two students, between 4 June and 24 August 2012 (southern part of NTS sheet 32G14) and by a team of one geologist, two geologists-in-training and three students, between 3 June and 23 August 2013 (northern part of sheet 32G14 and SW of sheet 32J03).

Mapping of the study area has produced and updated the information presented in the table below:

Data and Analyses

Element	Number
Outcrop described (“geofiche”)	1005
Total lithogeochemical analysis	201
Lithogeochemical analysis of metals of economic interest	109
Geochronological analysis	4
Covered thin section	125
Polished thin section	22
Sodium cobaltinitrite stain	–
Stratigraphic unit	36
Mineralization record	51

Previous Work

The table below provides a list of works carried out in the study area since 1936. An exhaustive list can be found in the EXAMINE documentary database.

Previous Work in the Study Area

Author(s)	Type of Work	Contribution
Norman, 1936 Beach, 1941a Beach, 1941b Shaw, 1942	Geological mapping of the Opawica, Opémisca and Lake Mechamego areas	First geological maps west of Chapais
Wolhuter, 1962 MacIntosh, 1966** Durocher, 1972*** Durocher, 1973*** Hocq, 1974* Durocher, 1975*** Hocq, 1977** MacIntosh, 1977** Durocher, 1979 Otis, 1980 Charbonneau, 1981a Charbonneau, 1981b Dubé, 1981 Chartrand, 1982 Otis, 1983 Chartrand, 1984	Mapping by the Ministère at scale 1:20,000 and older surveys at scale 1:15,840 (*), 1:63,360(**) and 1:12,000 (***)	First detailed geological map of the Branssat-Chapais segment
Durocher, 1978 Otis, 1985	Stream sediment surveys	Geochemical anomaly maps
Otis, 1986	Soil geochemistry	Geochemical anomaly maps
Charbonneau et al., 1991	Mapping, compilation and stratigraphic correlations	Geological synthesis of the Branssat-Chapais area
Brangier, 1984 Picard, 1984 Piché, 1985 Simoneau, 1986 Bédard, 1988 Brisson, 1989 Bédard, 1992	University works	Better understanding of local and regional geology
Paradis, 2000	Cartography, photo interpretation	Map of surface formations
David et al., 2012 Augland et al., 2016	Geochronological data acquisition	General knowledge of the lithotectonic context in the Abitibi Subprovince
Lafrance, 2014	Compilation of case studies	Development of a new fertility diagram for alkaline intrusions
Legault and Lalonde, 2009 Legault and Goutier, 2014	Characterization, sampling and analysis	Identification of fertile syenites using geochemical diagrams
Daoudene et al., 2014 Daoudene et al., 2016	Acquisition of thermochronological data 40Ar/39Ar	Comparison of the tectonometamorphic evolution of the Abitibi and Opatica subprovinces
Keating and d’Amours, 2010	Aeromagnetic survey data acquisition	The entire region is covered by aeromagnetic surveys

Lithostratigraphy

The study area is located in the NE part of the Abitibi Subprovince, which refers to an assemblage of Neoarchean volcano-sedimentary and plutonic rocks found in the southeast of the Superior Province (Thurston et al., 2008; Goutier and Melançon). The units in the Deux Orignaux Lake area will be presented in the following six groups:

• volcanic rocks older than those of the Roy Group;
• volcano-sedimentary rocks of the Roy Group;
• sedimentary rocks of the Opémisca Group;
• mafic to ultramafic intrusive rocks;
• felsic intrusive rocks;
• Paleoproterozoic dykes.

The stratigraphic diagram below illustrates the crosscutting relationships and relative positions of these units to the south (block A) and north (block B) of the Lamarck Shear Zone. These observations are supported by U-Pb geochronological data from 15 units in the area. The size of units presented in the diagram is consistent with the areas mapped on the surface.

Archean Units

The oldest rocks in the region are found in the Chrissie Formation, the lower part of which is dominated by basalt and numerous glomeroporphyritic gabbro sills (nAcs1). The upper part comprises mafic to intermediate volcaniclastic rocks, andesite and exhalite (nAcs2).

Volcanosedimentary Rocks of the Roy Group

First Volcanic Cycle

The Obatogamau Formation comprises basalt and andesitic basalt (nAob1), as well as lenses of mafic to intermediate volcaniclastic rocks (nAob2). In the NW part of the study area, this formation includes the Pichamobi Member, made up of a 1 km by 10 km lens of andesite and porphyritic rhyolite (nApm1), as well as intermediate to felsic volcaniclastic rocks, mudrock and exhalite (nApm2). The Waconichi Formation is represented by the Queylus Member (nAqu1), which refers to a unit of mafic to intermediate volcaniclastic rocks containing rare mudrock beds. We have assigned the rocks of the Waconichi Formation west and north of the Deux Orignaux Lake to the Deux Orignaux Member (nAduo). These rocks, composed of mafic to intermediate volcaniclastic rocks and a lesser proportion of dacite and rhyolite, are exposed at the heart of a structural dome that corresponds to the axial trace of the Chibougamau Anticline.

Second Volcanic Cycle

The Bruneau Formation is composed of basalt and andesitic basalt (nAbnu1), along with a few lenses of mafic to intermediate volcaniclastic rocks and rhyolite (nAbnu2). The Blondeau Formation comprises a lower part dominated by basalt and andesitic basalt (nAbl1), and an upper part composed of mafic to intermediate lapilli tuff, polygenic conglomerate, lithic arenite, lithic wacke and mudrock (nAbl). The Scorpion Formation (nAsc), which includes andesitic basalt, trachybasalt, mafic volcaniclastic rocks and rhyodacite, is a unit that outcrops almost exclusively in the study area.

Sedimentary Rocks of the Opémisca Group The sedimentary rocks at the base of the Opémisca Group (nAop) unconformably overlie those of the Roy Group.

The Daubrée Formation (nAda) is characterized by thick turbidite sequences composed of feldspathic arenite, arkosic arenite, siltstone and mudstone, in addition to a minor proportion of polygenic conglomerate. The Stella Formation (nAst) consists of polygenic conglomerate, sandstone and mudstone. The unit appears over a width of ~1 km in the SW part of sheet 32G14 and disappears between the Daubrée and Haüy formations in the Progress Lake area. North of the Gwillim Shear Zone, the Daubrée Formation is succeeded by the La Trêve Formation (nAlt), which is considered to be stratigraphically equivalent to the Stella Formation west of Chapais. It is composed of polygenic conglomerate, arenite, lithic wacke, basalt, and mafic to felsic volcaniclastic rocks. The top of the Opémisca Group is represented by the Haüy Formation, subdivided into five members in the study area: a) the Vanina Member (nAva), composed of basalt and andesitic basalt; b) the Christian Member (nAcn), characterized by andesitic basalt, andesite and trachytic lapilli tuff; c) the Gribouille Member (nAgb), which consists of lithic arenite, arkose, mudrock, monogenic and polygenic conglomerate, and felsic volcaniclastic rocks; d) the Pantoufle Member (nApa), which includes potassic basalt, volcaniclastic rocks, lithic arenite and mudrock; and e) the Dolomieu Member (nAdo), which comprises potassic andesite, lithic arenite and coarse mafic to intermediate lapilli tuff.

The Chebistuan Formation (nAch) is considered to be the stratigraphic equivalent of the Stella and Haüy formations to the north of the Chibougamau Anticline (Daigneault and Allard, 1990). In the study area, it comprises polygenic conglomerate, lithic arenite and mudrock. Mapping revealed areas dominated by polygenic conglomerate and a lesser proportion of arkosic wacke and arenite (nAch2), along with other areas dominated by mudrock (nAch3).

Mafic to Ultramafic Intrusive Rocks

In the study area, the Cummings Intrusive Suite comprises the Ventures Sill (nAven), composed of peridotite, pyroxenite, gabbro and quartz gabbro, and the Bourbeau Sill characterized by informal units of pyroxenite (nAbou1), gabbro and leucogabbro (nAbou2), and diorite, quartz gabbro and quartz-rich granitoid (nAbou3). The Cummings Intrusive Suite rocks cut those of the Blondeau Formation.

In accordance with the recommendations of the North American Stratigraphic Code regarding the use of the term « complex » (articles 37d and 38, NASC, 1986; 2005) and to ensure consistency with the changes that have been proposed to the nomenclature of the Lac Doré (now the « Lac Doré Intrusive Suite« ) and Cummings (now the « Cummings Intrusive Suite ») complexes, it is proposed that the « Lac Chaleur Complex » be renamed the « Lac de la Chaleur Intrusive Suite ». The Lac de la Chaleur Intrusive Suite is composed of anorthosite and gabbro (nAcha1), leucogabbro (nAcha2), melanocratic gabbro (nAcha3) and a unit of dunite, peridotite, pyroxenite and troctolite (nAcha4). The rocks of this suite cut those of the Roy Group and are characterized by an unconformable contact with the overlying rocks of the Opémisca Group. They are cut by the Opémisca Pluton.

The Rita Pluton (nArit) consists of diorite containing leucocratic biotite. It cuts the rocks of the Daubrée Formation and highlights a synclinal structure on either side of the Saussure Stock, west of the mapped area.

Intermediate to Felsic Intrusive Rocks

The Lapparent Intrusive Suite (nAlap) includes, in the study area, a tonalitic to dioritic gneiss unit (nAlap1), the Ouest Granodiorite (nAgro), and the Houghton and Anville plutons. The Houghton Pluton contains monzodiorite zones (nAhou1), and brecciated tonalite containing hornblendite and gabbro enclaves (nAhou2). The Anville Pluton (nAanv) is dominated by tonalite and also includes enclaves of hornblendite and gabbro.

Granodiorite and Granite

The Berey Massif (nAber) consists of granodiorite. The eastern edge of the massif is exposed in the study area. It injects the basalt layers of the Obatogamau Formation at the boundary between the Abitibi and Opatica subprovinces. The Opémisca Pluton (nAope) is composed of granodiorite and locally porphyroid monzodiorite. It cuts the volcano-sedimentary rocks of the Roy Group and those of the Lac de la Chaleur Intrusive Suite. The Envoûtant (Aenv) and Lantagnac (Alan) stocks are granodioritic, while the Deux Granites (Adgr), Marie-Hélène (Amah) and Thomelet (Atho) stocks are granitic. These intrusions cut through the Obatogamau Formation rocks. As for the Deux Granites Stock, an unconformity characterizes the contact with the sedimentary rocks of the Chebistuan Formation. The Eau Noire Stock (nAaen) syenite cuts the rocks of the Bruneau and Chebistuan formations as well as an ultramafic intrusion (I4Ma). It is cut by a dioritic intrusion (I2Ja) and the Poudingue Dyke. The Guettard Stock (nAgue) granodiorite cuts the rocks of the Opémisca Group. It is cut by the Paleoproterozoic Abitibi and Poudingue dykes.

Syenite and Carbonatite

The Dolodau Stock consists of an outer zone of granodiorite and monzodiorite (Adol1) successively cut by felsic dykes, muscovite syenite, carbonatite, and an inner zone of quartz syenite (nAdol2). The stock is hosted by volcaniclastic rocks in the upper part of the Chrissie Formation (nAcs2). The Fardoche Stock (nAfar), which cuts the rocks of the Obatogamau Formation and Lapparent Intrusive Suite, and the Jean-Luc Stock (nAjlu), which injects the rocks of the Obatogamau Formation, have a similar syenitic composition. The Saussure Stock (nAsau) syenite injects the sedimentary rocks of the Daubrée Formation. North of Dussault Bay, the Mildred Stock (nAmdr) cuts the eastern edge of the Berey Massif granodiorite at the contact with amphibolitized basalt from the Obatogamau Formation. West of the Eau Noire Lake, the Moraine Stock (nAmor) consists of porphyroid syenite. It cuts through the rocks of the Obatogamau and Bruneau formations and the associated gabbroic sills (I3Ac).

Paleoproterozoic Units

The Chibougamau Formation (pPcb) is not a mappable unit in the study area and corresponds to a series of five outcrops aligned along a NW-SE axis, from the area NE of Anville Lake to the east of Pacific Lake (Chown and Gobeil, 1990). The unit is characterized by sandstone filling in NE to NNE trending fractures.

It is proposed that the Janus, Anville and Anne-Marie dykes (Charbonneau et al., 1991) be attributed to the Senneterre Dykes (pPsen) due to their similar orientation and geochemical composition.

The En Boucle Dyke (pPbou), trending 25°, is interpreted from a strong positive magnetic anomaly (Charbonneau et al., 1991).

It is also proposed that the Poing and Geneviève dykes (Charbonneau et al., 1991) be attributed to the Abitibi Dykes (pPab) because of their similar orientation and petrographic and geochemical characteristics.

The Poudingue Dykes (pPpou) consist of NNW-SSE trending layers of medium-grained gabbro cutting the Abitibi Dykes.

Structural Geology

Neoarchean deformation of rocks in the Deux Orignaux Lake area comprises two ductile events (D₁ and D₂) and one brittle event (D₄). The dextral NE-SW shear zones that characterize deformation event D₃ in the Chibougamau area (Leclerc et al., 2017) have not been observed in the study area.

Primary Structures (S₀)

The primary structures (S₀) that establish the polarity of stratigraphic and lithodemic units are generally well preserved outside of flattening and shear zones. The morphology of the pillows, the abundance of vesicles and amygdules atop the pillows, and the presence of quartz chambers (Dimroth et al., 1978) are used as polarity criteria in basalt flows. Reworked volcaniclastic rocks (epiclastites) and sedimentary rocks are characterized by sorting, synvolcanic and synsedimentary faults, oblique and cross-bedded laminations, channels, water escape structures and sandstone dykes. The mafic to ultramafic rocks of the Lac de la Chaleur Intrusive Suite and the differentiated sills reveal magmatic bedding. Some areas are characterized by outcrops where primary structures suggest divergent polarities. These opposing polarities are the result of folding of the rocks during regional deformation, which is illustrated on the map by the axial traces of anticlinal and synclinal folds.

D₁ Deformation Event

In the study area, this deformation is characterized by S₁ schistosity visible in the P_2a fold hinge zones (photo of outcrop 12-YD-2541), but completely transposed on the flanks of these same folds. However, this schistosity is not associated with P₁ regional folds, unlike the Chapais and Chibougamau areas (Daigneault et al., 1990; Leclerc and Houle, 2013).

D₂ Deformation Event

The main deformation is called D_2a and is defined by an axial plane S_2a schistosity of P_2a folds. The S_2a schistosity corresponds to the plane of the main anisotropy, which is characterized by the alignment of metamorphic minerals at the greenschist and amphibolite facies, as well as by the flattening and stretching of anisotropic elements such as basalt pillows, lapilli and blocks of volcaniclastic rocks, and clasts of conglomerate. The S_2a schistosity generally trends E-W and bifurcates along a NE-SW orientation near the Lamarck Shear Zone. The dip is steep to subvertical, with a stretching lineation that has a moderate to subvertical plunge.

The main P_2a regional folds with an E-W axial trace found SE of the Lamarck Shear Zone are the Chibougamau Anticline and the Chapais Syncline. These structures have also been recognized in Chapais (Morin, 1994; Leclerc et al., 2011; Leclerc and Houle, 2013) and Chibougamau (Daigneault and Allard, 1990; Leclerc et al., 2017). The Chibougamau Anticline follows the apical ridge of the Opémisca Pluton (eastern part of sheet 32G14-200-0202) and a structural dome exposing the volcaniclastic rocks of the Waconichi Formation NE of Deux Orignaux Lake (Charbonneau et al., 1991). The axial trace of the Chapais Syncline follows the centre of the basin where the volcanic and sedimentary rocks of the Opémisca Group were deposited, and also corresponds to the trace of the E-W trending Kapunapotagen Shear Zone (Daigneault et al., 1990; Morin, 1994). In the SE part of sheet 32G14, this structure with reverse movement from south to north obliterates the southern part of the basin, directly juxtaposing rocks from the Roy Group, which have a northern polarity, with those of the Opémisca Group, which have a southern polarity. West of Kapunapotagen Lake, the extension of the Chapais Syncline along the Kapunapotagen Shear Zone contrasts the north-polarity rocks of the Blondeau Formation (Abl1) (south of the shear zone) with the south-polarity rocks of the Scorpion Formation (Asc) found north of the shear zone. The Chapais Syncline in this area also explains the repetition of Blondeau Formation (Abl1) rocks on either side of the Kapunapotagen Shear Zone displaying opposing polarities.

North of the Lamarck Shear Zone, P_2a folds are isoclinal with steeply plunging axes colinear with the stretching lineation (Daigneault and Allard, 1990). They have a NE-SW orientation that is parallel to the contact between lithological units and shear zones. Rocks of the Christian and Gribouille members (Haüy Formation), south of the Dussault Shear Zone, occupy the centre of a synclinal structure that causes the repetition of the Daubrée Formation rocks on either flanks of the fold. The Dussault Shear Zone does not appear to alter the interpreted geometry of this syncline.

North of the Lamarck Shear Zone, the Opémisca Group sedimentary rocks form a synclinal basin whose centre corresponds to the thin unit of mafic volcanic rocks with a trachytic structure in the Christian Member (nAcn). The extension of the Chebistuan Formation (nAch1) to the NE of the Eau Noire Stock (nAst) can also be explained by the folding of sedimentary rocks (photo of outcrop 13-YD-2969) synchronously with the intrusion of the Moraine Stock (nAmor) and Eau Noire Stock (nAaen), as well as the movement along the Lac à l’Eau Noire and Dussault shear zones. The volcanic rocks of the Pichamobi Member, north of La Trêve Lake, form a homoclinal sequence with SE polarity. The northern part of the unit consists of beds of intermediate to felsic volcaniclastic rocks, graphitic mudrock and locally garnet-bearing chert containing a disseminated, lenticular or massive pyrite and/or pyrrhotite mineralization (Honeyman, 1958; Gajaria, 1976). The graphitic layer and the sulphide mineralization produce a positive magnetic anomaly, making it possible to interpret the outline of the unit, the shape of which suggests the presence of a regional P_2a fold.

Synchronous E-W and NW-SE Structural Discontinuities (F_2a)

The Lac des Misérables, Kapunapotagen and Dussault shear zones are the main E-W discontinuities with reverse-dextral movement and a dip to the south or north. They are synchronous with the NW-SE trending brittle-ductile faults, with which they share several features. There is no clear crosscutting relationship between these two orientations of structural discontinuities which form an anastomosed network (Daigneault et al., 1990). On a regional scale, NW-SE structures form dextral shear bands between which the rocks undergo a rotation (i.e., folding) counter-clockwise to the direction of the main dextral movement. Some portions of the E-W structural discontinuities are characterized by the absence of asymmetrical fabrics. The development of kink bands (photo of outcrop 12-FL-9605) in these highly anisotropic zones suggests the predominance of the flattening mechanism. The increase in deformation intensity generally manifests itself within a ~200 m thick corridor. The mafic rocks are transformed into schist containing chlorite ± sericite and ankerite, while the felsic rocks are transformed into schist containing sericite ± chlorite ± ankerite.

NE Sinistral Lamarck Shear Zone (F_2b)

The Lamarck Shear Zone outcrops mainly to the NW of Deux Orignaux Lake, on the shores of Cheeman Bay (eastern part of sheet 32G14-200-0201). It separates the turbidite layers of the Daubrée Formation from the volcaniclastic rocks of the Deux Orignaux Member (Waconichi Formation). The shear zone is contained within a kilometre-wide deformation corridor, where the E-W trending S_2a schistosity is crenulated by a NE-SW trending S_2b schistosity (photo of outcrop 13-FL-9791). In the centre of the corridor, the NE trending shear zone dips to the SE and has an essentially sinistral movement as well as a minor normal component (photo of outcrop 13-FL-9795).

D₄ Deformation Event

The NNE-SSW reverse-sinistral faults are mostly associated with the main E-W deformation corridors and could, in this case, constitute conjugate structures developed more or less synchronously with the NW-SE shear bands. However, several of these structures cut the Lamarck Shear Zone and have therefore developed later. These faults are generally characterized by a <250 m sinistral rejection and a <10 m area of influence, reflecting generally brittle deformation.

A number of NNE-SSW reverse-dextral faults have been identified in the Maryse Lake area, where they cut the Ventures and Bourbeau sills. The Au-Ag-Cu vein mineralization in the Alouette mineralized zone is associated with one of these faults. West of the Opémisca Pluton, a number of NNE-SSW to N-S trending faults follow the curved edge of the intrusion, causing the dextral offset of basalt and gabbro layers from the Bruneau Formation. The shear zone west of the Dolodau Stock (photo of outcrop 12-YD-2612), which hosts the Simard (Dolodau) mineralized zone (Au-Ag-W), is also part of this group.

Metamorphism

The volcanic rocks of the Abitibi Subprovince, which cover most of the study area, are characterized by mineral assemblages indicative of a greenschist facies regional metamorphism. Mafic volcanic rocks have a chlorite ± carbonate ± actinote ± albite ± epidote assemblage, while felsic volcanic rocks have a sericite ± chlorite ± carbonate ± albite ± quartz assemblage. Amphibolite facies contact metamorphism locally characterizes the edge of synkinematic to post-kinematic plutons. Mafic volcanic rocks at the edge of the Houghton and Opémisca plutons have hornblende ± garnet ± albite ± quartz mineral assemblages, while sedimentary rocks at the edge of the Eau Noire Stock contain millimetric porphyroblasts of andalusite in a plagioclase and chlorite matrix (MacIntosh, 1966; Charbonneau et al., 1991; Bédard, 1992). The northern part of the study area, located at the boundary between the Abitibi and Opatica subprovinces, shows a gradual transition over ~10 km between greenschist and amphibolite facies assemblages (MacIntosh, 1966; Daoudene et al., 2016). The increase in metamorphism intensity is first manifested by the appearance of biotite in the mineral assemblage of mafic volcanic rocks, to the detriment of chlorite. The boundary between the two subprovinces is represented by the HB+GR isograd indicating the appearance of amphibole and garnet in the volcanic rocks of the Obatogamau Formation (hornblende ± garnet ± plagioclase ± biotite ± quartz mineral assemblage).

Economic Geology

The Deux Orignaux Lake area comprises six types of mineralization:

• orogenic gold veins;
• disseminated and replacement gold mineralization;
• copper-bearing veins;
• rare metal mineralization associated with peralkaline rocks;
• magmatic or hydrothermal Ni-Cu-PGE mineralization;
• Ni-Cu mineralization associated with anorthosite and troctolite;
• exhalative sulphide mineralization.

The table of mineralized zones below presents analytical results for the 51 known mineralized zones in the area.

Mineralized Zones in the Deux Orignaux Lake Area

Known

Name	Contents
Mesothermal Gold Vein in Quartz-Carbonate Gangue
Anville-Bouchard	2100 ppb Au (T); 11,000 ppm Cu (T); 9.1 ppm Ag (T)
Gladstone	10,900 ppb Au (G)
Golden Moose Gold	1460 ppb Au over 1 m (R)
Grizzly	5180 ppb Au over 0.9 m (R); 5180 ppb Au over 0.9 m (R)
Guettard-Nord	34,170 ppb Au (G); 21.6 ppm Ag over 1.8 m (R)
Lac Grey Goose-NE	1800 ppb Au (G)
Queenimich	2690 ppb Au (G)
Rivière Chibougamau	4900 ppb Au (G); 11,900 ppm As (G)
Simard (Dolodau)	8300 ppb Au over 1.5 m (R); 44 ppm Ag over 1.5 m (R); 75,500 ppm W (G)
Gold Mineralization, Disseminated and Replacement
Dome Pluton	2400 ppb Au (G)
Copper Vein
Alouette	8490 ppb Au (G); 148,000 ppm Cu (G); 10.89 ppm Ag (G)
Baie de l’Ouest	22,500 ppm Cu over 0.6 m (D); 1700 ppm Ni over 2.1 m (D)
Collines Pachydermes-Est	6600 ppm Cu (G)
Dionne	29,000 ppm Cu over 0.6 m (D)
Lac Chaleur-Sud	16,000 ppm Cu over 0.6 m (D)
Lac Michwacho-Nord	21,700 ppm Cu (G); 200 ppb PGE (G); 200 ppb Pd (G)
Lac des Misérables	14,200 ppm Cu over 0.2 m (D)
Patino-Sud	11,000 ppm Cu over 0.6 m (D)
Pennbec	10,000 ppm Cu (G)
Pennbec-2	21,000 ppm Cu (G); 21,000 ppm Cu (G)
Q-4	7500 ppm Cu over 0.6 m (D)
Rare Metal Mineralization Associated With Peralkaline Rocks
Oriana	9915 ppm REE over 1.5 m (D); 23 ppm Ag over 1.5 m (D); 1090 ppm Nb over 1.5 m (D); 4410 ppm Ce over 1.5 m (D); 1920 ppm Nd over 1.5 m (D); 2700 ppm La over 1.5 m (D)
Magmatic and Hydrothermal Ni-Cu-PGE Mineralization
Baie Dussault	9600 ppm Ni (G); 23,100 ppm Cu (G); 600 ppm Co (G)
La Trève 2 – Flint Rock	1015 ppb PGE (G); 2518 ppm Ni (G); 5691 ppm Cu (G); 171 ppb Au (G); 1960 ppm Cr (G); 659 ppb Pd (G); 356 ppb Pt (G)
Lac Keller-Nord	5000 ppm Cu over 4 m (D); 8000 ppm Ni over 4 m (D)
Rivière Obatogamau-Rapides	13,000 ppm Cu over 2.2 m (D); 1400 ppm Ni over 2.2 m (D)
Ruisseau Daladier	4500 ppm Ni (G); 3300 ppm Cu (G); 1300 ppm Co (G)
Ruisseau Daladier-Nord	7500 ppm Ni over 3 m (D); 9000 ppm Cu over 3 m (D)
Ruisseau Voyageur-Nord	18,300 ppm Cu over 1.5 m (D)
Ni-Cu Dominant (±Co ±PGE) Magmatic Mineralization Associated With Anorthositic-Troctolitic Massifs
Eddy	5230 ppb Au (G); 2055 ppm Cu (G)
Pennbec-Sud	110,000 ppm Cu (G); 16,700 ppb Au (G)
Rivière Chibougamau-Nord	55,300 ppm Cu (G); 620 ppb Au (G); 8.9 ppm Ag (G)
Ryan	14,300 ppm Cu (G); 947 ppb Au (G)
PGE dominant (±Cr ±Au ±Ni ±Cu) Magmatic Mineralization
La Trève 1	16,398 ppb PGE (G); 18,042 ppm Ni (G); 18,800 ppm Cu (G); 1634 ppm Co (G); 347 ppb Au (G); 0.7 ppm Ag (G); 11,531 ppb Pd (G); 4867 ppb Pt (G); 152.71 ppb Rh (G)
Exhalative Sulphides Mineralization
7607-78-4	8000 ppm Zn over 1.1 m (D); 1500 ppm Cu over 1.1 m (D)
Baie Wabanock	28.12 ppm Ag (D); 12,000 ppm Pb (D); 8000 ppm Cu (G); 1782 ppb Au (G)
Branche Pichamobi	5000 ppm Cu (G)
Collines Pachidermes	8800 ppm Cu over 1.8 m (D)
Daubrée-Bouchard	32,000 ppm Zn (G); 8349 ppm Cu (G); 9.4 ppm Ag (G)
Dolomieu	22,500 ppm Cu (G); 1198 ppm Zn (G)
Est de Île Tepeka	10,146 ppm Cu over 0.3 m (R); 2.7 ppm Ag over 0.3 m (R)
Lac Coeur-Pendant	10,000 ppm Zn over 0.6 m (D); 310 ppb Au (D); 4000 ppm Cu (D); 7 ppm Ag over 0.6 m (D)
Lac Dolomieu-Sud	5.14 ppm Ag over 1 m (D); 2400 ppm Zn over 1 m (D)
Lac Grey Goose-Nord	24.7 ppm Ag (G); 6100 ppm Cu (G)
Lac Porphyre-SW	18 ppm Ag over 1.3 m (D); 1500 ppm Zn over 1.8 m (D)
Lac Porphyre-Sud	6.52 ppm Ag over 23.5 m (D)
Lac des Trois-Iles	7900 ppm Zn over 1.6 m (D)
Lamarck-SE	18,000 ppm Zn over 0.6 m (D)
Patino-Nord	9000 ppm Zn over 1.1 m (D); 1030 ppb Au over 1 m (D); 1500 ppm Cu over 1.1 m (D)
Propriété V.Roy	12.3 ppm Ag (G); 10,200 ppm Cu (G); 200 ppm Co (G); 1000 ppb Au (G)
Undetermined Type of Mineralization
Lac Grenier-NE	6.85 ppm Ag over 0.2 m (D)
Non-Metallic Substances
Sondage OS-4	Content: drill hole OS-4 intersected in weakly magnetic carbonatites, 5.95% P2O5 (13.6% apatite) over 1.45 m and 4% P2O5 (9.2% apatite) over 1.0 m (drilling OS-4, GM-50758). These P2O5 contents are related to irregular dissemination of apatite in the weakly magnetic carbonatite dykes.

(D) Diamond drilling, (T) Trench, (G) Selected sample, (R) Groove – chip sample

The table of lithogeochemical analyses of metals of economic interest provides the location, description and analytical results for 109 selected samples in order to assess the economic potential of the area.
The mapping and compilation work carried out by the Ministère between 2012 and 2013 identified five prospective zones for mineral exploration.

Gold-Bearing Deformation Corridors and Associated Fertile Syenites, NW of Chapais

Most gold-bearing quartz-carbonate veins in the Deux Orignaux Lake area are spatially associated with the E-W trending regional shear zones that characterize the Keller Lake area (Keller prospective zone) and the NW of Dussault Bay (Dussault prospective zone). The structural interpretation map shows folded magnetic anomalies corresponding to contacts (S₀) between pillow and brecciated basalts and the gabbroic and felsic intrusive rocks. Parallel rectilinear magnetic anomalies are evidence of the transposition of these contacts into gold-bearing shear zones (F_2a). A disseminated pyrite ± pyrrhotite ± chalcopyrite mineralization characterizes the interstitial breccia matrix of pillow basalts. It is also present in brecciated basalt units several metres thick that are in contact with gabbroic and felsic intrusions. Brecciated basalts and gabbros are typically affected by intense diffuse ankerite alteration, which gives them an ochre-orange colour. The quartz-tourmaline-pyrite ± arsenopyrite ± fuchsite and native gold veins (1.02 g/t Au to 34.17 g/t Au; Hashimoto, 1980; Boucher, 2013; see also table of mineralized zones) have a banded texture. They are oriented NE-SW to NNE-SSW and folded by the S_2a regional schistosity. The boundaries of the Dussault prospective zone follow the generally sheared contacts between the differentiated sills and volcanic rocks of the Bruneau Formation. The Keller prospective zone corresponds to a series of shear zones observed on outcrops at the contact between gabbroic sills, felsic intrusive rocks containing QZ-PG phenocrysts and mafic volcanic rocks.

Gold-Bearing Veins in Sills of Ankeritized Quartz Diorite, West of Chapais

The Sunset prospective zone is characterized by gold-bearing QZ-CB veins appearing atop a differentiated sill cutting the volcanic rocks of the Bruneau and Blondeau formations. At the Golden Moose Gold mineralized zone (up to 1460 ppm Au over 1 m in groove sampling; Leblanc, 2013), quartz diorite is commonly ankeritized and includes a disseminated pyrite and specular hematite mineralization with lesser proportions of chalcopyrite (Allard, 2011; Leblanc, 2013). The contacts are brecciated between the diorite, the underlying gabbro and the host rock, which is a coarse to fine mafic lapilli tuff. The millimetric to centimetric gold-bearing QZ-CB veins are composed of quartz-tourmaline-pyrite ± hematite ± chalcopyrite and locally define anastomosing arrays having a general E-W orientation, parallel to the axial planes of regional P_2a folds. The location of the veins in the upper differentiated part of the comagmatic sills as well as the ankerite alteration observed are reminiscent of the veins in the Cooke and Norbeau mines, located in the upper differentiated part of the Bourbeau Sill (Dubé and Guha, 1987).

Ni-Cu-PGE Mineralization on the Edge of the Berey Massif, NW of Chapais

The Berey-Bordure prospective zone refers to an area at the edge of the Mildred Stock and the Berey Massif where mafic to ultramafic intrusions are abundant. The role of tonalite and syenite intrusions has yet to be assessed, but the crosscutting and brecciation of mafic to ultramafic intrusions by felsic intrusions appear to be decisive in the development of Ni-Cu-PGE mineralization. The La Trêve 1 mineralized zone (western part of sheet 32J03-200-0101) is hosted in a gabbro dyke, oriented 320° and having a moderate to steep dip, which cuts the Obatogamau Formation pillow basalts. The Mildred Stock alkali feldspar syenite also appears as dykes that cut the gabbro and basalts, locally forming a breccia (photo of outcrop 13-YD-2780-2). Stripping reveals a mesocratic to melanocratic gabbro containing a semi-massive mineralization, locally in an anastomosing array, composed mostly of pyrrhotite and incidentally containing up to 7% chalcopyrite and 4% pentlandite (Barrie, 2001). The best values collected from three selected samples in the stripped zone are: 347 ppb Au, 3554 ppb Pt, 9304 ppb Pd, 12,945 ppb PGE, 13,060 ppm Cu, 693 ppm Co and 7518 ppm Ni (Beauregard and Gaudreault, 2000). A similar context is described for the La Trêve 4 mineralized zone, located in the western part of sheet 32G13, south of the Berey Massif (1.17 g/t Pt+Pd+Au and 0.63% Cu+Ni+Co over 6.95 m in groove samples; Banas, 2003).

New Prospective Zone for Volcanogenic Massive Sulphides (VMS) Mineralization on the Eastern Edge of the Mildred Stock, NW of Chapais

The potential for VMS-type mineralization in the Deux Orignaux Lake area lies in the exploration for chert-pyrite ± pyrrhotite ± chalcopyrite exhalites. These exhalites, which characterize a hiatus in volcanism (Thurston et al., 2008), have been recognized at the top of all volcanic cycles and are targets of interest for VMS exploration. The Mildred-Est prospective zone, located on the eastern edge of the Mildred Stock (west of sheet 32J03-200-0101), corresponds to the pillow and brecciated basalts of the Obatogamau Formation, characterized by silicification and disseminated pyrite-pyrrhotite-magnetite mineralization. These volcanic rocks are cut by a large network of gabbroic sills and felsic intrusions containing quartz phenocrysts and/or plagioclase. Chlorite, epidote and silica alteration are spatially associated with these intrusions, suggesting that these lithological heterogeneities are located in brittle portions of the crust that allow the circulation of hydrothermal fluids. In addition, the Mildred-Est prospective zone is centred on two intrusions (the Envoûtant and Lantagnac stocks), which may have acted as a heat source to activate the circulation of fluids. Analyses carried out on samples 13-YD-2801-A2 and 13-YD-2802-B1 did not yield any anomalous or showing values, but the combination of the various elements mentioned above (mineralization, alteration, lithological heterogeneity, heat source) suggest a high degree of prospectivity for VMS-type mineralization.

Contributors

Contributors

Authors	François Leclerc, P. Geo., Ph.D. francois.leclerc@mrnf.gouv.qc.ca Yannick Daoudene, GIT, Ph.D. yannick.daoudene@mrnf.gouv.qc.ca
Geochemistry	Fabien Solgadi, P. Geo., Ph.D.
Geophysics	Siham Benahmed, GIT, M.Sc. Rachid Intissar, P. Geo., M.Sc.
Potential assessment	Hanafi Hammouche, P. Geo., M.Sc.
Logistics	Marie-France Beaulieu, GIT, B.Sc.
Geomatics	Julie Sauvageau Kathleen O’Brien
Template and content compliance	François Leclerc, P. Geo., Ph.D.
Coaching/mentoring and critical review	James Moorhead, P. Geo., M.Sc.
Coordination	Marie-Andrée Vézina, P. Geo.
Organism	General Direction of Géologie Québec, Ministère de l’Énergie et des Ressources naturelles, Government of Québec

Acknowledgements:

This Geological Bulletin was made possible through the cooperation of many people who actively took part in the various stages of the project. We would like to thank geologist Christine Vézina, as well as students Anne-Sophie Corriveau, Sébastien Dallaire, Pierrick Lamontagne-Hallé and Alix Moïse. We would also like to thank prospectors Marc Bouchard, Gilbert Lamothe and André Leclerc, who took the time to show us their discoveries in the Chapais area. We’re also grateful to our host in Chapais, Gaston Gobeil, who helped us out in so many ways.

References

Publications of the Government of Québec

Autres publications