|Type area:||Aiguebelle area (NTS sheet 32D07)|
|Geological province:||Superior Province|
|Geological subdivision:||Abitibi Subprovince|
|Lithology:||Volcanic rocks of komatiitic, mafic and felsic composition (komatiite, basalt, dacite, rhyolite)|
Table des matières
Units of this formation were originally located in NTS sheets 32D07 and 32D06, specifically in the Aiguebelle and Destor townships. They are successively described by Larouche (1974), Hocq (1979), Sanschagrin and Leduc (1979) and Dimroth et al. (1982) as the Destor Volcanic Complex. At the same time, Boivin (1974) interpreted the west extension of these units (sheet 32D06, west of Road 101, Destor and Duparquet townships) and assigned them to the Lac Lanaudière Formation. Goutier and Lacroix (1992) use the name Lanaudière Complex to refer to this unit because of the abundance of intrusions into its western part and the high intensity of regional deformation. To remain consistent with mapping work of Goutier and Lacroix (1992), Goutier (1997) and Pilote et al. (2009), the names « Héva-Nord » and « Dubuisson Supérieur » proposed by Imreh (1984) are abandoned and combined in favour of the name « Lanaudière Formation » on maps 32D08- 200-0202 and 32C05-200-0201.
The base of the Lanaudière Formation was arbitrarily set for the appearance of the first rhyolitic volcanics (Goutier and Lacroix, 1992). The Deguisier Formation, located at the base, and the Lanaudière Formation, located at the top, make the Kinojévis Group (Goutier, 1997). This group is located on the north side of the Porcupine-Destor Fault Zone.
The Lanaudière Formation consists of ultramafic lava, mafic and felsic volcanics (Sanschagrin and Leduc, 1979; Goutier 1997), as well as numerous tonalitic to monzonitic intrusions. Volcanic units are E-W oriented and have moderate to shallow dip to the north. Their polarity systematically faces south. Two of the rhyolitic complexes of this formation, which define tholeitic suites, delivered zircon U-Pb ages of 2718.7 ±0.7 Ma and 2716.2 ±0.8 Ma (McNicoll, in Pilote et al., 2009). These ages, as well as the close spatial association observed between ultramafic lava and rhyolitic complexes of this formation, have significant similarities with the Kidd-Munro assemblage (Bleeker et al., 1999; Berger, 2002; Ayer et al., 2002). The Lanaudière Formation is bounded to the north by the Aiguebelle Fault and to the south by the Manneville Nord Fault, which has shallow to moderate dip to the north (Mueller et al., 1996; Daigneault et al., 2002; Pilote et al., 2009). Goutier (1997) proposed that the Deguisier and Lanaudière formations were initially contiguous and subsequently separated by faults.
Basalts are predominant in the Lanaudière Formation. They are interbedded with felsic and ultramafic rocks. This formation also contains felsic pyroclastics and rhyolitic flows. Rhyolites form strips 10 to 150 m thick. Facies of rhyolites are wide ranging. Rocks are aphanitic, quartz, feldspath or both porphyritic, or spherulitic. The most commonly encountered facies are lobes and breccias, which have fluid flow structures. These structures are indicative of submarine flows fed by small felsic centres. Isotopic dating on a rhyolite sample taken in sheet 32D06 yielded an age of 2718 ±2 Ma (Zhang et al., 1993).
Ultramafic lava flows, magnesian basalts and komatiites with breccia, cumulate and spinifex facies, outcrop throughout this formation. These ultramafic and mafic units, in normal contact with other lithologies, are commonly located in the upper half of this formation. In addition, peridotite intrusions and pyroxenite are in several locations adjacent to and likely genetically associated with ultramafic lava.
Regional metamorphism is mainly to the greenschist facies. However, in the Barraute-La Corne area (sheet 32C05-NW), the degree of metamorphism reach the amphibolite facies in the south half of this sheet (outcrops 17-PP-80 and 17-PP-81). The typical mineralogical assemblage of massive and pillow mafic volcanics is thus albite-actinolite or pale green hornblende-chlorite-epidote-quartz-carbonate. Ultramafic units are tremolitized and serpentinized, i.e. converted to talc and chlorite schists. The mineralogical assemblage of serpentinized ultramaphics consists, more precisely, of serpentine-magnetite-chlorite ± talc ± carbonate ± quartz (Jones, 1964; Brett et al., 1976; Imreh, 1984, 1991; Daigneault et al., 2002, 2004).
The following units were mapped in the area west of Barraute by Pilot in 2017: nAln1, nAln2, nAln3, nAln5 and nAln13. The remaining units have been compiled from SIGEOM mapping (MNRF, 2010) or other older documents and will be subject to revision in future mapping work.
This unit was observed only at the west end of sheet 32C05-NW. The presence of this unit was determined primarily from drilling observations in sheets 32D08 (Love, 1963a) and 32C05 (Love, 1963b), and some compilation outcrops (Sharpe, 1961). It consists of massive rhyolitic and dacitic flows, accompanied by poorly sorted coarse-grained volcaniclastic sequences. The deformation level is generally high, with well-developed regional schistosity.
This unit consists of basaltic flows with massive, pillowed and brecciated morphofacies. Flow thickness varies on average from less than 10 to rarely more than 20 . Schistosity is generally well developed. These lithologies are metamorphosed to the amphibolite facies in sheet 32C05, immediately north of the La Corne Batholith. These lithologies are E-W oriented with inclined dips of 30 to 45° northward. These sequences are overturned, with polarities to the south.
This unit contains komatic flows, ultramafic sills and some horizons of basalt and mafic volcaniclastics. The deformation level varies from moderate to severe. Ultramafic lithologies are usually replaced by the talc-chlorite-serpentine assemblage. True komatiitic flows with spinifex are uncommon. Dunitic or peridotitic sills dominate in the central and eastern portions of sheet 32C05-NW. These lithologies are E-W oriented with inclined dips of 30 to 45° northward. These sequences are overturned, with polarities facing south.
The andesite unit is located on the edge of sheets 32D06 and 32D11, in the eastern portion of these sheets. It has a vesicular, pillowed and massive appearance. Unlike Lanaudière basalt, andesite is distinguished by a significant amount of plagioclase and absence of actinolite. On the other hand, this unit has carbonation of the same intensity as basalts bordering it to the north (Goutier and Lacroix, 1992).
This unit is similar to unit nAla2, except that magnesian basalts replace komatiitic flows. The deformation level varies from moderate to severe. These lithologies are E-W oriented with inclined dips of 30 to 45° northward. These sequences are overturned, with polarities to the south.
This unit consists of a basaltic flow with thin magnetite beds and medium-grained ferromagnesian gabbroic sills (Beauregard and Gaudreault, 2014). It is located in the southern portion of the Lanaudière Formation, between Pascalis and Laverdière lakes.
This unit consists mainly of block and lapilli tuffs of intermediate to felsic composition located south of Tiblemont Lake (sheet 32C03; Pilote et al., 2016). These lithologies are likely the result of erosion or destruction of volcanic edifices that compose unit nAln9, which is spatially closely associated with it.
This unit, consisting of ferrugineous sedimentary rocks and thin iron formation horizons, is interbedded into mafic volcanics (Pilote et al., 2016). It is located in the southeast corner of sheet 32C05 and has deformation similar to that of units nAln1 and nAln3.
These lithologies are located south of Tiblemont Lake. They are composed mainly of pyroclastic rocks and felsic to intermediate flows (Bubar et al., 1988; Pilote et al., 2016). Hosted in rhyolitic flows about 60 metres thick, pyroclastic rock is massive and composed of ash and lapilli green tuffs. The felsic part contains quartz phenocrystals, while the intermediate part contains up to 5% lepidoblastic biotite porphyroblasts (Ali and Plante, 2012).
This unit consists of four sedimentary strips of up to 45 thick. These well-bedded strips may contain aprroximately 1% pyrite (Ali and Plante, 2012). Descriptions from diamond drilling report the presence of thin graphitic claystone, graphitic tuff and black claystone bands interbedded with pyroclastic volcanic sequences and mafic flows (Bubar et al., 1988).
This thin unit is easily recognizable on aeromagnetic surveys (Geological Survey of Canada, Mines d’Or Virginia Inc., Noranda Exploration, 2008) because of its high magnetic susceptibility. It is interbedded in unit nAln2 in the centre of sheet 32C03.
Drilling has identified this unit which appears to be intebedded with unit nAln1 dacite and chert beds. Tuff is light grey to light green and contains disseminated pyrite and pyrrhotite (Goyette and Ingham, 1953).
Lithologies of this unit are generally spatially associated with ultramafic flows or sills. They are observed mainly in drilling, rarely in outcrop. Beds, homogeneous and well-stratified, are 20 to 40 cm thick.
The Lanaudière Formation is a package of overall E-W-oriented volcanic and intrusive lithologies with stratigraphic thicknesses ranging from 1 to nearly 5 km and affected by the Abijévis Synclinal (Dimroth et al., 1973; Hocq, 1979; Sanschagrin and Leduc, 1979; Leduc, 1981; Sanschagrin, 1981; Goutier, 1997). Various volcanic units belonging to this formation are found from west to east in sheets 32D06, 32D07, 32D08, 32C05 and 32C04, north of the Porcupine-Destor–Manneville Nord Fault Zone and Caste Formation sedimentary units.
The Lanaudière Formation is bounded by the Aiguebelle and Manneville Nord faults, which shallow dip to the north (Mueller et al., 1996; Daigneault et al., 2002). These faults are possible subsidiary to the Destor-Porcupine system identified further west (Goutier, 1997; Legault et al., 2005).
Two of the rhyolitic complexes of this formation, which define tholeiitic suites, have recently been dated and gave zircon U-Pb ages of 2718.7 ±0.7 Ma and 2716.2 ±0.8 Ma (McNicoll, in Pilote et al., 2009). These ages indicate that the Lanaudière Formation was emplaced in a relatively short period of time of approximately 2 Ma.
This formation is the summit of the Kinojévis Group. The Lanaudière and Deguisier formations are in fault contact (Aiguebelle Fault) throughout sheets 32C05 to 32D11, a distance of more than 70 km. To the east of the intersection of the Abijévis Synclinal axial plane with the Aiguebelle Fault, volcanics of these two formations show opposite polarities.
The ages obtained for the Lanaudière Formation, as well as the close spatial association observed between ultramafic lava and rhyolitic complexes, show significant similarities with the Kidd-Munro assemblage described on the Ontario side of the Abitibi Subprovince (Berger, 2002; Ayer et al., 2002; Thurston et al., 2008), host of the Kidd Creek volcanogenic massive sulphide mine (Bleeker et al., 1999).
Does not apply.