|Type area:||Various volcanic units belonging to this formation are located in NTS sheets 32D08 and 32C05. However, the most representative outcrops are located on forest roads of sheet 32C05.|
|Geological province:||Superior Province|
|Geological subdivision:||Abitibi Subprovince|
|Lithology:||Volcanic and volcano-sedimentary rocks|
Table des matières
Sharpe (1961) was one of the first to describe these volcanic lithologies during regional mapping, but did not assign them to any particular formation. Imreh (1984) had grouped these and other lithologies under the name “Harricana Group”. This group, which at the time included the Landrienne, Lower Figuery and Higher Figuery formations, was the lithostratigraphic roof of the Héva-Nord Formation (now the Lanaudière Formation). Labbé (1998) reused the name “Landrienne Formation” but gave it a smaller area.
The Landrienne Formation is characterized by the preponderance of chloritic basalts, occasionally with magnetite, arranged in massive, pillowed and brecciated flows, as well as large and voluminous dacitic to rhyolitic flows of tholeiitic affinity. East of the Harricana River, massive and pillow basaltic horizons predominate, accompanied by brecciated flows. Gabbroic sills are common. The following units were mapped in the area west of Barraute by Pilote (2017): nAla1, nAla2, nAla5, nAla7, nAla10, nAla11, nAla12, nAla13, nAla14 and nAla15. The remaining units are described based on the work of Sharpe (1961) and McDougall (1965), as well as mapping compilations of the Ministère (MNRF, 2010).
It is the most commonly encountered unit in the area west of Barraute. Flows have an E-W orientation, a dip varying from 35 to 50° north and reverse polarities. The amphibolite metamorphic facies is reached on the northern contact with the La Corne Batholith, along an N-S axis more than one kilometre long.
This unit consists of thin volcanic and volcaniclastic mafic horizons having strong magnetic susceptibility. They are widespread over the entire area of the Landrienne Formation and define several large folds interpreted from their folded trajectory, visible on aeromagnetic surveys (Geological Survey of Canada et al., 2008).
This unit consists of thin flows of light-grey to white trachyte generally porphyritic and pillowed (McDougall, 1965). It is located in the north-central portion of sheet 32C05 and extends intermittently for approximately 3 km in a direction varying from ENE-WSW to NE-SW.
This unit consists of greenish, porphyritic, massive and pillowed andesitic flows (McDougall, 1965). These flows are generally heavily deformed and sheared. In the southern part of the unit, especially near granite intrusions, volcanics were silicified and carbonatized, while in the NW part they were amphibolitized. This unit consists of the Landrienne Formation dominant lithologies in sheet 32C05-200-0202 (northeast corner) and probably represents the ESE extension of the basalt unit (nAla1) recently mapped by Pilote (2017). Future mapping will clarify this transition or apparent variation in volcanic rock composition between different sheets.
This unit consists of massive, lobed and fragmented dacitic to rhyolitic flows of tholeiitic affinity. This unit, with a maximum thickness of one kilometre, extends over 20 km in an E-W orientation in the northern portion of sheet 32C05-200-0201 and NE portion of sheet 32D08-200-0202. In the NW portion of sheet 32C05-200-02020, this unit extends just over 7 km in an ENE-WSW orientation. Other smaller horizons of this unit continue towards the SW, parallel to trachyte flows (nAla3). Unit nAla5 hosts the Projet 70-Landome mineralized zone.
This unit is described in a very general and summary manner as tuffs and andesites by McDougall (1965). These tuffs are usually intermediate in composition and are associated with andesites or trachytes of the same composition. The unit forms irregular flows oriented ENE-WSW to NE-SW in the NW portion of sheet 32C05. In a westerly direction, this unit is 12 km long and 1 km wide, while in the east, it does not exceed 200 m wide for approximately 4 km long. This unit is subparallel to trachyte flows (nAla3).
This unit consists of thin sedimentary horizons ranging in thickness from 20 to 60 m. These are relatively persistent along stratification and arranged within unit nAla11.
This unit consists of a thin horizon oriented NE-SW, 2.5 km long by 50 to 100 m wide. It is located at the SW end of the Landrienne Formation on the north side of Tiblemont Lake (sheet 32C06).
This unit consists of three horizons of mafic tuffs interbedded in chlorite-epidote basalt (nAla1) horizons. It extends over 1.5 km in a NW-SE direction west of Courville Lake (sheet 32C06).
This unit is located in the southern half of unit nAla5. The largest flow, located in the centre of sheet 32C05-200-0202, follows the general NE-SW orientation of flows in the area west of Barraute.
This fragmentary unit is located on the south side of unit nAla5, at its interpreted stratigraphic summit.
This fragmentary unit is located on the north side of unit nAla5, towards its interpreted stratigraphic base.
This unit consists of thin sedimentary horizons, ranging in thickness from 5 to 30 m, within the nAla5 unit.
This unit was primarily recognized in drilling in the vicinity of the Marcoland and Projet 70-Landome mineralized zones, within unit nAla5.
This unit is located in the central-south part of unit nAla5. It consists of massive rhyolitic to dacitic volcanics, block, lapilli and crystal tuffs, as well as thin horizons of graphitic mudrock of limited extent, less than a few hundred metres. Unit nAla15 hosts the Marcoland mineralized zone.
The Landrienne Formation is located in the heart of the Barraute region and appears intensely folded. Its actual thickness is difficult to estimate due to the many folds observed and interpreted (Geological Survey of Canada et al., 2008). It is in contact with the Deguisier Formation in the north and the Lanaudière Formation in the south. Some lithologies are less severely folded, particularly those on the north and south edges of the formation. These units continue west in sheet 32C05-200-0201 and east in sheet 32C06-200-201.
Felsic volcaniclastics were dated 2727 ±2 Ma (Labbé, 1998). This age is 8 to 10 My older than volcanics of the Deguisier and Lanaudière formations, immediately adjacent to the north and south.
|Isotopic System||Mineral||Crystallization Age (Ma)||(+)||(-)||Reference(s)|
The Landrienne Formation occupies a particular geometric situation in sheets 32D08, 32C05 and 32C06. It is in regional-fault contact with volcanics from neighbouring formations, with which it shows a gap in age of almost 10 Ma, which accentuates the importance of these faults. This formation is located in the heart of the Manneville Thrust Zone. Regional schistosity and stratification are subparallel and slightly inclined northward, with angles ranging from 30º to 45°. This formation has a particular structural style involving many synform and antiform folds. Such folds are absent from the formations immediately adjacent to the north and south. These observations raise the hypothesis that this formation represents a tectonic slice carried in the Manneville Thrust Zone.
Does not apply.