Lac Brulé is a Ni-Cu exploration project located in the upper Laurentian region of Québec. The maiden 2023 drill program is informed by an airborne HELITEM II survey which defined large-scale deformation patterns with intense isolated gravity highs together with strong conductive zones, a favorable geological setting for base metals.
Sama Resources Inc. launched the Lac Brulé Ni-Cu project in the province of Québec, Canada by acquiring a total of 420 exploration claims in the Nivernais and Esgriseilles Townships in 2020, 21 and 22. The project area is located a six-hour drive north of Montreal.
Back in the 1980s while working for Falconbridge, Dr. Audet had become aware of the geological potential in this region. Regional magnetometry, gravity maps as well as data from provincial stream and lake sediment sampling programs were used to delineate the geological potential that led to the discovery of a Ni-Cu gossan in May 2021.
No previous exploration had been carried out on the Lac Brulé property.
The closest mining activity was some 50 km away at the old Renzy nickel-copper mine, which operated until the early 1970s. Following the 1955 discovery of Renzy mineralization, a series of prospectors and mining companies carried out field scouting trips but only in proximity to the mine site.
The property was selected using data available on GESTIM (province of Quebec’s public Exploration & Mining database), encouraged by the excellent combination of magnetism and high gravity responses (vertical gradient of gravity anomaly) and more importantly SRQ’s own base metal index.
In May 2021, Dr. Audet made the first field visit with the intention of validating his assumptions. This led to the discovery of a mineralized ultramafic horizon to the east of the property, which can be easily spotted from the large gossan that is present at the surface (more than 450m in length and 65m in width).
The host of the gossan was described as mainly made up of massive pyroxenite with large crystals of pyroxene (and/or amphibole) and inclusions of serpentinized olivine. Puddles of interstitial sulfides (up to 5%) are present throughout, the latter being mainly formed of chalcopyrite, pyrrhotite, and possibly pyrite and pentlandite. The surrounding units that were observed in the field predominantly consist of gneiss and granulites, and one may also notice the presence of massive garnet amphibolites.
Later in December 2021, and as a part of the ongoing exploration program, SRQ commissioned Xcalibur Multiphysics to complete a MAG-HELITEM II survey on the Lac Brulé property. The survey took place between December 5 and 14, 2021 and allowed for the acquisition of 1,493 line-km of MAG and EM data.
Metamorphism is of high grade. It varies from amphibolite facies sup to granulite facies. The regional structure has significant deformations, but it is notable that the regional foliation is characterized by a very low dip of 15 to 20 °. The pyroxenite unit shows a discreet mineralogical foliation that weakly slopes towards the south.
More geological detailed works are needed but already it could be interpreted that the mineralization observed in the pyroxenite horizon clearly corresponds to the roof of a structure that is open downwards.
In August 2022, ground IP and EM surveys were performed on two distinct grids called North grid (IP survey) and South grid, also called the Gossan grid, (EM survey). Results for these surveys confirmed location and intensities of conductors outlined by the airborne EM survey. A 1,500-meter maiden drilling program is planned at the Gossan grid in H1- 2023 in the summer of 2023.
Analogies with Renzy historical mine and Nova Bollinger deposit, Australia
Several similarities can be drawn between the defunct Renzy Ni-Cu mine and the Australian Nova Bollinger Ni-Cu deposit. According to the literature, the “Renzy peridotite might have been injected in a pre-existent fold structure at a late stage of folding. i.e., its actual form is essentially the same as at the time of its emplacement and therefore has not been affected by any posterior folds. If true, this statement implies that the location of all the magmatic sulphide segregations is linked to the present contour of the peridotite body and not related to the sill’s original contours, which have been folded after solidification”.
This concept is important for the exploration of magmatic sulphides at Renzy ultramafic bodies as well as for the Lac Brulé area. The Lac Brulé gossan material is associated to similar host rock as described at the Renzy mine. The Renzy’s host rock is composed of olivine clinopyroxenite, an intermediate product of the differentiation of a basaltic magma. The locally well-defined primary bedding, the presence of cumulate textures (cumulus olivine, poecilitic orthopyroxenes) and the presence of mineral lineation parallel to the bedding suggest that crystallization processes were a primary factor of the intrusion (Johnson, 1972).
As for the Nova Bollinger Ni-Cu deposit recently discovered in Australia, it can be seen that the geological host is very similar to host rock at the Renzy and at the Lac Brule area: Greenville type metamorphism with sub-horizontal layering.
The Lac Brulé project area lies within the western part of the Grenville geological province. The Grenville province has been the subject of only a handful of studies, most of which were close to the former Renzi Ni-Cu-PGE mine. No detailed study or prospective activity was ever reported over the area of the Lac Brulé project.
According to J. Martignole et al., 1997, the Grenville Province consists of a reworked Archean promontory partly covered by Proterozoic allochthons and two Proterozoic metasedimentary and metaigneous terranes, which are probably allochthonous. J. Martignole et al., 1997 proposed the possibility of late-Archean exhumation of high-grade terranes along the Front. South of the Front, two types of ductile shear zone are responsible for the geometry of terranes in this part of the Grenville Province. The first type corresponds to the boundary of allochthons transported onto the Archean parautochthon. The corresponding structures are not directly dated but reheating of the parautochthon at about 1,020 Ma (U–Pb ages on monazite) sets a minimum age for thrusting in this area.
Late movement along an east-dipping shear zone located within the parautochthon, the Cabonga thrust (CT; 998+9/−5Ma), involves rocks of the parautochthon and is characterized by a westerly directed transport. The shear zones of the second type are subvertical, NE-trending, generally sinistral and intersect the parautochthon, the allochthon or both. From the fFront towards the SE, these shear zones are: the Cadgecrib shear zone (998+16/−6Ma) intersecting the parautochthon;, the Renzy shear zone (1,003+4/−5 Ma) involving allochthonous metasediments;, the Baskatong shear zone (1,020+2/−1 Ma) which marks the NW limit of Proterozoic rocks of the Mont-Laurier terrane;, the Labelle shear zone (1,078±6Ma) separating the Mont-Laurier and the Morin terrane;, and the Taureau shear zone (1,074±4 Ma) bounding the Morin terrane to the east.
J. Martignole et al., 1997 considered that the above timing constraints are from U–Pb ages on syn- to post-kinematic pegmatites emplaced within the respective shear zones. This age distribution suggests a propagation of transcurrent deformation towards the NW, which is responsible for the final configuration of terranes.
