The Garson mine, part of Sudbury Operations, is owned and operated by Vale Canada Limited, a wholly-owned subsidiary of Vale Base Metals Ltd., the holding entity of Vale’s Energy Transition Metals business.
On April 30, 2024, Vale S.A. announced the completion of the sale of Vale Base Metals Ltd. (“VBM”) to Manara Minerals, under which Manara Minerals acquired a 10% interest in VBM.
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Summary:
The Garson deposit includes the actively mined McConnell deposit, surface ramp (13 and 360), and
Garson mine #1 Shear, #4 Shear deposits. Inactive deposits include the Garson ramp (600) zones.
Garson is a deformed Contact-style deposit. Contact-style mineralized zones are remobilized into a series of near-parallel ductile shear zones. Shear-hosted copper–nickel sulphides are offset by later stage dykes and possible late-stage shearing. The 1 Shear and 4 Shear are the primary mineralized zones.
The 1 Shear extends from surface to below 6500 Level, a distance of approximately 1,980 m. It has a strike length of 120–600 m, with strike length decreasing with depth. Hanging wall to footwall widths along the orebody vary between 3–60 m, with an average width of 10 m.
The 4 Shear extends from the 2800 Level to a currently known limit of 6700 Level, a distance of approximately 1,200 m. It has a strike extent of 685 m and an average width of 7 m. It strikes east– west and generally dips 70° south. The 4 Shear orebody runs parallel to the 1 Shear orebody, lying approximately 45 m to 60 m to the northwest.
Both shears dip at a slightly shallower angles than the SIC contact, which means that above the 4000 Level the shears are mostly hosted in the SIC with the dominant lithology being Sublayer Norite and below the 4000 Level the shears cut the metasedimentary and metavolcanic Huronian footwall rocks.
The deposit is crosscut by two separate olivine diabase dykes. These dykes are sub-parallel to each other and range in width from 15–60 m.
Structure
The Garson region was subjected to significantly more structural activity than the rest of the Sudbury Basin. This structural activity caused the Huronian footwall rocks to overturn and form the hanging wall. This overturning caused a significant amount of shearing sub-parallel to the strike of the Garson Contact-style deposits producing a series of near-parallel shears.
Major geological structures include the Garson Fault, the 2500 Shear, and the 3500 Shear. The 2500 shear and the 3500 structures and are roughly 12–23 m wide, strike north–northwest and dip steeply to the east. Fractures are commonly filled with calcite, galena, marcasite and sphalerite. Late-stage faults and fractures also deform the orebodies.
There are a number of “cross-over” sulphide zones that connect the 1 Shear and 4 Shear Orebodies. These cross-over zones are near vertical and <3 m wide.
Mineralization
The mineralization is dominated by inclusion massive sulphide and massive sulphide lenses and stringers, contorted schist inclusion sulphide, ragged disseminated and sulphide breccia. Pyrrhotite is the most common sulphide mineral. Pentlandite is the main nickel-bearing mineral. Chalcopyrite is the main copper-bearing mineral, and is locally associated with elevated precious metals. Trace to minor amounts of cobaltite–gersdorffite, niccolite (NiAs), nickeliferous pyrite, marcasite, sphalerite, galena and argentopentlandite (Ag(Fe, Ni)8S8) are distributed throughout the 4 Shear.
Platinum-group minerals include michenerite, hollingworthite, irarsite, froodite, Pd-melonite and sperrylite. The oxide mineral assemblage is composed of magnetite, with magnetite content varying from 0.5–2%. Rare and local clustering of lead and zinc mineralization occurs as veinlets associated with late fracture zones and within major structures. The hydrothermal alteration assemblage consists of marcasite (FeS2) and violarite (FeNi2S4).
Arsenic-bearing mineral assemblages occur primarily along the strongly sheared hanging wall and footwall-sulphide contacts. Arsenic also occurs within the main sulphide zones associated with latestage structural/schistose zones. Commonly, occurrences can be found associated with shear planes in the halo of the main mineral zone associated with low-grade disseminated and copper rich veinlets. The dominant As-bearing minerals are niccolite and cobaltite–gersdorffite. Maucherite (Ni11As8) has been reported but is relatively rare. Other arsenide and sulpharsenide minerals are present in trace amounts including sperrylite. Stockpiling and re-handling of high arsenic content ore is done to ensure processing requirements are achieved.
Garson– McConnell
Although proximal to, and along strike from the Garson mine orebodies, the McConnell deposit is in a different geological setting with different geological and mineralogical characteristics and is classified as an Offset-type deposit.
The McConnell deposit is approximately 1,425 ft (434 m) long, ranges from 200–570 ft (61–174 m) in width, averaging 430 ft (131 m), and ranges in thickness from 30–100 ft (9–30 m), averaging 60 ft (18 m). The deposit is currently delineated from surface to a depth of 1,350 ft (411 m), dips at about 75º, and plunges to the south at 70º.
Mineralization at the McConnell deposit is associated with a narrow, concentric, quartz–diorite dyke that has intruded into metasedimentary units within the Stobie Formation. The dyke strikes at 85º east and dips at 70º south. The immediate foot and hanging walls consist of quartz diorite acting as an envelope around the mineralization. Beyond this, the country rocks consist of embedded greenstone and quartzite with zones of Sudbury Breccia.
The mineralization consists of massive sulphide and contorted schist inclusion sulphide with a high pyrrhotite/nickel ratio, above-average precious metals content and negligible arsenic content. The sulphides occur as 1–2 cm blebs within the quartz diorite, but mainly as disseminated sulphides in the surrounding breccia.