On May 13, 2024, Equinox Gold announced the completion of the acquisition of the remaining 40% of Greenstone Gold Mine GP Inc. from certain funds managed by Orion Mine Finance Management LP, giving Equinox Gold 100% ownership of the Greenstone Mine.
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Summary:
The Greenstone Mine (formerly Hardrock Property or Hardrock Project) lies within the granite-greenstone Wabigoon Subprovince of the Archean Superior craton, in eastern Canada. The Wabigoon Subprovince, averaging 100 km wide, is exposed for some 900 km eastward from Manitoba and Minnesota, beneath the Mesoproterozoic cover of the Nipigon Embayment, to the Phanerozoic cover of the James Bay Lowlands (Card and Poulsen, 1998). The Wabigoon Subprovince is bounded on the south by the metasedimentary Quetico Subprovince, on the northwest by the plutonic Winnipeg River Subprovince, and on the northeast by the metasedimentary English River Subprovince. The Wabigoon-Quetico Subprovince boundary is a structurally complex, largely faulted interface.
The Hardrock Property is located within the Beardmore-Geraldton Greenstone belt that contains several narrow, east-west striking sequences of volcanic and sedimentary rocks of Archean age. The southern edges of these sequences are spatially related to the through-going, major structural discontinuities thought to be thrust faults that have imbricated the sedimentary sequences. A comprehensive description of the regional geology can be found in Smyk et al., 2005. In the Geraldton area, most of the gold mines and a number of gold showings occur within or in proximity to the Bankfield-Tombill Deformation Zone (also known as the Barton Bay Deformation Zone), a zone of folding and shearing up to 1 km wide. The southern limit of the Tombill-Bankfield Deformation Zone is marked by the Tombill-Bankfield Fault, a zone of intense shearing up to 12 m wide.
In the immediate Geraldton area, the dominant rock types are clastic sediments (greywacke and arenite), oxide facies iron formations (“BIF”) and minor mafic metavolcanics. There are a number of younger intrusives, including an albite-rich porphyry unit (Hard Rock Porphyry) that is spatially associated with much of the gold mineralization on the Hard Rock, MacLeod-Cockshutt and Mosher Mines. Significant gold mineralization is also often spatially associated with BIF. In the case of the Little Long Lac Mine, gold mineralization is primarily hosted by an arkosic unit.
Gold mineralization in the Hard Rock, MacLeod-Cockshutt, Mosher Mines and the Little Long Lac Mine generally occurs in association with subvertical structures associated with quartz veins or stringers, minor to semi-massive sulphides (associated with replacement zones in BIF), weak to moderate carbonate and weak to strong sericite alteration. The ore zones rake shallowly towards the west in the vicinity of the Hard Rock, MacLeod-Cockshutt and Mosher Mines (15-30° W) and slightly more steeply towards the west at the Little Long Lac Mines (50-60° W), indicative of a strong structural control that post-dates the tight folding of the primary lithological units.
The gold mineralization occurs in a variety of host rocks and the style of mineralization is partly a function of the host rock. While the location and overall orientation of the ore bodies appear to have been largely structurally controlled, the deformation of the ore bodies has not been as intense as that of the host rocks. Nevertheless, there are areas where local folding and boundinage of mineralized veins is apparent. Additionally, there are strong secondary controls that influence the extent and intensity of gold mineralization such as the competency contrast between host rocks (e.g. the Hard Rock Porphyry and its contacts with either wacke or BIF) and the chemical character of the host rocks (e.g. oxide facies BIF being replaced by sulphides).
The following discussion on mineralization was taken from Smyk et al. (2005). “Gold mineralization in the BGB has resulted from the introduction of hydrothermal fluids in zones of high crustal permeability (Smyk et al., 2005). Permeability was generated by prolonged, multiple periods of deformation, which focused not only fluids, but magmatic activity and intrusions. In the Hardrock Deposit area, a major zone of deformation in which the gold mines are located has been alternatively termed the Bankfield-Tombill Fault Zone (Pye, 1951; Horwood and Pye, 1951) or the Tombill-Bankfield Deformation Zone (Lafrance et al., 2004, and herein).
Most mineralized occurrences in the Hardrock Deposit area lie in a zone of deformation to the immediate north of, and genetically linked to, the Tombill-Bankfield Deformation Zone. This zone of deformation varies from 600 to 100 m in total width, while the crush zone of the Tombill- Bankfield Fault proper ranges from metres to hundreds of metres in width. Gold mineralization is associated with D3 brittle shear zones and folds overprinting regional F2 folds (Lafrance et al., 2004). The plunge of the mineralized zones is parallel to F3 fold axes and to the intersection of D3 shear zones with F2 and F3 folds. On a sub-province scale, regional folds cut by D3 dextral shear zones are promising targets for discovering the next generation of large gold deposits.”