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Geology and Mineralisation

The Ardeen Gold Project is located within the western portion of the Shebandowan Greenstone Belt which forms part of the Wawa Subprovince of the Archaean-age Superior Province of Canada.

The western Thunder Bay area contains three distinct bedrock domains. The centrally-located Wawa Subprovince, within which the Shebandowan Greenstone Belt occurs, is faulted-bounded to the north by metasedimentary and felsic intrusive rocks of the Quetico Subprovince and uncomformably overlain to the south by Palaeoproterozoic metasedimentary rocks of the Animikie Group.

The Shebandowan Greenstone Belt (SGB) comprises a sequence of metavolcanic and metasedimentary rocks that trend east-west from Thunder Bay, becoming southwesterly-oriented in the project area. The belt is bounded to the north by metasedimentary rocks of the Quetico Subprovince and to the south by large felsic intrusive complexes of Archaean age. The supracrustal rocks of the SGB and the Quetico metasedimentary belt are intruded by a number of intrusive bodies of varying age, including a suite of ten Late Archaean, composite granitoid bodies which includes the Moss Lake intrusion.

 

Regional Geological Map showing the extent of the Shebandowan Greenstone Belt and the location of the Ardeen Gold Project

 

Supracrustal rocks of the SGB were previously subdivided into two contrasting packages of metavolcanic and metasedimentary rocks:

• an older (>2733 Ma) suite of mafic to felsic, tholeiitic to calc-alkaline volcanic rocks with minor komatiite;
• an unconformably-overlying younger (2689 Ma) suite of metasedimentary and metavolcanic rocks, including units of alkalic affinity that overlie the older unit. These younger rocks closely resemble the Timiskaming-type rocks of the Kirkland Lake area in the Abitibi Subprovince.

This greenstone sequence is further subdivided into three mafic belts, termed the north, central and southern mafic metavolcanic belts (NMB, CMB and SMB, respectively), and the Central Felsic-Intermediate Belt (CFB). The Moss Township, within which the Ardeen Gold Project lies, contains rocks of the NMB, CFB and SMB.

The NMB extends through the main part of the Ardeen Gold Project and is bounded to the northwest by the Quetico metasedimentary belt (QSB) by the large-scale Boundary Fault. The CFB is located to the south of the NMB, and comprises the southern portion of the geology of the project. The southern contact of the NMB with the CFB is formed by the Corner Shear Zone, a large-scale, northwest-southeast trending structure. The SMB is located in the southwest part of Moss Township and does not extend into the project area. More than 95% of the project area encompasses the older and younger suites of the SGB with the remaining area covering the QSB.

The regional metamorphic grade within the SGB is lower greenschist facies, except proximal to large granitoid stocks where is it upgraded to upper greenschist to amphibolites facies. Previous studies in the west-central parts of the SGB suggest that the older volcanic and sedimentary rocks have been subjected to at least three deformation events.

One of the major structural features of the SGB is the large- to crustal-scale structure which forms the contact between rocks of the QSB and the SGB, termed the Boundary Fault Zone (BFZ). The contact comprises a several hundred metre wide zone of numerous discrete, northeast-trending shear zones. Major rock types within the contact zone are moderately- to extremely-schistose and are variably affected by chloritisation, silicification and in places, sulphidisation. Many smaller faults and shear zones related to the BFZ occur in the supracrustal rocks within the Ardeen Gold Deposit area. Some of these structures and their associated quartz veins host gold mineralization.

The local geology of the Ardeen Gold Project comprises massive and pillowed basalt with associated pillow breccias, iron formation, mafic volcanic breccia, intermediate ashflow tuff, dolerite/gabbro, feldspar porphyry, alkaline mafic rocks, conglomerate and late syn-tectonic syenite intrusive.

The structure of the Ardeen Gold Deposit area is dominated by numerous, steeply-dipping, northeast-striking Ardeen Shear Zone, which forms the contact between gabbro and mafic volcanic rocks at the Ardeen Gold Mine.

Some high strain zones in the Ardeen mine area host massive sulphide-bearing quartz veins with gold mineralisation. These shear zones have anastomosing forms in outcrop, most likely due to variation in mechanical properties of the rocks they intersect. Northeast-trending high strain zones are locally offset by east-northeast to east-trending, moderately-intense shear zones. These zones have a fragmental appearance, with the foliation being defined by aligned rock fragments. They are characterised especially by quartz ribbons which are fragmented, with the fragments being offset and transposed along the foliation.

Both shear zones described above are cut by late-stage, vuggy quartz- or calcite-filled faults which are sub-perpendicular to the lineation. Overall, the structure of the Project is dominated by a large-scale flexure within the pressure shadow of the Moss Lake intrusive body. This intrusion is spatially- and temporally-associated the Moss Lake/Snodgrass Gold Deposit (1.5 Moz), located 4.5 km to the east of the Ardeen Gold Project.

 

The geology of the Ardeen Gold Project showing main prospects and gold occurrences

 

Gold mineralisation in the vicinity of the Project is associated with sulphides and occurring as three different styles, namely:

1. Quartz (+/- carbonate) veins which are emplaced along northeast and east-northeast striking ductile shear zones (e.g. the Ardeen Gold Deposit and the Minoletti, Beaver and Fisher prospects).
2. Within mineralised, ductile to brittle shear zones and associated fractures in the central felsic volcanic unit (CFB), and within mafic and felsic intrusive rocks emplaced within intermediate to felsic volcanic rocks (e.g. the Moss Lake/Snodgrass Deposit (east of project area) and the Pearce Lake areas).
3. Within deformed (folded and/or sheared) sulphide-bearing ironstone units, often in conjunction with minor copper-lead-zinc mineralisation (e.g. the Ardeen Gold Deposit and the Fisher prospect).