The BGGB is dominated by an E-NE trending, isoclinally folded sequence of mafic to felsic metavolcanics and overlying metasedimentary rocks. These rocks are cut by a series of felsic to intermediate dykes and plutons. Lower Proterozoic diabase dykes crosscut all of the above units and felsic intrusives and are interpreted to postdate mineralization.
In detail, the OTGB consists of felsic to mafic metavolcanic (calc‐alkaline and tholeiitic) sequences bound to the south by the BGB’s northern contact defined by the Paint Lake Deformation Zone. Metavolcanic rocks of the OTGB are deformed into arcuate shaped belts related to the emplacement of ovoid granitoid intrusions.
Regional structures and stratigraphy exhibit N-NE trends while late NW-SE trending fragile structures are common in the southern part of the OTGB. The mafic metavolcanic rocks are interbedded with felsic pyroclastic rocks and quartz-feldspar porphyries with rhyolite flows. The mafic meta-volcanic rocks consist of massive to foliated, pillowed, porphyritic and amygdaloidal flows and chlorite schists, tuffs and agglomerates. The felsic metavolcanics consist of rhyolitic to rhyodacitic flows, rhyolite porphyry, crystal tuff, lapilli‐tuff, tuff breccia, rhyolitic quartz feldspar porphyry and pyroclastic breccia.
The Ishkoday Project is hosted entirely in Archean volcanic, subvolcanic, volcaniclastic and intrusive rocks of the Onaman-Tashota greenstone belt, part of the eastern extent of the Wabigoon Subprovince of NW Ontario. The SE margin of the property, including the main mineralized trend, is hosted in subvolcanic diorites, rhyolitic flows, felsic volcaniclastic fragmental rocks, and in an interpreted Tonalite-Trondhjemite-Granodiorite (TTG) termed the “Sturgeon Stock”.
The subvolcanic diorite, termed the “Ishkoday Stock”, is interpreted to intrude the felsic rhyolitic flows and felsic volcaniclastic rocks during progressive volcanism. The Sturgeon Stock and Coyle Lake Batholith (TTG plutons) are interpreted to postdate the volcanic/subvolcanic rocks.
Polymetallic (Zn-Cu-Fe +/-Ag, Au) veins, termed “Ishkoday-style”, occur within and adjacent to the main Ishkoday Stock subvolcanic diorite; and this mineralization is cut by the TTG intrusive rocks. These veins are interpreted to represent subvolcanic, intrusion-related mineralization, potentially analogous to basal parts of modern epithermal or VMS style mineralization. The mineralization is interpreted to occur in an extensional rift, as indicated by the presence of significant (up to 50% by volume) intermediate dikes and sills that are geochemically and texturally related to the Ishkoday Stock (Keaton Strongman, personal communication).
Gold and silver-bearing orogenic quartz veins, termed “Sturgeon River style”, postdate and overprint the early mineralization. These veins, and associated shear zones, commonly overprint and reactivate early mineralized planes, making discrimination of the mineralization type, and relative age, difficult. (David Lewis 2020).
Three deformational events are recognized at the Ishkoday Project. D2 can be directly related to orogenic gold mineralization (Sturgeon River style. The Paint Lake Fault and local TTG plutons are interpreted to be the major controls on gold-bearing quartz veins on the Ishkoday property.
The Paint Lake Fault most likely initiated as a D1, block-bounding, reverse fault during accretionary tectonics at the contact between the southern Quetico and northern Wabigoon subprovinces. During D2 transpression, the structure was reactivated as a first-order dextral strike slip fault. Bends in the structure are likely due to semi-rigid body deformation (rheology) of the Coyle, Sturgeon and Elmhirst plutons, which resulted in second-order NE-striking sinistral conjugate Riedel faults that most likely reactivated D0/D1 fault or vein planes.
Local variable (magnitude and orientation) stress fields around the Sturgeon Stock resulted in third-order folding and N-striking Riedel extensional faults. Late D3 deformation most likely resulted in N- to NW-striking brittle faults) (David Lewis 2020).