Summary:
The McIlvenna Bay and Bigstone Deposits, along with the Tesla Zone, consist of structurally-modified, stratabound, volcanic-hosted polymetallic massive sulphide mineralization and associated stringer-style mineralization. The massive to semi-massive sulphides contain copper and/or zinc, with lower concentrations of silver, gold, and lead, while the stringer-style mineralization generally contains elevated copper and gold.
McIlvenna Bay Deposit
The McIlvenna Bay Deposit includes five separate zones and two styles of mineralization that are mineralogically and texturally distinct:
• Massive to semi-massive sulphide mineralization in the Lens 2 and Lens 3.
• Stockwork-style sulphide mineralization in the CS Zone directly beneath Lens 2.
• Two other small lenses of stockwork-style mineralization:
- The Stringer Zone (SZ), which is located between Lens 2 and Lens 3.
- The CS Footwall Zone (FW), which occurs as a separate lens underneath the CS Zone for approximately 150 m of strike length and could represent a fault offset and repetition of the Main Lens and CS Zone.
The Main Lens at McIlvenna Bay is a large-massive to semi-massive sulphide horizon containing a metal zonation consisting of Cu- and Au-rich material near the uppermost dip extent of the deposit which transitions down-dip into a more Zn and Ag dominant massive sulphide.
The Lens 2 Massive Sulphide is a continuous mineralized horizon which varies from 0.1 m to 18.0 m in thickness and averages 3.5 m overall. The CS Zone is a zone of stockwork style copper-rich mineralization that directly underlies and is in contact with the Massive Sulphide. The zone is wedge shaped, running parallel to the plunge line of the Lens 2 Massive Sulphide.
Lens 3 is a massive sulphide that sits approximately 10 m to 30 m in the hangingwall above the Main Lens and could represent a stacked massive sulphide lens within the deposit .
The SZ comprises a narrow, intermittent lens of stringer-style sulphide mineralization that occurs sporadically between the massive sulphides of the Main Lens and Lens 3.
The FW is a separate lens that underlies the SZ and has been intersected in nine drill holes over approximately 150 m of strike length in the shallow, central part of the deposit. The lens varies in thickness from 0.3 to 38 m, with an average thickness of 30 m.
Massive to locally semi-massive sulphides are typical of the Main Lens (Lens 2) and Lens 3 horizons in the deposit. The massive sulphide mineralization tends to be composed of 70% to 80% medium-sized and subrounded pyrite grains resembling “buckshot” in a fine-grained sphalerite-rich matrix.
The CS Zone mineralization is confined to the area below the Lens 2 Massive Sulphide, but locally a similar stringer style of mineralization has also been observed between the Main Lens and Lens 3.
The nature of the stockwork zone mineralization varies according to the host rock alteration, but this style of mineralization is dominantly associated with moderate to strong chlorite alteration.
Tesla Zone
The Tesla Zone represents a significant new discovery located just 300 m from the northernmost drilling of the McIlvenna Bay Deposit. Tesla is quickly evolving into an important discovery due to its close proximity to McIlvenna Bay and due to the tenor of the assay results that have been received to date.
The mineralization at Tesla tends to be similar in character to the ore zones intersected at McIlvenna Bay, often associated with moderate to strong chlorite +/- sericite alteration and hosted in felsic igneous rocks.
Bigstone Deposit
There are three main styles of mineralization present in the Bigstone deposit, with the bulk of the mineralization in the deposit hosted in the following zones.
• A zinc rich massive sulphide horizon (Massive Sulphide Zone), which would have been extruded at or near the paleosurface.
• An underlying copper rich zone (Copper Zone) consisting of disseminated to semi-massive sulphide mineralization that is thought to represent a feeder system to the overlying massive sulphide.
• A zone of zinc stringer style mineralization (Zinc Stringer Zone) located locally, peripheral to the Copper Zone, and which tends to be associated with strong silicification and bleaching of the units.
The Massive Sulphide Zone is a zinc rich massive sulphide horizon that varies in thickness from less than 1 m to greater than 15 m through the deposit, averaging 5.9 m. The zone has been defined by drilling over a strike length of 400 m. The massive sulphide mineralization is dominated by massive to semi-massive pyrrhotite and/or pyrite with abundant red sphalerite.
The Copper Zone tends to be located approximately 20 m stratigraphically below the massive sulphide horizon in a zone of strong chlorite alteration and silicification. The Copper Zone occurs as a vertically oriented, flattened cylindrical body that has been drill tested in part between 100 m and 600 m below surface.
The Zinc Stringer Zone occurs peripheral to portions of the copper zone and generally comprises sphalerite rich stringers with lesser pyrrhotite, pyrite, and/or chalcopyrite in bleached and silicified volcanic rocks.
Deposit Type
The McIlvenna Bay Project is geologically part of the Flin Flon Greenstone Belt, which contains VHMS deposits of a type commonly found in Canada in Precambrian to Mesozoic volcano-sedimentary greenstone belts that occupy extensional arc environments such as a rifts or calderas.
In addition to VHMS deposits, the McIlvenna Bay Project area has the geological potential to host other economic mineral deposit styles, such as orogenic gold associated with syn- to post-metamorphic, crustal-scale structures, and intrusion-related or skarn deposits associated with pre-, syn- or postorogenic intrusions.
The McIlvenna Bay Deposit
The McIlvenna Bay Deposit consists of structurally modified, stratabound, polymetallic massive sulphide mineralization and associated stringer zone mineralization. The structural deformation and related transposition of the stratigraphy in the deposit area appears to be responsible for the current geometry of the CS Zone, which occurs as a continuous zone of stringer-style mineralization directly underlying the Massive Sulphide. The sulphides contain copper, zinc and gold, with low lead and silver values.
The McIlvenna Bay Deposit has undergone strong deformation and upper greenschist to amphibolite facies metamorphism. The Massive Sulphide lenses now plunge to the northwest, with typical aspect ratios of length down-plunge to width exceeding 10:1. The exact timing of sulphide ingress, remobilization and paragenesis within the deposit is the subject of ongoing research.
The Tesla Zone
The Tesla Zone is not yet drilled to the same density as McIlvenna Bay and is therefore less well understood. Currently, the zone is thought to have formed in a similar setting as the McIlvenna Bay Deposit and then moved into its current geometry during subsequent deformation through folding and/or faulting of the stratigraphy. The mineralization and local stratigraphy at Tesla have many similarities to McIlvenna Bay and Tesla is thought to have been influenced by a similar structural and metamorphic regime.
The Bigstone Deposit
The Bigstone Deposit is hosted by a north trending, steeply dipping, and west facing succession of volcanic and subvolcanic intrusive rocks and minor sediments. Mineralization at the Bigstone Deposit is represented by three zones of mineralization: 1) a laterally extensive zinc rich massive sulphide horizon that is currently thought to have been extruded onto the seafloor, underlain by 2) a copper rich zone of mineralization that may represent a feeder zone to the overlying massive sulphide horizon, and 3) a peripheral zinc rich halo associated with portions of the copper zone.