Summary:
Deposit Types
Orthomagmatic Sulphide
Deposits Orthomagmatic deposits, or magmatic ore deposits, are mineral deposits within igneous rocks or along their contacts in which ore minerals crystallized from a melt or were transported in a melt. A diverse range of metal deposits are classified as orthomagmatic, ranging from typical sulphide deposits hosting the chalcophile elements (Ni, Cu, PGE, Co, Au, Ag) to rare earth and large ion lithophile element deposits in pegmatites, to chromium, iron, titanium, phosphate associated with magmatic oxides in a diverse compositional range of intrusions. The following description is limited to orthomagmatic sulphide as only this type is relevant to the Project.
Orthomagmatic sulphide deposits occur in predominantly mafic to ultramafic igneous rocks, in both intrusive and extrusive phases and a diverse range of geological settings, including deformed greenstone belts, and calc-alkaline batholiths associated with convergent plate margins; ophiolite complexes that formed at constructive plate margins; intraplate magmatic provinces associated with flood basalt type magmatism; and passively rifted continental margins. The commonality between all these rock types and tectonic settings is the generation of a silicate magma that is sulphur undersaturated when it leaves the source area. Silicate magmas that are not S-undersaturated in the source will leave the highly chalcophile elements (PGE-Cu) in the source area sulphide restite.
Cu-Ni-(PGE) Dominant Orthomagmatic Sulphide Deposits
Cu-Ni dominant sulphide deposits are generally high sulphide percentage deposits with Ni and Cu usually as the main economic metals. Ni usually constitutes the main economic commodity with Cu as either a co-product or by-product, and with Co, the PGE, and Au as common by-products.
PGE Dominant Orthomagmatic Sulphide Deposits
PGE dominant, low sulphide deposits, with the PGEs associated with low percentages of disseminated CuNi-Fe sulphides (<3%), usually occur within very large to medium sized, mafic/ultramafic layered intrusions.
The Thunder Bay North Intrusive Complex comprising Current and Escape chonoliths and respective PGECu-Ni deposits are part of the 1.1 Ga MCR interpreted to be the result of mantle plume impinging on the Archean plate causing intra-plate magmatism, similar to other rift-type and continental flood basalt settings (Noril’sk, Raglan). Parental magmas are hypothesized to be high MgO-basalts with olivine as a primary crystallizing phase and the effective accumulation of this phase resulting in the production of olivine rich lithologies. The two deposits are hosted in intrusions with no known extrusive component due to the present erosion level. Similar analogs for tectonic setting are Noril’sk-Talnach of Russia and the lower stratigraphy of the Raglan terrain in Northern Québec, although intrusions in both of these settings are emplaced within similar aged metasedimentary sequences rather than Archean rocks. Within the 1.1 Ga MCR, known Ni-Cu-PGE deposits of Eagle and East Eagle (Lundin Mining Corporation) and Tamarack (Talon Metals Corp.) are of the same type/family with some slight variations in host rock and metal tenors.
Mineralization
Mineralization discovered within the property and hosted within the Current and Escape chonoliths is classified as orthomagmatic. Orthomagmatic deposits are the product of direct segregation, accumulation, or crystallization of an immiscible phase (sulphide commonly) from a silicate magma. These types of deposits are commonly polymetallic containing a diverse suite of chalcophile elements. The following metals: nickel (Ni), copper (Cu), platinum group element (PGE) which comprise platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os), and cobalt (Co) are commonly found in orthomagmatic deposits along with the precious metals gold (Au) and silver (Ag). All of these elements are identified within the mineralization at the Current and Escape deposits. Immiscible sulphide has acted as a collector phase for the chalcophile elements and all elements show strong inter-elemental correlations with sulphur. Within orthomagmatic deposits that have components of massive and semimassive sulphide, a cooling/crystallization fractionation of the sulphide liquid into intermediate solid solution (ISS) and monosulphide solid solution (MSS) is commonly observed resulting in metal zonation (e.g., Cu-PGE rich vs. Ni rich areas). Within the mineralization at Current and Escape, this metal zonation is not significant.
The mineralization identified within the Project to date is considered to be somewhat atypical of orthomagmatic Cu-Ni sulphide deposits. The sub-class of deposits associated with rift and flood basalts and their associated magmatic conduits (Noril’sk type: Naldrett 2004) commonly contain Ni rich massive sulphide accumulations as observed at Voisey’s Bay, Noril’sk, Eagle, and Tamarack. The Thunder Bay North Intrusive Complex is PGE and Cu enriched, with limited massive Ni-sulphide accumulations giving it an atypical flavour. There still remains the potential for large massive sulphide bodies within both the Current and Escape intrusions.
Within the Thunder Bay North Intrusive Complex, most of the presently known mineralization is hosted within the Current and Escape intrusions. In almost all cases, mineralization within both deposits and corresponding zones is hosted by variably felspathic lherzolite or wehrlite and olivine melagabbro. Additionally, disseminated Pt-Pd-Cu-Ni mineralization has also been observed within the LIL and 025 intrusions.
Current Deposit
The drill-defined length of the Current deposit is approximately 4.0 km with the chonolith remaining open at depth. The Current deposit has six well defined zones of mineralization that are contiguous along the plunge of the intrusion as shown. Other zones do exist within the intrusion and are discussed in this section; however, they are not part of the current Mineral Resource estimate.
Escape Deposit
The Escape chonolith which hosts the Escape deposit has a drill-defined strike length of approximately 4.6 km and is open down-plunge with an approximately 2.3 km magnetically interpreted, non drill tested extension. Mineralization within the Escape Intrusion occurs intermittently along the entire strike length and is subdivided into four zones. The zones from north to south comprise Steepledge, Escape North, Escape South, and the HGZ.
Lone Island Lake North and South Intrusion
The LIL North and South intrusions are located to the west of Current and Escape along the same structural corridor (Quetico and Escape faults). LIL North has had more exploration work completed to date, however, mineralization identified has been finely disseminated, in three different settings. Anomalous chalcophile element abundances are observed proximal to the basal intrusive contact. Anomalous values are also spatially associated with a stratigraphic interval that contains gabbroic autoliths in the lower half of the intrusion. The third setting occurs in the upper half of the intrusion and appears to be a reef-type setting with a change in lithogeochemistry proximal to the mineralization. The lack of olivine bearing phases and the general S-undersaturated nature of the rocks comprising the intrusion suggest that this intrusion is not prospective at the current stratigraphic level.
Within LIL South, anomalous chalcophile element abundances have been identified as localized, finely disseminated pyrrhotite and chalcopyrite mineralization that is contact-proximal and is exposed at surface. However, no distinct mineralized zones have been identified by surface sampling or limited diamond drilling.
025 Intrusion
The 025 Intrusion is the only location within the Project where peridotite/olivine cumulate rocks are exposed in outcrop at surface.