The Mesoproterozoic Current Intrusion, part of the Thunder Bay North Intrusive Complex, hosts PGE-Cu-Ni mineralization (indicated minerals resource of 8.2 million tonnes grading 0.33% Cu, 0.22% Ni, and 2.7g/t Pt+Pd and an inferred mineral resource of 1.6 million tonnes grading 0.32% Cu, 0.20% Ni, and 1.7g/t Pt+Pd). The intrusion consists of a northwest-trending conduit-type body, consisting of wehrlite, lherzolite, olivine gabbronorite ± troctolite, associated with the earliest stages of the Midcontinent Rift System (MRS) and the Keweenaw plume that intruded Archean rocks. The intrusion is associated with multiple splays related to the Quetico fault that cross the boundaries between the Quetico basin and the Wabigoon terrane of the Superior Province. The intrusion hosts four mineralized zones: the Current and Bridge Zone in the northwest, the Beaver-Cloud Zone in the middle, and the 437-Southeast Anomaly Zone in the southeast.

Geochemical analysis reveals that the intrusion displays a well-defined primitive mantle-normalized pattern resembling Oceanic Island Basalt and a lack of continental crust contamination given the slightly positive Nb, La, and Ce anomalies relative to Th. The La/Smn values for the intrusion (from 1.8 to 2.6) indicate a mafic magma was derived from an enriched mantle plume; this is consistent with other intrusions associated with the MRS, including the Nipigon Sills and the Lone Island, the Escape, and the Seagull intrusions. The Sri (from 0.7021 to 0.7043) and εNd (from -1.18 to -4.02) values of the Current Intrusion are slightly lower than those typical values of the mantle source at 1100 Ma. Given the absence of geochemical anomalies that indicate assimilation of the Archean crust, an enriched Subcontitnetal Lithospheric Mantle (SCLM) is suggested to have interacted with the parental magma to generate the slightly negative radiogenic isotope values. 

Stable isotope analysis suggests that the rocks of the intrusion underwent interactions with mantle-derived fluids (δ2H from −40 to −80‰, δ18O from 5.5 to 7.0‰), meteoric fluids (δ2H <-80‰, δ18O <5.5‰), and crustal-derived fluids (δ18O >7‰). Analysis of the hydrothermal phases reveals three distinct mineral assemblages (domains) that altered the intrusive rocks. i) Domain A, influenced by the interaction of mantle-derived and meteoric fluids, formed antigorite, magnetite ± actinolite-tremolite after olivine, actinolite-tremolite and clinochlore after pyroxene, epidote-sericite and clinochlore after plagioclase, pyrite and magnetite after pyrrhotite, magnetite after pentlandite, secondary pyrrhotite after pyrite, chamosite and pyrite after magnetite. ii) Domain B consists of lizardite-chrysotile and an increase in mineral modal abundances of clinochlore, chamosite, epidote, sericite, pyrite, and secondary magnetite relative to Domain A. Stable isotopes in this domain indicate interaction with mixed mantle-derived and meteoric fluids. iii) Domain C, characterized by talc and carbonate minerals that replace domains A and B, with stable isotopes, indicating crustal-derived fluids.

In summary, this study indicates the Current Intrusion was derived from magmas that originated from an enriched mantle plume that interacted with an enriched SCLM as it ascended towards the crust. The documented alteration types resulted from fluid:rock interaction between the host intrusion and fluids derived from mantle-derived, crustal, and meteoric sources. These fluids also generated the mineral volume reduction of primary sulfides

This thesis presents a detailed investigation of the geology, geochemistry, and geochronology of the Archean Shebandowan Greenstone Belt (SGB) in the vicinity of the Moss Lake gold deposit in Northwestern Ontario. The Moss Lake property is located in the western part of the SGB and consists primarily of rocks belonging to the Greenwater and Burchell assemblages. The study characterizes the geological attributes, tectonic setting, and timing of magmatism within the belt and provides regional context for ongoing mineral exploration.

The research involved extensive fieldwork, including detailed lithological descriptions and structural analysis, supported by petrographic analysis of thin sections. Whole-rock geochemical analysis was performed on 56 samples to classify rock types, determine magmatic affinities, and evaluate element mobility, revealing distinct geochemical signatures between the Greenwater and Burchell assemblages and various intrusive bodies. 

The Greenwater assemblage mafic rocks exhibit tholeiitic affinities with flat HREE, enriched LREE, and negative Nb anomalies. The Burchell assemblage mafic rocks are calc-alkaline, with moderately enriched LREE, flat HREE, and negative Nb-Ti anomalies. Similarly, the felsic and intermediate metavolcanic rocks show distinct geochemical signatures between assemblages. Greenwater rocks are more enriched in LREE and display stronger negative Ti anomalies compared to the less enriched LREE and weaker Ti anomalies observed in Burchell rocks.

U-Pb zircon geochronology on four key samples yielded new ages: 2716.0 ± 0.45 Ma for the Moss Lake syenogranite stock, 2718.34 ± 0.14 Ma for the Obadinaw quartz syenite stock, 2711.80 ± 0.14 Ma for an intermediate metavolcanic rock, and 2707.35 ± 0.14 Ma for the Greenwater Lake quartz monzonite stock. These ages complement and refine the existing geochronological framework of the SGB.

Neodymium isotope analysis of thirteen samples provided insights into the mantle source and crustal contamination processes. The Greenwater assemblage exhibits consistently positive εNd(t) values in both mafic and felsic-intermediate rocks (+1.6 to +2.7), indicating a dominantly juvenile mantle source with limited crustal involvement. In contrast, the Burchell assemblage shows a broader εNd(t) range (+0.01 to +3.2), suggesting a more heterogeneous source and greater influence from crustal assimilation, despite an overall juvenile magmatic character.

The integration of geological, geochemical, and geochronological data supports models of a complex Neoarchean tectonic evolution involving distinct magmatic pulses and settings for the Greenwater and Burchell assemblages. Geochemical evidence suggested the Greenwater assemblage originated from an oceanic plateau evolving to a primitive arc, whereas the Burchell assemblage formed in a primitive arc environment. Intrusive bodies were classified as tonalite trondjhemite granodiorite, sanukitoids, and Archean hybrid granites, reflecting diverse sources and conditions of formation. The results confirm independent magmatic histories for the two assemblages and highlight a protracted crustal evolution involving juvenile mantle input and crustal assimilation.

The Saddle North porphyry Cu-Au deposit, northwestern British Columbia, Canada, is located in the Upper Triassic Stuhini Group and is associated with the Late Triassic to Early Jurassic Tatogga Suite intrusions. This study integrates petrographic, geochemical, and geochronological data to characterize the deposit's intrusive evolution, alteration assemblages, and mineralization processes. Four intrusive phases (FQMP-I1 to FQMP-I4) of feldspar–quartz–monzodiorite porphyry were identified based on petrographic and geochemical criteria, demonstrating a progressive compositional evolution and varying intensities of potassic alteration. High-precision LA-ICP-MS U–Pb zircon geochronology yielded crystallization ages ranging from 205.3 ± 1.7 Ma to 208.2 ± 1.8 Ma, confirming the temporal overlap between intrusive emplacement and hydrothermal activity. Re-Os dating of molybdenite veins returned a model age of 205.6 ± 0.8 Ma, corroborating a genetic link between mineralization and magmatism. 

Whole-rock geochemistry reveals that the intrusions are alkaline to weakly calc-alkaline, with moderate to strong Nb, Ti, and Eu depletions consistent with subduction-related arc magmas. Micro-XRF maps further constrain the spatial distribution of key alteration minerals and elemental enrichments within the core of the deposit. Eight vein types were recognized and categorized into four paragenetic stages: early (A–D), main (C, F, G), late (E, F, G), and post-mineral (G, H). Early-stage veins (A- and B-type) are associated with magnetite, chalcopyrite, and molybdenite and are found in potassic-altered FQMP-I1 and I2 intrusions. The vein paragenesis and alteration zoning indicate a progressive decline in temperature and fluid metal content during hydrothermal evolution. These findings collectively support a magmatic-hydrothermal continuum model for Saddle North, similar to other porphyry systems in the Golden Triangle, such as Red Chris and Galore Creek, emphasizing its potential as a significant Cu-Au mineralizing centre in the Canadian Cordillera.

The Lundmark Akow area is located in the south-central portion of the South Rim assemblage of the North Caribou Greenstone Belt. The mineralization consists of several base metal-bearing massive sulphide horizons hosted in a sequence of garnetiferous staurolite mica schists in the southern portion of the study area, to a northern host rock sequence dominated by volcanic and intrusive mafic to felsic rocks. The igneous host rock portion of the study has been dated between 2973 to 2980 Ma through zircon U/Pb geochronology. The meta-sedimentary sequence which hosts the mineralization is built upon a basement of intrusive and volcanic rocks which formed in an oceanic plateau through plume magmatism before impinging upon a subduction zone. Negative high field strength element (HFSE) anomalies show that arc related magmatism built upon the oceanic plateau. Sm/Nd isotope values from the mafic to felsic volcanic and intrusive rocks show a spread in εNd from -1.53 to 3.07 suggesting that melts were derived from both depleted mantle and plume sources, with some melts being contaminated by an older crustal basement. 

The characteristics of the massive sulphide horizons, as well as the host meta-sedimentary rocks are consistent with them having formed through distal VMS processes including hydrothermal particulate fallout from buoyant plumes combined with pooling of dense sulphide-rich fluids in topographic lows on the sea floor. The garnet-rich meta-sedimentary rocks show Fe and Mn enrichment when normalized to immobile Al and Ti, consistent with addition through hydrothermal plume particulate processes. The characteristics of the garnet layers suggest they formed through metamorphism of a sediment derived from the intermixing of hydrothermal and terrigenous particulates. The garnet compositions show prograde growth with a Mn- and Ca-rich core to a Fe- and Mg-rich rim, supporting their formation as a result of metamorphic conditions post exhalative activity.  

The massive sulphide horizons occur in lenses of 5 to 50 cm in width and do not show any clear alteration zonation leading up to the mineralization, suggesting they formed distal to the vent likely from a dense bottom-hugging sulphide-rich brine. Tourmalinite occurrences associated with the massive sulphide horizons formed through metasomatic interactions between the plume fluids and the underlying seafloor sediments, forming continuous stratigraphic beds. The tourmaline composistions were very Fe-rich with base metal concentrations similar to the host massive sulphide, supporting the formation of the tourmaline coevally with the sulphides in an Fe rich hydrothermal plume. 

The sedimentary nature of the host rocks to the mineralization did not allow for the evaluation of hydrothermal alteration through methods of Rb/Sr ratios or alteration index/ chlorite carbonate pyrite index alteration box plots. An evaluation of SWIR data on white micas showed the Al-OH band occurring at around 2200 nm, suggesting formation due to regional metamorphism rather than through a high heat and fluid/rock interaction associated with proximal VMS mineralization. 

Efforts to vector to mineralization through mineral compositions were not successful. The presence of Mn-rich garnet was more dependent on host rock composition rather than proximity to massive sulphide. Zinc enrichment in staurolite was limited and no values greater than 2 wt.% were observed which suggests there is no massive sulphide mineralization in the vicinity of all tested staurolite. Evaluating a change in XFe in ferromagnesian silicates (garnet, biotite, staurolite, chlorite) in proximity to metamorphosed massive sulphide horizons due to the formation of a sulphidation oxidation halo showed that the composition of garnet, biotite, and chlorite were modified. However, the extent of this halo was limited to within a few meters of a metamorphosed massive sulphide horizon and as such the usefulness of this as a vector is limited. 

Geothermometry using a Ti in biotite and  garnet biotite composistion as well as a garnet, biotite, plagioclase muscovite barometer was applied to show an increasing metamorphic grade from the north to the south across the belt. Temperatures range from 573 ± 32.2° C in the north to 651 ± 32.6° C in the southern portion of the Lundmark Akow area.  Pressure variation likewise varies from 3.0 Kbar in the north to 5.3 Kbar in the southern most sample. Calculating peak metamorphic conditions based on calculated theoretical mineral assemblages from whole rock data through the use of a pseudosection is broadly consistent with the geothermobarometry, with a stable field for the coexistence of biotite garnet and staurolite occurs from between 510-600 °C and pressure between 2-5 Kbars.

The Mine Block Intrusion (MBI) is a 3 km by 1.5 km tear-shaped mafic complex that was emplaced along with other mafic-ultramafic plutonic rocks of the South Lac des Iles Complex (LDIC) between 2,699 and 2,686 Ma in the Marmion terrane of the Superior Province. The MBI consists of gabbronorite and magnetite-rich gabbronorite, and a later series of noritic rocks and their metamorphosed altered equivalents. 

Major element data of the MBI indicate that the rocks have a broadly gabbroic composition with protoliths dominated by plagioclase, a predominance of orthopyroxenes over clinopyroxene, and titano-magnetite, which is consistent with the petrographic observations. Magnetite gabbronorite rocks in the MBI were derived from a metasomatized mantle, consistent with the arc setting proposed for the Lac des Iles Complex as a whole. 

Plagioclase compositions decrease up the analyzed section, with no sharp change, suggesting a normal fractionation process with no magma injection events.  Plagioclase identified within the magnetite gabbronorite of the MBI is labradorite-bytownite (An-number ranging from 0.58 to 0.75), which is less evolved than observed in layered intrusions globally suggesting that saturation of Fe-Ti oxides occurred at an early stage of differentiation compared with other mafic intrusions. 

Coarse primary ilmenite grains with hematite lamellae in the MBI indicate early ilmenite crystallization, which could suggest a high TiO2 concentration in the magma. However, comparison with rocks of deposits dominated by hemo-ilmenite (high Ti content) and titanomagnetite (low Ti content) suggest that the primary ilmenite crystallized from a low-Ti magma. 

When comparing the analyzed samples of magnetite gabbronorite from the MBI with Fe-oxides of well-characterized rocks from the lowermost layers of Fe-Ti-V deposits (primitive signature) and the uppermost layers of Fe-Ti-P deposits (evolved signature), the pattern of compatible elements such as V, Ni, and Cr in magnetite show a distribution from primitive to evolved magnetite. This suggests that magnetite at the MBI crystallized from a magma of primitive composition associated with Fe-Ti-V deposits rather than from a more evolved magma typically linked to Fe-Ti-P mineralisation. This is consistent with the absence of apatite and the low P contents observed in whole rock geochemistry in the MBI. The upward decrease of elements compatible with magnetite, such as Mg, Ni, V, and Cr, and the upward increase of magnetite from elements incompatible with magnetite, such as Mo, Zn, and Ti in the magnetite from the MBI, indicate fractionation of the silicate melt from a less evolved melt to a more evolved one. It is likely that during fractionation plagioclase would have accumulated at the top of the magma chamber whereas the denser iron oxides would sink, resulting in the cumulate textures observed in the magnetite gabbronorite in the MBI.

The magnetite in the MBI gabbronorite at Lac des Iles can be considered to belong to the Fe-Ti-V deposit group hosted in the lower parts of a layered intrusion, characterized by titanomagnetite as the dominant oxide mineral occurring in layers and oxide mineralization associated with gabbronoritic cumulates. Magnetite chemistry also suggests a magmatic Fe-Ti-V deposit with a potential for V mineralization at Lac des Iles since several samples have concentrations (up to 1.3 wt. % V2O5) above those of the Panzhihua V mine (0.3 wt. % V2O5) or the Rhovan (Bushveld Complex) mine (0.5 wt. % V2O5).

The Eagle River mine is a mesothermal orogenic gold deposit hosted within the Archean Mishibishu Lake greenstone belt, approximately 50 km west of Wawa, Ontario. The underground mine has been in constant production since 1995, mining multiple steeply dipping quartz-bearing, shear-hosted gold horizons that dip to the north. As of the end of 2021 the Eagle River Mine has produced a total of 7.4 Mt of ore averaging 9.86 g/t Au yielding 1.5 M oz of refined Au (SRK, 2022). The majority of the gold mineralization is hosted within an ellipsoidal quartz diorite, with the remainder hosted within the surrounding calc-alkaline to tholeiitic volcanic rocks. The Mishibishu Lake greenstone belt is surrounded by granitic units which include the Bowman Lake batholith to the north-east, the Floating Heart batholith to the south and the Central pluton to the northwest. The objective of the study was to correlate veining in the chaotic unit to mineralization, investigate alteration geochemistry, and to compare Eagle River to other Archean Au deposits. This was undertaken using a combination of geochronology, petrography, and whole rock lithogeochemistry. The thesis focused on four zones within the deposit, the 8, Falcon, Newt Lake, and Peek-a-Boo zones.

For the thesis, drill core within the four zones has been reexamined (154 drillholes) to have consistent logs between drillholes, and to focus on the chaotic and Laminated units. This constrained the extent of the units and how they are related to one another. Within the Falcon zone part of the mineralization is hosted within the Laminated unit that cuts the chaotic unit. Due to the association with the mineralization a vein paragenesis of the chaotic unit has been developed to determine how the veins are related to one another, and if there is any association with mineralization. To assess the tectonic history of the Eagle River area, geochronological, geochemical, and petrographical samples were collected to determine the ages of the surrounding batholiths and the diorite, to determine the geodynamic setting of the area, as well as to see how the rocks are geochemically related. 

A total of 95 samples (geochronology=4, geochemistry=57, and thin sections=34) were selected from the four zones. The new U-Pb zircon ages from this study include the Central pluton (2656.38 ± 0.41 Ma), the Bowman Lake batholith (2658.35 ± 0.41 Ma), the Floating Heart batholith (2687.26 ± 0.42 Ma), and the mine diorite (2716.22 ± 0.41 Ma). The new age of the Bowman Lake batholith provides a tighter constraint on plutonism whereas the mine diorite age constrains the lower limit of mineralization. 

Whole rock geochemistry was completed on the volcanic rocks, gabbro, feldspar porphyry, granite, and diorite, as well as the chaotic and Laminated units from the four zones. The Laminated unit has been subdivided into two subgroups (A and B) based on the volcanic classification of Pearce (1996). The volcanic rocks, gabbro, and Laminated Group B unit are characterized by La/Smpm ratios of 0.8-1.4, variable Ti anomalies (Ti/Ti* of 0.5-1.2), and negative Nb anomalies (Nb/Nb* of 0.5-0.9), consistent with a magmatic arc affinity and melts derived by slab dehydration. The feldspar porphyry, chaotic, and Laminated Group A units are characterized by enriched La/Smpm ratios of 2.1-6.1, variable Ti anomalies (Ti/Ti* of 0.3-1.0), and Zr anomalies (Zr/Zr* of 0.7-2.3), as well as negative Nb anomalies (Nb/Nb* of 0.3-0.6) consistent with a magmatic arc origin with a higher degree of crustal contamination. The granites are characterized by La/Smpm ratios of 2.8-7.1, generally negative Ti anomalies (Ti/Ti* of 0.1-0.6), and negative Nb anomalies (Nb/Nb* of 0.1-0.3), consistent with an arc origin possibly related to melting of the downgoing slab. The diorite is characterized by La/Smpm ratios of 1.7-3.5, variable Ti anomalies (Ti/Ti* of 0.6-1.8), and negative Nb anomalies (Nb/Nb* of 0.3-0.5), consistent with an arc origin with magmas derived from either a mix of slab melts and slab-dehydration or garnet-bearing source rocks. Based on the geochemical differences, the rocks from Eagle River area suggest a switch between slab melting and slab-dehydration in the arc source, but further geochronological dating is required to constrain the timing.

Eight different vein types were identified within the chaotic unit, as well as five different generations of quartz veining. The chaotic unit veins are similar between the zones, suggesting that the chaotic unit is continuous between the zones. The chaotic unit veins are variably striking, have variable infill and alteration halos, and the sequence of younging is dominantly unidirectional (with exception of Q3 which has multiple cross-cutting relationships, and Q4 which has poor constraints) based on cross-cutting relationships. From the vein types there were a total of six occurrences of gold found within the 8 and the Falcon zones, all of which are hosted within quartz veins (Q2 and Q5 veins) that are parallel to the bands within the Laminated unit. The gold can either be found as inclusions within pyrite, or along grain boundaries that include pyrite-pyrite, quartz-clinochlore, or quartz-pyrite. The alteration within the Eagle River complex is dominated by albitization, K-feldspar, chloritization and carbonatization. The potassic and hematite alteration commonly increases towards the quartz veining within the mine, but not consistently. Potassic and hematite alteration are associated with faulting and generally increases towards the fault. The sericite alteration is commonly associated with the Laminated unit, and can be categorized based on thickness, alteration intensity and associated minerals to point towards the center of the deformation zone, as well as potentially used as markers when cut by younger units or faults. The albite alteration is dominantly associated with the chaotic unit and the variable striking veining. In general, the alteration types and intensity are variable, but the alteration intensities do not consistently increase towards mineralization and consequently do not serve as reliable vectors towards it.

The Thunder Bay North Igneous Complex (TBNIC) is located approximately 50 km northeast of Thunder Bay, Ontario, Canada. It comprises two Cu–Ni–PGE-mineralized mafic–ultramafic intrusions, the Escape and Current Intrusions, and five smaller mafic–ultramafic intrusions whose mineralization potential has yet to be fully assessed, namely the Lone Island Lake, Greenwich, Southeast Anomaly (SEA), and 025 intrusions, and the East–West Connector (EWC). The five gabbroic to peridotitic intrusions are the focus of this study. They are characterized by high magnetic anomalies and crosscut the Archean granitoids and metasedimentary rocks of the Quetico Subprovince. U-Pb dating yielded an age of 1107.6 ± 0.9 Ma for the Escape intrusion, which is the oldest date among TBN intrusions, and an age of 1105 ± 0.9 Ma for the Greenwich intrusion.  

Field observations and drill core logging of the five intrusions indicates that they are gabbroic to peridotitic in composition with approximately 6-9% sulfides. The sulphides are dominantly pyrite, with lesser amounts of chalcopyrite and pyrrhotite. Petrographic analysis of the five intrusions show them to comprise gabbronorite with lesser leuco-gabbro, gabbro, and websterites for the Lone Island intrusion, gabbronorite to websterite and lherzolite for 025,  gabbro to websterite for SEA, and highly altered gabbro in the EWC and Greenwich intrusions.       

The five intrusions are characterized by negative Nb, Zr, Hf, Ti, Y and Sc anomalies, and contain high incompatible element contents, enriched light rare-earth elements (LREE) with La/Smn = 2-3.7, flat to fractionated heavy REE (HREE) with Gd/Ybn = 1-6, and Th/Nbn = 0.09-0.11. The five intrusions also have moderate to strong negative Nb anomalies with Nb/Nb* ranging between 0.90 and 0.05. Generally, the five intrusions show slightly positive Eu anomalies with Eu/Eu*range between 0.53 and 1.14, which is consistent with the elevated plagioclase content of the five intrusions.   

Based on major and trace element chemistry, three sample populations were identified. Population A includes Lone Island, EWC, and SEA intrusions, and population B includes part of the 025 intrusion (025-1) and part of the Greenwich intrusion (Greenwich-1). Populations A and B are OIB-like magmas with enriched LREE and steep patterns on primitive mantle-normalized diagrams. They are similar to the Eva Kitto, Jackfish, Seagull, and McIntyre intrusions and relatively close to the Thunder intrusions from the MCR. Population C includes Greenwich-2 and 25-2. This population is less enriched in LREE and has a flatter pattern on primitive mantle-normalized diagrams, and they are similar to Nipigon Sills, Inspiration, Crystal Lake, Coubran Lake and Tamarack intrusions.    

Sm–Nd and Rb–Sr isotopes were utilized to assess the role of crustal contamination in the formation of the five intrusions. The intrusions are characterized by generally negative εNd(T)  values of -7.4 to +0.14 and Sri of 0.70309 to 0.70587. The most negative εNd(T) values of -7.20 and -7.49 were recorded in samples from the most LREE enriched portions of the Greenwich, whereas the +0.14  value is a hybrid grey (altered grey gabbro) sample from the 025 intrusion. Two country rock samples (an Archean metasedimentary rock and a granitoid) have εNd(1.1 Ga)  values of -20.50 and -20.19, Sri values of 0.7636 and 0.7057, and Th/Nbn of 2.33 and 1.50 respectively. The negative εNd(T) values for the intrusions and the country rocks, along with their elevated bulk-rock Th/Nbn ratios, and negative Nb anomalies suggest that the intrusions were contaminated by older crustal material. Three possible sources of contamination were identified, one with less negative εNd(T) and lower Sri that affected Lone Island, SEA, EWC, Greenwich-1, and 025-1. Secondly, one with higher Sri and more negative εNd(T) that affected Greenwich-2. The third type of contamination affected 025-2, and  is characterized by a lesser LREE enrichment and lower degree of crustal contamination and it affected 025-2.  

The three types of magmas from TBNIC that have been characterized in this study are all plume derived magmas, were generated from distinct melt sources and went through different types and degrees of crustal contamination. 

The Eagle’s Nest intrusion is a mafic-ultramafic, blade-shaped dike that hosts the only known economically significant orthomagmatic Ni-Cu-(PGE) mineralization in the Ring of Fire region of Ontario. It is part of the Koper Lake subsuite of the more voluminous Ring of Fire Intrusive Suite (~2736–2732 Ma) and occurs within the Meso- to Neoarchean in age McFaulds Lake Greenstone Belt. The Ring of Fire Intrusive Suite is host to chromite, Fe-Ti-V, and Ni-Cu-(PGE) mineralization. Previous studies investigated the orebody and mineralization hosted by the Eagle’s Nest intrusion, with limited attention to the unmineralized parts of the system. This study applied multidisciplinary petrological and geochemical techniques to evaluate the petrogenetic controls on the formation of the Eagle’s Nest intrusion through the examination of the less mineralized portions of the intrusion and genetically related mafic dikes. The Eagle’s Nest intrusion can be subdivided into the marginal and the inner zone. The marginal zone is composed of gabbroic rocks that exhibit the most evolved mineralogical and geochemical characteristics, with evidence of intense pseudomorphic alteration that often preserves primary magmatic textures. Contacts with the host tonalite vary, generally reflecting a prolonged high magma flux, but only rarely preserving evidence of rapid cooling and chilled margins. The marginal zone gradationally transitions into the inner zones, which consists of ultramafic ortho- to mesocumulate rocks. The inner zone is characterized by coherent linear geochemical trends that reflect olivine and chromite accumulation with variable proportions of intercumulus silicate phases and interstitial sulfides, consistent with petrographic observations. Most inner zone rocks are characterized by a strong positive correlation between MgO and Cr2O3, reflecting the crystallization of olivine and chromite in cotectic proportions. However, several of the mineralized peridotite samples deviate from this trend despite containing similar proportions of these minerals. Petrographic observations and intercumulus pyroxene mineral chemistry suggest that the deviation from the cotectic trend may be caused by sulfide percolation and displacement of a Cr-rich intercumulus silicate melt, rather than the presence of less than cotectic proportions of olivine and chromite. A new parental magma composition estimate was established using olivine and chromite mineral chemistry, as well as whole rock geochemistry of ultramafic cumulate rocks interpreted to reflect cotectic proportions olivine and chromite, with variable proportions of intercumulus silicate melt. The estimate yielded a parental magma composition that contained ~15 wt% MgO and ~11 wt% FeOt, consistent with a komatiitic basalt magma. The new composition is more evolved than previous estimates, however, it is in close agreement with the composition of identified chilled margins, associated mafic dikes, and olivine. Forward thermodynamic modeling simulations of the new parental magma, reproduce the petrographically determined crystallization sequence at low pressures, suggesting that the Eagle’s Nest intrusion formed at shallow crustal levels. Whole rock geochemistry and Sm-Nd isotopes show that the Eagle’s Nest magma was derived from a depleted mantle source, above the garnet stability field, which then underwent extensive crustal contamination from multiple sources that included both the host tonalite, and older supracrustal rocks. Crustal contamination by sulfur-bearing supracrustal rocks likely contributed to attaining sulfide saturation of the magma, as evidenced by Δ³³S values consistent with mass-independent fractionation. The distinctive petrological and metallogenic characteristics of the Eagle’s Nest intrusion in the Esker Intrusive Complex may be a result of several distinct processes involving both emplacement dynamics and parental magma composition, resulting in unique metal endowments relative to other intrusions in the McFaulds Lake Greenstone Belt. 

The Red Lake greenstone belt located in northwestern Ontario, Canada, hosts a world class gold camp that contains the high grade Campbell-Red Lake, Cochenour-Willans, Howey, and Hasaga deposits, as well as several other gold deposits and gold occurrences. This thesis examined textures, trace element chemistry and sulfur isotope evolution of pyrite and its use as a tool to discriminate Red Lake gold deposits, as well as the potential to use of pyrite chemistry as vectoring and fertility assessment tools. Field and petrographic observations, along with results from scanning electron microscopy, LA-ICP-MS analyses and sulfur isotope composition of pyrite, were integrated to achieve the objectives of this study.

Petrographic analyses of chemically etched pyrite grains reveal two main groups of pyrites associated with Red Lake deposits namely hydrothermal zoned pyrites (Py1a, Py1b and Py2) and recrystallized pyrites (Py3). At the Campbell-Red Lake (CRL) deposit, Py1a which is a mineral inclusion rich pyrite is enriched in element suite of Sb-Tl-Au-Ag-Te-W ± Hg with average δ34S values of approximately +6.6 ‰ and forms the core of zoned pyrites. It represent a stage of low temperature hydrothermal alteration. The second stage pyrite of pyrite growth at CRL is identified by the formation of arsenian, Au-rich Py1b crystals which represents metamorphic devolatization and mobilization of main stage mineralizing fluids with a narrow range of δ34S (+3‰ to +6.7‰). Py2, interpreted as the last stage of pyrite growth represents retrograde cooling of CRL deposit hydrothermal system resulting in the enrichment of Co, Ni and As and has δ34S value  around +6‰ consistent with a metamorphic fluid source. Py3 at the CRL represents recrystallization of early pyrites under high temperature contact metamorphism from plutonic rocks with trace element content of Co, Ni and As around 1000ppm and average δ34S of +1.1‰ whereas Py3 at the Howey deposit with similar trace element contents to the CRL have δ34S of +2.5‰ consistent with association with fluids from intrusive rocks of the Howey diorite complex. In contrast to the CRL deposit, oscillatory zoned P1yb and Py2 are the early pyrite whereas mineral inclusion rich Py1a is the latest pyrite at the East Bay area deposits and gold occurrences. The paragenetic sequence of pyrite at the East Bay area and intrusion related deposits show evidence of coupled dissolution and reprecipitation of early pyrites to form gold-rich late stage Py1a. Sulfur isotope data from the East Bay area deposits suggests that early Py1b and Py2 formed from metamorphic fluid whereas Py1a have magmatic fluid input. The intrusion related Howey and Hasaga deposit have similar pyrite paragenesis and sulfur isotope characteristics compared to East Bay area deposit except the non occurrence of As-rich Py1b.  

The Sb/Tl, Sb/Bi and Bi/Te ratios of Py1a across several Red Lake deposits and occurrences provide potential fertility indicator tools. The Sb/Bi ratio of pyrite decreases with decreasing deposit size whereas Bi/Te increases. Gold, Te, and Mo concentrations of ore related Py1b is appears to be a good discriminator between the large CRL and the smaller systems in the Red Lake greenstone belt. 

Various elements in pyrite including Se, Te, Bi and Ni/Co ratio show systematic changes in concentration from the center of the CRL deposit to about 3km away approximately 1-2km more than the footprint of whole rock samples. Pyrite trace element composition from other Red Lake deposits effectively discriminates between deposit proximal or distal signature from a mineralized zone. 

The Sunday Lake Intrusion (SLI) is an early-phase (1109.0±1.3 Ma) mafic-ultramafic intrusion associated with the Midcontinent Rift System. It was emplaced along the Crock Lake Fault, a splay of the regional Quetico fault. The intrusion is a layered funnel/tabular-shaped intrusion divided into Gabbro, Upper Ultramafic, Lower Ultramafic and Marginal zones. The intrusion hosts significant Ni-Cu-Platinum group-elements (PGE) mineralization within the Marginal Zone, which contains up to 2.11 g/t platinum, 0.95 g/t palladium, 0.16 g/t gold, 0.26% copper and 0.11% nickel. In total, this contact-type deposit hosts an estimated 20.4 Mt at an average grade of 2.5 g/t combined Pt+Pd+Au. Mineralization reflects late-stage exsolution of PGM from sulfide melt, including maslovite, michenerite, sperrylite and native silver, platinum and palladium.

The SLI comprises wehrlite, olivine clinopyroxenite, feldspathic olivine clinopyroxenite, melagabbro, gabbro, leucogabbro, quartz monzonite and quartz gabbro. Trace element and radiogenic isotope data support a mantle plume origin, with patterns resembling ocean island basalts (OIB) and likely tied to the Keweenaw Plume. Mass-balance calculations yield a calculated parental magma composition of ~11.15 wt. % FeO and ~19.5 wt. % MgO, consistent with a high-Mg tholeiitic basaltic magma. Compositional variations in olivine and whole-rock MgO (wt. %) suggest the SLI was formed from two discrete magma injections: the first formed the Lower Ultramafic Zone and Marginal Zone, and the second formed the Upper Ultramafic Zone.

Radiogenic isotopes values (ɛNd and 87Sr/86Sr) are mostly mantle-like, though early-pulse samples show negative Nb anomalies from limited interaction with the subcontinental lithospheric mantle beneath the lithosphere. A later injection of purely primitive, plume-derived magma appears to have flushed the staging chamber, depleting the subcontinental lithosphere mantle (SCLM) signature and resetting the sulfur isotope system to near-mantle values. This two-stage model explains the combination of mantle-like isotopes with localized Nb depletion.

Some radiogenic samples from the Gabbro and Marginal zones record isotopic and trace element evidence for assimilation of Quetico metasedimentary rocks. Negative ɛNd values and Nb-Th anomalies, together with decreased Fo in olivine at the Lower Ultramafic Zone-Marginal Zone contact, suggest localized interaction of magma with country rocks. Although this process may have introduced a crustal sulfur signature into the system, it was largely diluted or reset by the later primitive recharge, leaving the overall sulfur isotope system dominated by mantle values.