Ragi Ramesh HBSc Thesis Abstract

Thesis Title: 
Exploring the primary mineralogy of Archean calcite crystal fans
Ragi
Ramesh
HBSc
2022

Archean precipitates such as crystal fans can be used to investigate the difference between Archean ocean and modern-day seawater chemistry. The globose radiating masses of crystal fans in the Hogarth Member of Steep Rock, the crystal fan fabric in the Elbow Point member of Steep Rock, and the vertically stacked acicular crystal fans from Red Lake carbonates were included in this study. These vertical crystals which grew off the substrates precipitating from anoxic Archean seawater are suggested to be primarily aragonite or gypsum. By analyzing Sr and Ba in the Steep Rock and Red Lake samples and comparing them with gathered literature data of old and modern-day carbonates, the primary mineralogy of these crystal fans is investigated. Sr and Ba show preferential substitution in aragonite, calcite and dolomite with high preservation of Sr concentrations in aragonite. Steep Rock fans have significantly higher Sr concentrations relative to older and dolomitized Red Lake fans representing tidal flats, while the Red Lake atikokania showed a relatively higher Sr value representative of deeper waters. Dolomite samples from both study areas showed a notable distinction in their Sr value from calcite samples. However, Sr concentrations for Steep Rock and Red Lake are significantly lower when compared to modern aragonites. This result concurs with the Sr loss that happens during recrystallization over time, i.e., as the mineral transforms from aragonite to calcite to dolomite. The primary mineralogy of these crystal fans is inconclusive due to this significant Sr loss, however, it is most likely that they were carbonates than gypsum or anhydrite.

Nina Buchanan HBSc Thesis Abstract

Thesis Title: 
Mineralogy and Petrology of the Saturday Night Intrusion, NW Ontario, Canada
Nina
Buchanan
HBSc
2022
The Saturday Night Intrusion (SNI) was identified due to its remnantly polarized magnetic anomaly, similar to mafic-ultramafic intrusions in the area related to the early/plateau stage of the Midcontinent Rift (MCR). A single hole (SN-16-001) was drilled through the SNI to a depth of 601m. Different units of the SNI were identified: leucogabbro, gabbro, peridotite, and melagabbro/gabbro. This study provides the first report of the mineralogy and petrology of the SNI.
 
Leucogabbro is the dominant lithology within the SNI composed of medium-grained mesocumulate plagioclase, interstitial quartz, and hornblende altered to chlorite and associated fine-grained clay alteration. The gabbro unit is mainly medium-grained orthocumulate
clinopyroxne with interstitial plagioclase and olivine altered to chlorite and associated finegrained clay alteration. The peridotite is dominantly mesocumulate olivine pseudomorphed into serpentine, talc, calcite and magnetite with interstitial clinopyroxene, orthopyroxene and plagioclase. Melagabbro/gabbro is the basal unit, dominantly composed of medium-grained anhedral/subhedral plagioclase with clinopyroxene altered to chlorite. The SNI was emplaced within the Trout Lake granites of the Dog Lake Granitoid Chain. Two phases of the Trout Lake granite are present; the first phase is dominantly plagioclase, orthoclase, and biotite altered to chlorite present within the hanging wall; and, the second phase is dominantly plagioclase, quartz, chlorite, with microcline megacrysts found in the footwall. An important aspect of the SNI and surrounding Trout Lake granites is the extensive hydrothermal alteration. The alteration assemblage consists of chlorite, epidote, calcite, clay and iron oxide staining. 
 
The SNI is a mafic-ultramafic intrusion related to the early/plateau stage of the MCR. The majority of the Saturday Night Intrusion has a trace element and REE geochemical signature of enriched LREE compared to depleted HREE, enriched Th, and depleted Nb. Depleted HREE signature is indicative of a partial melt from depth. Enriched Th and depleted Nb is characteristic of crustal contamination. A source of the crustal contamination may be the Trout Lake granites. The magma source of the SNI is between N-MORB and OIB with some degree of crustal contamination. The trace element and REE geochemical trends are similar to other maficultramafic intrusions related to the early/plateau phase of the MCR.

Blaize Briggs HBSc Thesis Abstract

Thesis Title: 
Quetico-Wabigoon Subprovince Boundary in the Superior Province North of Thunder Bay, Ontario, Canada
Blaize A.
Briggs
HBSc
2022

The boundary zone between the Quetico and Wabigoon subprovinces is a complex zone of deformation and metamorphism that is marked by a fault, change in metamorphic grade and lithology. The Quetico-Wabigoon subprovince boundary zone is exposed along Highway 527 within a roughly 23km stretch of highway. At the south end of this zone the DeCourcey Lake outcrop is a strongly foliated, mylonitic rock containing quartz, feldspar, garnet, sillimanite, muscovite, and biotite with pegmatites and boudinaged quartz veins and is classified as part of the Quetico subprovince. The north end of the zone is marked by a weakly foliated conglomerate that displays primary sedimentary textures and is classified as part of the Wabigoon subprovince. Catacalsis was discovered 9.8km north of the DeCourcey Lake outcrop and marks a sharp change between the high-grade amphibolite to granulite facies Quetico rock to the south and sub-greenschist to greenschist facies Wabigoon rock to the north. This cataclasis is evidence for a fault that has not been recorded in previous studies. The fault is mapped parallel to the foliation of the cataclasite. This fault is interpreted to be a boundary fault marking the boundary at this location between the Quetico and Wabigoon subprovince.

Conner Arts HBSc Thesis Abstract

Thesis Title: 
Depositional Processes of Massive Sandstone Layers in the Sub-Aqueous Portion of the 1.4Ga Sibley Group Delta, Northwestern Ontario
Conner
Arts
HBSc
2022

This research was focused on constructing a depositional model for the thick, massive sandstone layers present in the Pass Lake and Outan Island Formations of the 1.4Ga Sibley Group Delta, east of Thunder Bay, Ontario. Massive sandstone beds are not typically deposited in a distributary-mouth bar environment and are anomalous in this instance. To develop a depositional model, field mapping and core logging was conducted, and thin sections of samples were used to ascertain grain orientation in the massive sandstone. The results were compared to established literature on sediment gravity flows and prevegetated delta environments in order to discern the nature of the depositional mechanisms that resulted in the formation of the thick massive sandstone layers. It is likely that these layers were deposited by high-energy flood events that created turbulent flows of sediment and water, ranging from high density to moderate density. These flows would have deposited the sediment rapidly from suspension and consolidated quickly, creating largely ungraded deposits with poorly oriented grains. Understanding the Sibley Group massive sandstone may assist in identifying other types of flow deposits in both Precambrian and extraterrestrial environments.

Louis Covello HBSc Thesis Abstract

Thesis Title: 
The Structure, Stratigraphy and Petrology of the North End of Abitibi Block Seven, Sturgeon Lake
Louis
Covello
HBSc
1971

Abstract to follow.

Josh McQuade HBSc thesis abstract

Thesis Title: 
Sulfur isotopes as a record of differential contamination along the Cu-PGE mineralized Eastern Gabbro, Coldwell Complex, Canada
Josh
McQuade
HBSc
2022
The Eastern Gabbro of the Coldwell Complex is a composite pluton that wraps around the eastern and northern margins of the complex and hosts a number orthomagmatic Ni–Cu–platinum group element (PGE) sulfide deposits (Good et al., 2015; 2019). The most well-characterized deposit is the Marathon conduit-type Cu–PGE deposit situated in the southern portion of the Eastern Gabbro. It, along with the other zones of mineralization, are largely hosted by the Two Duck Lake (TDL) gabbro, a coarse to pegmatitic gabbro that exhibits a subophitic texture. Three zones of mineralization occur in the Marathon deposit: the lower Footwall Zone, the Main Zone, and the upper W Horizon. The Footwall Zone is characterized by the highest Cu/Pd ratios that are within the range of mantle values, whereas the W Horizon is characterized by Cu/Pd values lower than mantle (Brzozowski et al., 2020). Base-metal sulfides (BMS) range from semi-massive to disseminated, and largely comprise variable amounts of pyrrhotite, chalcopyrite, and lesser pentlandite; the W Horizon is unique in that it contains significant bornite, limited pyrrhotite, and low abundance of base metal-bearing sulphides. Several zones of mineralization occur north of the Marathon deposit; from south to north these are the Four Dams and Boyer prospect, the Sally deposit, and the Redstone prospect (Good et al., 2017). Mineralization here is characterized by elevated Cu/Pd ratios and comprises a BMS assemblage similar to the Footwall and Main zones at Marathon, but with notably higher abundances of cubanite (Brzozowski et al., 2020).
 
In the Marathon deposit, the sulfide liquid was carried upwards to the site of emplacement from a sulfide pool located at depth, which formed by the addition of externally derived S from Archean sedimentary rocks. This Archean contamination is evident in the multiple S isotope compositions of BMS in the Footwall and Main zones, namely a negative correlation between δ33S –δ36S and non-zero Δ33S, which is characteristic of Archean S reservoirs (Shahabi Far et al., 2018). Similarly, the S/Se ratio of BMS in the Footwall Zone are elevated compared to mantle values, indicative of the addition of external S to the mineralizing system (Brzozowski et al., 2020).
 
In contrast to the Marathon deposit, BMS in the northern zones of mineralization are characterized by S/Se ratios that are largely lower than mantle ranges, indicating either i) contamination of these mineralized zones by a low S/Se source or ii) S loss. To attempt to address this ambiguity, the S isotope (δ34S) composition of BMS at Four Dams, Boyer, Sally, and Redstone were characterized. In all of these zones of mineralization, BMS are characterized by δ34S values within the range of mantle values (Four Dams = 0.2 to 2.3, Boyer = 0.3 to 2.6, Sally = -0.7 to 2.5, Redstone = -0.1 to 2.6). Considering the propensity of Ni–Cu–PGE systems to record evidence of external S addition, and the general inefficiency of other saturation mechanisms (e.g., decreasing fO2, magma mixing; Ripley and Li, 2013) to generate economic sulfide deposits, the lack of δ34S signature could be the result of either i) dilution/destruction of the isotopic signature by interaction of the contaminated sulfide liquid with uncontaminated silicate melt (i.e., R factor), or ii) contamination by an Archean S source characterized by δ34S ~ 0‰. To assess the effect of R factor on the S isotope composition of BMS, δ34S was compared to bulk-rock Cu/Pd (i.e., a proxy for R factor). Although the Cu/Pd values of these mineralized zones varies over more than two orders of magnitude (525–909,000), no systematic change is evident in the δ34S composition of BMS, suggesting that dilution of the contaminant signature may not be the cause of the mantle-like values, but rather that the contaminant contained S that was processed through the Archean atmosphere. Given the current dataset, it is not possible to robustly assess the role of Archean contamination in the S saturation history of the northern mineralized zones in the Eastern Gabbro. This preliminary study, therefore, serves as the foundation for a future study characterizing the multiple S isotope composition of these mineralized zones and development of a more detailed mineral deposit model.

Andrew Jedemann MSc thesis abstract

Thesis Title: 
Tectonomagmatic evolution and green rock mineral chemistry of Jurassic Bonanza arc rocks at Pemberton Hills, Vancouver Island, British Columbia, Canada
Andrew
Jedemann
MSc
2021

The Pemberton Hills study site is situated in northern Vancouver Island, British Columbia, and forms part of a northwest trending belt of porphyry deposits and prospects within the Wrangellia Terrane. The study site is underlain by late Triassic to middle Jurassic Bonanza Group volcanic rocks, with porphyry-related alteration and mineralization thought to be related to the emplacement of the Jurassic Island Plutonic Suite (181 – 141 Ma).

Whole-rock geochemistry, high precision geochronology combined with trace element and Hf isotope analysis of zircons from various intrusive units has led to an improved understanding of the magmatic evolution of plutonic rocks at Pemberton Hills. The oldest unit is a granodiorite dated at 172.34 ± 0.11 Ma. Following this is a quartz diorite with an age of 172.01 ± 0.17 Ma, which overlaps with a tonalite dyke sample dated at 171.77 ± 0.13 Ma. A second quartz diorite sample yielded the youngest reported age at 171.44 ± 0.25 Ma. These results imply that felsic and intermediate plutonism were broadly synchronous at Pemberton Hills.

Zircon trace element geochemistry reveals contrasting conditions in the felsic and intermediate plutonic magmas, despite broadly similar emplacement ages. The granodiorite and tonalite dyke samples are characterized by higher, overlapping Eu/Eu* (~0.2-0.3) and lower, overlapping Dy/Yb (~0.15-0.2) ratios, whereas the quartz diorite samples show low and increasing Eu/Eu* ratios (~0.1-0.17) as well as high and decreasing Dy/Yb ratios (0.25-0.45) over time. These results suggest that conditions remained stable throughout the emplacement history of the felsic plutonic magmas, but varied during the emplacement of the intermediate magmas.  Zircon Hf isotope compositions of the granodiorite (+11.4), tonalite dyke (+11.2), and one of the quartz diorite samples (+9.5) suggest these rocks were derived from a juvenile mantle source that experienced minimal crustal contamination. Together, zircon chemistry and Hf isotope compositions suggest that the granodiorite and tonalite dyke magmas were the most fertile, meaning that felsic plutonic rocks have the most potential to be associated with a larger and more mineralized porphyry system at Pemberton Hills.

Field mapping combined with detailed petrography have shown propylitic alteration assemblages to be present throughout most of the porphyry environment at Pemberton Hills.  Laser ablation inductively coupled mass spectrometry (LA-ICP-MS) analyses of epidote, chlorite, and pyrite have identified that major and trace element variations in these minerals vary systematically across the study site, and can be used to discriminate multiple porphyry-related alteration events at Pemberton Hills more effectively than whole-rock geochemistry.

Distal pathfinder elements displayed the most variation in epidote. Elements such as As and Sb in epidote were highest in a cluster of samples from the center of study site to the northeast of the lithocap. A small group of samples proximal to the southwestern margin of the quartz diorite pluton also displayed high As in epidote. Chlorite displayed clear systematic spatial distribution patterns, illustrated by increasing Ca and Sr concentrations in chlorite from samples moving towards the east from the southeast margin of the quartz diorite pluton. Fertility assessment plots of Sb vs. As in epidote and Zn vs. Mn in chlorite were used to discriminate spatially distinct groups of samples interpreted to relate to discrete porphyry alteration events at Pemberton Hills.

Pyrite mineral chemistry combined with pyrite element maps illustrate a complex paragenetic history at Pemberton Hills. Pyrite in samples located around the southeastern margin of the quartz diorite pluton are enriched in elements such as Au, As, Sb, Te, and Ag, whereas pyrite from samples overprinted by phyllic alteration assemblages are enriched in Mn, V, and Zn, consistent with abundant silicate micro-inclusions in these pyrites. Pyrite in samples located along the surficial margin of the lithocap are enriched in Re, likely reflecting the overprinting of fluids derived from the lithocap.

Trace element mineral chemistry of epidote, chlorite, and pyrite have proven to be effective at vectoring towards potential porphyry targets in an area with limited geologic context, and as a useful method to discriminate samples from different porphyry alteration events. The results of this study demonstrate the application of mineral chemistry as a tool for exploration in greenfield porphyry environments.

URI:

https://knowledgecommons.lakeheadu.ca/handle/2453/4881

Michael D'Angelo MSc thesis abstract

Thesis Title: 
Geochemistry, petrography and mineral chemistry of the Guichon Creek and Nicola batholiths, southcentral British Columbia
Michael
D'Angelo
MSc
2016

The Guichon Creek Batholith (GCB) is a Late Triassic calc-alkaline intrusive complex approximately 60km x 35km in size and located approximately 54km southwest of Kamloops, British Columbia, Canada. The Guichon Creek Batholith forms part of the Quesnel Terrane, comprised of stacked volcanic-arc assemblages and associated sedimentary units, which in addition to the Stikine and Cache Creek terranes, comprise the Intermontane Belt of central British Columbia. The Guichon Creek Batholith intrudes the western volcanic belt of the Upper Triassic Nicola Group and is partially overlain by volcanic and sedimentary rocks belonging to the Kamloops Group and are of Jurassic age and younger.

The Guichon Creek Batholith is host to the Highland Valley Cu-Mo porphyry system comprised of at least five known significant porphyry centers (Valley, Lornex, Highmont, Bethlehem and J.A.). It is one of two mineralized calc-alkaline batholiths that form a Late Triassic belt parallel to younger mineralized, alkaline and calc-alkaline belts to the east. Most of this belt is buried under a thin veneer of Jurassic and younger cover. Understanding the petrogenesis and composition of the Guichon Creek Batholith is important in developing exploration strategies to locate similar buried porphyry deposits along this belt.

The Guichon Creek Batholith consists of six concentrically zoned intrusive facies ranging from diorite in the core to granodiorite in the margin. Field relationships indicate that the facies young towards the centre of the batholith although observable contacts are rare in outcrop. The six intrusive facies are from the margin inward: 1) Border facies; Highland Valley facies [subdivided into the 2) Guichon sub-facies; and 3) Chataway sub-facies]; 4) Bethlehem facies; 5) Skeena facies; and 6) Bethsaida facies. 

The marginal Border facies is the most heterogeneous facies and contains numerous autoliths near the contact between Guichon Creek Batholith and the host Nicola Group basalts which are brecciated and intruded by the Border facies. Rocks belonging to the Border facies are olivine-bearing leuco-gabbros to diorites with equigranular, phaneritic textures. 

The Highland Valley facies is comprised of the Guichon and Chataway sub-facies. The composition of both sub-facies is similar, varying from quartz monzodiorite to granodiorite compositions and the Guichon sub-facies is most prominent to the northeast of the batholith whereas the Chataway sub-facies is most prominent to the southeast. The key difference between both sub-facies is the presence of conspicuous pink K-feldspar in the Guichon sub-facies and white K-feldspar in the Chataway sub-facies. Optically continuous, interstitial, sub-ophitic amphibole, K-feldspar and quartz are characteristic of all rocks belonging to the Highland Valley facies. 

The three youngest facies are all similar in composition (granodiorite) and show a progressive increase in quartz and K-feldspar, decrease in total mafic minerals (with an increase in biotite relative to hornblende) and nearly constant plagioclase contents progressing from the Bethlehem facies to the Bethsaida facies. The Bethlehem facies is characterized by ophitic amphibole phenocrysts that poikilitically enclose smaller plagioclase chadacrysts, whereas the Bethsaida facies is characterized by biotite and amoeboid quartz phenocrysts. The Skeena facies is texturally and compositionally intermediate to the Bethlehem and Bethsaida facies, lacking both amphibole and biotite phenocrysts but containing finer-grained amoeboid quartz phenocrysts than those present in the Bethsaida facies. 

Weak chlorite-epidote-sericite alteration is ubiquitous across the batholith, and even least altered samples typically contain biotite and amphibole crystals that have been affected by <5 to 60% alteration to chlorite and epidote and plagioclase that has been weakly to moderately sericitized. Alteration is most prominent in samples of the Bethsaida facies, particularly those closest to the mineralized porphyry centers. 

The Guichon Creek Batholith is a magnesian, calcic to calc-alkalic (MALI = -5 to 7.3) and metaluminous to weakly peraluminous (ASI = 0.77 to 1.28; AI = 0.02 to 0.13) batholith. Major and trace element geochemistry are consistent with fractional crystallization of the predominant minerals observed petrographically and plots of Zr vs. molar Al/Ti and Al2O3 vs. TiO2 are effective at discriminating between the Border, Highland Valley and Bethlehem-Skeena-Bethsaida facies. 

The petrographic and geochemical characteristics of the Guichon Creek Batholith in addition to cross-cutting relationships between facies and recent U-Pb ages suggest that the batholith was emplaced as at least two, but possibly three different magma pulses. 

High Sr/Y, low La/Yb, fractionated LREE and HREE relative to MREE and concave primitive-mantle-normalized multi-element diagrams indicate fractional crystallization of hornblende and clinopyroxene in a deep crustal magma reservoir. These geochemical signatures also preclude a significant role for garnet in magma genesis, either as a restite phase left behind by adakite melts of eclogite-facies subducted slabs or by assimilation and contamination by garnetiferous metamorphic rocks in the deep crust. This is consistent with Sm-Nd systematics (Nd(T) = +6.7 to +7.5) which are consistent with <2% contamination of primitive mantle melts by partial melts of subducted sediment, although 87Sr/86Sri values of 0.703367 to 0.703493 suggest minor contamination of the Border and Guichon facies by radiogenic Sr derived from Nicola Group limestones or contaminated Nicola Group basalts. 

Plots of Sr/Y, Al2O3 and V/Sc vs. SiO2 suggest that the parent magmas for the Guichon Creek Batholith were hydrous and oxidized, two criteria key for the production of porphyry deposits. Amphibole chemistry indicates temperature, pressure and ƒO2 conditions of crystallization were 712 ± 23.5 to 846 ± 23.5°C, 2.5 ± 0.3 to 0.9 ± 0.1 kbar (equivalent to 7.4 to 2.6km depth) and ΔNNO = 0.03 to 1.81, respectively. Pressure estimates are consistent with gentle tilting to the northeast, and imply that the Valley deposit may have formed at pressures where a single-phase supercritical fluid would have been stable, possibly leading to mineralization styles and an alteration footprint that are atypical of porphyry environments.

Ettore Colaiacovo HBSc Thesis Abstract

Thesis Title: 
Relationships between Shear Zones and Mineralization of the Rainy River deposit
Ettore
Colaiacovo
HBSc
2021

The Rainy River gold mine is located in northwestern Ontario and has been operating since 2015. The deposit has three major high-strain zones striking NW to SE across the main ore zones. Thin sections taken from sampling transects across each zone provide evidence that these high strain zones are ductile shear zones. Microstructural evidence including strong preferred mineral orientation, folded quartz veins and grainsize reduction indicate dislocation creep as the ductile deformation mechanism in these zones. These shear zones also seem to influence the shape of each mapped ore zone, seeming to bound each ore zone and separating them from each other. It is likely that these major structures are responsible for the multiple ore zones and the shape of each ore body being mined today.

Megan Landman HBSc Thesis Abstract

Thesis Title: 
Archean Orogenesis to Proterozoic Rifting: A structural history of Pass Lake, Thunder Bay, Ontario
Megan
Landman
HBSc
2021

New roadside outcrops along the Trans-Canada Highway 11/17 near Pass Lake, ON, expose the basal unconformity between Archean basement rock and the Proterozoic Gunflint Formation. Shear fractures, joints, and the Blende Lake fault damage zone seen in these two outcrops record the brittle deformation history of the area before and after the Gunflint Formation was deposited.  The unconformity represents a temporal gap in the stratigraphic sequence of at least 800 million years.  The Archean rock belongs to the Wawa subprovince of the Superior province, in close proximity to the Wawa-Quetico subprovince boundary.  Structural measurements, stereographic projections, and qualitative observations have allowed deeper insight and analysis of how structural controls have changed over an approximately 2.7 billion year-old geological history.  The Archean basement unit underneath the unconformity is a coarse-grained amphibolite that contains accessory epidote and biotite, and is homogeneous throughout the length of both high-standing outcrops.  This is interpreted to be a mafic pluton that has undergone amphibolite-facies metamorphism.  The amphibolite records a scatter in orientation of joints and shear fractures, but some trends align well with data from Mackenzie River granite plutons, including an overall east-northeast and west-southwest strike.  Later Proterozoic features, including the Blende Lake fault, have a common strike of east-northeast, which aligns with the orientation of the 1.1 Ga Mid-Continent Rift in Thunder Bay.  This similarity is further reflected by the Blende Lake fault being oriented subparallel to silver veins related to the Mid-Continent Rift.  Similarities between orientations of brittle structures in the amphibolite and Gunflint Formation suggest that the Mid-Continent Rift in Thunder Bay may have reactivated some Archean-aged orogenic-related faults and shear fractures.  Minor folding in the Gunflint Formation truncated by the Blende Lake fault, as well as reverse reactivation along the plane, may be evidence of compression during the later stage of the Mid-Continent Rift.

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