Geology - Master's Theses

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A textural and trace-element study of pre-ore pyrite types at the Kamoa-Kakula sedimentary-rock-hosted copper deposit, Democratic Republic of Congo
(2024-03-27) Frost, Christian
Pyrite is known or assumed to be an important precursor phase in a variety of sedimentary-rock- hosted ore deposits. The probable role of framboidal pyrite has been identified in the origin of the giant Kamoa-Kakula Cu deposits in Democratic Republic of Congo, which are hosted by multiple-km-thick mid-Neoproterozoic diamictite, but the nature and paragenesis of pre-ore pyrite(s) in the system is poorly known. Using samples from a least-altered, least-mineralised drill-hole, this study identified and characterised four types of pre-ore pyrite in the Kamoa- Kakula system: (a) framboidal (‘sedimentary’) pyrite; (b) aggregate pyrite, consisting of irregular patches of pyrite microcrysts; (c) microcrystalline euhedral pyrite, consisting of independent very small euhedra; and (d) cluster pyrite, characterised by inclusion-rich amorphous centres overlain by groups of large, interlocking, inclusion-free euhedra. Textural relationships indicate that framboidal pyrite formation was followed by euhedral pyrite, aggregate pyrite, and then cluster pyrite. There is no textural evidence that euhedral or aggregate pyrite formed through recrystallisation of framboids. Trace element geochemistry indicates that framboidal, aggregate, and (some) euhedral pyrite formed under related, early diagenetic conditions, whereas (most) euhedral pyrite and cluster pyrite formed later, under different (“hydrothermal”) geochemical conditions. The trace element geochemistry indicates that, in contrast to the textural evidence, the paragenetic order of the pre-ore pyrite types is framboidal, aggregate, euhedral, and cluster. An ore-phase pyrite (clast-rimming pyrite) is texturally and geochemically distinct from all four pre-ore pyrite types.
Geology and structural evolution of the Tashota Deformation Zone and implications for orogenic gold mineralization
(2023-10-18) Mark, Benjamin
The Tashota Deformation Zone (TDZ) is a north-striking, ductile structure within the Onaman- Tashota Belt in the eastern Wabigoon subprovince of the Archean Superior Province in northwestern Ontario. The < 2700 Ma TDZ has never been studied in detail, despite its location along the boundary between a large batholith and Mesoarchean and Neoarchean volcanic rocks, its north trend in a belt where most ductile structures trend east-west, and the presence of orogenic gold mineralization. The TDZ is a high strain zone that formed along the batholith- volcanic rock boundary during the development of a dome-and-keel architecture in the central Onaman-Tashota Belt. During this deformation event, gold was emplaced along the TDZ contemporaneously with significant gold deposit formation to the south in the Beardmore- Geraldton Belt during syn-accretionary imbrication of volcanic and sedimentary rocks along the southern margin of the Wabigoon subprovince.
Structural evolution, geochemistry, and geochronology of the Magino Gold Deposit, Michipicoten Greenstone Belt, Northern Ontario
(2023-12-06) Campos, Ian C.
The Magino gold mine is located approximately 40 km northeast of the town of Wawa within the Michipicoten greenstone belt of the Archean Wawa subprovince. Mineralization is hosted by the ca. 2724 Ma tonalitic Webb Lake stock within the Goudreau Lake Deformation Zone. The Magino deposit formed during two gold mineralization events. The first mineralizing event is coeval with the emplacement of the Webb Lake stock and is manifested by corridors of strong phengite/muscovite-quartz-pyrite alteration and saccharoidal quartz veins. The latter are dated at 2731 ± 6.9 Ma (Re-Os molybdenite) and overlap within error with the age of the host intrusion. The second gold mineralization event is associated with epigenetic quartz-tourmaline-carbonate veins, which were emplaced during the formation of the steep regional foliation along the Goudreau Lake Deformation Zone. The Magino deposit is an excellent example of an Archean intrusion-related gold system later overprinted by deformation, orogenic mineralization, and metamorphism.
Geochemistry of gold from Ontario gold deposits
(2023-10-12) Melo-Gómez, Julian David
Gold is one of the most crucial metals in human history, and still, few investigations have directly studied gold composition to understand gold systems. Ontario (Canada) provides a natural example of gold systems because of the abundance and distribution of world class gold deposits. The present study constrains the geochemical signature of free gold using SEM-EDS, EPMA and LA-ICP-MS to characterize 242 samples from 71 gold deposits and occurrences. Generally, Ag, Cu, and Hg occur over 100 ppm, with Sb, Pd, Cd, and Bi typically as trace elements between 0.001 and 100 ppm. The geochemical signature of gold varies at the craton scale but is consistent at the camp scale. These spatially distinct trace element signatures are independent of local host rock and deposit types, which have implications regarding the controls on ore-forming mechanisms and reflect district-scale variations in the primary and secondary composition of gold. This elemental signature has important practical applications for industry; for example, in using elemental vectors that reflect local gold composition and/or in metallurgical processing.
Biostratigraphy of the sekwi and rockslide formations (lower to middle Cambrian; Wrigley lake and Sekwi mountain areas; NTS 95M and 105P, Northwest Territories, Canada); implications for basin development and regions correlation
(2023-05-17) Scott, R. William
The lower and middle Cambrian, carbonate-dominated Sekwi and Rockslide formations were deposited in the Selwyn basin, a Neoproterzoic-Paleozoic depositional entity that occupied most of the ancestral western margin of Laurentia and spans parts of modern-day Yukon and Northwest Territories. Biostratigraphic data and limited chemostratigraphic data (δ13Cvpdb) from two Sekwi Formation sections in the Sekwi Mountain map-area (NTS 105P) are used to refine the current understanding of the spatial and temporal distribution of trilobite faunas in the area and to correlate the Sekwi Formation with other units throughout the Canadian Cordillera. Two species-based trilobite biozones (in ascending order: the Nevadia addyensis and Nevadella eucharis zones) previously best known from Arizona, California, and Nevada are documented in the lower Sekwi Formation, and a new genus-based assemblage zone, the Elliptocephala Zone, is proposed for the lower Dyeran of the Selwyn basin and surrounding areas. Trilobite data from three sections in the Wrigley Lake area (NTS 95M) are used to determine the chronology of basin events adjacent to the Redstone arch during the early and middle Cambrian, and lithostratigraphic data from other locations in the same map area is discussed to illuminate the nature of the basin events. There is evidence for two tectonic events during the late (traditional) early Cambrian and earliest middle Cambrian: (1) Event I, a regional uplift that eroded strata proximal to the Redstone Arch, and (2) Event II, a regional deepening event that heralded the onset of Rockslide Formation deposition. Trilobite biostratigraphy remains a mainstay of correlation in the Cambrian and is a powerful tool. However, further refinement is needed for the current biostratigraphic synthesis of the Cambrian of Laurentia, and biostratigraphy is enhanced when combined with chemostratigraphic curves.
Gold mineralisation in a chemically reactive host: the Archean Gold Mineralised Vickers Dioritic Intrusive Complex, Nunavut Canada.
(2023-03-31) Tokaryk, Scott Arnold Jack
The Vickers albitised dioritic intrusion (VDI, 2668 ± 6 Ma), located in the central Hearne sub- domain of Nunavut, hosts a significant gold discovery (2012; e.g., hole PB-12-09 164.41 m @ 5.39 ppm Au). The intrusion (equilibrated to lower-greenschist-facies) is located in the northern part of the 2.72 to 2.65 Ga Tavani greenstone belt, an area that has been interpreted to contain the Pistol Bay Corridor, a west-northwest-trending brittle/ductile deformation zone. The VDI is an elliptical (900 x 600 m) heterogeneous igneous intrusion emplaced into the siliclastic Evitaruktuk Formation, part of the sedimentary Kaminak Group, and contains highly anomalous Au mineralisation focused along its northeastern contact. Pyrite and arsenopyrite, spatially associated with gold mineralisation, occur proximal to quartz- carbonate± chlorite veins that increase relative to the severity of hydrothermal alteration. Several gradational alteration assemblages are present in the mineralised zone, including chlorite- (CF1+CF2) and silica-facies (SF1I + SF2I) that are restricted to the VDI, and sericite-facies (SF1FW+SF2FW) in the footwall. By integrating petrographic observations, LA-ICP-MS analysis (sulphide mapping, Pb isotopes), in situ SIMS δ18Oquartz and δ34Spyrite, arsenopyrite, and other geochemical data (whole rock, SEM, etc.), a working model is proposed. The preferred model suggests that a metamorphic fluid carrying Au as a bi-sulphide complex was focused along a rheologically favourable contact and subsequently reacted with the Fe-oxide - rich VDI and precipitated Au via sulphidation reactions.
The Archean Hammond Reef deposit: the formation of an orogenic gold deposit in a contractional step-over-zone along a major strike-slip fault system
(2023-01-20) Fouillard, Gabrielle
Hammond Reef is an orogenic gold deposit with a measured and indicated resource estimate of 3.3 Moz at an average grade of 0.84 g/t gold. It is located within the south-central region of the Wabigoon Subprovince in northwest Ontario. It is hosted within a system of north- to northeasttrending anastomosing shear zones, called the Marmion Shear System (MSS), which straddles the contact between the Mesoarchean Diversion stock to the west and Marmion Batholith to the east. Multiple shear sense indicators, including the deflection of mylonitic foliations in shear zones, drag folds, and shear bands, suggests that the MSS is a major sinistral transcurrent fault system. The bulk of gold mineralization is concentrated in an ENE-trending bend along the MSS, characterized by intense sericite and carbonate alteration. Mineralization formed between 2700- 2690 Ma and is associated with syn-tectonic hydrothermal quartz breccias and shallowly dipping quartz-carbonate veins with down-dip striations, which formed during bulk NNW-directed shortening across the bend. This suggests that the Hammond Reef deposit formed along a contractional step-over-zone between two regional sinistral transcurrent faults. Compression across the bend resulted in more fracturing that localized the migration of hydrothermal fluids and the precipitation and concentration of gold.
Depositional history of the Ament Bay Assemblage in the Sturgeon Lake Greenstone Belt, Northwestern Ontario: implications for gold metallogeny
(2023-02-01) Tamosauskas, Michael
The Sturgeon Lake greenstone belt makes up the easternmost portion of the western Wabigoon terrane of the Superior craton, and is comprised of mostly Neoarchean volcanic assemblages, minor siliciclastic successions, and subalkalic- to alkalic intrusions. The Ament Bay assemblage is the youngest supracrustal assemblage of the Sturgeon Lake greenstone belt with a newly determined maximum depositional age of 2695.2 ± 7.8 Ma. Ament Bay consists dominantly of polymictic conglomerates, subarkosic- to arkosic arenites and wacke-mudstone sequences, interpreted as a sub-aerial fan delta that is transitional into subaqueous turbidites. These lithofacies are intruded by syenites of the Sturgeon Narrows Alkalic Complex (ca: 2693.2 ± 0.9 Ma), which are also incorporated as clasts in conglomerates of the Ament Bay assemblage, indicating a coeval relationship between alkalic magmatism, uplift erosion and sedimentation. Both the Ament Bay assemblage and Sturgeon Narrows Alkalic Complex are cross-cut by the Sturgeon Lake fault zone. Coeval alkalic magmatism and sedimentation in a fault-controlled basin are features of the 2680-2670 Ma Timiskaming assemblage which controls much of the orogenic-style gold endowment in the Abitibi greenstone belt. The Ament Bay assemblage has similar features but gold mineralization is not recognized in the belt. The lack of gold endowment in the Ament Bay assemblage could be a result of crustal influence on the alkalic melts and shallow-penetrating faults, in contrast to the juvenile nature of alkalic magmatism and deep-penetrating faults associated with the Timiskaming assemblage.
Signal processing for a three-component transmitting (3CTx) electromagnetic device
(2021-04-23) Finlayson, Michael
When a three-component transmitter (3CTx) transmits simultaneously from all three transmitters, the signal measured in a receiver coil will be the sum of the three primary and secondary fields. In order to interpret the data, it is necessary to separate the signals from each transmitter. In a numerical experiment utilizing time-domain type sources, a synthesized signal comprised of the sum of three transmitter signals, a powerline signal and a low-frequency noise signal was created. Frequency spectra showed that for multiple specific combinations of base frequencies it is possible for the harmonics to be unique (not overlapping) and hence identifiable. For these combinations, the transmitter signals can be separated using a stacking filter in the time-domain. One specific combination is 30 Hz, 32.5 Hz, and 35 Hz for the three transmitters, when the powerline is operating at 60 Hz. The secondary fields generated by these three base frequencies were modelled using a wire-loop. Analyzing the response in three off-time and five on-time windows, it was determined that the maximum differences caused by having three different base frequencies are predictable and correctable. Thus, building and field testing the 3CTx is practical.
Chemostratigraphy and structural framework for gold mineralization at the Goliath Deposit, Western Wabigoon Subprovince, Ontario
(2022-05-15) McRae, Mattea
The Goliath deposit (32 Mt at 1.09 g/t Au and 3.42 g/t Ag) is one of the larger gold deposits within the western Wabigoon subprovince, 20 km east of Dryden, Ontario. The economic potential of the Goliath deposit makes it important to understand its geological setting to improve exploration models for such significant targets. Felsic volcanic sedimentary rocks (maximum age of ~ 2703 Ma) host the mineralization, were sericitized, and metamorphosed into the muscovite- sericite schist and biotite-muscovite schist. This package is enclosed within a similarly aged turbidite sequence (maximum age of ~2701 Ma). The mineralization consists of base metal sulphides with gold and silver hosted in As-rich pyrite and remobilized along pyrite fractures. The mineralization is likely pre-deformation as the regional compressional D1 deformation and transpressional D2 deformation reoriented the grade shells to be subparallel to the S1 foliation (075°/78°), and higher-grade shells subparallel to the intersection lineation of S1 and S2 fabric (52°/218°), and subparallel to the F1 fold axial plane (28°/81°). The Goliath gold deposit is thus interpreted to have formed in a synvolcanic, pre-orogenic environment.
Occurrence, release and alteration of chromite nanoparticles
(2021-04-29) McClenaghan, Neal
Many environmental risk assessments are based on the total concentration of elements in natural waters/ soils, ignoring that a significant proportion of elements is associated with nanoparticles. TEM analysis of the silicate minerals from a chromitite sample from the Mum and Alice June claims, California confirmed that Cr-rich silicates contained an abundance of chromite nanoparticles. Subsequently, the colloidal fraction of a Cr-rich silicate leaching experiment revealed that the chromite nanoparticles persist through the weathering of their host silicate, confirming that chromite nanoparticles can be a significant form of Cr in the environment. The oxidation of chromite nanoparticles in the presence of Mn-oxides (best known environmental oxidiser of Cr3+) was tested with 6 batch experiments at pH 5 over a 9-month period. These experiments reveal that the dominant redox reaction between chromite nanoparticles and Mn-oxides is the oxidation of Fe2+(rather than Cr3+) by Mn3+.
Geostatistical analysis and integration of soil chemistry data with remote sensing information in the Sudbury area, Ontario.
(2022-03-28) Nethavhani, Phathutshedzo Molly
The presence of anomalous concentrations of metals within the soil profile can strongly affect its biological availability to plants, causing potential toxicity when exceeding threshold concentrations, and favoring numerous chemical exchanges. These interactions further facilitate metal dispersion in the hydrogeological and ecological systems, in response to weathering and erosion. Studies of the geospatial distribution of trace metal contaminants in Sudbury soils is thus important to unravel the dominant processes controlling dispersion patterns, contributing to sustainability of mining practice. A kriging geostatistical approach was applied to geochemical data obtained from the Sudbury Soil Survey to map multiscale geographic, enrichment trends in metal concentrations. Ordinary kriging prediction maps were developed to re-evaluate the multiscale spatial distribution of the chemicals of concern. Results show an anomalous distribution of metals centered on historical smelters, forming dominant northeast and southwest enrichment trends. The existence of these trends was validated by implementing a geostatistical Gaussian conditional simulation method, which reproduced the same spatial variability observed in the ordinary kriging maps and efficiently replicated the observed trends. The correlation analysis of the trends with remote sensing data, suggests that prevailing wind directions are likely one of the dominant driving forces controlling the trends. Integrating these results with satellite data showed improved vegetation regrowth patterns consistent with the geochemical northeast-southwest trend providing further, independent validation of the kriging results. Re-evaluation of the regional, geospatial distribution of the measured trace element concentrations will assist the monitoring and improved understanding of soil contamination trends and their impact on vegetation and other aspects of the biosphere in the Greater Sudbury area.
Volcanogenic massive sulphide targeting in the Noranda Camp: Using a 3D implicit modelling platform for deeper exploration through the integration of structural and geochemical vectors.
(2021-08-31) Ali, Sahibzada Hussain
The Noranda camp is a world-class region for volcanogenic massive sulphide (VMS) deposits hosted in the 2704-2695 Ma volcanic Blake River assemblage, Abitibi greenstone belt. Of the ~20 VMS deposits (past production ~225 Mt ore) in the Noranda camp, the most recent discovery of the West Ansil deposit in 2005 was attributed to the integration of multidisciplinary data (geological mapping, drilling data, geochemical data and geophysical surveys), in a 3D modelling platform (GoCAD). Although there has been limited success since the discovery of West Ansil (depth from the surface: 270 m), continued exploration has shown some potential at greater depth, such as the showing at 1300 m depth in the Ribago area evident by drill logs and core samples. VMS deposits in the study area occur less than 750 m below the surface, with the exception of Ansil, which occurs at a depth of 1260 m below the surface. This research focuses on the potential for new deeper discoveries of VMS mineralization along known synvolcanic structures to help guide camp-scale exploration. A new implicit (interpolant-based) 3D geological model was built from an updated 2017 drill hole database combined with primary lithological interpretation from the 2005 3D GoCAD geological model in Seequent’s Leapfrog® Geo®. The 3D geological model is coupled with a 3D representation of geochemical alteration signatures, mass-balance calculations, and normative minerals. Compared to existing models, the new model has a depth of 2.5 km compared to the previous 1.5 km and provides geochemical vectors that consider structural trends resulting from synvolcanic faults, which are the inferred pathways for hydrothermal fluids. Structural trends guide the 3D interpolation of alteration models and extend to greater depths, highlighting metal-bearing hydrothermal fluid pathways. The proposed VMS targets were developed using 3D block model integration of the 3D geological model and all the developed 3D numeric models of alteration. Using queries, the block model highlights the proximal alteration zones associated with VMS deposits at the intersection of known synvolcanic faults and exhalite horizons in the area. In addition, the targets were developed considering the possibility of multiple stacked sulphide lenses deeper in the stratigraphy and the effect of zone refining was evaluated. The developed queries yielded two potential targets in the Noranda South camp and seven potential targets in the Noranda Main camp. The Main camp targets are associated with the Beecham, Lewis, and Corbet exhalite along synvolcanic faults associated with high values of alteration and the gains/losses of major elements. Despite the sparse structural data, alterationmodelling results of the South camp targets show VMS-style alteration extending southwest of the Beauchastel fault, with high values of normative alteration index and gains in Fe and Mg concentrated in the Powell andesite of the Powell block. Most of the potential targets occur at a depth range between 400-800 m, with the exception of three targets (MCT-3, MCT5, and MCT7) that occur below 1,000 m depth. In addition, most of the drilling in the area did not extend deeper than the developed targets, as in the case of one potential target associated with Beecham exhalite. The target shows substantial alteration near the Beecham breccia horizon, but none of the drill holes in the area intersects the horizon. The new 3D model and exploration targets presented here highlight the potential for VMS discoveries at greater depth if specific key structural trends are integrated with 3D alteration models. The potential targets are deeper than existing drill holes in the area (historical and new). The new 3D implicit geological model has improved on Noranda's previous 3D explicit geological model, mainly as the exhalite horizons have been updated using new contact points derived from recent and historical drill holes. The new 3D model can be dynamically updated as exploration progresses and new data becomes available. In addition, structural trends control the flow of rising hydrothermal fluids and are a key input to highlight deeper prospects.
Characterization of alteration and mineralization at the Archean Grey Fox and Hislop magmatic-hydrothermal gold deposits, Matheson, Ontario
(2021-06-30) Kelly, Christopher Hugh
The Abitibi Greenstone belt (AGB) is host to some of the world’s largest gold deposits and their study has led to various gold deposit models and classifications. The latter includes a syenite- associated deposit type, which was first recognized in the early 2000s. This type of mineralization is present at the Grey Fox and Hislop deposits, which are located 80 km east of Timmins, Ontario. A study of their geologic setting, alteration, mineralogy, mineral chemistry, veining styles, and metal associations, suggest that these deposits, as well as others in the area, developed in different zones of a larger magmatic-hydrothermal system associated with alkalic intrusions of probable Timiskaming age (i.e., <2680 Ma). As such, they formed relatively early in the deformation history of the belt and predate the formation of the more common orogenic or greenstone-hosted quartz- carbonate vein deposits, such as the nearby Black Fox, which make up much of the gold budget in the AGB. A strong host-rock control is present at both deposits and their complex alteration histories provide insights on the formation of multiple mineralization styles within a single system. These different mineralization styles are described here to provide guidelines for mineral exploration for this deposit type in the Abitibi greenstone belt, as well as in other greenstone belts globally.
A fluid-flow modeling approach for predictive mapping of orogenic gold mineralization in the Malartic camp, Canada
(2021-09-21) Xu, Limin
Orogenic gold deposits are structurally controlled and commonly formed in the transition zone between brittle and ductile crustal domains. Formation of disseminated or localized gold mineralization involves structural features (e.g., fault zones, fold hinges), contrasts in physical properties (e.g., rock competency and permeability, lithostatic and hydrostatic pressure, temperature) or chemical variability (e.g., rock chemistry, fluid composition). Orogenic gold deposits form in convergent tectonic settings, at crustal depths of between 3 and 18 km, from the Paleoarchean to the present. However, the goal of this study is just to investigate the hydrothermal properties of a model and predict the influence of deformation zones, rock types and the associated physical parameters on fluid-flow associated with orogenic gold systems, and subsequently develop new feature-engineered layers for mineral exploration purpose. Open-source numerical modeling software OpenGeoSys, has been used to reconstruct the major fault network in the Malartic mining district, in an area 19.7 km long and 7.3 km wide. This model can compare thermal convection fluid flow with deformation induced fluid flow. Results of numerical simulations conducted in OpenGeoSys and relative calculations from different physical parameters along faults or intrusive contacts explain the existence of a spatial association with the distribution of orogenic gold prospects and mines in the Malartic camp. Results of Weight of Evidence demonstrate that the incorporation of faults in 3D finite element models for coupled fluid and heat transport simulations has the potential of indicating favorable areas for gold mineralization in a 3D space, which can ultimately lead to new mineral discoveries.
3D geological modelling of the northern Swayze area of the Abitibi greenstone belt: assisting mineral exploration by mapping controls on gold (Au) deposits
(2021-08-20) Mogashoa, Lawraine Lerato
A 3D geological model of the northern Swayze area is constructed through the integration of lithological, structural, geological cross-sections, and seismic information in a Leapfrog Geo® modelling software to delineate structural geometry and geological distribution of rock units in the area. Using a mineral system approach, important geological features are extracted from the 3D geological model. A log-linear 3D weights of evidence method is used to quantify the spatial association between orogenic gold (Au) mineralization and various geological features that might represent ore-controlling factors. This method reveals that the dominant controls on Au mineralization are the second and third generation of deformation zones (D2 and D3), lithological contacts, and second and third-order faults. The posterior probability model is effective in capturing most of the Au occurrences (81%) within 18% of the study area, and the predictive rate curve indicates that the model performs better than random, as it is effective in predicting 71% of the validation points within 30% of the study area.
A new model for an old camp: the enigmatic Ag-Co-Ni-As-Bi mineralization of Cobalt, Ontario
(2021-04-29) Rush, Louise Victoria
The recent emergence of Co as a critical metal used in a variety of high-technology industries has refocused exploration at Cobalt, Ontario. This district represents an unusual ore deposit-type termed the five-element (Ag-Ni-Co-As-Bi) assemblage and was important historically as Canada’s former premier Ag producer at over 460 Moz (1904-1989). This study applies a sophisticated analytical protocol consisting of whole rock analysis, petrography, and insitu mineral analyses (SEM-EDS, LA-ICP-MS) to a sample suite with spatial coverage across the district. These methods constrain geological controls on regional metal distribution, the sequence of alteration and mineralization, and the physiochemical evolution of the system. An updated genetic model for the mineralization involves the veins representing a district-scale homogeneous hydrothermal-metal melt system driven by contact metamorphism and partial melting of pre-existing sulfides in underlying Archean basement rocks. This model enhances understanding of deposit formation and offers refined geochemical vectors to aid ongoing exploration efforts.
The geology of the Windfall gold deposit, Québec, Canada
(2021-04-21) Choquette, Brandon G.
The Windfall deposit is an advanced-stage exploration gold project owned and operated by Osisko Mining Inc. and is located in the northeastern portion of the Abitibi greenstone belt, Québec, Canada. This is the first deposit-scale study and as such aims to provide an understanding of its geological setting and the evolution with a focus on the origin of gold mineralization. The study integrates several aspects, including: 1) geological mapping; 2) characterization of the various host rock lithologies and their alteration; 3) results of new age dating; and 4) characterization of the different vein types, their mineralogy and chemical and textural nature of the gold mineralization. The overall conclusion of the study suggests that the gold deposit formed ca. 2.7 Ga due to a magmatic-hydrothermal fluid exsolved from an underlying magma now represented by a swarm of felsic dike rocks spatially associated with the ore body.
The mineralogy, geochemistry and microbiology of Cobalt-bearing mine tailings from the Cobalt Mining Camp in Northeastern Ontario, Canada
(2020-11-23) Courchesne, Brittaney
Advancements in the field of biotechnology have proven bioleaching processes as an economic and environmentally safe form of mining. Most bioleaching studies to date however have been focused on Fe, Cu, and Au-sulfidic mine tailings, rather than metalloid-rich, neutral-pH tailings. This thesis will apply a multidisciplinary and multi-variate statistical approach to explore whether the neutral, Co and As-rich tailings material within the Cobalt mining camp can be efficiently bioleached. Tailings material within 30-cm depth profiles from three tailings sites (sites A, B and C) were characterized for their mineralogical, chemical and microbial community compositions, followed by the execution of bench-scale oxidative and reductive bioleaching experiments. Tailings material from sites A, B and C are composed primarily of quartz, albite, clinochlore, calcite and dolomite with minor safflorite, arsenopyrite, erythrite and annabergite. The material at site A contains on average more (sulf-)arsenides and higher concentrations of Fe than site B. Site C however is altogether geochemically and mineralogically dissimilar, with the presence of distinct reduced and oxidized zones. Variations in the Co+As+Sb+Zn (Co#), Fe (Fe#), and total S (S#) have been identified as geochemical markers for the presence of Fe, Coarsenides versus secondary Co, Ni, Zn-arsenates, e.g. tailings material with a high Co# and low Fe# tend to have a higher proportion of secondary arsenate minerals. In the tailings material of sites B and C, a lower average As valence coincides with a higher S#. Three distinct site-specific groupings are observed for 1) the Co vs Fe and S#’s and 2) the microbial communities. The Cobalt tailings are primarily composed of Actinobacteria and Proteobacteria and N, S, Fe, methane, and (possible) As-cycling bacteria. The tailings from sites B and C have a larger abundance of Fe- and S-cycling bacteria (e.g. Sulfurifustis and Thiobacillus), of which are more abundant at greater depths, whereas the tailings of site A have a higher proportion of potential As-cycling and -resistant genera (e.g. Methylocystis and Sphingomonas). The microbial communities appear to be highly correlated to depth, S#, Fe#, pH, and the average valence of As. The variation in the average valence of As correlates well with the abundances of N, S, Fe, and methane-cycling bacteria (e.g. Nitrospira sp., the order Thermodesulfovibrionia, and Methylocystis sp.). Aerobic and anaerobic bioleaching experiments were conducted on three samples (in duplicate) from each site, with six samples characterized by high and/or low Co, Fe and S#’s and three bulk, site-specific samples. The experiments used the tailings native consortia and had three methods/treatments. The first two were for chemolithotrophic and heterotrophic bacteria enrichment, with the third serving as a control or baseline experiment. The experiments ran for 18-weeks, with (1) biweekly measurements of pH, Eh, and total and dissolved metals, and (2) analysis of the microbial community composition through 16S rRNA DNA extraction at experiment completion. The highest abundance of As-reducing and -oxidizing genera (i.e. Delftia and Dechloromonas) were observed in the heterotroph-enrichments, which was additionally characterized as having the highest Co and As recovery (0.94 and 29.8 %, respectively). Samples that were composed of a higher proportion of Co, Ni, Zn-arsenates and Fe, Co-arsenides were observed to be enriched in Fe-reducing bacteria or As-reducing and - oxidizing genera, respectively. The enrichments were able to successfully shift the microbial communities to those involved in As-cycling. However, further work is required to determine what hindered the metal recovery process, i.e. future micro- and/or nano-scale studies may indicate that Co and As precipitated as Co-phosphates.
Integrated seismic interpretation of the Larder Lake area, Southern Abitibi greenstone belt, Ontario, Canada
(2020-10-21) Mpongo, Elton
The southern Abitibi greenstone belt is characterized by a series of complex metavolcanic and metasedimentary rocks intruded by granitic plutons and batholiths, which makes the area a hardrock environment. In the Larder Lake area, these stratigraphic units are truncated by two major breaks, the Lincoln Nipissing shear zone (LNSZ) and Cadillac-Larder Lake deformation zone (CLLDZ) which trend NE-SW and E-W, respectively. This thesis is focused on the quantitative interpretation of a ∼44 km long seismic transect acquired as part of the Metal Earth project in the Larder Lake area. Seismic imaging and interpretation in a hardrock environment are challenging due to the lack of continuity of reflections and smaller acoustic impedance contrasts between different stratigraphic units. Hence, structural interpretation of the seismic data is favoured rather than stratigraphic interpretation. The application of curvelet transforms and seismic attribute analysis significantly increased the signal to noise ratio (SNR) of the seismic data. Seismic data have pitfalls in imaging the subsurface geology in a hardrock environment due to a strong degree of structural heterogeneity and complex geometry of targets. These pitfalls are overcome by the integration of seismic data with complementary geophysical methods. This study aims to determine the structural architecture of the area using seismic data and other depth resolving geophysical methods using an integrated modelling approach. The integrated modelling is achieved by extracting anomalies from the geophysical inversion models. The study uses the empirical relationship between physical properties derived from all the datasets and integrates these in a spatial domain. Physical properties from the individual models are differentiated by applying unsupervised learning algorithms for characterization. The recovered physical properties show correlations with the seismic data along deformation zones.

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