Flash Presentations of the Geoscience Research Challenge – Doctorate Level

Quebec is now recognized for the importance of Archean lithium-bearing granitic pegmatite deposits in the SE part of the Superior Province. However, the fundamental processes that controlled their distribution and led to their Li enrichment remain poorly documented. These pegmatites are mainly hosted in supracrustal rocks, such as the Frotet-Evans Belt, about 100 km north of Chibougamau. In this area, intrusions associated with Li mineralization are grouped into two main sectors: Moblan to the east and Sirmac to the west. A global study of the Sirmac pegmatite field has been undertaken to understand the main petrological and tectonic controls, the nature of the magmatic sources and the hydrothermal imprint in the host rocks. The research program includes two doctoral studies, one involving a structural, geochronological (U-Pb), geochemical and mineralogical study of the pegmatites and host rocks, and the other involving experiments aimed at reproducing the conditions under which these intrusions were formed, modelling Li enrichment processes and using noble gases as a petrogenetic tool.

The Sirmac deposit contains measured and indicated resources of 0.27 Mt at 1.4% Li₂O (43-101 report, 2023). It includes three main mineralized dykes that are 30 m wide and extend laterally for more than 600 m, but these are contained within a swarm of several barren pegmatites. Preliminary observations show that the spodumene mineralized dykes are mainly hosted by polygenic sandstones and conglomerates. They can be subdivided into different textural facies: 1) zones of coarse quartz-spodumene, 2) a heterogeneous facies of variable grain size and texture containing muscovite, tourmaline, biotite, apatite and garnet, and 3) a facies of medium to coarse grain size with a mineralogical composition similar to the previous one. Some thinner dykes (< 2 m) show a rich quartz-albite-spodumene core with centimetric beryl crystals. The pegmatites are NW-SE trending and show no penetrative tectonic foliation. They are relatively late in the region's tectonic history, since they post-date regional metamorphism (biotite zone) and cut the main foliation (E-W) in the surrounding rocks at a steep angle. However, the geometric arrangement of these intrusions appears to be relatively complex, with subhorizontal and steeply dipping dykes. The next stages of the project will involve the sampling the different facies for geochemical and mineralogical studies, the geological mapping to understand the geometry of the magmatic system, and the establishment of a collection of reference materials for experiments and modelling.

The increasing demand for lithium, fueled by advancements in battery technologies, requires more efficient exploration and exploitation methods. This PhD project focuses on developing and optimizing the use of portable Laser-Induced Breakdown Spectroscopy (LIBS) for in-situ quantification of trace elements, especially lithium, in mineral deposits.

The project addresses several key aspects: developing calibrations specific to complex geological matrices, improving detection sensitivity through instrumental adjustments, and evaluating the performance of portable LIBS in varied field conditions. Preliminary trials were conducted on samples from lithium-rich pegmatite deposits at the Lithium Amérique du Nord and Whabouchi mines. These trials demonstrated that LIBS is capable of detecting lithium at concentrations similar to those found in pulverized rock samples and drill chips. The results were compared with available reference values, laboratory LIBS analyses by Elemission, and inductively coupled plasma optical emission spectroscopy (ICP-OES) results. Additionally, analyses of stockpiled rocks at the Whabouchi mine successfully distinguished ore from waste material.

This research will offer field and mining geologists valuable tools to accelerate, refine, and lower the costs of exploring strategic mineral resources. The methods developed will address technical challenges related to low-concentration trace element analysis, while optimizing field and lab detection techniques, ultimately enhancing mining operations and reducing exploration costs.

In the Chapais-Chibougamau region, the Opémisca Group (< 2707 to < 2691 Ma) is characterized by several sedimentary units followed by a late volcanic episode that is potassic alkaline and subaerial in nature (Haüy Formation). In the Ruisseau aux Alouettes sector (NTS sheet 32G13), work carried out by Beaudette, Daoudene, Bats and Ross in the summer of 2022 demonstrated the presence of subalkaline underwater volcanism contemporaneous with the Opémisca Group. The aim of this study is therefore to reassess the age, geochemistry and depositional environment of the volcanic rocks in the rest of the Opémisca, and more specifically in the Haüy Formation. This work will be carried out as part of a PhD at INRS and will combine regional-scale and detailed mapping with laboratory work (total rock geochemistry, petrographic analyses, U-Pb geochronological data on zircons).

During the summer of 2024, two sectors associated with the Haüy Formation were mapped. In the western part of the Chapais Syncline (sheet 32G14), mapping of the northern flank of the syncline identified 6 distinct lithologies, from north to south:

- turbidites associated with the Daubrée Formation;

- a sequence associated with the Haüy Formation, about 2.5 km thick, composed of mafic (V3) to intermediate (V2) porphyritic pyroxene volcanic rocks interbedded with a layer of trachytic feldspar V3-V2 contemporaneous with sedimentary rocks (mainly conglomerates and sandstones);

- aphanitic V2.

In the western part of the Waconichi Syncline (sheet 32J02), mapping work in the area has revealed 6 distinct lithologies previously attributed to the Christian Member. This sequence shows a normal polarity towards the south and consists, from base to top, of:

- turbidites associated with the Chebistuan Formation;

- a unit at least 3.5 km thick of feldspar-bearing trachytic V3-V2 associated with the Haüy Formation, including pillow facies intercalated with a layer of porphyritic V3-V2 or pyroxene volcanoclastite;

- trachytic V3-V2 containing feldspar and pyroxene;

- pyroxene-bearing porphyritic V3-V2. Several levels of sedimentary rocks are contemporaneous with the volcanic rocks.

The characteristics of these sequences suggest that the depositional environments mark the transition from a deep submarine environment (turbidites) to a shallow submarine or even subaerial environment (overlying volcano-sedimentary rocks).

The purpose of this project is to gain a better understanding of regional stratigraphy, a key tool in mineral exploration.

VMS deposits are known to form clusters, but factors influencing the fertility of volcanic centers, assemblages, or entire belts remain unclear. This is evident in the Archean Abitibi greenstone belt, where the 2723‒2720 Ma Stoughton-Roquemaure (S-R) assemblage accounts for less than 1% of the total VMS tonnage of the belt with 5 deposits and occurrences, whereas the 2704‒2695 Ma Blake River (BR) assemblage hosts 46% of the total VMS tonnage of the belt with over 40 deposits and occurrences.

To explore these disparities from a petrological perspective, we performed a comparative analysis of major and trace geochemical data (n=4541) for subalkaline volcanic rocks. Both the S-R and BR assemblages have varied volcanic rock types, although significant differences exist. Ultramafic rocks represent about 4% of the S-R assemblage, whereas they are absent in the BR. For the mafic to felsic volcanic rocks, a Principal Component Analysis identified Th, Yb, Zr, and Ti as the most influential variables among immobile elements, which were used to create a Ti/Zr vs. Th/Yb discrimination diagram. That diagram revealed 12 distinct clusters (or rock types) with similar geochemical behaviour and compositions.

Two dominant groups emerged: tholeiitic basalts and high-Th basalts (primarily calc-alkaline), together comprising ~46% of the dataset. The petrogenesis of tholeiitic basalts, which closely resembles the mantle-derived magmatic source, was further examined using Fractional-Crystallization (Magma Chamber Simulator) models. This approach highlighted the importance of parameters such as water content, pressure, and oxygen fugacity in generating distinct basalt compositions. Additionally, Assimilation-Fractional-Crystallization (AFC) models were developed to explain the presence of more evolved products, hypothesizing that interaction between tholeiitic basalts and a TTG-like continental crust could account for part of the observed geochemical diversity. Magma mixing models were also created to further explain some of the geochemical variations.

Our analysis indicates that VMS deposits in both assemblages are predominantly associated with the presence of mafic to intermediate volcanic rocks, often with transitional to calc-alkaline affinities. These geochemical compositions may result from AFC or magma mixing processes, which are driven by interactions between asthenospheric magmas and the crust. Such interactions may lead to substantial thermal maturation of the crust, promoting the development of evolved (intermediate to felsic) compositions. This suggests that these magma-crust interactions may play a favorable role in creating conditions conducive to VMS formation.

The Val-d'Or region is known for its gold-bearing quartz-carbonate ± tourmaline (QTC) veins formed in shear zones and intersecting greenschist facies metamorphosed rocks. Identifying the alteration associated with these mineralizations is essential for exploration. However, in the case of orogenic gold deposits, the small size of the alteration halos discernible by conventional methods makes this process difficult. The objective of this project is to characterize and vectorize the alteration associated with orogenic-type gold veins in the Ormaque and Triangle deposits (Eldorado Gold Quebec) located in Val-d'Or.

The gold-bearing QTC veins in the Triangle deposit include shear veins and, to a lesser extent, extensional veins hosted in a tuff and dioritic chimney. Alteration sequences vary according to lithology. In the tuff, the proximal halo of the veins, around 1 m thick, is characterized by strong foliation and sericite-carbonate-pyrite alteration. This is followed by a distal zone about 5 m thick, rich in chlorite. In the diorite, the proximal halo is less than a metre thick and shows a sericite-albite-carbonate assemblage. This is followed for a few metres by an intermediate chlorite-hematite halo, then a distal zone of plagioclase epidotization that can reach up to 15 m locally.

Mineralization at the Ormaque deposit consists mainly of extensive QTC veins hosted in a porphyritic diorite known locally as ‘Porphyre C’. Proximal alteration associated with these veins is characterized by tourmaline-carbonate-pyrite or albite-carbonate-pyrite assemblages, with thicknesses ranging from a few centimetres to 3 metres. Distal alterations are difficult to discern due to widespread chlorite-carbonate alteration and silicification that do not appear to be related to the QTC veins, as well as the presence of alterations associated with vein systems formed during hydrothermal episodes prior to the latter.

Sampling of altered rocks was carried out at various depths and distances from the gold-bearing QTC veins in the two deposits. These samples will be used to petrographically characterize the alteration halos at Ormaque and Triangle, and to better determine the extent of distal alteration. The major and trace element content of the various alteration minerals will be determined by electron microprobe and LA-ICP-MS. These results will be used to determine the geochemical imprint of the distal alteration associated with the gold-bearing veins, in order to establish vectorization criteria for the mineralization.

The ~ 45 Ma Miguel Auza epithermal deposit Ag-Zn (Pb) is located in the northern sector of the Mesa Central province along the Mexican Silver Belt. It stands out due to its older age of mineralization relative to other vein systems of the Mesa Central, and to the geometric relationship between the NE-SW trending mineralized hydrothermal veins and NW-SW striking post-mineralization calcite-rich veins. The argentiferous mineralization is hosted by Late Cretaceous turbidites, and locally by intermediate porphyritic intrusions and felsic cryptodomes. In order to characterize the tectono-magmatic and thermo-chronological evolution of the hydrothermal system, systematic petrography, geochemistry of major and trace elements, and fluid-inclusion microthermometry were used to identify the context and physico-chemical evolution of the vein systems.

The intrusions are of monzonitic and dioritic composition, with a calc-alkaline affinity; REE and multi-element diagrams show a volcanic arc-derived magma pattern. In the case of the felsic domes, they exhibit significant negative Nb-Ta, Ti and P anomalies, and an enrichment of Zr and Hf. In contrast, andesitic lavas that overlie the mineralized turbidite succession and intrusions, show a trace element signature indicative of an alkalic composition. These rocks are probably representing the onset of the Oligocene magmatism associated with extensional tectonics of the Basin and Range Province, which is still active in central and northern Mexico.

This work indicates a hydrothermal evolution including metric to centimetric sulfide-rich quartz-calcite veins and mantos-like mineralized zones that are characterized by: 1a) calcite ± pyrite with sphalerite, chalcopyrite and galena; 1b) quartz ± calcite with sphalerite (blende and marmatite), galena, minor chalcopyrite and arsenopyrite, pyrargyrite, tetrahedrite and acanthite; and 2) barren calcite-rich meter-wide veins with characteristic lattice bladed textures that crosscut the 1a and 1b stages. Detailed microthermometric analyses of primary fluid inclusions in quartz, calcite and sphalerite of both stages determined homogenization temperatures between 310 and 130 C°; and salinities that vary from 16 to 5 (wt.% NaCl equiv.). Stage 2 veins display overall lower homogenization temperatures between 195 and 132 °C, and salinities varying from 12 and 3.5 (wt.% NaCl equiv.), which may indicate a shallower or lower temperature hydrothermal system than in stage 1. Additional oxygen isotope analyses on quartz and calcite are underway to calibrate the isochoric correction and to obtain the emplacement pressure and temperature of the syn- and post-mineralization veins.

The Central-Western Grenville Province hosts numerous REE-rich alkaline intrusions formed during and after the Grenvillian orogeny (1090-980 Ma), a continent-continent collision along the southeastern margin of Laurentia. This study focuses on the Rivière Noire Intrusive Suite (RNIS), located north of Dolbeau-Mistassini, which intrudes the Lac-Saint-Jean anorthosite complex. The RNIS predominantly consists of clinopyroxenitic to locally gabbroic cumulate rocks enriched in titanite, apatite, and allanite, with REE concentrations reaching up to 0.3 wt.%, primarily hosted by allanite. These cumulates are crosscut by centimetric to metric fine-grained dykes of gabbro to monzonite, as well as by monzonitic to granitic pegmatite and aplite dykes. LA-ICP-MS U-Pb dating was performed on titanite and apatite from two pyroxenite samples, and on zircon from one monzonite (7005_B1), one syenitic aplite (7012_C1), and two syenitic pegmatites (7003_C1 and 7012_E1).

In the pyroxenite samples, two distinct dates populations were identified on different titanite grains: older dates of 1148 ±8 Ma and 1131 ±28 Ma, and younger dates of 1096 ±11 Ma and 1061 ±14 Ma. Apatite yielded dates of 1055 ±37 Ma and 933 ±8 Ma. The older titanite dates are interpreted as crystallization ages, whereas the younger titanite and apatite dates correspond to resetting events and/or cooling ages. Samples 7003_C1, 7005_B1, and 7012_C1 are interpreted to be coeval, consistent with crosscutting relationships observed in the field, as all ages fall within analytical error: 1123 ±8 Ma, 1116 ±5 Ma, and 1125 ±8 Ma (²⁰⁶Pb/²⁰⁷Pb weighted mean ages), respectively. Pegmatite 7012_E1 is a younger intrusion, with a ²⁰⁶Pb/²⁰⁷Pb weighted mean age of 1103 ±6 Ma. The variation in zircon trace element content, particularly in Yb/Gd ratios, supports the interpretation of a distinct generation for this pegmatite. Hf isotopic analyses were conducted on the same dated zircons, yielding consistent εHf ~ +4.5 across all samples. This value suggests that the RNIS source involves a metasomatized mantle component, as well as contributions from the Quebecia crust. The RNIS with its REE-rich mafic cumulate rocks is atypical in the Central-Western Grenville Province and is the first documented pre-Grenvillian REE-rich alkaline intrusion. It provides crucial insights into the geodynamic setting preceding the Grenvillian orogeny.

The Medium Pressure Allochthon Belt of the Grenville Province contains numerous intrusions of light rare earth-rich granitic pegmatites. These pegmatites formed between 1060 Ma and 970 Ma and are the result of the differentiation and crystallization of anatectic liquids. The Jacques Lake Pegmatite Swarm, in the Lac-Saint-Jean region of Quebec, is a typical example of these mineralizations. It consists of more than 100 undeformed granitic pegmatite dykes that cut a deformed, migmatitic metagabbro. Two families of dykes are recognized: white pegmatites of syenogranite composition and pink granitic pegmatites. Only the pink pegmatites are enriched in light rare earths, Nb and Th, mainly contained in allanite, monazite and pyrochlore. The surrounding metagabbro contains in situ leucosomes parallel to the foliation and is cut by mobilized leucosomes.

U-Pb dating coupled with Lu-Hf isotopic analysis was carried out using the LA-ICP-MS method on zircons obtained from the metagabbro, the mobilized leucosome and the two families of pegmatites. The metagabbro contains two distinct populations of zircon with textures typical of metamorphic zircons. Concordant grains from these two populations have ages of 1121 ±20 Ma and 1022 ±20 Ma, respectively. The former is interpreted as the age of the metamorphic peak, while the latter records a younger thermal event that affected the region. Both zircon populations have ε(Hf)t signatures of around +7. Zircons from the mobilized leucosome show concordant ages between 1150 Ma and 1030 Ma, with the majority forming a population with an age of 1069 ±3 Ma, interpreted as the crystallization age, and a ε(Hf)t value of around -0.4. The crystallization age of zircons in a white syenogranite pegmatite is 1050 ±5 Ma with a ε(Hf)t signature of about -2. The two pink granitic pegmatites yielded crystallization ages of 1006 ±2 Ma and 999 ±6 Ma and ε(Hf)t signatures of about -8. These results indicate that the Jacques Lake pegmatites were emplaced during two distinct post-metamorphic events from anatectic liquids derived from the partial melting of different rocks, as indicated by the distinct ε(Hf)t signatures of the zircons. While the ε(Hf)t signature of around -2 for the white pegmatites is consistent with magma from the partial melting of Allochthonous rocks, the value of around -8 for the pink pegmatites indicates partial melting of Parautochthonous rocks.

Four carbonatites in the Waswanipi-Saguenay alignment show great disparities in their niobium mineralization. Do their sources impact their potential to be mineralized? This section of the project seeks to determine the source of the four carbonatites of Saint-Honoré, Shipshaw, Girardville and Crevier and its use for exploration. These intrusions correspond to two periods: between 950 Ma-883 Ma for Crevier and Girardville and between 580 Ma-512 Ma for Saint-Honoré and Shipshaw. The Saint-Honoré, Crevier and Girardville intrusions are associated with nepheline syenites found, among others, as enclaves in the carbonatites, which is not the case at Shipshaw. Their structure also differs, with Saint-Honoré and Crevier having a concentric structure, Girardville forming a single dyke, and Shipshaw a swarm of dykes. Niobium mineralizations vary, as Saint-Honoré is economic with a pyrochlore and columbite mineralization in Nb, Crevier is sub-economic with a pyrochlore mineralization in Nb-Ta, Girardville is non-economic with an ilmenite mineralization in Nb, and Shipshaw is non-economic with only one type of low-volume dykes containing pyrochlore pseudomorphs. New U-Pb dating on apatite from the Shipshaw carbonatite on two dyke families gave 554 ±18 Ma for the small-volume dykes with the highest concentrations in Nb, while the more voluminous, Nb-poor dykes gave an age of 512 ±13 Ma. Ar-Ar dating on micas (from core to rim) was performed for the Girardville carbonatite (915.6 ±2.9 to 889.2 ±2.9 Ma) and the Saint-Honoré carbonatite (586.1 ±2.9 to 576.9 ±2.9 Ma). The isotopic results of Saint-Honoré (87Sr/86Sr ratios between 0.70292 and 0.70313 and 143Nd/144Nd between 0.51205 and 0.51211) indicate a mantle source similar to that of the Fen carbonatite, the layered intrusion at Sept-Îles, and the Norwegian E-MORB suite, all magmatic intrusions related to the Central Iapetus Magmatic Province (CIMP, ~615-550 Ma). This suggests that the most mineralized intrusion (Saint-Honoré) is related to the last stage of activity of the CIMP mantle plume. For exploration, these preliminary conclusions suggest that carbonatites formed in the context of a large magmatic province offer better potential to be niobium mineralized.

The Gaspé Peninsula is part of the Quebec Appalachians, formed in the Palaeozoic by the successive accretion of several independent terranes at the margin of Laurentia during the Taconian (495-450 Ma), Salinic (450-423 Ma) and Acadian (421-370 Ma) orogenies. The latter culminated in the collision of the Avalonia and Laurentia continents around 380-370 Ma.

The Gaspé Peninsula is host to numerous intrusions, including the large plutons of central northern Gaspé (McGerrigle Plutons, Mont Vallières de Saint Réal Pluton, Hog's Back Sill, etc.), as well as dyke swarms and sills scattered throughout the peninsula. These intrusions have been grouped together in the Lemieux Intrusive Suite. Local dating of this unit indicates emplacement ages of 440 Ma to 370 Ma, between the Taconian and Acadian orogenies. The Lemieux Intrusive Suite comprises mafic to felsic intrusions with varied signatures (tholeiitic, calc-alkaline and alkaline), indicating emplacement in different geodynamic contexts.

Some of the felsic intrusions in the Lemieux Intrusive Suite are associated with mineralization related to porphyry systems (Cu-Mo porphyries, polymetallic skarns, polymetallic epithermals). These are concentrated in two main corridors: Lemieux-Murdochville Dome and Ristigouche-Grand Pabos. The paucity of recent geochronological and geochemical studies on these intrusions means that it is not possible to precisely define the geodynamic environment in which these mineralizations formed. The aim of this project is to fill this gap. An initial field campaign collected 115 samples of intrusions, volcanic rocks and associated mineralization from across the Gaspé Peninsula. A total of 27 samples located along the two mineralization corridors were selected for U-Pb dating, trace element chemistry and Lu-Hf isotopic analysis on zircons. These results will be combined with lithogeochemistry and mineral chemistry to determine the age and nature of the Siluro-Devonian magmatism in the Gaspé region, as well as the emplacement context of the intrusions and associated copper mineralization.

The Paleoproterozoic Trans-Hudson Orogen (THO) in North America formed through the collision of the Superior Craton with other Archean terranes during the assembly of the Nuna/Columbia supercontinent, marking a complete Wilson cycle. The Ungava Orogen (UO) is a segment of the THO located in northern Quebec (Nunavik), comprising a remarkably well-preserved foreland fold-and-thrust belt and a less documented hinterland. The hinterland is divided into two domains: the Kovik Domain, interpreted as an exposure of the Superior Craton, and the Narsajuaq Domain composed of rocks ranging from the Archean to the Paleoproterozoic, metamorphosed to amphibolite and granulite facies. The hinterland metasediments are attributed to two main units: the Crony Metamorphic Suite, which surrounds the Kovik Domain, and the Erik Cove Complex, which forms kilometer-scale outcrops in the Narsajuaq Domain. The main goal of this doctoral project is to study the tectonometamorphic evolution of the UO hinterland to assess its geodynamic models during the Trans-Hudson orogeny (2-1.8 Ga).

U-Pb geochronology on detrital zircons helps determine the ages of various zircon populations and their maximum depositional age (MDA). These results provide insight into their geodynamic and paleogeographic contexts. During upper amphibolite and granulite facies metamorphism, detrital zircons can retain their magmatic growth with metamorphic overgrowths, but they can also reset inherited age and compositional information. Part of the project focuses on U-Pb ages of detrital zircons and the analysis of their textures and trace elements to determine their maximum depositional age (MDA) and potential sediment sources. The study also aims to compare differences in sources between the Kovik and Narsajuaq domains, as well as between the eastern and western parts, the hinterland and the foreland—a postdoctoral project is currently focusing on detrital zircons from the foreland.

In this scientific communication, preliminary results of detrital zircon geochronology show a diverse provenance in the Crony Metamorphic Suite, with southern occurrences deriving exclusively from the Archean basement, while northern occurrences include both Archean and Paleoproterozoic sources. The Erik Cove Complex, dominated by a Paleoproterozoic population dating to about 1.8 Ga, has not clearly preserved detrital zircons, which were likely recrystallized and formed overgrowths during high-grade metamorphism, coinciding with the Trans-Hudson orogeny.

Characterizing the various magmatic phases within Precambrian orogenic belts is crucial to understanding their tectono-magmatic evolution and better defining their metallogenic potential. The Southern Domain (SD) of the Cape Smith Belt is a Palaeoproterozoic volcano-sedimentary basin composed of three magmatic units, the oldest of which is the Beauparlant Formation, followed by the Cecilia Formation and finally the Chukotat Formation. Studies have attempted to determine the geodynamic context in which these units originated, but interpretations differ. Early work interpreted them as the result of a complete Wilson cycle and therefore suggested continental rift, hot spot and oceanic rift environments to explain the emplacement of the Beauparlant, Cécilia and Chukotat formations respectively. More recent research contradicts these conclusions and opts instead for a mantle plume model to explain the origin of the Beauparlant and Chukotat formations.

The aim of this study is to geochemically characterize these different formations in order to determine the geodynamic contexts in which they were emplaced. This will also enable us to determine the differences between the Chukotat Formation, which is rich in Ni-Cu mineralization, and the Beauparlant Formation, which is almost devoid of it. To this end, we carried out three N-S transects across the SD in order to select samples for geochemical analysis. We supplemented our data with a compilation of the analyses available in SIGÉOM.

Analysis of rare earths and Th/Yb and Nb/Yb ratios indicates that the rocks in the Beauparlant Formation are E-MORB, those in the Cecilia Formation are E-MORB/OIB and those in the Chukotat Formation are N-MORB. In addition, there is a certain degree of contamination by continental crust in the rocks of the Beauparlant and Chukotat formations. The signature of this contamination is similar in both units, suggesting a single source of contamination.

These preliminary results do not allow us to conclude on the origin of the Beauparlant Formation, but indicate hot-spot environments for the Cecilia Formation and mantle plume environments for the Chukotat Formation. These results are consistent with other recent studies carried out in the SD. We also note that the Beauparlant Formation is much richer in light rare earths than the Chukotat Formation. Finally, these results seem to indicate the absence of oceanic crust in the SD.

The St. Lawrence Platform in southern Quebec consists of a sequence of Cambro-Ordovician carbonate and siliciclastic units. This sequence also contains beds of K-bentonites and layers of altered volcanic ash found in the Ordovician sedimentary basins of eastern North America. The bedrock of southeastern Ontario and the Mohawk River Valley of New York State displays Late Ordovician sedimentary successions comparable to those in the St. Lawrence Valley, which also include bentonite beds. The chemistry of the unaltered primary minerals, zircon and apatite, can provide the chemical imprint of the different bentonite beds associated with distinct eruptions and provide a better understanding of their formation.

In southern Quebec, eight bentonite beds from the Trenton Group were sampled in a quarry on the east side of the island of Montréal, and an additional 40 samples were taken from boreholes in the City of Montréal, at the Lafarge quarry in Montréal-Est, and in boreholes drilled for the construction of Montréal metro infrastructure (tunnel, extension project, garage). Samples from two other beds were collected north of Québec City, eleven in south-eastern Ontario and nine in the Mohawk River Valley in New York State in equivalent formations.

The chemical composition of apatite grains, i.e. major elements (Ca, P), volatile elements (Cl, F), minor and trace elements (Mg, Mn, Eu, Y, Fe, Sr, Nd, Pb, Th, U), has enabled beds in southern Quebec, south-eastern Ontario and the Mohawk Valley to be linked. This technique makes it possible to correlate several samples from the same bed over more than 300 km, as well as the surrounding geological units in each of these regions. This information is important for understanding the geological and biological evolution of the Laurentian margin.

A multivariate statistical analysis combining multidimensional scaling and dissimilarity measurements makes it possible to consider all the variations in the composition of the apatite in 2D, to refine the correlations already established and to establish a reference composition for each bed. High-precision U-Pb dating and Hf isotopes in the zircon and Sr isotopes in the apatite confirm the accuracy of these correlations and make it possible to estimate the composition of the volcanic source. The overall chemical composition (trace elements and isotopes) of the zircon and apatite indicates that the bentonites come mainly from mafic arc magmas. This work provides a better understanding of the evolution of the Ordovician Laurentian margin during the Appalachian Orogeny.

In Quebec, legislation, through Directive 019, requires mines to manage their tailings effectively to prevent environmental pollution from their final effluents. The major environmental concern in the mining sector remains the oxidation of certain acid-generating mine tailings. A number of strategies have been put in place to prevent this oxidation by blocking contact between mine tailings and water or air. These strategies are best suited to non-oxidized mine tailings. For oxidized mine tailings, on the other hand, remediation requires several years of monitoring and treatment of the contaminated drainage water. In fact, the reducing conditions created by certain remediation methods (coupled monolayer covers with an elevated water table, covers with capillary barrier effects [CCBE] and water covers) can destabilize the secondary minerals that have accumulated since the beginning of AMD formation. These secondary minerals, such as iron oxyhydroxides, are then partially dissolved, releasing ferric ions and other constituents, thereby increasing the contamination of drainage water during the first few years following restoration.

The aim of this study was to identify the elements that promote the passivation or dissolution of iron oxyhydroxide layers, as well as the optimum concentrations of passivating/complexing agents to stabilize oxidized mine tailings. This study was carried out using batch tests and mini weathering cells. Initial results indicate that the addition of metasilicate as a passivating agent reduces the calcium and magnesium content of leachates. Iron contents were low, due to the neutral to basic pH values. Sulphate levels were significantly higher in experiments with a high concentration of sodium metasilicate, indicating a destabilization of secondary sulphate minerals such as gypsum and jarosite. These results are promising and could be combined with existing remediation methods to make the rehabilitation of oxidized mine tailings more effective.

The accurate determination of precious metal concentrations in ore samples is crucial to the mining industry. Although laser-induced breakdown spectroscopy (LIBS) has been used for this purpose, its detection limits are often insufficient to measure trace metals in these materials. Our study explores the potential of combining LIBS and laser-induced fluorescence (LIF) methods to improve the detection of platinum and palladium in these samples.

As part of this study, we established calibration curves using certified reference materials from the Lac des Îles palladium mine. The LIBS-LIF technique demonstrated a remarkable improvement in sensitivity, with a detection limit for platinum of 0.15 ppm for an average of 200 laser shots, two orders of magnitude lower than that of conventional LIBS. For palladium, the reduction in the detection limit was even more impressive, at around ten times lower than for platinum.

To validate the method, we analysed six quartz fragments from core samples taken from the Lac des Îles palladium mine to estimate palladium and platinum concentrations. The results obtained using the LIBS-LIF technique were largely consistent with those obtained using conventional chemical analysis, both for the surface analyses and for the pulverised rock samples. However, highly heterogeneous palladium grades in the ore were revealed on two occasions, underlining the technique's ability to detect local variations.

This study highlights the significant potential of the LIBS-LIF technique for accurately measuring low concentrations of precious metals in ore samples. The advantages offered by this method, notably its improved detection limits and its ability to analyse samples in their solid state, should make it possible to optimise exploration and extraction processes in the mining industry.

The sulphur isotopic composition (δ³⁴S) of magmatic apatite provides valuable information on the sources of the sulphur, the presence of crustal contamination, fluid exsolution processes, as well as the sulphate or sulphide saturation of the silicate liquid during the evolution of the magmatic system.

We will discuss the calibration of an LA-ICP-MS/MS instrument, a rapid and cost-effective technique for the in situ analysis of sulphur isotopes in apatite. The MS/MS configuration uses two series quadrupoles operating in tandem, between which is placed a reaction cell, using oxygen in this case. This allows isobaric interference to be eliminated by modifying the target isotope masses of ³²S and ³⁴S to ³²S¹⁶O and ³⁴S¹⁶O, respectively.

Apatite standards with known sulphur isotopic compositions were used to verify the accuracy, precision and reproducibility of the LA-ICP-MS/MS analyses and to optimize the method. Promising results were obtained using the following analysis parameters: fluence of 4 J/cm², beam size of 80 µm and repetition frequency of 15 Hz. Accuracy, precision and reproducibility were assessed using several secondary standards as well as additional analyses of the primary standard treated as unknown.

Analytical precision was determined on the basis of 20 analyses of each standard. It is noted that analytical accuracy improves with increasing sulphur concentration in apatite. The standard deviations obtained (1σ) on the δ³⁴S value are ±2.5 ‰ for the DLS standard (1272 ppm S), ±2.0 ‰ for OL-1 (2112 ppm S), ±1.1 ‰ for SLAP (3097 ppm S), ±1.4 ‰ for BR96 (3477 ppm S), ±1.4 ‰ for MG (3666 ppm S) and ±2.2 ‰ for Sly-1 (4115 ppm S). This initial non-optimized test demonstrates a reproducibility of approximately 2 ‰ (1σ) for isotopic analyses of sulphur in apatite by LA-ICP-MS/MS. The decrease in accuracy and precision correlated with lower sulphur concentrations in apatite is due to a relatively low signal-to-noise ratio, which limits the application of this method to apatites with higher sulphur content (> 1500 ppm) for the time being. The accuracy of the method is currently sufficient to trace sulphur sources and magmatic processes such as fluid exsolution.

Laser ablation coupled to mass spectrometry (LA-ICP-MS) is used to quantify the concentration of trace elements in low concentrations (parts per billion - ppb) over a surface area of less than 50 µm. The technique is flexible and versatile, allowing the quantification of numerous elements in various minerals (sulphides, oxides, carbonates, silicates, etc.). The concentration of these trace elements is useful for studying the origin and evolution of geological systems. UQAC's LabMaTer is equipped with two laser ablation systems (Femtoseconde and Excimer 193 nm) coupled to a time-of-flight mass spectrometer (ICP-ToF-MS) that allows ultra-fast scanning of the spectrum of atomic masses ranging from ²³Na to ²³⁸U. We have developed an analytical protocol for producing millimetre-scale chemical mapping with a resolution of 4 µm to 25 µm, which can be achieved 10x faster than with a conventional system.

In hydrothermal systems or in zones of alteration and remobilization, the distribution of trace elements can be particularly heterogeneous within a single mineral. In some situations, the phenomena studied are so complex that they are difficult to visualize using simple spot analyses. Chemical mapping is used to characterize the spatial distribution of trace elements in minerals. Calibration and quality control materials produced as part of this study have enabled analytical expertise to be developed for minerals carrying critical and strategic metals such as sulphides (pyrite, chalcopyrite, arsenopyrite, etc.) and oxides (magnetite, chromite, ilmenite, etc.). The recent development of a data processing protocol, in which we actively participated, makes it possible to map the distribution of trace elements in a complex geochemical matrix made up of different minerals. This innovative microgeochemical imaging tool significantly enhances petrographic observations by providing the user with the mineral chemistry of major and trace elements. LabMaTer is also developing a new 3D analysis technique on a micrometric scale. This innovative chemical imaging technique will make it possible to carry out in-depth analyses, no longer limiting analyses to the surface of the sample. In situations where the mineral phases are very small and less exposed at the surface (platinum group minerals, magmatic and mineral inclusions, etc.), this technique will make it possible to identify them and establish their composition, size and spatial location.

Geological processes are recorded in crystal shape and geochemistry. However, their morphology has long been described by qualitative criteria, in plain text, with minimal quantification based on visual roundness or shape charters. Thanks to technological advances in imaging and image analysis, we have been able to extract over 50 shape descriptors, enabling a quantitative description of grains; and while pre-existing studies of crystal size distribution have provided significant information on petrogenesis, a multi-descriptor analysis of grain shape promises novel interpretations. This poster presents an innovative method for quantitatively describing grains from micrometer to centimeter, selecting the optimal combination of descriptors to interpret geological processes.

Based on a comprehensive multidisciplinary literature review, the approach uses significant shape descriptors, computed with Python, and validated on generated images. Principal component analysis (PCA) combined with the image descriptors enabled various ideal shapes to be efficiently discriminated, and was successfully applied to a sample of galena grains. The results highlight the mutual influence of roundness, roughness and shape, explaining the challenges in identifying the best descriptors. The discriminative capacity of PCA and the complexity of selecting ideal descriptors demonstrate the relevance of this approach for quantitative morphological description.