The West Ansil deposit was the first Cu discovery in 25 years in the Noranda Central Camp. It has a combined indicated and inferred resource of ~1.2 Mt. Grades for the indicated resource are 3.4% Cu, 0.4% Zn, 1.4 g/t Au and 9.2 g/t Ag. The bulk of the resource is located in three massive sulphide lenses (Upper, Middle and Lower) that are entirely within the Rusty Ridge Formation above the Lewis exhalite. The mineralization in all three ore lenses consists of massive pyrrhotite + chalcopyrite + magnetite. Semi-massive sphalerite is restricted to the upper and lower parts of the Middle lens. Massive magnetite occurs at the center of the Upper and Middle lenses, where it replaces massive pyrrhotite. A striking feature of West Ansil is the presence of abundant colloform and nodular pyrite (+marcasite) in the massive sulphides. Late-stage replacement of massive pyrrhotite by colloform pyrite and marcasite, occurs mostly along the upper and lower contacts of the lenses.

The Gull Rapids area, Manitoba, lies on the Superior craton margin and forms part of the Superior Boundary Zone (SBZ), a major collisional zone between the Archean Superior craton and the adjacent Paleoproterozoic Trans-Hudson Orogen. There are two main rock assemblages at Gull Rapids: orthogneisses (of possible Split Lake Block origin) and supracrustal rocks (metavolcanic and metasedimentary). Late, crosscutting felsic and mafic intrusive bodies (mostly dykes and sills) are used to constrain the relative and absolute timing of deformation and metamorphism. <br /><br /> The Gull Rapids area records a complex tectonic history. The area experienced four generations of Neoarchean ductile and brittle deformation (G1 ? G4) and one of Paleoproterozoic ductile-brittle deformation (G5). G1 deformation produced the main foliation in the map area, as well as local isoclinal folding which may be related to an early shearing event. M1a prograde mid-amphibolite facies metamorphism is contemporaneous with the early stages of G1. Widespread, tight to isoclinal sheath folding during G2 was recorded in the supracrustal assemblage, and is the result of southwest-side-up, dextral shearing during the early shearing event. A ca. 2. 68 Ga widespread phase of granitoid intrusion was emplaced late-G1 to early-G2, and is rich in metamorphic minerals that record conditions of M1b upper-amphibolite facies peak metamorphism. M1b metamorphism, late-G1 to early-G2 deformation, and intrusion of this felsic phase are contemporaneous. M2 retrograde metamorphism to mid-amphibolite facies was recorded sometime after M1b. G1 and G2 structures were re-folded during G3, which was then followed by G4 southwest-side-up, dextral and sinistral shearing, contemporaneous with late pegmatite intrusion at ca. 2. 61 Ga. This was followed by mafic dyke emplacement at ca. 2. 10 Ga, and then by G5 sinistral and dextral shearing and M3 greenschist facies metamorphism or hydrothermal alteration at ca. 1. 80 Ga. <br /><br /> Deformation and metamorphism at Gull Rapids post-dates emplacement and deposition of gneissic and supracrustal rocks, respectively. This deformation and metamorphism, except for G5 and M3, is Neoarchean (ca. 2. 68?2. 61 Ga), and represents a significant movement of crustal blocks: km-scale shearing of the supracrustal assemblage and consequent uplift of the Split Lake Block. Late deformation and metamorphism (G5, M3) may be related to the Paleoproterozoic Trans-Hudson orogeny. The Neoarchean and Paleoproterozoic zircon populations in the geochronological data suggest that the Gull Rapids area largely experienced Neoarchean deformation and metamorphism with a weak Paleoproterozoic overprint. All of the evidence presented above suggests that the Gull Rapids area lies in a part of the Superior Boundary Zone, yet does not lie at the exact margin of the Superior craton, and therefore does not mark the Archean-Proterozoic boundary proper in northeastern Manitoba.

The Gull Rapids area, Manitoba, lies on the Superior craton margin and forms part of the Superior Boundary Zone (SBZ), a major collisional zone between the Archean Superior craton and the adjacent Paleoproterozoic Trans-Hudson Orogen. There are two main rock assemblages at Gull Rapids: orthogneisses (of possible Split Lake Block origin) and supracrustal rocks (metavolcanic and metasedimentary). Late, crosscutting felsic and mafic intrusive bodies (mostly dykes and sills) are used to constrain the relative and absolute timing of deformation and metamorphism. <br /><br /> The Gull Rapids area records a complex tectonic history. The area experienced four generations of Neoarchean ductile and brittle deformation (G1 ? G4) and one of Paleoproterozoic ductile-brittle deformation (G5). G1 deformation produced the main foliation in the map area, as well as local isoclinal folding which may be related to an early shearing event. M1a prograde mid-amphibolite facies metamorphism is contemporaneous with the early stages of G1. Widespread, tight to isoclinal sheath folding during G2 was recorded in the supracrustal assemblage, and is the result of southwest-side-up, dextral shearing during the early shearing event. A ca. 2. 68 Ga widespread phase of granitoid intrusion was emplaced late-G1 to early-G2, and is rich in metamorphic minerals that record conditions of M1b upper-amphibolite facies peak metamorphism. M1b metamorphism, late-G1 to early-G2 deformation, and intrusion of this felsic phase are contemporaneous. M2 retrograde metamorphism to mid-amphibolite facies was recorded sometime after M1b. G1 and G2 structures were re-folded during G3, which was then followed by G4 southwest-side-up, dextral and sinistral shearing, contemporaneous with late pegmatite intrusion at ca. 2. 61 Ga. This was followed by mafic dyke emplacement at ca. 2. 10 Ga, and then by G5 sinistral and dextral shearing and M3 greenschist facies metamorphism or hydrothermal alteration at ca. 1. 80 Ga. <br /><br /> Deformation and metamorphism at Gull Rapids post-dates emplacement and deposition of gneissic and supracrustal rocks, respectively. This deformation and metamorphism, except for G5 and M3, is Neoarchean (ca. 2. 68?2. 61 Ga), and represents a significant movement of crustal blocks: km-scale shearing of the supracrustal assemblage and consequent uplift of the Split Lake Block. Late deformation and metamorphism (G5, M3) may be related to the Paleoproterozoic Trans-Hudson orogeny. The Neoarchean and Paleoproterozoic zircon populations in the geochronological data suggest that the Gull Rapids area largely experienced Neoarchean deformation and metamorphism with a weak Paleoproterozoic overprint. All of the evidence presented above suggests that the Gull Rapids area lies in a part of the Superior Boundary Zone, yet does not lie at the exact margin of the Superior craton, and therefore does not mark the Archean-Proterozoic boundary proper in northeastern Manitoba.

Les cherts archéens permettent de contraindre les environnements primitifs qui ont vu l'apparition de la vie sur Terre. Ces roches siliceuses se forment selon trois processus : les C-cherts (cherts primaires) se forment par précipitation chimique de silice océanique sur le plancher, sous la forme d'une boue siliceuse ou en tant que ciment dans les sédiments de surface; les F-cherts (cherts de fracture) précipitent dans les fractures de la crôute depuis les fluides circulant; les S-cherts (cherts secondaires) sont issus de la silicification de roches préexistantes lors de la percolation de fluides enrichis en silice. Ces processus sont largement acceptés mais des questions majeures subsistent : comment reconnaître ces différents types de chert ? Quelle est l'origine de la silice et sous quelle forme a-t-elle précipité ? Quel signal chimique est porté par les cherts et comment s'en servir pour les reconstructions paléo-environnementales ? Ces questions sont abordées à travers trois sites de la ceinture de roches vertes de Barberton, en Afrique du Sud. L'approche adoptée combine l'analyse des structures sédimentaires et de déformation, de la pétrologie et de la composition chimique et isotopique de ces unités. Dans ces sites, la formation des cherts est étroitement liée à l'environnement de mise en place. La sédimentation clastique (turbidites) est à l'origine des C-cherts de Komati River, déposés sous la forme d'une boue siliceuse par adsorption de silice sur les particules argileuses en suspension. En absence de contribution continentale, les alternances de cherts noirs et blancs de Buck Reef sont interprétées comme issues de variations climatiques à l'échelle saisonnières (chert noir), voire glaciaires/inter-glaciaires (chert blanc). Les cherts de fracture de Barite Valley sont liés à la précipitation de silice depuis une suspension colloïdale thixotrope remontant à travers la croûte. La composition chimique des cherts est contrôlée par leur environnement de mise en place, et représente un mélange entre une phase siliceuse et une phase contaminante, indépendamment des processus qui ont précipité la silice. Les cherts de Komati River et de Barite Valley sont enrichis en Al, K, Ti, HFSE et en REE, ce qui est attribué à la contamination de la matrice siliceuse par la présence de phyllosilicate. Une telle contribution clastique peut expliquer les larges gammes de δ30Si dans les cherts de Komati River (-0.69‰à +3.89‰), et la majorité des valeurs positives est probablement liée à la contribution de l'eau de mer. Dans les dykes de Barite Valley, les δ30Si très négatifs (-4.5‰ à +0.22‰) sont cohérents avec l'origine hydrothermale basse température des fluides initiaux. A Buck Reef, l'absence de contribution continentale s'exprime dans les cherts blancs par une minéralogie exclusivement microquartzitique et par des concentrations extrêmement faibles en éléments traces (i.e. ΣHFSE et ΣREE<1ppm). 2% de carbonates et 3-4% de matériel continental (e.g. argiles) suffisent à masquer le signal siliceux dans ces cherts purs. Nous ne pouvons conclure sur la présence d'un signal océanique dans ces cherts par manque de fiabilité des proxys océaniques modernes (appauvrissement en LREE, enrichissement en La et Y). Reconnus à la fois dans des quartz océaniques, hydrothermaux, magmatiques et pegmatitiques, ils ne permettent pas d'identifier un signal d'eau de mer dans les cherts archéens. Les δ 18O de ces cherts indiquent la présence de circulations fluides secondaires à moins de 100°C, et leurs δ 30Si négatifs ou positifs (-2.23‰ et +1.13‰ en moyenne) montrent la contribution de fluides différents au moment de leur formation. Le couplage des observations pétrologiques et de terrain est la seule approche fiable pour reconnaître le mode de mise en place des cherts. Leur composition chimique dépend plus des conditions environnementales que des caractéristiques du fluide initial.

The West Ansil deposit was the first Cu discovery in 25 years in the Noranda Central Camp. It has a combined indicated and inferred resource of ~1.2 Mt. Grades for the indicated resource are 3.4% Cu, 0.4% Zn, 1.4 g/t Au and 9.2 g/t Ag. The bulk of the resource is located in three massive sulphide lenses (Upper, Middle and Lower) that are entirely within the Rusty Ridge Formation above the Lewis exhalite. The mineralization in all three ore lenses consists of massive pyrrhotite + chalcopyrite + magnetite. Semi-massive sphalerite is restricted to the upper and lower parts of the Middle lens. Massive magnetite occurs at the center of the Upper and Middle lenses, where it replaces massive pyrrhotite. A striking feature of West Ansil is the presence of abundant colloform and nodular pyrite (+marcasite) in the massive sulphides. Late-stage replacement of massive pyrrhotite by colloform pyrite and marcasite, occurs mostly along the upper and lower contacts of the lenses.

The North Caribou Terrane forms the core of Superior Province and records a protracted history of crustal growth and modification. At the centre of the North Caribou Terrane, lies the North Caribou greenstone belt, which is surrounded by granitoids of diverse compositions and ages. This study reports whole-rock geochemistry, zircon and titanite geochronology, and hornblende geobarometry on these plutonic rocks. Although zircons as old as 3132 ± 7 Ma were found, the main magmatic pulse occurred between 2880 and 2830 Ma, and geobarometry indicates tectonic thickening during this period. This was followed by widespread hydrothermal alteration and limited magmatism from 2760 to 2680 Ma, and shallow, brittle-ductile intrusions at circa 2630 Ma. From 2730 to 2630 Ma, intrusions were emplaced at increasingly shallow crustal levels. All of the rocks, except for the youngest pegmatitic intrusions, show similar patterns in major and trace elements, with a general trend toward more evolved compositions through time. These patterns indicate that the granitoids record mostly reworking of early intrusions, which is also consistent with patterns observed in the geochronology.

The giant Kidd Creek Mine is an Archean Cu-Zn-Ag deposit in the Abitibi Greenstone belt, located in the Superior Province of Canada and is one of the largest known base metal massive sulfide mines in the world with a tonnage of 170.7 Mt (Past production, Resource and Reserve). The massive sulfides in Mine D comprise a number of ore lenses that are interpreted to be the downplunge continuation of the Central orebody from the upper mine. These are referred to as the West, Main, and South lenses. The massive sulfides overlie a silicified rhyolitic unit at the top of a mixed assemblage of rhyolite flows, volcaniclastic sediments and ultramafic flows. The sheared nature of the fragmental units in the hanging wall of the deposit, at depth, illustrates the greater deformation that has occurred than in the upper mine. Metal zonation and the distribution of Cu stringer mineralization suggest that the West and Main lenses may be part of a single massive sulfide body (Main orebody) that has been structurally dismembered. The South Lens is a detached body, separated by late faults. The large Cu stringer zone beneath the West and Main lenses has a thickness of up to 150 metres, and is much broader and structurally remobilized in Mine D partially due to a newly identified series of vertically trending offset faults, that extends along the entire length of the massive sulfide bodies. A number of features of the North, Central and South orebodies in the upper part of the mine (e.g., Se-rich halo around Cu-rich zones) have been recognized in Mine D and provide an important framework for correlating the deep orebodies with the upper levels of the mine. Drilling below the current mine levels indicates that the massive sulfide and Cu stringer zones continue below 10,200 feet (3109 m) and highlight the remarkable continuity of the deposit downplunge with no end in sight. Two main ore suites have been recognized in the upper part of the mine and in Mine D: a low-temperature, polymetallic assemblage of Zn, Ag, Pb, Cd, Sn, Sb, As, Hg, ±Tl, ±W, and a higher-temperature suite of Cu, Co, As, Bi, Se, In, ±Ni. More than 25 different ore minerals and ore-related gangue minerals are present, including Co-As-sulfides, Cu-Sn-sulfides, Ag-minerals, and selenides. The massive ores consist mainly of pyrite, pyrrhotite, sphalerite, magnetite and chalcopyrite, together with minor galena, tetrahedrite, arsenopyrite, and native silver with a quartz and siderite gangue. Despite the high Ag content of the ores, the majority of the massive sulfides are remarkably Au poor except for a local gold zone that has been recognized in the deep mine in association with high-temperature mineralization. The trace elements in the ores exhibit strong zonation and diverse mineralogy. Spectacular albite porphyroblasts, up to 1 cm in size occur in the most Cu-rich ores of Mine D which are coincident with the peak of regional metamorphism and likely represent higher metamorphic or hydrothermal temperatures. Overall the orebodies have remained remarkably similar downplunge. However, unlike the upper part of the mine, pyrrhotite is dominantly hexagonal, only tetrahedrite was observed as the dominant sulfosalt, and magnetite occurs as both blebby porphyroblasts and as abundant intergrowths with sphalerite-chalcopyrite ores and siderite. These characteristics suggest that the deep mine has been subjected to higher metamorphic temperatures, possibly related to depth of burial, and that the original hydrothermal fluids may of had a lower H2S/CO2 and/or higher temperatures.

The North Caribou Greenstone Belt (NCGB) lies at the core the granitoid-dominant North Caribou Terrane (NCT). Two sedimentary assemblages; the Eyapamikama (ELS) and Zeemal-Heaton Lake (ZHA) form the core of the NCGB. Geochemistry of garnets from the orogenic Au deposit at Musselwhite suggest that the auriferous fluids have a contribution of metamorphic fluids and mineralization consisted of prolonged, multi-stage periods. Chemical zoning suggests changes in the influx of chalcophile and lithophile elements and that Au/sulphide ratios during nucleation were lower relative to later growth events. Zircons from the ELS and ZHA suggest a c. 100 My hiatus in the onset of sedimentation, with the ZHA showing younger, “Timiskaming-type” ages. Age distributions from each assemblage reflect proximal, igneous sources. Nd isotopic compositions of the ZHA suggest a mixture of ancient and contemporaneous sources which are similar to external TTG rocks. Deplete mantle model ages of the ZHA rocks indicate a Mesoarchean inheritance.

Les processus d’anatéxie représentent la première étape dans la genèse des granites. La fusion partielle de la croûte inférieure peut produire des structures leucocrates à signatures chimiques particulières, très différentes. Par conséquent le lien qui existe entre certaines migmatites et les granites crûstaux peut être ambigu. Ce projet de thèse est une étude de l’évolution des processus d’anatexie au sein des métapelites de la formation de Bandelierkop dans le Zone Marginale Sud de la Ceinture du Limpopo en Afrique du Sud. Ce travail comprend une étude complête du métamorphisme, de la géochimie et de la géochronologie des paragneiss granulitiques de deux carrières dans la zone nord de la Zone Marginal Sud, la carrière de Bandelierkop et la carrière de Brakspruit, où la fusion partielle d’une croûte néoarchéenne peut être observée. Le projet a pour but de répondre à deux problématiques principales: (1) contraindre de manière précise les conditions et l’âge de l’épisode métamorphique de la Zone Marginale Sud, avec ce que cela implique pour la géodynamique archéenne, (2) comprendre les réactions de fusion partielle en absence de fluide et leur contrôle sur la chimie des migmatites et le liens qui existent entre les leucosomes, la source, le liquide de fusion et les granites de type S. Les informations P-T-t enregistrées dans les métapelites de la formation de Bandelierkop, contraintes par des diagrammes d’équilibre de phase ainsi que de la géochronologie sur zircon, donnent une idée sur les processus de différentiation crustale dans la croûte inférieure. Les roches des deux carrières enregistrent les conditions de pic de métamorphisme de 840-860 oC et 9-11 kbar a c. 2.71 Ga. Cet épisode est accompagné d’une production importante de leucosome (L1). Des leucosomes de seconde génération (L2) sont produits pendant la décompression à 6-7 kbar. La fin de l’épisode métamorphique est marquée par la transition granulites/amphibolites (< 640 oC) à c. 2.68 Ga. L’âge de dépôt maximum (c. 2.73 Ga) des zircons détritiques dans les métapelites indique un enfouissement rapide ( 0.17 cm.y-1). L’ensemble de ces données montre que la Zone Marginale Sud contient des sédiments déposés dans des conditions de marge active durant un phénomène de convergence. Les métapelites ont par conséquent subi leur métamorphisme et leur fusion partielle durant une collision continentale le long de la marge nord du craton du Kaapvaal à c. 2.7 Ga. Les formations leucocrates générées le long du trajet P-T-t possèdent une signature géochimique spécifique caractérisée par une teneur en K2O et FeO+MgO faible et une teneur élevée en CaO. La combinaison des observations de terrains, de la cartographie chimique et des analyses géochimiques permet de conclure que la majeure partie des leucosomes (L1) cristallisent avant le pic de métamorphisme après extraction du liquide de la source. En s’appuyant sur le laboratoire naturel qu’est la Zone Marginale Sud et utilisant une approche modélisatrice, cette étude présente les détails de la formation des leucosomes. Ce travail démontre que la formation de leucosomes pauvres en potassium dans les sédiments de la croûte inférieure et les processus qui contrôlent la chimie du résidu et des granites de type S sont les différences des volumes d’équilibration et l’hétérogénéité de la source couplées avec des pertes de liquide et diffusion de l’eau dans les structures d’anatexies / Anatexis is the first step in granite genesis. Partial melting in the lower crust may produce leucoratic features of unusual chemical compositions, very different from the final products of crustal differentiation. Therefore, the links that exists between some migmatites and crustal-derived granites can be ambiguous. This study is an investigation of the anatectic history of a high-grade terrain: the Southern Marginal Zone of the Limpopo Belt (SMZ), north to the Kaapvaal Craton in South Africa. The work involved an integrated field, metamorphic, geochemical and geochronogical study of the metasedimentary granulites from two separate quarries in the northern zone of the Southern Marginal Zone, the Bandelierkop quarry and the Brakspruit quarry, where Neoarchean high-grade partial melting features can be observed. The project has aimed to address two main issues: (1) to accurately constrain the pressure temperature conditions and the age of the metamorphic episode in the SMZ, with implication for the geodynamic processes near the end of the Archean, (2) to investigate the fluid-absent partial melting reactions that control formation of K2O-poor leucosomes and to understand the chemical relationships in the system source-leucosome-melt–S-type granite. The P-T-t record retained in the Bandelierkop Formation metapelites, constrained by phase equilibria modelling as well as zircon LA-ICP-MS geochronology, gives an insight into crustal differentiation processes in the lower crust. Rocks in both quarries indicate high-temperature metamorphism episodes with peak conditions of 840-860 oC and 9-11 kbar at c. 2.71 Ga with formation of leucosomes (L1) during the prograde path. Minor leucocratic features (L2) were produced during decompression to 6-7 kbar. The end of the metamorphic event is marked by the granulites/amphibolites facies transition (< 640 oC) at c. 2.68 Ga. The maximum deposit age for the detrital zircons in the metapelites (c. 2.73 Ga) indicates a rapid burial process ( 0.17 cm.y-1). Those evidences strongly support that the Southern Marginal Zone contains sediments deposited in an active margin during convergence, and that the metapelites were metamorphosed and partially melted as a consequence of continental collision along the northern margin of the Kaapvaal Craton at c. 2.7 Ga. The leucocratic features generated along this P-T-t path display an unusual chemistry with low K2O and FeO+MgO content and high CaO content. The combination of field observations, chemical mapping and geochemical analyses leads to the conclusion the major part of the leucosomes (L1) crystallized prior to syn-peak of metamorphism concurrent with melt extraction from the source. This study documents the details of leucosomes formation using field observations in the Southern Marginal Zone and numerical modelling. This work demonstrates that the formation of K2O-poor leucosome in the metasedimentary lower crust is controlled by the difference in volume of equilibration and heterogeneities within the migmatites. The partial melting of the source coupled with melt loss and water diffusivity within the melt transfer site is a potential mechanism to explain the chemical link in the system residuum–melt–S-type granite

The West Ansil deposit was the first Cu discovery in 25 years in the Noranda Central Camp. It has a combined indicated and inferred resource of ~1.2 Mt. Grades for the indicated resource are 3.4% Cu, 0.4% Zn, 1.4 g/t Au and 9.2 g/t Ag. The bulk of the resource is located in three massive sulphide lenses (Upper, Middle and Lower) that are entirely within the Rusty Ridge Formation above the Lewis exhalite. The mineralization in all three ore lenses consists of massive pyrrhotite + chalcopyrite + magnetite. Semi-massive sphalerite is restricted to the upper and lower parts of the Middle lens. Massive magnetite occurs at the center of the Upper and Middle lenses, where it replaces massive pyrrhotite. A striking feature of West Ansil is the presence of abundant colloform and nodular pyrite (+marcasite) in the massive sulphides. Late-stage replacement of massive pyrrhotite by colloform pyrite and marcasite, occurs mostly along the upper and lower contacts of the lenses.