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Abstract
The Labrador Trough contains world-class iron deposits which have been mined since 1954. The direct shipping of Knob Lake ores were mined at Schefferville from 1954 to 1982. Concentrate production began in 1961 in the southwest end of the Trough, with three mines currently producing concentrate and pellets at a rate of 35 Mt per year. West and north of Schefferville, several billion tonnes of taconite have been outlined in fine-grained, cherty magnetite iron formation. Several deposits of highly metamorphosed magnetite-specularite iron formation are located west of Ungava Bay. Numerous studies have shown that this medium- to fine-grained iron formation can be beneficated to 66% to 68% iron. In the area from Wabush Lake to Mont-Wright, a medium- to coarse-grained friable specularite-quartz iron formation is repeated by folding to form several large deposits. In this area, three mining operations are located with reserves and resources in the order of 5 billion tonnes. The iron deposits occur within iron formation in sediments in the extensive Proterozoic geosyncline called the Labrador Trough. Several facies of iron formation within the Sokoman Formation reflect variations in chemical composition and depositional conditions. The correlation between the mineralogy and textures is discussed to illustrate the development of different types of iron ores. This band extends for about 1100 km southeast of Ungava Bay through both Quebec and Labrador. Further south, it turns southwest past the Wabush and Mont-Wright areas to within 300 km of the St. Lawrence River. The iron formation is essentially folded and faulted along most of its length. The degree of metamorphism is variable, ranging from intense in the northern and southern portions to greenschist facies in the central portion. The stratigraphy, structure and mineralogy of the producing mines are described along with the history of discoveries. Geological input is required to achieve the strict specifications of the international iron ore market. © 2001 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.
... Mining exploration in the area began around 1950. It later led to the creation of the Mont-Wright mining complex and the municipality of Fermont, which were built between 1971 and 1974 (Neal 2000). The mine is located 15 km west of the town, outside the watershed of Lac Carheil. ...
... The Fermont region is part of the parautochthonous belt in the Grenville geological province of the Canadian Shield (Rivers et al. 1989). It is also located in the southern part of the Labrador Trough, rich in iron ore deposits (Neal 2000). The bedrock is mainly composed of gneisses, schists, and metasedimentary iron units, including small amounts of carbonates that are overlain by younger layers of gabbros, granites, syenites, migmatites, and amphibolites. ...
... We interpret their high concentrations in the black laminae as a sign of high abundance of clastic iron and manganese oxide minerals in the sediments (e.g., magnetite, hematite, manganite). Many of these minerals have a dark (black) color and can be abundant in the Labrador Trough (Neal 2000). Observations of both pale and black sand deposits on the beaches of Lac Carheil and other lakes around Fermont clearly demonstrate that the erosion of the bedrock in this region provides 2 different types of naturally segregated sediments ( Figure S3). ...
Jacques O, Pienitz R, Ibrahim G. 2020. Paleolimnological assessment of long-term changes in a boreal recreational lake of the Fermont mining region (subarctic Quebec, Canada). Lake Reserv Manage. 36:314–334.
Lac Carheil is a boreal recreational lake located near Fermont, a remote town of subarctic Quebec built in the 1970s to support iron ore mining activities. Harmful cyanobacterial blooms were recently observed at its surface, suggesting that it suffered from eutrophication. However, long-term water quality data were lacking to properly understand its current condition. We therefore undertook a paleolimnological study to investigate past limnological changes in the lake based on the multiproxy analysis of sediment cores. The cores retrieved from Lac Carheil were marked by numerous distinct laminae representing past episodes of high-energy events in the lake catchment. Furthermore, diatom assemblages of the sediments revealed that the limnological conditions of the lake had been relatively stable for more than a thousand years before beginning to change around 1840 AD. This was mainly evidenced by the emergence of species indicative of nutrient enrichment (e.g., Aulacoseira subarctica, Fragilaria crotonensis), which suggested an early eutrophication potentially attributable to climate change. The period of modern settlement (1971–2015) was characterized by a decrease in the carbon to nitrogen ratio (C/N) of the sediments, and marked increases in their organic matter content, diatom total abundance, and diatom-inferred total phosphorus concentrations, which indicated an enhanced primary production. Nevertheless, our results suggested that the disturbance level of the lake was weak and that its prospect for recovery is good. Our study provides valuable reference data to assist the management of Lac Carheil, and reveals first insights into the sedimentological and limnological history of the Fermont mining region.
... Unenriched primary iron formation is a major source of iron ore in many parts of the world, especially China and North America, and includes both magnetite-and hematiterich iron formation. In North America, the term taconite is used to describe magnetite-and hematite-rich BIF and/or GIF ore with >30 wt percent Fe (James, 1954;Neal, 2000). In Australia and Brazil, little unenriched iron formation ore has been mined to date due to the presence of significant resources of direct-ship or easy to beneficiate high-grade hematite and martite-goethite ore. ...
... Where observed, the geology and mineralogy of the iron formation ores are similar to the surrounding uneconomic iron formation, except that the ore zone contains more abundant and coarser grained magnetite (Fig. 5A) or hematite, less gangue inclusions in magnetite, or a higher percentage of iron oxide meso-and/or microbands compared to silicate-or carbonate-rich mesobands (Fig. 5B). Iron formation ores are commonly located in greenschist-to amphibolite-facies terrane, with the higher metamorphic grade associated with coarser magnetite grain size and more discrete grains of gangue (Neal, 2000). Sub-to lower greenschist-facies iron formations such as those in Australia and Brazil are commonly uneconomic, since the magnetite is either very fine (Fig. 5C, D) or contains very fine inclusions of gangue which require expensive fine grinding to liberate prior to beneficiation. ...
... In taconites that are easier to process, the ore and gangue minerals may be coarse grained (0.05-2.0 mm) and low in porosity, and the ore minerals may be relatively free of very fine (<5 µm) gangue inclusions. They are primarily the result of metamorphic recrystallization to relatively coarse grain size (Neal, 2000). ...
... Mont-Wright is an iron ore deposit occurring in the Labrador Trough, located in Northeastern Quebec, Canada. It is the largest openpit mine in Quebec with an ore having iron content varying between 25% and 35%, and low contents of aluminium, manganese and phosphorus (Neal, 2000). Exploited by ArcelorMittal Mines Canada, Mont-Wright produces annually 25 million tonnes of iron ore concentrate by spirals, grading 66% Fe. ...
... More than 90% of the iron ore at Mont-Wright occurs as hematite. The most important unit consists of granular recrystallized specular hematite and minor amounts of magnetite normally found as small inclusions in hematite (Neal, 2000;Petruk, 2000). The main gangue mineral is quartz, which usually presents a sugary texture, with less than 3% of other gangue minerals (especially muscovite, biotite and hornblende, but also Ti oxides, such as ilmenite and Ti-magnetite, and garnet). ...
... The main gangue mineral is quartz, which usually presents a sugary texture, with less than 3% of other gangue minerals (especially muscovite, biotite and hornblende, but also Ti oxides, such as ilmenite and Ti-magnetite, and garnet). At the eastern part of the deposit, an amphibole quartz iron formation with higher magnetite content is found (Neal, 2000). Amphibolite (which is a highly altered gabbro) occurs commonly adjacent to or within the iron formation (Neal, 2000). ...
Ore texture has been traditionally used by geologists during geological mapping and logging for mine planning. However, using textural information for mineral processing prediction has been rarely explored. In this paper, the correlation between the ore texture (as observed from the surface of drill cores) and the core samples response to lab scale mineral processing operations was studied for the Mont-Wright iron ore deposit (Quebec, Canada). The potential of drill core textures as a geometallurgical indicator was assessed.
Through the mineralogical characterization of the Mont-Wright textures, differences were observed in the iron oxides liberation and grain size distribution, and in the iron-by-size pattern associated to each drill core texture. These differences were reflected in the samples processing performance: different trends were observed in the comminution response and iron oxides separability by heavy liquid separation. According to these results, a classification of ore textures calibrated to mineral processing performances was established for the Mont-Wright deposit. This classification is intended to serve as geometallurgical indicator.
... Unenriched primary iron formation is a major source of iron ore in many parts of the world, especially China and North America, and includes both magnetite-and hematiterich iron formation. In North America, the term taconite is used to describe magnetite-and hematite-rich BIF and/or GIF ore with >30 wt percent Fe (James, 1954;Neal, 2000). In Australia and Brazil, little unenriched iron formation ore has been mined to date due to the presence of significant resources of direct-ship or easy to beneficiate high-grade hematite and martite-goethite ore. ...
... Where observed, the geology and mineralogy of the iron formation ores are similar to the surrounding uneconomic iron formation, except that the ore zone contains more abundant and coarser grained magnetite (Fig. 5A) or hematite, less gangue inclusions in magnetite, or a higher percentage of iron oxide meso-and/or microbands compared to silicate-or carbonate-rich mesobands (Fig. 5B). Iron formation ores are commonly located in greenschist-to amphibolite-facies terrane, with the higher metamorphic grade associated with coarser magnetite grain size and more discrete grains of gangue (Neal, 2000). Sub-to lower greenschist-facies iron formations such as those in Australia and Brazil are commonly uneconomic, since the magnetite is either very fine (Fig. 5C, D) or contains very fine inclusions of gangue which require expensive fine grinding to liberate prior to beneficiation. ...
... In taconites that are easier to process, the ore and gangue minerals may be coarse grained (0.05-2.0 mm) and low in porosity, and the ore minerals may be relatively free of very fine (<5 µm) gangue inclusions. They are primarily the result of metamorphic recrystallization to relatively coarse grain size (Neal, 2000). ...
... One of the typical examples of late Palaeoproterozoic iron formations is the 1.88 Ga Sokoman Iron Formation in the Labrador Trough, Canada. The world-class late Palaeoproterozoic iron ore deposits, hosted extensively in the Sokoman Formation along the trough, have been mined for more than half a century (Clark & Wares, 2006;Neal, 2000). The Sokoman Formation, a 100 m-thick succession composed of alternating bands of silica and iron oxide accompanied by late silicate and early carbonate facies (Neal, 2000), is a remarkable unit of iron formation which hosts 80% of iron ores in the central Labrador Trough (Gross, 1968). ...
... The world-class late Palaeoproterozoic iron ore deposits, hosted extensively in the Sokoman Formation along the trough, have been mined for more than half a century (Clark & Wares, 2006;Neal, 2000). The Sokoman Formation, a 100 m-thick succession composed of alternating bands of silica and iron oxide accompanied by late silicate and early carbonate facies (Neal, 2000), is a remarkable unit of iron formation which hosts 80% of iron ores in the central Labrador Trough (Gross, 1968). Iron formations in Sokoman thus provide an opportunity to examine the origin of the late Palaeoproterozoic GIFs. ...
... The western part of the central Labrador Trough preserves 'early' mineral assemblages, showing rather original sedimentary textures and structures. It has only undergone late-diagenesis and low-grade metamorphism of sub-greenschist to greenschist (Dimroth and Chauvel, 1973;Zajac, 1974;Klein, 1974;Klein & Fink, 1976;Neal, 2000;Williams and Schmidt, 2004). Multiple volcanism in the Nimish area commenced at the first cycle of the Kaniapiskau Supergroup. ...
... One of the typical examples of late Palaeoproterozoic iron formations is the 1.88 Ga Sokoman Iron Formation in the Labrador Trough, Canada. The world-class late Palaeoproterozoic iron ore deposits, hosted extensively in the Sokoman Formation along the trough, have been mined for more than half a century (Clark & Wares, 2006; Neal, 2000). The Sokoman Formation, a 100 m-thick succession composed of alternating bands of silica and iron oxide accompanied by late silicate and early carbonate facies (Neal, 2000), is a remarkable unit of iron formation which hosts 80% of iron ores in the central Labrador Trough (Gross, 1968 ). ...
... The world-class late Palaeoproterozoic iron ore deposits, hosted extensively in the Sokoman Formation along the trough, have been mined for more than half a century (Clark & Wares, 2006; Neal, 2000). The Sokoman Formation, a 100 m-thick succession composed of alternating bands of silica and iron oxide accompanied by late silicate and early carbonate facies (Neal, 2000), is a remarkable unit of iron formation which hosts 80% of iron ores in the central Labrador Trough (Gross, 1968 ). Iron formations in Sokoman thus provide an opportunity to examine the origin of the late Palaeoproterozoic GIFs. ...
... The western part of the central Labrador Trough preserves 'early' mineral assemblages, showing rather original sedimentary textures and structures. It has only undergone late-diagenesis and low-grade metamorphism of sub-greenschist to greenschist (Dimroth and Chauvel, 1973; Zajac, 1974; Klein, 1974; Klein & Fink, 1976; Neal, 2000; Williams and Schmidt, 2004). Multiple volcanism in the Nimish area commenced at the first cycle of the Kaniapiskau Supergroup. ...
This is one of our studies on compositions of magnetite using Laser-ICP-MS.
... The Labrador trough was first described by Father Babel, a Jesuit Priest, who observed iron-rich rocks during his travels from 1866 to 1870 (Conliffe et al., 2013). In 1892, Dr. A. P. Low of the Geological Survey of Canada investigated this discovery, describing iron ore in the Dyke Lake and Koksoak River areas (Neal, 2000). These investigations spiked public interest and initiated a season of intense exploration. ...
... These investigations spiked public interest and initiated a season of intense exploration. In 1929, Dr. W. James and Dr. J. Gill discovered the first of many high-grade iron ore deposits near Knob Lake; however, exploration was halted as a result of the 1930s market crash (Neal, 2000). In 1936, private companies began to explore the Labrador Trough for base metals and, specifically, for iron. ...
3D geological modelling is becoming an effective tool for communication and development of geological understanding. This is due to increased computer performance and availability of improved geological modelling software. 3D geological modelling technology has reached the stage where it can be implemented in regionally extensive and geologically complex settings, with the ability to achieve geological insight beyond what could otherwise have been gained through 2D investigations alone. Insight includes better constrained fault and horizon topologies, refined fold geometries, improved understanding of tectonic processes, and characterization of deformational events. By integrating field observations, aeromagnetic maps, and 3D modelling techniques in the northern Labrador Trough, a regionally extensive and structurally complex geological environment, regional faults geometries and topological relationships were refined. Additionally, a new fault, the Ujaralialuk Fault, and two shear zones were interpreted. During modelling, several challenges were identified, including higher computational costs for regionally extensive models, sparse 3D constraints, algorithmic limitations related to complex geometries, and the large investment of time and effort required to produce a single model solution. A benefit of this investigation is that new insight was also gained for a greenfields region which may assist future exploration efforts. Developing 3D models in challenging environments allows for better definition of future workflow requirements, algorithm enhancements, and knowledge integration. These are needed to achieve a geologically reasonable modelling standard and gain insight for poorly constrained geological settings. iv
... The Iron Ore Company of Canada, which opened up these western Labrador deposits in 1954, was formed by the Hollinger North Shore Exploration, the M.A. Hanna Company (Cleveland) and other steel companies (Geren 1990;Neal 2000). The steel companies needed to replace output from the Lake Superior district, which was depleted after the war. ...
... The discovery and documentation of the iron-bearing rocks of the Labrador Trough is obviously a tremendously significant product of Low's geological work. The elemental compositions of some rocks that he collected as reported in 1896 are remarkably similar to those reported by Neal (2000) from modern geochemical analyses over 100 hundred years later. In addition to the iron, there has been mineral exploration conducted over the anorthosites that Low mapped at Lake Michikamau (Smallwood Reservoir) and Ossokmanuan Lake. ...
In 1893–1894, Albert Peter Low of the Geological Survey of Canada, along with D.I.V. Eaton and four indigenous assistants explored the Labrador Peninsula, then perceived as one of the last great unexplored wilderness areas of North America. The expedition left Lake St. John (now Lac St. Jean) on June 17, 1893, canoeing across the northeastern edge of the North American continent, arriving at Fort Chimo (now Kuujjuaq) on August 27, 1893. They departed Fort Chimo by steamer for Rigolet on the Labrador coast and the Hudson Bay Company post at North West River in the fall of 1893. On March 6, 1894 the party started up the Grand (now Churchill) River continuing through large central lakes into the Ashuanipi river system in western Labrador, then out via the Attikonak River to the Romaine River and finally the Saint Jean river system to arrive at Mingan on the north shore of the St. Lawrence River on August 23, 1894. Low described their fifteen-month journey as having covered over 8700 km including 1600 km on foot, over 4700 km in canoe, 800 km by dog team and 1600 km by steamer. The report from the expedition provides a compendium on the natural history of the region as well as the first geological maps. In terms of economic and scientific results, the greatest was documentation of the vast iron ore deposits of western Labrador; a world-class mining district that has been producing for sixty-three years since 1954. Low’s account also provides details on the essence of such an epic journey, which stands as a classic in the annals of Canadian geological surveying.RÉSUMÉEn 1893–1894, Albert Peter Low de la Commission géologique du Canada, accompagné du D.I.V. Eaton et quatre assistants autochtones ont exploré la péninsule du Labrador, alors perçue comme l'une des dernières grandes étendues sauvages inexplorées d’Amérique du Nord. L’équipe a quitté le Lake St. John (aujourd'hui le lac Saint-Jean) le 17 juin 1893, a traversé la bordure nord-est du continent nord-américain en canoë, et est arrivé à Fort Chimo (aujourd'hui Kuujjuaq) le 27 août 1893. À l'automne de 1893, ils ont quitté Fort Chimo à bord d'un vapeur pour Rigolet, sur la côte du Labrador, et le poste de la Compagnie de la Baie d'Hudson sur la rivière North West. Le 6 mars 1894, les membres de l'équipe ont remonté la rivière Grand (aujourd'hui Churchill), puis à travers les grands lacs centraux jusqu'au bassin de la rivière Ashuanipi, dans l'ouest du Labrador, puis, par la rivière Attikonak jusqu' à la rivière Romaine et, enfin, le réseau de la rivière Saint-Jean jusqu’à Mingan, sur la rive nord du fleuve Saint-Laurent, le 23 août 1894. L’excursion décrite par Low a duré quinze mois et parcouru plus de 8700 km dont 1600 km à pied, plus de 4700 km en canoë, 800 km en attelage de chiens et 1600 km en bateau à vapeur. Le rapport de l'expédition constitue un recueil sur l'histoire naturelle de la région ainsi que des premières cartes géologiques. En ce qui concerne les répercussions économiques et scientifiques, la plus importante en a été la documentation des vastes gisements de minerai de fer de l'ouest du Labrador, un district minier de classe mondiale, en production pendant soixante-trois ans depuis 1954. Le récit de Low fournit également des détails sur le caractère épique d’une telle expédition, laquelle est un classique dans les annales de la Commission géologique du Canada.
... In a previous work, Pérez-Barnuevo et al. (2017) established a rock texture classification calibrated to mineral processing performance for the Mont-Wright iron ore deposit. This deposit is located in Northeastern Québec (Canada) where more than 90% of the iron ore consists of granular recrystallized specular hematite (Neal, 2000;Petruk, 2000). At the eastern part of the deposit, an amphibole quartz iron formation with higher magnetite content is found (Neal, 2000). ...
... This deposit is located in Northeastern Québec (Canada) where more than 90% of the iron ore consists of granular recrystallized specular hematite (Neal, 2000;Petruk, 2000). At the eastern part of the deposit, an amphibole quartz iron formation with higher magnetite content is found (Neal, 2000). The main gangue mineral is quartz that usually presents a sugary texture, with less than 3% of other gangue minerals, such as micas, amphiboles, ilmenite and garnet. ...
In a previous work, the use of drill core texture as a geometallurgical indicator was explored for the Mont-Wright
iron ore deposit. At this deposit, the link between texture and mineral performance during comminution and
heavy liquid separation was assessed by laboratory tests. Additionally, the micro-texture associated to each
macro-texture was characterized by Mineral Liberation Analyzer (MLA). As a result, a classification of drill core
textures calibrated to mineral processing performance was established.
To integrate the ore mesotexture into predictive block models, a core logging tool for automated textural
pattern recognition is being developed. This paper presents the first step in this development: a methodology for
the automated recognition of drill core textures. The proposed methodology is based on 2-D digital image
analysis of drill cores. Texture information is extracted from digital images using gray level co-occurrence matrix
(GLCM) and gray level run length matrix (GLRLM). Based on the information provided by these two methods,
images were classified into six texture categories using multivariate discriminant analysis. A high classification
success was obtained: 88% of the drill core images were correctly classified into their textural pattern category.
... In a previous work, Pérez-Barnuevo et al. (2017) established a rock texture classification calibrated to mineral processing performance for the Mont-Wright iron ore deposit. This deposit is located in Northeastern Québec (Canada) where more than 90% of the iron ore consists of granular recrystallized specular hematite (Neal, 2000;Petruk, 2000). At the eastern part of the deposit, an amphibole quartz iron formation with higher magnetite content is found (Neal, 2000). ...
... This deposit is located in Northeastern Québec (Canada) where more than 90% of the iron ore consists of granular recrystallized specular hematite (Neal, 2000;Petruk, 2000). At the eastern part of the deposit, an amphibole quartz iron formation with higher magnetite content is found (Neal, 2000). The main gangue mineral is quartz that usually presents a sugary texture, with less than 3% of other gangue minerals, such as micas, amphiboles, ilmenite and garnet. ...
... This encompasses not only the mining equipment but also a crushing station, the concentration plant, the maintenance workshops, and a train loading system. Operations in this region started back in 1974, and the mine still contains significant mineral resources, estimated at around 5.1 billion metric tons (Neal, 2000). Consequently, the ongoing mining plan outlines operations within the Mont-Wright complex until 2053. ...
... Goethite, a mineral known to be abundant throughout the Labrador Trough's iron-bearing formations (Neal, 2000), is observed in highest abundances in the western part of the study area, with dispersal to the northeast and east (Fig. 18). Within the centre of the study area, orthopyroxene, which was reported to have elevated concentrations in the western orthogneiss (Sanborn-Barrie, 2016), shows a strong eastward dispersal pattern from the source area (i.e. ...
The complex glacial geomorphology of east-central Quebec and western Labrador has resulted in conflicting ice sheet reconstructions leaving many questions regarding the behaviour of large ice sheets within their inner regions. Specifically, the ice-flow chronology and subglacial conditions remain poorly constrained. To address this, surficial geology investigations were conducted across the border of Quebec and Labrador. A complex glacial history consisting of five ice-flow phases influenced by regional ice stream dynamics was identified, including a near-complete ice-flow reversal. During each ice-flow phase, the subglacial thermal conditions fluctuated both spatially and temporally, resulting in palimpsest glacial dispersal patterns. Deglacial ages from samples collected as part of this research confirm deglaciation occurred relatively rapidly around 8 ka. The results of this work improve our understanding of the glacial history of an inner region of the Laurentide Ice Sheet and have important implications for mineral exploration in the southern Core Zone area.
La géomorphologie glaciaire complexe du centre-est du Québec et de l'ouest du Labrador a donné lieu à des reconstitutions conflictuelles de l’inlandsis, laissant de nombreuses questions sur le comportement des grandes calottes glaciaires dans leurs régions internes. Plus précisément, la chronologie de l'écoulement glaciaire et les conditions sous-glaciaires demeurent mal définies. Pour répondre à ces questions, des études en géologie de surface ont été menées à la frontière du Québec et du Labrador. Une histoire glaciaire complexe composée de cinq phases d'écoulement glaciaire influencées par la dynamique régionale des courants glaciaires a été identifiée, y compris une inversion presque complète de l’écoulement des glaces. Au cours de chaque phase d'écoulement glaciaire, les conditions thermiques sous-glaciaires ont fluctué à la fois dans l'espace et dans le temps, ce qui a entraîné des patrons de dispersion glaciaire palimpsestes. Les âges de la déglaciation provenant des échantillons collectés dans le cadre de cette recherche confirment que le retrait glaciaire s'est produit relativement rapidement vers 8 ka. Les résultats de ces travaux améliorent notre compréhension de l'histoire glaciaire d'une région intérieure de l'Inlandsis laurentidien et ont des implications importantes pour l'exploration minérale dans la région sud de la Core Zone.
... Within the THO, the New Québec Orogen (NQO) serves as one of the bestpreserved supracrustal belts and is a critical suture zone between the Superior Craton and the 'Core Zone' microcontinent ( Fig. 1; Henrique -Pinto et al., 2017;Konstantinovskaya et al., 2019;Wardle et al., 2002). The Labrador Trough, which constitutes the foreland of the NQO, is an elongate, NW-SE-trending, supracrustal fold-and-thrust belt that stretches over 1100 km, from near the mouth of Ungava Bay in the north to south of the Grenville Front where highly metamorphosed and deformed equivalents of the Labrador Trough rocks predominate (Baragar and Scoates, 1981;Machado et al., 1989Machado et al., , 1997Neal, 2000;Skulski et al., 1993;Wardle and Van Kranendonk, 1996;Wardle et al., 2002). ...
Detailed mineralogical and geochemical analysis of drill core samples from three previously unstudied localities (Sheps Lake, Lac Ritchie, Hayot Lake) of the ca. 1.88 Ga Sokoman continental margin-type iron formation (IF) was undertaken to better understand tectonically stable, shallow-marine environments and surface redox conditions during the late Paleoproterozoic. Suboxic (Fe-oxide-rich including paragenetically early hematite) and anoxic (Fe-silicate/carbonate-rich) mineral paragenetic pathways operated during IF deposition. Post-depositional alteration beyond late diagenesis/metamorphism was negligible, based on petrographic examination and analysis of bulk Fe(III)/Fe(II) ratios. High-precision trace element (TE) data of the Sokoman IF, in the context of new analyses of IF/iron ore reference materials (IOC-1, FeR-3, FeR-4), reveal similarities to contemporaneous continental margin-type IF. However, both the analytical approach and integration of chemostratigraphic variations in detrital element, rare earth element and yttrium (REE + Y), and other TE (Cr, V, U, Ni, Co, Zn) parameters with a previously published sequence-stratigraphic framework provides refined insight into the ca. 1.88 Ga marine surface environment. Specifically, this study dissects new details on the effects of base-level fluctuations, terrigenous input, basin redox stratification, and microbial activity that are collectively captured within the mineralogically and texturally complex units of the Sokoman IF.
The REE + Y signature of the Sokoman IF is confirmed to have developed during deposition/early diagenesis through a comparison of geochemical signatures of chert (jasper) intraclasts and surrounding bulk IF. Furthermore, the Sokoman IF REE + Y data show patterns reminiscent of modern seawater (LREE depletion, small negative Ce anomalies, small positive La, Gd, and Y anomalies), but in some cases also strong positive Ce anomalies. Modelling of hyperbolic trends in Ce/Ce*-Pr/Pr* plots, preserved despite varying detrital admixtures, provides supporting evidence for interaction of dissolved REE + Y with marine Fe- and Mn-(oxyhydr)oxides, and quantitatively constrains the amount of detritus required to overprint Ce anomalies. The co-existence of positive and negative bulk-rock Ce anomalies, similar to those of other ca. 1.88 Ga IF, implies the presence of a shallow marine redoxcline at that time. However, the absence of any strong covariations between these Ce anomalies and (1) Mn- or Fe-enrichments, (2) Y anomalies, (3) LREE/HREE ratios, or (4) tetrad coefficients (τ) is best explained by the separation of a shallow Mn-redoxcline from a slightly deeper and more diffuse Fe-redoxcline inferred here to be controlled by cyanobacteria and photoferrotrophs, respectively.
Combined plots of chemostratigraphic and TE/ΣFe vs. enrichment factors highlight variable input/scavenging of different TEs within the Sokoman IF; authigenic TE enrichment is more readily captured in deeper, suboxic to anoxic units relative to shallower, nearshore units where even low amounts of continental detritus can obscure low-magnitude, authigenic redox signatures. This approach confirms the low magnitude and limited range of authigenic enrichments in redox-sensitive and nutrient-type TEs in the Sokoman IF as being similar to those of other ca. 1.88 Ga IF localities, but reveals which depositional environments best capture specific authigenic signatures (e.g., Cr-V-U-P enrichments). Detritus-poor samples record highly fractionated Nb/Ta and Zr/Hf ratios (m/m; Nb/Ta: median 56.4, range 15.5–680; Zr/Hf: median 97.8, range 42.9–409) that exceed those observed in the modern hydrosphere, and are interpreted to reflect greater interaction of the “dissolved” load of these elements with abundant marine Fe/Mn colloids/fine-particulates. Detritus-rich samples have Nb/Ta and Zr/Hf ratios converging towards crustal values similar to those of shales within the Sokoman basin; both datasets support a model for a predominantly felsic (Archean plutonic/metamorphic rock) source.
New inferences from our data on the Sokoman IF support a close link between atmosphere–ocean oxygenation and microbial ecosystems via continental weathering under an oxygen-poor atmosphere (aided locally by arid conditions). In this model, such conditions limited the terrestrial supply of redox-sensitive and nutrient-type elements (most notably P) into the ocean, largely restricting the spatial extent of primary productivity to the photic zone of coastal regions. These processes are consistent with collective evidence from other ca. 1.88 Ga IF deposits that suggest low-O2 and nutrient-limited Earth surface conditions relative to preceding time intervals in the Paleoproterozoic.
... From an economic perspective, the Churchill Province is well known for the iron ore of the Labrador Trough (e.g. Neal, 2000). However, the mineral potential of the Churchill Province in northern Quebec for base and precious metals is poorly known due to the thick cover of Quaternary sediments. ...
Bedrock in arctic and subarctic regions is covered by glacial deposits making the discovery of new mineral deposits difficult. Indicator mineral methods using glacial sediment have thus been developed for mineral exploration in such drift-covered areas. However, sulfide indicator minerals have been under utilized because it was thought that they would not survive glacial transport and post-depositional oxidation during soil formation. In this contribution we show that the 0.25–1 mm non-ferromagnetic heavy mineral concentrates of Quaternary till and esker samples from the Churchill province in northern Quebec, Canada, contain thousands of pyrite and chalcopyrite grains and a few sulfarsenide grains. Accordingly, sulfide minerals do survive glacial and glaciofluvial transport, even in the relatively oxidizing environment of the eskers, and their presence indicates the potential presence of mineralized bedrock up ice. The study area is therefore ideal to test the use of sulfide mineral chemistry for mineral assessment and vectoring. The composition of the pyrite and chalcopyrite grains recovered from the glacial deposits have been determined by LA-ICP-MS and compared with known values for sulfides in magmatic and hydrothermal deposits. Although some elements (e.g. Ag, Cu, Zn, Pb, W, Ba, La, and Yb) are enriched in narrow rims on some sulfide grains, indicating their limited mobility during oxidation, most elements have not been mobilized and reflect initial sulfide compositions in bedrock sources. The binary diagram Co/Sb versus Se/As shows that most of the pyrite grains in surficial sediments are of magmatic origin although some are from hydrothermal sources. The hydrothermal pyrites are enriched in hydrothermal pathfinders (Au, Hg, Ag, Tl, Pb, Zn, Cu, and Mo). The ternary diagram Se-Cd-Ni shows that chalcopyrites from both magmatic and hydrothermal deposits are present in glacial sediments. The high Cd/Zn ratios of the hydrothermal chalcopyrites are indicative of a high crystallization temperature, typical of metamorphosed VMS or SEDEX deposits. Integrated maps combining bedrock geology, glacial transport directions, sample locations, and sulfide grain compositions and populations can be used to delineate target sectors for mineral exploration. Here sulfides have been transported over ~100 km roughly towards north, from sources in the Rachel-Laporte Zone and the Labrador Trough, where metasedimentary/metavolcanic rocks and mafic/ultramafic intrusive rocks are favorable hosts for hydrothermal and magmatic mineralization, respectively.
... In November 1950, the newly created Iron Ore Company of Canada (IOCC) began development of these deposits, and by 1954, a railway had been completed from the port of Sept-Îles to the new townsite at Schefferville , with production commencing in the Ruth Lake No. 3 deposit. The IOCC conducted mining operations from 1954 to 1982, during which time more than 250 million tonnes (Mt) of ore was produced (Neal, 2000). The iron-ore mines in the Schefferville and Menihek regions closed in 1982, mainly due to low iron-ore prices and increased competition from lower cost producers. ...
Drum-type wet low-intensity magnetic separation (WLIMS) is a versatile technique widely employed in the mining industry for the treatment of iron ores. Its design and operation are rather simple and straightforward. Yet, understanding the process performance from a fundamental point of view still remains a puzzling task due to a number of complex subprocesses involved in the separation. Most of the models for drum-type WLIMS thus are based on empirical approaches. This work presents a modeling strategy that integrates ore properties and equipment characteristics to describe the behavior of iron ore particles. It relies on interpreting a laboratory-scale drum-type wet magnetic separator as a continuously stirred tank reactor. It merges the benefits of phenomenological and empirical modeling to express the particle kinetic rate constants as a function of the separation principles and ore characteristics. Results suggest that the kinetic model satisfactorily reproduces the experimental observations in terms of particle-classified magnetite recovery. The approach is promising for obtaining early information on the behavior of the particles at different stages of the iron ore beneficiation chain, especially for production planning, circuit layout and optimization.
Magnetic separation is a versatile technique widely used in the mining industry. Drum-type wet low-intensity magnetic separation (WLIMS) represents the backbone of the iron ore upgrading circuits since the mid 19th century. However, it has been traditionally applied through guidelines that commonly disregard the ore properties and their interaction with the operating conditions to influence the final process selectivity. This work describes a three-stage methodology to achieve the comprehensive characterization and classification of an iron ore, seeking to recognize links between the ore properties and operating conditions, and their influence upon the process performance. This methodology integrates 1) laboratory testing, 2) particle-scale characterization of the ore and products from separation trials, and 3) data analysis to identify and categorize the particle attributes that control their behavior in a laboratory-scale magnetic separator. Dry sieving, Saturation Magnetization Analyzer (SATMAGAN) and Mineral Liberation Analysis (MLA) represent the basis to collect quantitative particle-level information for clustering the ore into classes of unique nature. The further determination of the volumetric magnetic susceptibility by particle class, together with the relative probability of particle capture, provides valuable insight on the ore magnetic behavior. The calculation of particle-classed partition coefficients resulted practical to assess the process selectivity in terms of particle attributes and operating conditions. The methodology proposes guidelines to comprehend the behavior of an ore from a particle-scale perspective. Moreover, the acquired data can be used for geometallurgical and process modeling, which represent promising forecasting tools to support decision-making in plants.
The Lower Proterozoic, Lake Superior-type Sokoman Iron Formation of the Labrador Trough is one of the world's largest iron formations. It represents a unique, major event in the history of the Trough. Originally a largely irregularly bedded, intraclastic, granular, locally oolitic, conglomeratic iron formation, it is highly variable in its stratigraphy, mineralogy, and textures, which are the consequence of sedimentology, diagenesis, metamorphism, structural deformation, and magmatic overprint. Despite its complexity, the regional characteristics of the iron formation within the 1200 km length of the Labrador Trough indicate three main stratigraphic units, defined by their dominant iron minerals: the lower and upper parts of the formation are characterized by the abundance of iron silicates and carbonates (silicate-carbonate facies), and the middle part is characterized by the dominance of iron oxides (oxide facies). The origin of these lithostratigraphic units of the iron formation is attributed to three main sea-level changes which changed the chemistry (oxidation–reduction potential) and the physical energy (wave and current action) of the sedimentary environment.
The vast amount of iron and some of the silica required for deposition of the Sokoman Formation is inferred to be the consequence of intense hydrothermal activity within a major rift created by the eastward extension of the Labrador Trough ca 1.88 Ga. The hydrothermal fluids venting within the rift saturated the deep and likely anoxic sea of the Trough with ferrous iron and some silica which then upwelled onto its oxygenated shallow waters to deposit the iron formation.
The end of the processes involved in creating the iron formation ca. 1.82 Ga is attributed to the westward contraction of the Trough induced by the Hudsonian (Trans-Hudson) orogeny, which closed the iron- and silica-generating rift and at the same time ended all magmatic activities and related sedimentation coeval with the deposition of the iron formation.
Whilst iron occurs in many different geological types of deposits, the iron formation-hosted iron ore deposits account for the majority of current world production and resources of iron ore, followed by the important Phanerozoic ooidal ironstone channel iron deposit (CID) sub-group. The iron formation-hosted iron ores are subdivided into unenriched iron formation ores, martite-goethite supergene ores, residual hematite ores and microplaty hematite ores. The three most common iron ore minerals are magnetite (Fe3O4), hematite (Fe2O3) and goethite (FeOOH), with the most common forms of goethite being brown, yellow ochreous, and dark brown vitreous goethite. Quartz, kaolinite and gibbsite are the most common gangue minerals. Whilst the mineralogy of iron formation-hosted iron ores and the CIDs are simple, complex ore textures control processing performance from crushing to screening, beneficiation, agglomeration (sintering or pelletizing) of fine ores or concentrates, and lump burden behaviour in the blast furnace.
The Labrador Trough in northern Québec and Labrador is a 900 km-long Rhyacian–Orosirian orogenic belt containing mixed sedimentary-volcanic successions. Despite having been studied intensively since the 1940s, relatively few chemostratigraphic studies have been conducted. To improve our understanding of the Labrador Trough in the context of Earth history, and better constrain the local record of the Lomagundi-Jatuli carbon isotope excursion, high-resolution sampling and carbon isotope analyses of the Le Fer and Denault formations were conducted. Carbonate carbon isotopes (δ<sup>13</sup>C) in the Le Fer Formation record a large range in values from -4.4 to +6.9‰. This large range is likely attributable to a combination of post-depositional alteration and variable abundance of authigenic carbonate minerals; elemental ratios suggest that the most <sup>13</sup>C-enriched samples reflect the composition of the water column at the time of deposition. Cumulatively, these data suggest that the Lomagundi-Jatuli Excursion was ongoing during deposition of the Le Fer Formation, approximately 2 km higher in the stratigraphy than previously recognised. However, the possibility of a post-Lomagundi-Jatuli Excursion carbon isotope event cannot conclusively be ruled out. The directly overlying Denault Formation records a range in δ<sup>13</sup>C values, from -0.5 to +4.3‰, suggesting that it was deposited after the conclusion of the Lomagundi-Jatuli Excursion and that the contact between the Le Fer and Denault formations occurred sometime during the transition out of the Lomagundi-Jatuli Excursion, ca. 2106 to 2057 Ma.
Reverse cationic flotation is a very efficient method of beneficiation of oxidized iron ores when you need to separate hematite and quartz. This method can be also applied to reduce silica content in the magnetite concentrates obtained by wet low-intensity magnetic separation. However, cationic flotation in this case is less effective due to the presence of Fe-Mg-Al-bearing silicates as amphiboles in magnetite ores. These silicates are concentrated in magnetic products and determine the difficulties of their separation from iron oxides when amines and starches are used as collectors and depressants, respectively. The recalculation of the results of the electron microprobe analysis of three calcic Fe-Mg-Al-bearing amphiboles used to characterize cation distributions in structural units and to obtain structural formulas in accord with stoichiometric limits was conducted. The Mössbauer spectroscopy was used to examine the validity of the empirical estimation of cation distributions in amphiboles. The studied samples are metamorphic pargasite and ferrotschermakite and volcanic magnesiohornblende. The crystallographic analyses of the amphibole samples exhibited their heterogeneous surfaces explaining worse floatability of amphiboles with dodecylamine at pH 10. The electrokinetic measurements showed that the position of the isoelectric point of amphiboles is related to a substitution of Al3+ for Si4+ in tetrahedral sites and to an amount of Mg2+ cations in octahedral sites. Thus, the dodecylamine adsorption onto amphiboles through electrostatic interactions is mainly affected by a distribution of these cations in tetrahedral and octahedral sites of amphiboles. In addition, the effect of starch on the depression of Fe-Mg-Al-bearing amphiboles during flotation can be attributed to the presence of metal ions on the amphibole surface, which are capable of forming strong chemical complexes with starch molecules.
Reverse cationic flotation is a very efficient method of beneficiation of oxidised iron ores when you need to separate hematite and quartz. This method can be also applied to reduce silica content in the magnetite concentrates obtained by wet low-intensity magnetic separation. However, cationic flotation in this case is less effective due to the presence of Fe–Mg–Al-bearing silicates as amphiboles in magnetite ores. These silicates are concentrated in magnetic products and determine the difficulties of their separation from iron oxides when amines and starches are used as collectors and depressants, respectively. The recalculation of the results of the electron microprobe analysis of five calcic Fe–Mg–Al-bearing amphiboles used to characterise cation distributions in structural units and to obtain structural formulae in accord with stoichiometric limits was conducted. The Mössbauer spectroscopy was used to examine the validity of the empirical estimation of cation distributions in amphiboles. The studied samples are metamorphic pargasite, ferrotschermakite and magnesiohornblende and volcanic kaersutite and magnesiohornblende. The crystallographic analyses of the amphibole samples exhibited their heterogeneous surfaces explaining worse floatability of amphiboles with amines at pH 10. The electrokinetic measurements showed that the position of the isoelectric point of amphiboles is related to a substitution of Al3 + for Si4 + in tetrahedral sites and to an amount of Mg2 + cations in octahedral sites. Thus, the amine adsorption onto amphiboles through electrostatic interactions is mainly affected by a distribution of these cations in tetrahedral and octahedral sites of amphiboles. In addition, the effect of starch on the depression of Fe–Mg–Al-bearing amphiboles during flotation can be attributed to the presence of metal ions on the amphibole surface, which are capable of forming strong chemical complexes with starch molecules.
This paper examines the entangled histories of post-WWII iron ore mining in the Quebec-Labrador region of Canada and the Lake Superior basin of the United States. After a brief look at the scale of iron mining in Labrador, we examine the so-called "Iron Ore Dilemma" in the United States-the fears that dwindling supplies of high-grade iron ore in the Lake Superior District threatened Cold War strategic interests. Using the case study of Reserve Mining Company along Minnesota's north shore, we examine how cold war concerns about the depletion of direct shipping ore led American mining interests to promote the technologies and tax incentives needed to exploit taconite ore bodies-a lower-grade iron ore that required new technologies and created new environmental consequences. We then turn to the Canadian subarctic where American iron and steel interests worked with Canadian partners and the state to establish mines that might replace depleted ores in the Lake Superior Basin. Tracing the webs of connections between Quebec-Labrador and the Lake Superior Basin illuminates the ways that transboundary processes draw distant mining regions together. It also illustrates how the effects of mining extend beyond the mine site, crossing scales of time and space.
DSO (Direct Shipping Ore) deposits, the high-grade iron ores (w(Fe)>50%, w(SiO2)<18%) in the Labrador Trough of Canada, attracted much attention for the high-grade and significant economic benefits.By studying the geology setting of DSO deposits and the characteristics of typical DSO deposits in the region of Scheffervill,we found that: (1)all DSO deposits are hosted by Precambrian Sokoman iron formation; (2)the structure is considered to be the most important factor that influence the location of the DSO deposits, and preparing the access to deep-hydrothermal fluid and developing enough space to concentrate new recrystallized minerals; (3)the genesis of soft DSO is related to supergene-modified hydrothermal model, while hard DSO only related to hydrothermal model. According to the characteristics of ore-forming processes, we divide the DSO targets of Labrador Trough into 3 zones: the Scheffervill soft DSO zone, Lac Le Fer-Attikamagen soft DSO zone and Astray Lake-Sawyer Lake hard DSO zone. Exploration activities should focus on the areas where the secondary extensional-faults, folds and the contact surfaces between basalt and iron formation intersect the NW striking regional faults, especially when the areas also have the geophysical characteristics of low magnetic-high gravity. Synthesize information of geology and geophysics to figure out the best points to mark as reconnaissance trenching and drilling stage,which can greatly improve the efficiency of prospecting.
Reduction of ore is the key process in its conversion to the metal form, and the reducibility of ore fragments is therefore a crucial parameter in smelting operations. At constant oxygen fugacity, reducibility is controlled by the texture of the ore fragments, which determines the transport length from reduction front to fragment interface, and the chemistry of the ore fragments, which impacts element mobility within the crystal lattice. Their relative contribution was studied here for iron-ore reduction by combining compositional analyses and thermo-gravitational reduction experiments on individual ore fragments. Results indicate that despite large, and ore-characteristic differences in chemistry, ore-fragment composition has a negligible impact on reducibility. The large variations among bulk ores; e.g. the start of hematite-to-magnetite reduction varies by over 300 C, is therefore attributable to ore-texture effects. Porous, goethite-dominated ores show the highest reducibility, followed by fractured and layered fragments and finally dense ore fragments.
This article examines the period leading up to the establishment of the Schefferville iron mine in subarctic Quebec, Canada, with a focus on the years 1937-54. The beginning of iron ore mining at Schefferville was a decisive moment in the growth of the modern Quebec state, opening the way for the industrial exploitation of the province's natural resources - mineral and otherwise - in the hinterland. Relying on oral and written sources, the research emphasizes the roles and actions of Innu individuals during this phase of development conducted by exploration companies and the Iron Ore Company of Canada at the heart of their ancestral homeland. If the early mining experience at Schefferville evolved largely to the detriment of the Indigenous communities inhabiting the region, a decentring approach to ethnohistory in the context of industrial colonialism reveals that the Innu also worked to determine their own engagement with the mining world, adjusting and maintaining their practices on the land while participating in the wage labour economy.
Four new petrogenetic and metallogenic models are proposed herein to explain the formation of important mineral deposits in the Grenville Province, providing a framework from which to reappraise Grenvillian mineral potential. Recognition of a high-pressure metamorphic belt within the Grenville Province suggests a potential for eclogite-hosted rutile deposits, an important and much-sought commodity. A recently developed Norwegian model proposes that anorthosite genesis occurred through lower crust underplating and coeval partial melting, rather than by plume magmatism. Applied to the Grenville Province, the new petrogenetic model may provide insight into the widespread occurrence of platinum group element (PGE) poor nickel showings and the distribution of chromite, Ti-rich, and low-Ti iron-oxide deposits within the Grenville and adjacent terranes. A new type of sedimentaryexhalative (SEDEX) mineralization formed by oxidized brines has been defined following the discovery of new deposits in Australia. Applied to the Grenville Province, it provides a possible explanation for two long-recognized features of marble-hosted zinc deposits: (i) the presence of meta-siderite beds occurring as distal haloes around SEDEX zinc deposits, and (ii) the mutually exclusive division of these SEDEX deposits into massive sulphide and nonsulphide groups. The discovery of the giant Olympic Dam iron-oxide coppergold (IOCG) deposit in Australia renewed the interest in magmatic low-Ti iron-oxide deposits in the Grenville Province that have been known and mined since early colonial times. Subsequent exploration in the northeastern part of the Grenville Province revealed the presence of breccia-hosted CuAuU rare-earth element (REE)-bearing iron-oxide mineralization. This deposit and other low-Ti iron-oxide deposits in the southwestern Grenville Province have a previously undocumented close spatial and temporal association with Ti-rich iron-oxide deposits. These examples demonstrate how new petrogenetic, tectonic, and ore deposit models developed in unmetamorphosed rocks can be successfully adapted to high-grade terranes, where they stimulate mineral exploration in these challenging conditions. Furthermore, by tracking the formation of ore deposits in the lower crust, the existence of unsuspected metallogenic associations in the higher crust, such as the low-Ti and high-Ti iron-oxide association observed in the Grenville Province, may be revealed.
Iron formation-hosted iron ore deposits account for the majority of current world iron ore production and consist of three classes: unenriched primary iron formation with typically 25 to 45 wt-%Fe; martite–goethite ore formed by supergene processes, with abundant hydrous iron oxides containing 60 to 63 wt-%Fe; high-grade hematite ores thought to be of hypogene or metamorphic origin overprinted by subsequent supergene enrichment with 60 to 68 wt-%Fe. Individual iron ore deposits range from a few millions of tonnes to over two billion tonnes at >64 wt-%Fe, although most are within the range of 200 to 500 Mt. In the Hamersley province of Western Australia, martite–goethite ores are largely developed in the Marra Mamba iron formation, although high (>0·08 %P) phosphorous mineralisation is also well developed in the stratigraphically higher Brockman iron formation. While the vast majority of high-grade microplaty hematite ore is best developed in the Brockman iron formation, the present paper provides the first textural evidence of locally significant microplaty hematite mineralisation in the Nammuldi member of the Marra Mamba iron formation, in the Chichester Ranges at the Christmas Creek, Cloud Break and Mount Nicholas prospects. Petrographic studies have identified a high-grade Fe texture composed of nanometre scale plates of hematite in mineralised sections of primary microplaty hematite deposits in the Pilbara and elsewhere, well below the normal depth of weathering or dehydration. The population of nanometre to micrometre scale hematite plates is interpreted to represent various stages of nucleation, crystallisation and progressive growth of hematite from the primary ore-forming fluid in areas that were once iron-rich carbonates or silicates in the banded iron formation.
Thirty-nine oriented block samples of iron-formation were collected at 13 sites, including opposite limbs of major folds, from the 1.88-Ga Sokoman Formation (Knob Lake Group) in the Schefferville–Knob Lake area of the central New Québec Orogen, northern Québec. The samples assayed up to 80.24% Fe2O3T (54.08% Fe), implying Fe-enrichment of the iron-formation up to ore grade. Anisotropy of magnetic susceptibility measurements on 245 standard specimens indicate a well preserved bedding-parallel fabric in the iron-formation, suggesting minimal alteration of the magnetic mineralogy since deposition and/or a mimetic secondary magnetic mineralogy. The iron-formation has not been internally deformed since the magnetic mineralogy was established. Analyses by variable-field translation balance and X-ray diffraction showed that the predominant magnetic mineral is hematite but a small amount of magnetite also is present in most samples. Following low-temperature pre-treatment as appropriate, stepwise thermal and alternating-field demagnetization of 218 specimens revealed a low-temperature, post-folding component (maximum Tub≈400 °C, D=27.1°, I=20.1°, α95=10.9°, from seven sites; pole position of 40.6°S, 257.0°E), and components carried by magnetite (maximum Tub≈580 °C, D=35.8°, I=3.9°, α95=9.1°, from 10 sites; pole position of 29.6°S, 250.9°E) and hematite (maximum Tub≈680 °C, D=40.0°, I=1.6°, α95=18.6°, from seven sites; pole position of 26.8°S, 247.0°E). The components carried by magnetite and hematite are pre-, syn- and post-folding depending on the sampling site, indicating that the magnetization was acquired continuously with deformation in the New Québec Orogen at 1.84–1.83 Ga. No evidence was found for acquisition of magnetization during the Mesozoic, when many of the iron oxide orebodies in the Schefferville–Knob Lake area are thought to have formed. Our findings imply that an episode of Fe-enrichment of iron-formation in the Sokoman Formation involved the circulation of hydrothermal fluids related to late Paleoproterozoic orogenesis. Such orogenic circulation of fluids may have contributed to the development of hematitic orebodies in the central New Québec Orogen.
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