Rouyn-Noranda Area Research Articles

Random forest classification for volcanogenic massive sulfide mineralization in the Rouyn-Noranda Area, Quebec

Random forest (RF) classification was applied to 37 predictor maps (vectors to mineralization) producing a Mineral Prospectivity Map (MPM) for volcanogenic massive sulfide (VMS) mineralization in the Noranda District, Abitibi subprovince, which is host to ∼ 20 VMS deposits and numerous subeconomic occurrences. The predictor maps were created using geological, geochemical, and geophysical data, and the known VMS deposits were used to train the RF classifier. The RF model was applied on two regions of interest (ROI) to investigate the effect of different sized ROIs on the results. Five sets of balanced and unbalanced training data were used in the experiments to examine the sensitivity of RF to different sets of training data. The probability/prospectivity maps showed very high success rate of classification with regard to training data particularly for the training sets with higher ratio of non-deposits/deposits. Accuracy assessment of classification maps using cross-validation also showed very high accuracy when assessed by the training data in all experiments again giving a higher accuracy for the training sets with higher ratios of non-deposits/deposits, however the later showed very low accuracy when applying k-fold cross-validation or when assessed by 15 VMS showings used as the test data indicating an overfitting problem with the unbalanced data. In most of the experiments, principal component 4 (PC4) of geochemical analysis, proximity to synvolcanic tonalite-trondhjemite-granodiorite (TTG) intrusions, lithology, and sericite alteration maps showed higher predictive power. The importance of individual variables changed when the ROI was changed to a smaller area suggesting that RF is sensitive to the study area.

Determination of Free Cd, Cu and Zn Concentrations in Lake Waters by In Situ Diffusion Followed by Column Equilibration Ion-exchange

Combining in situ diffusion and column ion-exchange equilibration, we measured free metal ion concentrations (Cd, Cu and Zn) in water samples collected from the epilimnion of 14 lakes in the Rouyn-Noranda area (600 km north-west of Montreal, QC, Canada). Lakes were selected to represent a wide range of physico-chemical characteristics (hardness, pH, dissolved organic matter—DOM, degree of metal contamination), to determine the influence of these parameters on metal speciation. Total dissolved metal concentrations, as determined within the diffusion cells, varied over one to two orders of magnitude: [Cd] 0.19–2.9 nM; [Cu] 36–190 nM; [Zn] 7–2,800 nM. The proportion of total dissolved metal present as free Cd2+ and Zn2+ was relatively constant for the 14 selected lakes, despite the wide pH (4.5–8) and DOM (3–23 mg C/L) ranges, probably reflecting the inverse relationship observed between pH and DOM; this proportion did, however, vary with DOM and pH for Cu. Our experimental free metal ion concentrations were compared with those calculated with the thermodynamic models WHAM (Windermere Humic Aqueous Model VI) and ECOSAT 4.7 (incorporating the NICA-Donnan model). Measured and calculated values were in reasonable agreement for both Cd and Zn although measured values were generally slightly higher, i.e. less than one order of magnitude. For several lakes, measured free Cu concentrations were, however, much higher than the calculated values, suggesting that these models overestimate Cu complexation. The gap between measured and calculated free metal ion concentration becomes more important as the total metal concentration decreases and as pH increases.

Linking changes in subcellular cadmium distribution to growth and mortality rates in transplanted freshwater bivalves ( Pyganodon grandis)

Relationships between Cd accumulation and subcellular distribution, and growth and mortality rates were examined in the freshwater bivalve Pyganodon grandis in a transplant experiment. Organisms were transferred from a clean lacustrine site to four lakes situated along a Cd concentration gradient in the mining region of Rouyn-Noranda. The bivalves were maintained in open enclosures placed in the bottom sediments of the littoral zone of all five lakes for 400 days. At the end of the experiment, metallothionein (MT) was measured in the bivalve gills with a Hg-saturation assay and Cd partitioning among the various cytosolic protein pools was determined by size-exclusion chromatography. Marked differences were observed among the five sites: the range in calculated free-cadmium ion concentrations in water overlying the sediments was 35-fold whereas Cd concentrations in the gill cytosol of the transplanted bivalves varied three-fold. In the transplanted bivalves, the distribution of gill Cd among the various cytosolic complexes also varied significantly among sites. For bivalves transplanted to the three most contaminated sites, Cd concentrations in the high molecular weight pool (HMW > 25 kDa) were significantly higher than the baseline levels determined from bivalves caged at the reference site; a similar trend was seen for Cd concentrations in the metallothionein pool (Cd–MT). For bivalves transferred to two of the high contamination sites, proportionately less of the gill cytosolic Cd was sequestered (i.e. detoxified) by MT-like proteins. Reductions in survival were also observed at these two sites, and these elevated mortalities, in turn, were consistent with the absence of indigenous bivalve populations at these sites. This result is compatible with our recent work on P. grandis populations living in lakes of the Rouyn-Noranda area, in which we demonstrated that excessive accumulation of Cd in the HMW pool of the gill cytosol of the individual mollusks could be related to the impairment of population health status.

Sub-cellular partitioning of Cd, Cu and Zn in tissues of indigenous unionid bivalves living along a metal exposure gradient and links to metal-induced effects

We studied organ and sub-cellular distributions of several trace metals in a freshwater bivalve that has been proposed for use as a metal biomonitor. Specimens of Pyganodon grandis were collected from nine lakes located along a Cd, Cu and Zn concentration gradient (Rouyn-Noranda area, Québec). Gills and digestive gland were isolated, homogenized and six sub-cellular fractions were separated by differential centrifugation and analysed for their Cd, Cu and Zn content. Metallothionein was quantified independently. Gill tissues contained abundant calcium concretions that accounted for over 60% of the total gill burden of each metal. Cadmium and Zn concentrations in this granule fraction reflected ambient metal concentrations. Metal concentrations in the digestive gland also responded to the metal contamination gradient, but to a lesser extent than the gills, reflecting the lower abundance of granules in the digestive gland. Metals (Cd, Cu) in this organ were present largely in the “heat-stable proteins” fraction, and metal concentrations in this fraction were strongly correlated with those of both metallothionein and, to a lesser extent, the “lysosomes + microsomes” and “mitochondria” fractions. In both organs, Cd concentrations in the “heat-denaturable protein” fraction remained low and constant, suggesting reasonably effective metal detoxification. Some evidence for oxidative stress was noted in the gills but not in the digestive gland. Overall, we conclude that in nature metals in P. grandis are bound differently in the gills and in the digestive gland and that metal detoxification in the former organ may be less effective than in the latter.

Sub-cellular partitioning of metals (Cd, Cu, Zn) in the gills of a freshwater bivalve, Pyganodon grandis: role of calcium concretions in metal sequestration

Indigenous unionid molluscs, Pyganodon grandis, were collected from nine lakes in the Rouyn–Noranda area (Québec, Canada) along a polymetallic concentration gradient (Cd, Cu, Zn). After excision, the gills were gently homogenised and the cellular compartments were separated by a differential centrifugation procedure that yielded the following particulate fractions: “nuclei + cellular debris”, “mitochondria”, “lysosomes + microsomes” and “granules”. The supernatant remaining after the final ultracentrifugation step, i.e., the operationally-defined cytosol, was separated into a “heat-denaturable proteins” (HDP) fraction and a “heat-stable proteins” (HSP) fraction containing metallothionein (MT). The Cd, Cu and Zn content of each particulate and cytosolic fraction was determined and gill metallothionein was quantified independently by a mercury saturation assay. Cytosolic Cd concentrations were significantly related to the dissolved Cd concentrations at each site, but cytosolic Cu and Zn (essential metals) were not related to their respective ambient dissolved metal concentrations. Metallothionein concentrations increased along the metal contamination gradient and were related to cytosolic Cd (and Zn) in a concentration-dependent manner. However mass balance calculations showed that binding to metallothionein could only account for a small proportion of total gill metal (∼10% Cd; ∼3% Cu; ∼1% Zn). Under these chronic exposure conditions, the three metals (Cd, Cu and Zn) were mainly located in calcium concretions present in the gills (respectively 58 ± 13% of the total gill Cd, 64 ± 6% of the total gill Cu and 73 ± 6% of the total gill Zn). The overall contribution of granules to the total gill dry weight remained relatively constant among the different lakes, suggesting that lake-to-lake variations in granule synthesis were independent of the metal contamination gradient, i.e., these constituent elements of unionid gills act as non-inducible metal sinks at the cellular level. Metal concentrations increased proportionally in both the granules and the MT pool along the polymetallic gradient, suggesting a constant partitioning between these two compartments. Overall, despite an increase in Cd in the “mitochondria” fraction, metal sequestration mechanisms seem to be reasonably effective in detoxifying cadmium: in the cytosol, Cd concentrations in the potentially metal-sensitive HDP fraction remained relatively low and constant, even in specimens collected from the most contaminated lakes.

Sub-cellular partitioning of essential and non-essential metals in a freshwater mollusc,Pyganodon grandis, collected in the field along a polymetallic environmental gradient

The cellular alterations normally induced by metals at high concentrations can be prevented by detoxification processes [1] such as sequestration into cellular compartments (calcium concretions, lysosoiues, etc.) or their binding to specific cellular ligands like metallothionein [2]. The aim of this project was to study and compare the subcellular partitioning of three metals (Cd. Cu, Zn) in gills of a freshwater molluse, Pyganodon grandis, collected along a polymetallic environmental gradient (nine lakes in the Rouyn-Noranda area, Abitibi, QC, Canada). Differential centrifugation was used to partition metals among different subcellular fractions. In the gills, along the environmental metal gradient, total tissue metal concentrations were positively correlated with concentrations in the granule traction; gill tissues contained high amounts of calcium concretions, which acted as preferential sites for sequestration of the three metals. An increase in Cd concentration was observed in the heat stable proteins fraction (including metallothionein), but not in the heat-denatured proteins fraction, suggesting that Cd-induced cell injury could be prevented by the involvement of maltiple cellular compartments in a protective role.

Stable Pb isotopes and PAHs as indicators of lead contamination sources in a lake of the Rouyn-Noranda area

We determined the depth distribution of total Pb and its stable isotope composition ( 206 Pb/ 207 Pb, 206 Pb/ 208 Pb, 206 Pb/ 204 Pb) in a dated sediment core collected at the deepest site, in the hypolimnion of a headwater Canadian Shield lake, located 25 km downstream from a metal smelter in operation since 1927. The isotopic ratios reveal the occurrence of one natural and two anthropogenic types of Pb over the last century. One of the anthropogenic Pb, predominant in the sediments accumulated in the early 20 th century, likely derives from coal combustion ( 206 Pb/ 207 Pb≃1.185). The second anthropogenic Pb has a signature similar to that of the ore processed during several decades at the smelter ( 206 Pb/ 207 Pb≃1.000); its contribution to the total Pb concentration sharply increased from 1927 to 1975 and then decreased steadily to the sediment surface.

Morphometric and metabolic indicators of metal stress in wild yellow perch (Perca flavescens) from Sudbury, Ontario: a review.

Eighteen lakes studied near Sudbury and across Northeastern Ontario (Canada) over a five-year period provided a wide contamination gradient of cadmium (Cd), copper (Cu) and other metals such as nickel (Ni) and zinc (Zn). All were inhabited by yellow perch (Perca flavescens), which was sometimes the only species present. Liver Cd and Cu concentrations were monitored in these lakes, in some cases for several consecutive years and for multiple seasons. This data suggests that yellow perch from clean to mildly-contaminated environments loosely control their hepatic Cu concentrations between 7 and 50 microg g dry weight(-1), and a threshold of 50 microg g dry weight(-1) is suggested as the normal range of homeostatic control. Similar data collected by others support this value. Liver Cd concentrations appeared more variable among lake samples, but consistently remained below 10 microg g dry weight(-1) in clean to mildly-contaminated lakes, also supported by data collected elsewhere. Condition factors allowed the discrimination between clean and polluted yellow perch, a conclusion consistent with data for the same species collected in the Rouyn-Noranda area (Quebec, Canada). Values of weight-to-length scaling coefficient lower than 3.0 also discriminated between clean and metal-polluted yellow perch. Finally, three studies indicated that chronic metal exposure can lead to an impairment of aerobic capacities in wild yellow perch, as indicated by lower muscle activity of citrate synthase (CS), aerobic swim performance and respiration rate. We propose that the combination of liver metal concentrations, scaling coefficient, condition factor and an indicator of physiological impairment such as muscle CS activity can provide a suitable range of parameters to adequately assess the effects of metal contamination on the health of yellow perch. Although yellow perch are ubiquitous in North America, this approach can potentially be applied to other small fish species more suitable to other study areas.

Conditions and timing of metamorphism in the southern Abitibi greenstone belt, Quebec

Regional metamorphism, ranging in grade from the subgreenschist-facies to the greenschist–amphibolite-facies transition, affects all Archean supracrustal rocks (>2677 Ma) in the Rouyn–Noranda area. Contact metamorphic minerals associated with the posttectonic Preissac–Lacorne batholith (2643 Ma) show no evidence of a regional retrograde event. Accordingly, the age of regional metamorphism can be bracketed between 2677 and 2643 Ma. Three reaction isograds were mapped in subgreenschist-facies metabasites, dividing the low-grade rocks into three metamorphic zones: the pumpellyite–actinolite zone, the prehnite–pumpellyite zone, and the prehnite–epidote zone. In addition, the pumpellyite–actinolite–epidote–quartz bathograd, corresponding to a pressure of approximately 200 MPa, occurs on both sides of the Porcupine–Destor fault. Low-pressure regional metamorphism is also indicated both by the occurrence of an actinolite–oligoclase zone, and the persistence of pre-regional-metamorphic andalusite. The coincidence of andalusite and the actinolite-oligoclase zone indicates that pressure was <330 MPa at the greenschist-amphibolite transition. The geothermal gradient during metamorphism was approximately 30 °C/km. Regionally, isograds dip shallowly to the north and trend subparallel to lithological and structural trends. Metamorphic minerals in metabasites define tectonic fabrics only near major fault zones and in zones of CO2 metasomatism. In biotite zone metasedimentary rocks the schistosity is defined by mica and amphibole. These textures indicate that metamorphism and fabric development were coeval. However, the actinolite–epidote isograd cuts the Porcupine–Destor fault, indicating that regional metamorphism postdates movement along this fault. The strong fabrics associated with the Porcupine–Destor and Larder Lake–Cadillac faults must have developed through a process dominated by flattening strain.

A comparison of the Horne volcanogenic massive sulfide deposit and intracauldron deposits of the Mine Sequence, Noranda, Quebec

Most of the massive sulfide deposits of the Rouyn-Noranda area are associated with rhyolite and andesite flows of the Mine sequence and occur within the Noranda cauldron, a volcanic subsidence structure related to partial evacuation of an underlying magma chamber (the Flavrian pluton). The Horne massive sulfide orebodies lie within a sequence of rhyolitic breccias located just south of the inferred margin of the subsidence structure and are separated from the Mine sequence by the Horne Creek fault. Traditionally, the Horne deposits and the intracauldron deposits have been interpreted to occur within the same stratigraphic interval. Even though they share some characteristics such as mineral zoning patterns, alteration assemblages, and an association with synvolcanic faults, the two deposit groups are clearly distinguishable.Intracauldron massive sulfide deposits are small (<5 Mt), Cu-Zn-rich, concordant mounds associated with interflow horizons and are closely linked to vent zones where synvolcanic faulting provided hydrothermal fluids with cross-stratal structural permeability. The three major sulfide deposits at the Horne mine are much larger (20-150 Mt) and formed in a fault-bounded, sediment-filled graben on the flank of a rhyolitic vent complex. The orebodies are Au-Cu rich but Zn poor and have bowl-shaped morphologies which resulted from extensive subsea-floor sulfide precipitation. Whereas the intracauldron sulfide deposits lie within a bimodal, flow-dominated succession consisting mainly of andesite-basalt and high silica rhyolite, with volumetrically insignificant pyroclastic rocks, the Horne orebodies occur in felsic fragmental rocks and rhyolite flows which are part of a stratigraphic sequence which contains virtually no mafic volcanic rocks. Also, compared to all intracauldron rhyolites, the Horne rhyolites show a fundamental depletion in incompatible trace elements such as the high field strength and rare earth elements, which implies that the Horne rhyolites may have followed a different magmatic evolutionary path.Such differences in deposit characteristics, their paleoenvironments of formation, and the physical volcanology and geochemistry of their host volcanic successions suggest that, contrary to previous interpretations, the massive sulfide deposits of the intracauldron Mine sequence and those of the Horne sequence may have formed at different stages in the evolution of the Noranda cauldron.

Interpretation of the gravity anomaly field in the Noranda – Val d'Or region, Abitibi Greenstone Belt, Canadian Shield

Gravity data from the Noranda – Val d'Or region have been reprocessed: the Bouguer anomaly map, the first vertical derivative map, and an apparent density map have been used for geological interpretation of the gravity field in this region. It is found that variations in the Bouguer anomaly can be mainly explained by density structures located within the uppermost 5 km of the crust. The vertical derivative map helps to better locate some geological contacts, and the apparent density map allows the easy distinction between thin and thick batholiths. Generalized inversion was used to calculate density cross sections from the Bouguer anomaly values, and measured surface formation densities were used as constraints. Analysis of a detailed profile in the Rouyn–Noranda area shows that steep north-dipping reflectors observed in a seismic reflection survey are associated with a north-dipping density structure.

Chemostratigraphic division of the Blake River Group, Rouyn–Noranda area, Abitibi, Quebec

The effusive rocks of the Blake River Group in the Abitibi volcanic belt, Rouyn–Noranda region, belong to a bimodal sequence in which andesites and rhyolites clearly dominate. The identification of calc-alkaline and tholeiitic affinities is made upon examination of the major, trace, and rare earth element (REE) content. Thus, the andesites (58% normalized SiO2 value without volatiles) of the calc-alkaline units have average K (4800 ppm), Ba (160 ppm), and Rb (13 ppm) values that are greater than the average K (1800 ppm), Ba (130 ppm), and Rb (3 ppm) values for andésites (57% SiO2) that belong to associated tholeiitic units. Furthermore, tholeiitic andesites have distinctive average values of Ti (9600 ppm) and Y (40 ppm) that are higher than the average values of Ti (6700 ppm) and Y (25 ppm) of calc-alkaline andesites. An effective discrimination between the calc-alkaline and tholeiitic affinities is obtained using the Zr/Y and Ti/Zr ratios, which are, respectively, less than 4 and greater than 70 in andesites of the tholeiitic units.REE profiles of tholeiitic andesites are flat when compared with those of calc-alkaline andesites, which show an enrichment in light rare earths.The tholeiitic units of the Blake River Group are found in the proximity of the Porcupine-Destor and Larder Lake – Cadillac faults, the major faults of the region, and at the periphery of an ensemble of calc-alkaline units. Four of the five tholeiitic units are differentiated, showing an enrichment of iron passing from basalt to andesite. These units possess felsic variole-bearing flows, the result of an unmixing, which was probably responsible for the formation of minor associated quantities of porphyries and rhyolitic volcaniclastites.A progressive increase in the concentration of hygromagmatophile elements (REE, Zr, Nb) is observed in the tholeiitic units from the Pelletier unit beginning at the base and passing through the Trémoy, Destor, and Dufresnoy units, at the top of the Blake River Group. The calc-alkaline units are characterized by an alternation of rhyolitic complexes and calc-alkaline andesites. This cyclic repetition occurs without significant modification of the calc-alkaline andesite composition.It is proposed that the volcanism responsible for the formation of the Blake River Group was restricted to a concentric zone centring on a continental environment. Mafic magmas nourished the central reservoir where melting of the sialic crust took place. The rhyolitic magma occupying the upper part of this reservoir mixed with the basaltic magma, producing calc-alkaline andesites. Successive mantle melt products were also emplaced into subsidiary reservoirs peripheral to the central chamber. Injections of tholeiitic magma in the peripheral reservoirs underwent differentiation and unmixing during emplacement of a part of the magma at the surface.

Paleomagnetism and magnetic fabric of the Gallen massive sulfide deposit, Rouyn-Noranda, Canada

Twenty oriented drill cores were collected from the outcrop of the Gallen massive sulfide deposit in the Rouyn-Noranda area in order to investigate remanent magnetization and anisotropy of magnetic susceptibility in the deposit. The purpose was to obtain inforrnation on the emplacement of the deposit. Electrical resistivity is high enough to allow 60-Hz alternating fields (AF) to be used for stability testing of the remanent magnetization. For thermal demagnetization, the heating chamber was first evacuated and then filled with argon. Alternating field demagnetization in a peak field of 30 mT yielded well-grouped stable directions carried by relatively high coercivity magnetite. The mean direction and pole position are: 137, +50, and 43 degrees W, 2 degrees S, dm=9 degrees , dp=6 degrees , respectively. The pole position falls on the 1,750- to 1,700-m.y. part of the apparent polar wander curve for North America, suggesting that the magnetization was acquired after the probable Archean formation of the deposit. The anisotropy of susceptibility (generally

Comparative Morphology of Ancient and Modern Pillow Lavas

Pillow lava is a common feature of volcanic stratigraphy throughout geologic time. A comparison is made between the morphology of oceanic pillows from the FAMOUS area of the Mid-Atlantic Ridge, recent pillows from Iceland, and Archean pillows from the Rouyn-Noranda area of northwestern Quebec. In two dimensions the shapes and sizes of pillows from the three areas are similar but not identical. Abyssal and subglacial lava flows, when viewed in three dimensions, appear to be tubular lava forms similar to subaerial pahoehoe flows. Archean pillows also appear to be interconnected. Evidence of this includes broken selvages, lenticular quartz-filled cavities representing fossil lava levels, and the "pinch and swell" nature of elongate pillows. The stratigraphy of Archean volcanics and modern-day oceanic crust as seen in DSDP holes is similar. Both consist of interlayered massive, pillowed, and breccia units in an apparent random order. However, there appears to be a preponderance of pillowed flows in the modern volcanics compared to the ancient examples. Archean flows appear to be longer and, possibly, thicker than those at present-day ocean ridges and individual Archean pillows are in some places flattened and welded. These observations suggest that the rate of eruption in the Archean may have been greater than in known areas of the Mid-Atlantic Ridge. Pillow morphology and vesicle size and distribution in the Archean examples are consistent with a relatively shallow depth of eruption for the Archean sequences. Overall, the styles of eruption of both the Archean and modern pillow sequences appear to have been similar.

Structure and organization of Archean subaqueous basalt flows, Rouyn–Noranda area, Quebec, Canada

Archean subaqueous basalt flows in Rouyn–Noranda area consist of several structural divisions in vertical sequence. The complete, ideal sequence of structural divisions within a typical flow is, from base to top: massive lava, pillow lava, isolated- and broken-pillow breccia (pillow breccia), and stratified hyalotuff. Any variant of this standard sequence, formed by omission of one or several of the structural divisions, has been observed. Most commonly encountered are the following four sequences: (1) massive lava – pillow breccia, associated in the field with the sequence pillow lava – ± pillow breccia, and (2) massive lava – pillow breccia – hyalotuff, associated with the sequence pillow lava – pillow breccia – hyalotuff.Lateral transitions from massive lava into pillow lava have been mapped and suggest that pillow lava is distal relative to massive lava. Large flow lobes or tubes (megapillows) are present in the transition zone. Mapping of the relations of megapillows and normal-size pillows suggests that pillows form by a budding and branching process, rather like present-day pillows observed to form during the flow of lava into the sea. Relations between massive lava, pillow lava, and pillow breccia suggest that massive lava formed by the surging advance of large volumes of hot lava of low viscosity; pillows formed at the distal flow front due to a decrease of temperature and an increase of viscosity, resulting in a decrease of the flow velocity; pillow breccias apparently formed at the waning stage of the eruption, when the supply of fresh lava was reduced. Hyalotuff apparently formed by lava-fountaining at the fissure, in shallow water.

Genèse des roches à cordiérite–anthophyllite des gisements cupro-zincifères de la région de Rouyn–Noranda, Québec, Canada

Cordierite–anthophyllite-bearing rocks are found in alteration pipes below some of the copper–zinc deposits of the Rouyn–Noranda area that occur in Archean volcanics. The cordierite and anthophyllite have been developed around the contact of the Dufault granodiorite, by isochemical metamorphism of ripidolite of ancient alteration pipes of volcanic origin.