Musselwhite Mine Research Articles

Optimizing stope design in a deeper mining zone at the Musselwhite Mine

ABSTRACT The PQ Deeps (PQD) is a production zone located at Newmont’s Musselwhite Mine in northern Ontario, Canada. Development started for PQD in late 2017, and the first stopes were mined starting in early 2021. Unlike most historical longitudinal stoping of narrower orebodies at Musselwhite, the PQD is a wider orebody following the plunge of a fold hinge and is extracted primarily by transverse stoping. Some geotechnical challenges were experienced during early stoping efforts, necessitating design changes throughout late 2021 and early 2022 to optimize the stope design. This work describes the mining methods and design changes to transverse PQD stoping based on geotechnical lessons learned during early stoping efforts.

Maximizing Power Generation of a Solar PV System for a Potential Application at Musselwhite Gold Mine Site in Northwestern Ontario, Canada

Increasing global concern for greenhouse gas emission, air pollution, fossil fuel prices, and electricity demand has generated a significant increase in research of promising renewable energy technologies for green electrical power generation. Solar photovoltaic (PV) systems are known for their capabilities to directly convert renewable solar energy into electrical energy for locations with abundant solar energy where there is a desperate need and demand for electrical power. This includes mining industries in remote locations. Solar PV systems generate more power if they are installed and operated efficiently. The inclination angle at which a PV panel is tilted from the horizontal plane is one of the most influential system parameters that affect the amount of electrical power output from the PV system and the system’s overall efficiency. Typically, the variation in the PV tilt angle determines the amount of incident solar radiation received on a PV panel to be utilized by a connected electrical load for use at a given site. In this paper, a mathematical model with numerical simulations are used to determine the total solar radiation incident on a tilted PV surface and to predict the optimum tilt angle for maximizing power generation from a solar PV system for potential application in Musselwhite Mine located in the remote northwestern region of Ontario, Canada. The total solar energy received on the optimally tilted PV surface is computed for all months in a year at the Musselwhite mine site. The results show that the monthly average optimum tilt angle of the PV system varied from a minimum value of 4o in the month of June to a maximum value of 74o in the months of January and December. It was also found that the highest maximum incident radiation of approximately 22.89 MJ/m2 for the whole year occurred in the month of April, whereas approximately 43.9% of this value (the lowest in the year) occurred in the month of December. The numerical simulation results suggest that PV systems are best be installed directly facing south at a fixed optimum tilt angle of 43o throughout the year at the Musselwhitemine site. This will improve the overall efficiency and save operating cost of the proposed PV system which in turn improves the commercial feasibility for the mining industry as an example of application.

In-situ study of beneficial utilization of coal fly ash in reactive mine tailings

Oxidation of reactive mine tailings and subsequent generation of acid mine drainage (AMD) have been long recognized as the largest environmental concern for the mining industry. Laboratory studies on utilization of coal fly ash in management of reactive mine tailings have shown reducing water and oxygen infiltration into tailings matrix, thus preventing oxidation of sulphide minerals and acid generation. However, few data from field studies to evaluate the performance of co-placement of mine tailings and fly ash (CMF hereafter) are reported in the open literature. This paper documents the construction and instrumentation of three CMF systems on the Musselwhite mine located in Ontario, Canada and presents results of 3-year real time monitoring. The field data indicates that the CMFs reduced the ingress of water due to cementation generated by hydration of fly ash. It was also found that the electrical conductivity of leachate from CMFs decreased in the early stage of co-placement, compared to the control. With further study, the principle and approach demonstrated in this paper can be adopted as a sustainable technology in the mine tailings management.

Effect of operating parameters on desulphurization of mine tailings by froth flotation

A site-specific study is carried out to assess the suitability of froth flotation for desulphurization of reactive mine tailings at the Musselwhite Mine, Northern Ontario, Canada, to prevent acid mine drainage (AMD). The results from pilot scale flotation tests on an Outokumpu flotation unit are presented, which confirm that froth flotation is effective to reduce sulphide contents of tailings. The factors affecting the treatment effectiveness, such as the froth depth, air flow rate, pulp density and impeller speed are studied. The sulphur recoveries after 0.25, 0.5, 1, 2, 5, and 12 min of flotation time are fitted to a second-order kinetic model. It is found that the second order rate constant, k(2) is negatively correlated with the froth depth and positively correlated with the air flow rate. Based on the data presented in this study; the maximum recovery of total sulphur was achieved when the operational parameters were set to the froth depth of 5 cm, air flow rate 125 L/min, impeller speed 1300 rpm and pulp density 35%.

Geochronology of the North Caribou greenstone belt, Superior Province Canada: Implications for tectonic history and gold mineralization at the Musselwhite mine

The ∼3 Ga North Caribou greenstone belt comprises a package of volcanic and sedimentary rocks metamorphosed from greenschist to upper amphibolite grade, surrounded by ∼2.7–3.0 Ga granitoids and gneisses and is host to the Musselwhite gold mine, a large orogenic gold deposit. New U–Pb (zircon, monazite), Ar–Ar (biotite) and Sm–Nd (garnet) ages for volcanic, sedimentary and intrusive rocks from the Musselwhite mine and surrounding plutons have been obtained. Felsic volcanic rocks yielded ages of 2972.4 ± 1.6 and 2982.4 ± 0.8 Ma, broadly consistent with existing ages for volcanic rocks and plutonism. An age of 2857.3 ± 1.4 Ma for the Schade Lake gneiss is consistent with published plutonic and volcanic ages. A younger, and previously unrecognized, plutonic event is represented by three granites dated at 2723.1 ± 0.8, 2727.7 ± 1.0 and 2729.4 ± 7.1 Ma. An Sm–Nd age of 2690 ± 9 Ma for garnets associated with gold mineralization is bracketed by peraluminous granites with ages of 2668.8 ± 1.1 and 2715.8 ± 1.6 Ma. Ar–Ar ages range from 2420 ± 11.97 to 2658 ± 13.46 Ma, broadly synchronous with the youngest intrusive age, and are consistent with progressive resetting due to metamorphism. The new geochronological data for the NCGB show that volcanism in the Opapimiskan Lake area spanned 10 million years from 2982.4 to 2972.4 Ma, allow for new stratigraphic interpretations of the belt and are broadly correlative with other greenstone belts in the North Caribou terrane. The new data for the NCGB and associated plutons are consistent with ∼3 Ga plume-related activity forming a proto-craton that was the site of successive sedimentary basins over the next ∼150 million years. Subsequent plutonism is consistent with supra-subduction zone processes at the margins of this proto-continent by ∼2.87 Ga and is best interpreted as the result of horizontal tectonic processes consistent with those operating in the Phanerozoic, with the plutons emplaced behind continental margin arcs on the edges of the craton. Sm–Nd ages of garnets that are coeval with mineralization suggest that the orogenic gold mineralization at the Musselwhite mine was broadly synchronous with the ∼2700 Ma orogeny caused by the collision of the Oxford-Stull domain with the North Caribou terrane ∼75 km northeast of the Musselwhite mine and furthermore argues that S-type granites may play a greater role in the formation of some orogenic gold deposits than has been previously recognized.

Optimization of digestion parameters for analysing the total sulphur of mine tailings by inductively coupled plasma optical emission spectrometry

The oxidation of sulphidic mine tailings and consequent acid generation poses challenges for the environment. Accurate and precise analysis of sulphur content is necessary for impact assessment and management of mine tailings. Here, the authors aim at developing a rapid and easy digestion procedure, which may analyse and measure the total amount of sulphur in mine tailings by using inductively coupled plasma. For evaluating effects of several variables, the researchers used a univariate (analysis of variance (ANOVA)) strategy and considered factors such as composition of the acid mixture, heating time, and refluxing device to optimize the performance. To do the experiment, the researchers have used two certified reference materials (KZK-1 and RTS-2) and samples of tailings from Musselwhite mine. ANOVA result shows that heating time is the most influencing factor on acid digestion of the reference materials whereas in case of a digestion of tailings sample, hydrochloric acid proved to be the most significant parameter. Satisfactory results between the measured and referenced values are found for all experiments. It is found that the aqua regia (1ml HNO(3) + 3ml HCl) digestion of 0.1g of samples after only 40min of heating at 95°C produced fast, safe, and accurate analytical results with a recovery of 97% for the selected reference materials.

Long-term evaluation of coal fly ash and mine tailings co-placement: A site-specific study

This study presents the results of a laboratory investigation conducted to evaluate the efficiency of coal fly ash to control the formation of acid mine drainage (AMD) from mine waste. Site-specific materials, coal fly ash from Atikokan Thermal Generating Station and mine tailings from Musselwhite mine, were mixed at different proportions for the investigation of the drainage chemistry and the optimal mix using static testing (acid–base accounting) and kinetic (column) testing. The acid–base accounting (ABA) results indicated that the fly ash possessed strong alkaline (neutralization) potential (NP) and could be used in the management of reactive mine tailings, thus ensuring prevention of AMD in the long-term. Column tests conducted in the laboratory to further investigate long-term performance of fly ash in the neutralization and prevention of acid mine drainage from tailings similarly showed that mixing fly ash with mine tailings reduces dissolution of many heavy metals from tailings by providing alkalinity to the system. It was found that a fly ash to tailings mass ratio equal to or greater than 15% can effectively prevent AMD generation from Musselwhite mine tailings in the co-placement approach.

3D Modelling of Banded Iron Formation incorporating demagnetisation – a case study at the Musselwhite Mine, Ontario, Canada

Three-dimensional (3D) high-susceptibility tabular models of Banded Iron Formation (BIF) were built for the area of an aeromagnetic survey at the Musselwhite Mine, Ontario. The study used all available drill information to create geologically plausible models built from a central axis of nodes with geometrical and susceptibility attributes assigned to each node. The forward total magnetic intensity was then computed using an algorithm that includes a calculation for the demagnetisation effect. The model-building process greatly enhanced the understanding of the BIF geometry and demonstrated the importance of the interaction of these strongly magnetic units with the Earth’s magnetic field. As BIF is associated with mineralisation at the mine, the interpretation of the observed magnetic anomalies has strong implications for target generation.

Utilization of Atikokan coal fly ash in acid rock drainage control from Musselwhite Mine tailings

A site-specific study is carried out to assess the suitability of utilizing Atikokan coal fly ash (AFA) as a buffering material to control and mitigate the generation of acid rock drainage from reactive Musselwhite Mine tailings. The physical, chemical, and mineralogical properties of the fly ash and mine tailings are determined via experiments, followed by six kinetic column permeation tests to monitor the leaching properties of the coal fly ash and coal fly ash – mine tailings mixtures. The results of the experiments indicate that the hydraulic conductivities of high-calcium AFA and the ash–tailings mixtures are significantly reduced upon contact with acidic drainage. The pH of the pore fluid has increased from acidic (pH 4) to alkaline (pH 8 and above). Chemical analyses after the kinetic column permeation tests further indicate that concentrations of regulated elements in the leachate from the ash–tailings mixtures are well below the guideline limits set by the Ontario environmental authority for accelerated flow conditions.Key words: coal fly ash, mine tailings, hydraulic conductivity, pH, heavy metals, acid rock drainage.

The Nature and Distribution of Tantalum-bearing Minerals in Newly Discovered, Rare-Element Pegmatites at the Musselwhite Mine, Northwestern Ontario

Newly discovered pegmatites distributed throughout the sub-surface environs of the Musselwhite Archean gold deposit occur as narrow dikes that intrude most of the major lithological units. The mineralogy and textures of the pegmatite dikes are characteristic of granitic pegmatites of the “Rare-Element Class”; more specifically, they closely resemble varieties of the “Complex-type” granitic pegmatites that are commonly associated with zones of tantalum mineralization. The essential minerals in the dikes comprise albite, quartz, and K-feldspar, together with lesser amounts of mica (including lepidolite), spessartine, tourmaline, and locally, spodumene. Fine-grained (30 μm to 300 μm), tantalum-bearing minerals occur in the quartzo-feldspathic matrix of the dikes as disseminations, in interstices, and in small vugs. The nature of the tantalum-bearing mineral assemblage present in individual pegmatite dikes varies from a simple mineral assemblage composed of ferrocolumbite (with around 39 wt% Ta2O5) in the most northerly dike, to more complex assemblages comprised of manganotantalite (with up to 75 wt% Ta2O5), ferrotapiolite (with up to 79 wt% Ta2O5), and microlite (with up to 76 wt% Ta2O5) that are present in dikes located several kilometers to the south and southwest. The compositional characteristics and textural relationships of the tantalum-bearing minerals in the dikes provide evidence of igneous fractionation trends that are typical of rare-element granitic pegmatites. Such trends suggest that the newly discovered pegmatites represent part of a more extensive group of cogenetic, tantalum-mineralized dikes.