Massive Sulfide Ore Research Articles

Flotation activity of pyrite in the separation of massive sulphide ores

Flotation activity of pyrite in the separation of massive sulphide ores

Mineral and textural-structural features of the ore facies of Yubileynoye massive sulfide deposit (the Southern Urals)

A study of the ore facies of the massive sulfide ores from the Yubileynoe deposit (ore body № 2) has been shown. The sub-seafloor and seafloor hydrothermal, biogenic, clastic and seafloor hypergenic facies have been diagnosed in the studied ores, reflecting different formation conditions within the ore body № 2. The seafloor and sub-seafloor hydrothermal facies occur in the central part of the ore body, while clastic with seafloor hypergenic facies dominate at the flanks of the ore body. Rare minerals are native gold, minerals of Ag, Te, Bi and Pb widespread in seafloor hydrothermal and clastic ore facies. The ratio of the ore facies in the ore body № 2 shows the simiiar ore-forming processes within the Yubileynoe deposit and other massive sulfide deposits of the Urals.

Thermomechanical erosion of ore-hosting embayments beneath komatiite lava channels: Textural evidence from Kambalda, Western Australia

Archean komatiite-hosted nickel deposits at Kambalda, Western Australia, are located in embayments within channelized lava flows. The origin of these embayments is controversial. The currently favoured model invokes pre-existing topographic features filled in by the komatiite and sulfide melt and subsequently modified by thermomechanical erosion. New evidence from sulfide deposits on the eastern limb of the Kambalda Dome includes well preserved magmatic textural relationships of the sulfides with the surrounding rocks suggesting the entire embayment was formed by thermomechanical erosion. These textures are particularly well preserved within the Moran deposit of the Long-Victor Complex which lacks the younger intense structural deformation that other Kambalda deposits have undergone. The vestiges of an older, broad concave embayment are represented by sediment-sulfide textures present on the flanks up to 150m away from the younger steep-sided embayment. Sediment-sulfide contacts are marked here by a globular silicate-sulfide intergrowth, interpreted as emulsion, and cumulate-like mono-sulfide solid-solution (MSS) grains surrounded by interstitial silicate melt. Textures preserved from the formation of a steep-sided embayment are frozen into the basalt-sulfide contact and include an undulating contact with sulfide-filled microfractures and a ferrichromite layer, basalt-sulfide breccia and interpreted crystallized silicate-sulfide liquid emulsions and basalt plumes rising into the sulfides. Textures from the last step of embayment formation are found in the pinchouts, i.e. where the massive sulfide ore is bounded top and bottom by basalt. They include the same textures that were formed during the excavation of the steep-sided embayment but they also feature interpreted basalt-sulfide emulsions on the upper contact, cm-scale silicate-sulfide-ferrichromite layering on the upper contact, and a vesicular basalt “scum layer” floating on the sulfides beneath the solid older basalt.All these textures represent frozen examples of different stages during the excavation and formation of the embayment, and reflect physical processes responsible for thermomechanical erosion. The initial disposition and orientation of ore-hosting channels was controlled by paleo-topography, probably defined by syn-volcanic faults, but the textures we describe show that within the channel the geometry of the entire embayment was the product of erosion. The sulfide melt itself played a major role in the process owing to its high density, high heat content and very low viscosity, but the hydrated nature of the underlying altered basalt was also critical. Fluids were released from the basalt due to the high temperature in the 1–2cm immediately beneath the sulfide melt with instant flash boiling creating a network of microfractures. Pre-existing fracture networks and breccia in the basalt allowed the sulfide melt to locally infiltrate the substrate to a greater depth increasing the hydraulic head at the tip of the fracture, thus accelerating the erosion process. Once a critical sulfide melt thickness is reached, partly aided by a growing pile of matrix (net-textured) sulfides, the pressure difference on the embayment floor compared to the basalt at the bottom edges of the embayment becomes high enough to allow the liquid sulfides to melt sideways to form a pinchout.

Advanced Identification and Quantification of In-Bearing Minerals by Scanning Electron Microscope-Based Image Analysis

The identification and accurate characterization of discrete grains of rare minerals in sulfide base-metal ores is usually a cumbersome procedure due to the small grain sizes (typically <10 μm) and complex mineral assemblages in the material. In this article, a new strategy for finding and identifying indium minerals, and quantifying their composition and abundance is presented, making use of mineral liberation analysis (MLA) and electron probe microanalysis (EPMA). The method was successfully applied to polymetallic massive sulfide ores from the Neves-Corvo deposit in Portugal. The presence of roquesite and sakuraiite could be systematically detected, their concentration quantified by MLA measurements, and their identity later confirmed by EPMA analyses. Based on these results, an almost complete indium deportment could be obtained for the studied samples. This validates the approach taken, combining automated mineralogy data with electron microprobe analysis. A similar approach could be used to find minerals of other common minor and trace elements in complex base-metal sulfide ores, for example Se, Ge, Sb, or Ag, thus permitting the targeted development of resource technologies suitable for by-product recovery.

Минералы Fe в зоне окисления колчеданных руд Южно-Печенгской структурной зоны, Кольский регион: идентификация методом рамановской спектроскопии

Минералы Fe в зоне окисления колчеданных руд Южно-Печенгской структурной зоны, Кольский регион: идентификация методом рамановской спектроскопии

Investigations of CuFeS2 semiconductor mineral from ocean rift hydrothermal vent fields by Cu NMR in a local field

The results of investigating natural samples of chalcopyrite mineral CuFeS2 from massive oceanic sulfide ores of the Mid-Atlantic ridge by the 63Cu nuclear magnetic resonance (NMR 63Cu) in a local field at room temperature are presented. The significant width of the resonance lines found in the 63Cu NMR spectrum directly testifies to a wide distribution of local magnetic and electric fields in the investigated chalcopyrite samples. This distribution can be the consequence of an appreciable deviation of the structure of the investigated chalcopyrite samples from the stoichiometric one. The obtained results show that the pulsed 63Cu NMR can be an efficient method for studying the physical properties of deep-water polymetallic sulfides of the World Ocean.

Distribution of indium in ores of some base metal and tin–sulfide deposits in Siberia and the Russian Far East

The study of base-metal massive sulfide and tin–sulfide deposits in Siberia and the Russian Far East has revealed that the indium content in ores exceeding the average statistical value at similar deposits worldwide could be economically important. Sphalerite and chalcopyrite and chalcopyrite, bornite, and sphalerite are the major indium carriers in the base-metal massive sulfide and tin–sulfide ores, respectively. In addition, base-metal massive sulfide ores have high Cd, Ag, and Te contents, whereas tin–sulfide ores have elevated Ge, Ga, and Nb contents. This has stimulated the investment attractiveness of these deposits.

3D vector finite-element electromagnetic forward modeling for large loop sources using a total-field algorithm and unstructured tetrahedral grids

Unstructured tetrahedral grids with local refinement facilitate the use of total-field solution approaches to geophysical electromagnetic (EM) forward problems. These approaches, when combined with the vector finite-element (FE) method and with refinement near transmitters and receivers, can give accurate solutions and can easily handle realistic models with complex geometry and topography. We have applied this approach to 3D forward modeling for fixed- and moving-loop configurations. MUMPS, a direct solver, was used to solve the linear system of equations generated by FE analysis. A direct solver is particularly suited to the moving-loop configuration for which the right side is different for every transmitter loop, but for which the coefficient matrix is unchanged. Therefore, the coefficient matrix need only be factorized once, and then the system can be solved efficiently for all different right sides. We compared our results with several typical scenarios from the literature: a conductive brick in a homogeneous half-space and a complex conductor at a vertical contact both for fixed-loop configurations, and a homogeneous half-space for a moving-loop configuration. We also evaluated results for the massive sulfide ore deposit of the Ovoid Zone at Voisey’s Bay, Labrador, Canada, for which we considered fixed- and moving-loop configurations. This model also provides an illustration of the complex vortex current systems that are generated by time-domain EM methods within highly conductive ore bodies in a resistive host.

THE 3D TRANSIENT ELECTROMAGNETIC FORWARD MODELING OF VOLCANOGENIC MASSIVE SULFIDE ORE DEPOSITS

AbstractThe transient electromagnetic forward modeling of volcanogenic massive sulfide (VMS) ore deposits is to calculate the eddy currents electromagnetic response of a three dimensional body in the full space of deep‐sea environment. We simulated the three dimensional transient electromagnetic response of the VMS deposits using full‐domain vector finite element method. The ore body was discretized with brick rectangular elements. The finite element equation was deduced in frequency domain by employing Galerkin procedure, and the conversion to time domain was by inverse Fourier transform. We confirmed the validity of the full‐domain vector finite element algorithm by comparing simulated results with analytical solutions of double half‐space model. The results have a good agreement with each other, which indicates that the vector finite element method is capable of solving whole space problem. In order to demonstrate the ability of the numerical method in calculating the response of VMS deposits containing complex boundary conditions, we compared vector finite element solution of a three dimensional electrical model with physical experiment results according to electromagnetic physical scale modeling rules. The comparison suggests that for the complex electromagnetic boundary of seawater, ore body and country rocks, the transient electromagnetic response of VMS deposits calculated by full‐domain vector finite element method has same features with the physical scale modeling result. The vector finite element method is simple and its results are precise with obvious and clear anomaly response.

First results regarding the influence of mineralogy on the mechanical properties of seafloor massive sulfide samples

Seafloor Massive Sulfides (SMS) are increasingly accepted as important marine raw material resources for the future, in particular because of their polymetallic character. Many industrial nations are researching not only on the scientific importance of these deposits but also on their economic value. Regarding the current state of the international exploration, mainly two-dimensional surface-close observations are accessible, whereas only some core data and measurements are publicly available to date. In fact, there are few successful drilling campaigns containing information about the size and shape, which also give information on the structure and content of modern massive sulfide ore bodies in their third dimension. Regarding the mechanical properties of SMS samples, only few data are available. Geotechnical data of these deposits are important in order to develop an efficient mining technology for exploitation. In this research, 12 SMS samples from two different locations were investigated. Based on the mineralogical characterization of the studied samples the geotechnical properties were preliminary correlated with the mineralogical results. The comparative study indicates how far the geotechnical data are controlled by mineral type and composition, including the porosity. A regression relation between compressive strength and the porosity based on the mineralogy shows a distinct relation between these parameters. Therefore, the geomechanical and mineralogical features have a strong importance for deep-sea mining applications and this should be kept in mind considering the hyperbaric effects on the rock cutting.

Structural evolution of the Palaeoproterozoic Sala stratabound Zn-Pb-Ag carbonate-replacement deposit, Bergslagen, Sweden

A structural investigation of the Sala Zn–Pb–Ag deposit in the Bergslagen mining district of southern Sweden shows that it is associated with two tectonic structures: the N–NW-trending Storgruveskölen shear zone (SSZ), which is parallel to the strike of the mined ore bodies, and the F1 Sala syncline with a fold hinge plunging c. 35° towards NNW, which is parallel to the plunge of the entire mineralised system. The Sala syncline was refolded by F2 folds, leading to flattening and local reversals in the plunge of F1 folds and the ore bodies. Field evidence suggests that the SSZ represents both a phase of D3 reverse dip-slip shearing and a later (D4) phase of dextral strike-slip reactivation. However, a high concentration of pre- to syn-D1 skarn- and sulphide-bearing vein networks and breccias adjacent to the SSZ, which are gradational into the mined massive sulphide ore bodies, suggest that stages in the formation of the SSZ predated D3 and D4. It may consequently constitute a reactivated pre- to syn-D1 structure. The distribution of breccia and hydrothermal alteration together with the highly discordant nature of the deposit are consistent with a pre- to syn-D1 timing of ore formation, involving of cross-stratal fluid flow along the proto-SSZ and subordinate fluid flow parallel to volcanic interbeds in the host carbonate rock. Three δ34S determinations on sphalerite (2.1–2.4‰) and galena (1.2‰), respectively, are consistent with a magmatic source for ore sulphur, as has been suggested for many other sulphide deposits in Bergslagen.

Determination of acid forming potential of massive sulfide minerals and the tailings situated in lead/zinc mining district of Balya (NW Turkey)

Weathering of sulfide minerals is a major source of acid production in nature and especially in mining territories. Pyrite is not the only principal mineral that generates acid drainage: other sulfide minerals (sphalerite, galena, chalcopyrite, etc.) may also be responsible for acid production. In addition to massive sulfide minerals, sulfide-bearing mine tailings may also produce acid drainage due to oxidation and hydrolysis reactions in waste dumps. The lead/zinc (Pb/Zn) mining region in Balya and Balıkesir, in Turkey, has operated mines intensively since the 1860s; so that characterization of the sulfide minerals and tailings situated and formed around the mining site is of great importance to secure a sustainable environment. For this purpose, acid production and neutralization potentials of massive sulfide ores of the region, and in the Pb/Zn process facility mine tailings from ten different points of tailings dam, have been determined by applied conventional Acid-Base Accounting (ABA) and Net Acid Generation (NAG) static tests after chemical and mineralogical analysis. The NAG pH and net acid production potential (NAPP) values were compared on a chart in order to classify the samples as either acid generating or non-acid generating. According to the comparisons, the sulfide minerals were classified as potentially acid forming (PAF). Massive pyrite had the highest NAPP and NAG pH value of 1966.6 kg H2SO4/ton and 1.91, respectively and the galena had the lowest NAPP value of 558.9 kg H2SO4/ton. However, the sphalerite NAG leachate pH value of 4.30 was the highest in sulfide minerals so that the sphalerite plotted near the uncertainty reference border in the PAF zone. In the mine tailings, NAPP values of 105.9 kg H2SO4/ton on average and the NAG pH values of over 7.5 were determined. In addition to these tests, water leaching (agitation test) was carried out on tailings in order to generate more information. The tailings did not generate acidic leachates as they lie on limestone bed rock which neutralized the acidity.

An Early Cretaceous carbonate replacement origin for the Xinqiao stratabound massive sulfide deposit, Middle-Lower Yangtze Metallogenic Belt, China

Stratabound massive sulfide deposits are widespread along the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and serve as an important copper producer in China. Two contrasting genetic models have been proposed, interpreting the stratabound massive sulfide deposits as a Carboniferous SEDEX protore overprinted by Cretaceous magmatic-hydrothermal system or an Early Cretaceous carbonate replacement deposit. These two contrasting models have been applied to the Xinqiao stratabound Cu-Au sulfide deposit, which is dominated by massive sulfide ores hosted in marine carbonates of the Carboniferous Chuanshan and Huanglong Formations, with minor Cu-Au skarn ores localized in the contact zone between the Cretaceous diorite Jitou stock and the Carboniferous carbonate rocks. New SIMS zircon U-Pb dating suggests that the Jitou stock formed at 138.5±1.1Ma (2σ, MSWD=0.6). Pyrite Re-Os dating yields an imprecise date of 142±47Ma (2σ, MSWD=7.8). The geochronological data thus constrain the mineralization of the Xinqiao deposit at Early Cretaceous.Fluid inclusions in prograde skarn diopside have homogenization temperatures of 450–600°C and calculated salinities of 13–58wt.% NaCl equiv. Quartz from the stratabound ores and pyrite-quartz vein networks beneath the stratabound ores have homogenization temperatures of 290–360 and 200–300°C, with calculated salinities of 5–12 and 2–10wt.% NaCl equiv., respectively. Quartz from the skarn ores and veins beneath the stratabound ores have δ18O values of 12.32±0.55 (2 SD, n=22) and 15.57±1.92‰ (2 SD, n=60), respectively, corresponding to calculated δ18O values of 6.22±1.59 (2σ) and 6.81±2.76‰ (2σ) for the equilibrated ore-forming fluids. The fluid inclusion and oxygen isotope data thus support a magmatic-hydrothermal origin rather than a SEDEX system for the stratabound ores, with the hydrothermal fluids most likely being derived from the Jitou stock or associated concealed intrusion. Results from this study have broad implications for the genesis and exploration of other stratabound massive sulfide deposits along the MLYMB.

New 40Ar/39Ar ages from the Kalatag district in the Eastern Tianshan, NW China: Constraints on the timing of Cu mineralization and stratigraphy

The Kalatag region in the Eastern Tianshan of NW China contains a number of economically important Cu deposits. Among these, the South Meiling VMS deposit is hosted in the Late Ordovician to Early Silurian dacitic tuff belonging to the Daliugou Formation. The deposit is composed of two domains: a concordant massive sulfide ore domain and a discordant vein-type ore domain located in the footwall phyllic alteration zone. Here we report new 40Ar/39Ar ages on sericite from the phyllic alteration zone to better constrain the timing and genesis of mineralization. The sericite displays markedly flat 40Ar/39Ar age spectra, yielding a 40Ar/39Ar plateau age of 438.8±3.0Ma, and an isochron age of 443.0±11.0Ma. The 40Ar/39Ar age is in good agreement with the ReOs age reported earlier, placing the timing of CuZn mineralization at 434.2±3.9Ma. The age is also consistent with the field relationships that concordant massive sulfide orebody formed later than discordant vein-type orebody. Another deposit at Hongshi is hosted in basaltic andesites of the Daliugou Formation. The orebodies cut the phyllic alteration zone indicating that the Cu mineralization formed later than the phyllic alteration. Hydrothermal sericite from the phyllic alteration zone from this deposit yielded flat 40Ar/39Ar age spectra, with 40Ar/39Ar plateau ages of 441.5±3.2Ma and 446.4±4.6Ma, and isochron ages of 445.8±5.6Ma and 448.8±7.3Ma, respectively. This age is obviously older than the ReOs age, which is also in conformity with the field relations that quartz-sulfide veins cut the sericitization zone.Our 40Ar/39Ar ages offer precise constraints on Early Paleozoic Cu mineralization in the Eastern Tianshan Orogen. These results indicate that the Lower Unit basaltic andesites of the Daliugou Formation formed earlier than 446Ma. We thus consider that the Daliugou Formation formed during Middle Ordovician to Early Silurian. We also propose several metallogenic events in the Kalatag area including: (1) an Early VMS CuZn and hydrothermal vein Cu mineralization at 440–430Ma; (2) porphyry Cu and skarn Fe mineralization at 390–380Ma; and (3) a Late CuAu mineralization at ca. 300Ma. These three metallogenic events were coeval with the distinct magmatic pulses in the Kalatag area.

Interspinifex Ni Sulfide Ore from the Coronet Shoot, Kambalda: Characterization Using Microbeam X-Ray Fluorescence Mapping and 3-D X-Ray Computed Tomography

Interspinifex ores are developed where pools of sulfide liquid overlie thermally eroded komatiite flows, such that sulfide occupies the space between spinifex olivine plates. Microbeam X-ray fluorescence mapping and 3-D X-ray computed tomography have been used to investigate microstructures and chemical zonation within interspinifex ores from Coronet shoot, Kambalda. Sulfide compositions in the interspinifex space match the composition of the overlying sulfide pool. Aluminous silicate, interpreted as displaced silicate melt, forms a film at the silicate-sulfide interface, locally developing dome-like plumes. The film and plumes are characterized by fine skeletal chromite that diminishes in abundance over about a decimeter downward into the interspinifex zone. These relationships are strong evidence for a primary magmatic origin for this ore type, driven by the strong tendency of dense, inviscid sulfide liquid to infiltrate and melt underlying rocks. Such infiltration-melting interfaces may be a common feature at the base of massive sulfide ores, taking different forms depending on the lithological and fracturing characteristics of the footwall rocks.

A magnetite-rich Cyprus-type VMS deposit in Ortaklar: A unique VMS style in the Tethyan metallogenic belt, Gaziantep, Turkey

The Ortaklar VMS deposit is hosted in the Koçali Complex consisting of basalts and deep sea pelagic sediments, which formed by rifting and continental break-up of the southern Neotethyan in Late Triassic. The basalts are of NMORB-type without notable crustal contamination. From the surface to depth, the Ortaklar deposit consists of a gossan zone, a thick massive ore zone and a poorly developed stockwork zone. Primary mineralisation is characterised by distinctive facies including sulphide breccias (proximal), graded beds (distal), stockworks and chimney fragments. Ore mineral abundances decrease in the order of pyrite, magnetite, chalcopyrite, and sphalerite. Two distinct phases of mineralisation, massive magnetite and massive sulphide, are present in the Ortaklar deposit. Textural evidence (e.g., magnetite replacing sulphides) and the spatial relationships with the host rocks indicate that magnetite and sulphide minerals were generated in different stages. The transition from sulphide to magnetite mineralisation is interpreted to relate to variation in H2S content of ore fluids. The 1st stage massive sulphide ore might have formed by early hydrothermal fluids rich in Fe and H2S. The 2nd stage massive magnetite might have formed by later neutral hydrothermal fluids rich in Fe but poor in H2S, replacing the pre-existing sulphide ore.The alteration patterns, mineral paragenesis, lithological features (massive ore-stockwork ore-gossan) of the Ortaklar deposit together with its trace elements, Cu-Pb-Zn-Au-Ag and REE signatures are all consistent with a Cyprus-type VMS system. The δ34S values in pyrite and chalcopyrite samples range from 2.6 to 5.7‰, indicating that the hydrothermal fluids were associated with sub-seafloor igneous activity, typical of Cyprus-type VMS deposits. However, magnetite formed later than sulphide minerals in the Ortaklar deposit, contrasting with typical Cyprus-type VMS deposits where magnetite generally occurs in lower sections. Consequently, although the Ortaklar deposit generally conforms to Cyprus-type deposits, it is distinguished from them by its late stage and high magnetite concentration. Thus, the Ortaklar deposit is thought to be an exceptional and perhaps unique Cyprus-type VMS deposit.

3-D Geologic Modeling in the Flin Flon Mining District, Trans-Hudson Orogen, Canada: Evidence for Polyphase Imbrication of the Flin Flon-777-Callinan Volcanogenic Massive Sulfide Ore System

Three-dimensional geologic modeling by integrated analysis and interpretation of drill core, 2-D and 3-D seismic, mine survey, and geologic map data provides new insights into the structural setting of the 85.5 million tonne (Mt) Flin Flon-Callinan-777 volcanogenic massive sulfide (VMS) ore system hosted in the Paleoproterozoic Flin Flon belt of Manitoba and Saskatchewan, Canada. The resultant camp-scale 3-D geologic model was, in addition to the densely drill intersected VMS-hosting mine horizon, constrained by lithostratigraphic reference drill holes intersecting the footwall and hanging-wall rock successions of the ore system, which were established by relogging 52 drill holes and systematically reconciling the lithofacies classes in their log descriptions with the lithofacies units of the 1:10,000-scale Flin Flon mining district geologic map. The lateral persistence and large stratigraphic range of these drill hole markers supported seismic interpretation and allowed tracing lithostratigraphic horizons and structures in areas with low drill hole density, expanding 3-D subsurface insight from the local to the more regional structural setting of the ore system. The overall 3-D modeled geometry and topological relationships between lithostratigraphic surfaces and multiple generations of thrust faults suggest that the Flin Flon mining district is underlain by an E-dipping stack of W-vergent thrust imbricates that formed during precollisional and collisional stages of the 1.9 to 1.8 Ga Trans-Hudson orogeny. The imbricate stack was subsequently deformed by E-trending ductile thrust faults that internally imbricated the Flin Flon arc assemblage and the molasse cover rocks of the Missi Group and brought up rocks of the former over the latter in a northerly direction. The VMS-hosting Millrock Member has been stacked on at least four structural levels, enhancing the VMS potential in the footwall and hanging wall of the known ore deposits where both thrust systems intersect.

Drill Targeting with 3-D Seismics for Volcanogenic Massive Sulfide Exploration in the Flin Flon Mining Camp

A 17-km2 3-D seismic survey was conducted in 2007 within the Flin Flon volcanogenic massive sulfide (VMS) mining camp as part of the Targeted Geoscience Initiative-3. The resultant 3-D images show strong reflectivity associated with the ore-hosting mine horizon and prominent reflections attributed to the known ore zones. Structural repetition of the mine horizon is clearly identified in the seismic images with at least three levels identified. The 3-D seismic images have been used in conjunction with detailed geologic and geophysical drill hole logs to identify new exploration drill targets. Results from the first three seismic-based exploration drill holes are presented. The drill holes encountered reflective geologic contacts at depths within 3 to 8% of those predicted from the 3-D seismic images. In the first case, a gabbro of no economic significance was encountered at the target depth. In the second case, a highly altered mafic volcanic panel with stringer mineralization was identified sitting blind beneath surface exposures of sandstone. In the third case, the target turned out to be an additional structural level of the mine rhyolite, which provides a new horizon for further exploration. A small massive sulfide ore lens was discovered during follow-up drilling around the third target. These results demonstrate that seismic methods can be successfully applied for mineral exploration in areas of existing infrastructure and cultural noise.

Petrogenesis and Geodynamic Evolution of the Paleoproterozoic (~1878 Ma) Trout Lake Volcanogenic Massive Sulfide Deposit, Flin Flon, Manitoba, Canada

The Trout Lake deposit (1878 ± 1 Ma) is a rhyolite-hosted, bimodal-mafic, volcanogenic massive sulfide (VMS) deposit. It is one of the largest VMS deposits in the Flin Flon mining district, containing 21.8 Mt of Cu-Zn rich ore. The deposit underwent greenschist facies metamorphism and polyphase synvolcanic to postvolcanic hydrothermal alteration. Footwall and hanging-wall lithostratigraphic units of the Trout Lake deposit occur as an upright, steeply NE dipping, homoclinal succession of thrust-repeated volcanic and siliciclastic sedimentary units. The deposit consists of several massive sulfide ore lenses hosted within a felsic volcanic unit that represents a localized felsic eruptive center composed of flows, synvolcanic sills, and volcaniclastic lithofacies with an FIIIb-type tholeiitic to transitional rhyolite composition (Zr = 213–385 ppm; Ybcn = 47–100; La/Ybcn = 0.97–2.33). The felsic unit occurs along strike of an andesitic unit comprising an intercalation of high-MgO andesite (MgO > 5.0 wt %) and Nb-enriched andesite (Nb = 10–13 ppm) flows that are underlain by a footwall basaltic unit composed of flow lithofacies with a low-Ti tholeiitic basaltic composition (TiO2 < 0.48 wt %; Zr = 15–17 ppm; Al2O3/TiO2 = 37–45). Postvolcanic gabbros with back-arc basin basalt composition intrude the volcanic units, which are unconformably covered by a younger argillite unit deposited at ca. <1843 ± 9 Ma. The felsic volcanic and argillite units were repeated and structurally interleaved during west-directed thrusting. The presence of low-Ti tholeiitic basalts indicates high-temperature melting (1,200°–1,500°C) of strongly depleted refractory mantle sources (Nb/Yb 1.45) variably affected by slab-derived hydrous melts. These petrologic characteristics suggest a geochemically heterogeneous mantle wedge that underwent metasomatism by slab-derived components. In addition, zircon saturation thermometry indicates that FIIIb-type rhyolites formed at temperatures >900°C during partial melting of mafic lower crust. Collectively, the occurrence of high-temperature melts indicates that the Trout Lake VMS deposit formed in a hot, intraoceanic, extensional-arc geodynamic setting. Intra-arc rifting, asthenospheric upwelling, and subduction of young and hot oceanic crust are mechanisms that explain the high-temperature magmatism and are features consistent with the formation of the massive sulfide ore lenses. The back-arc basalt geochemical signatures of the postvolcanic gabbros suggest that the tectonic environment of the Trout Lake area evolved from an intra-arc rift, during the deposition of the ore lenses, to an incipient back-arc basin during the intrusion of the gabbros.

Structural Reconstruction of the Flin Flon Volcanogenic Massive Sulfide Mining District, Saskatchewan and Manitoba, Canada

The Flin Flon mining district is part of a greenstone belt, the Flin Flon-Glennie Complex, in the Paleoproterozoic Trans-Hudson orogen. Its tectonic history began prior to 1872 Ma with the development of regional folds—the faulted F1 Burley Lake syncline and F2 Hidden Lake syncline—during D1 and D2 intraoceanic accretion of the 1888 Ma Flin Flon arc to other volcanic terranes. Amalgamation of the Flin Flon to Glennie terrane, possibly during D3, produced a W-propagating thrust-fold belt and basins in which fluvial sedimentary rocks were deposited between 1847 Ma and 1842 Ma. As the fold-thrust belt migrated westward, these rocks were incorporated into a stack of E-dipping thrust sheets bounded by NNW-striking thrust faults (1920 fault) and internally folded by W-verging folds (Pipeline, Mud Lake, and Grant Lake synclines). Subsequent D4 collision of the Flin Flon-Glennie Complex with the Archean Sask microcontinent was broadly coeval with but outlasted the emplacement of 1840 Ma Phantom Lake dikes. D4 produced a second truncating fold-thrust system characterized by N-directed thrust faults (Club Lake and Railway faults) and E-trending folds (Flin Flon Creek syncline). These folds were overprinted by two regional cleavages, and the thrust faults were reactivated as oblique-slip shear zones, either late during the same collisional event (D5) or during terminal collision (D6) of the Sask craton and Flin Flon-Glennie Complex with the Superior craton at 1.83 to 1.79 Ga. The Flin Flon volcanogenic massive sulfide ore system was thrust-imbricated during D3 and D4, and ore lenses were stretched parallel to a regional, SE-plunging, stretching lineation that formed during D4 and was later modified during D5.