scholarly journals Accessory mineral thermobarometry, trace element chemistry, and stable O isotope systematics, Mooshla Intrusive Complex (MIC), Doyon-Bousquet-LaRonde mining camp, Abitibi greenstone belt, Québec

2021 ◽  
Author(s):  
K Neyedley ◽  
J J Hanley ◽  
Z Zajacz ◽  
M Fayek
Keyword(s):  
Trace Element ◽  
Greenstone Belt ◽  
Analytical Techniques ◽  
Accessory Mineral ◽  
Intrusive Complex ◽  
Magmatic Complex ◽  
Accessory Minerals ◽  
Abitibi Greenstone Belt ◽  
Magmatic Body ◽  
World Class

The Mooshla Intrusive Complex (MIC) is an Archean polyphase magmatic body located in the Doyon-Bousquet-LaRonde (DBL) mining camp of the Abitibi greenstone belt, Québec, that is spatially associated with numerous gold (Au)-rich VMS, epizonal 'intrusion-related' Au-Cu vein systems, and shear zone-hosted (orogenic?) Au deposits. To elucidate the P-T conditions of crystallization, and oxidation state of the MIC magmas, accessory minerals (zircon, rutile, titanite) have been characterized using a variety of analytical techniques (e.g., trace element thermobarometry). The resulting trace element and oxythermobarometric database for accessory minerals in the MIC represents the first examination of such parameters in an Archean magmatic complex in a world-class mineralized district. Mineral thermobarometry yields P-T constraints on accessory mineral crystallization consistent with the expected conditions of tonalite-trondhjemite-granite (TTG) magma genesis, well above peak metamorphic conditions in the DBL camp. Together with textural observations, and mineral trace element data, the P-T estimates reassert that the studied minerals are of magmatic origin and not a product of metamorphism. Oxygen fugacity constraints indicate that while the magmas are relatively oxidizing (as indicated by the presence of magmatic epidote, titanite, and anhydrite), zircon trace element systematics indicate that the magmas were not as oxidized as arc magmas in younger (post-Archean) porphyry environments. The data presented provides first constraints on the depth and other conditions of melt generation and crystallization of the MIC. The P-T estimates and qualitative fO2 constraints have significant implications for the overall model for formation (crystallization, emplacement) of the MIC and potentially related mineral deposits.

Ore mineralogy, pyrite chemistry, and S isotope systematics of magmatic-hydrothermal Au mineralization associated with the Mooshla Intrusive Complex (MIC), Doyon-Bousquet-LaRonde mining camp, Abitibi greenstone belt, Québec

2021 ◽  
Author(s):  
K Neyedley ◽  
J J Hanley ◽  
P Mercier-Langevin ◽  
M Fayek
Keyword(s):  
Trace Element ◽  
Base Metal ◽  
Greenstone Belt ◽  
Analytical Techniques ◽  
Trace Element Distribution ◽  
Intrusive Complex ◽  
Sulphur Isotope ◽  
Distribution Maps ◽  
Abitibi Greenstone Belt ◽  
Base Metal Sulphides

The Mooshla Intrusive Complex (MIC) is an Archean polyphase magmatic body located in the Doyon-Bousquet-LaRonde (DBL) mining camp of the Abitibi greenstone belt, Québec. The MIC is spatially associated with numerous gold (Au)-rich VMS, epizonal 'intrusion-related' Au-Cu vein systems, and shear zone-hosted (orogenic?) Au deposits. To elucidate genetic links between deposits and the MIC, mineralized samples from two of the epizonal 'intrusion-related' Au-Cu vein systems (Doyon and Grand Duc Au-Cu) have been characterized using a variety of analytical techniques. Preliminary results indicate gold (as electrum) from both deposits occurs relatively late in the systems as it is primarily observed along fractures in pyrite and gangue minerals. At Grand Duc gold appears to have formed syn- to post-crystallization relative to base metal sulphides (e.g. chalcopyrite, sphalerite, pyrrhotite), whereas base metal sulphides at Doyon are relatively rare. The accessory ore mineral assemblage at Doyon is relatively simple compared to Grand Duc, consisting of petzite (Ag3AuTe2), calaverite (AuTe2), and hessite (Ag2Te), while accessory ore minerals at Grand Duc are comprised of tellurobismuthite (Bi2Te3), volynskite (AgBiTe2), native Te, tsumoite (BiTe) or tetradymite (Bi2Te2S), altaite (PbTe), petzite, calaverite, and hessite. Pyrite trace element distribution maps from representative pyrite grains from Doyon and Grand Duc were collected and confirm petrographic observations that Au occurs relatively late. Pyrite from Doyon appears to have been initially trace-element poor, then became enriched in As, followed by the ore metal stage consisting of Au-Ag-Te-Bi-Pb-Cu enrichment and lastly a Co-Ni-Se(?) stage enrichment. Grand Duc pyrite is more complex with initial enrichments in Co-Se-As (Stage 1) followed by an increase in As-Co(?) concentrations (Stage 2). The ore metal stage (Stage 3) is indicated by another increase in As coupled with Au-Ag-Bi-Te-Sb-Pb-Ni-Cu-Zn-Sn-Cd-In enrichment. The final stage of pyrite growth (Stage 4) is represented by the same element assemblage as Stage 3 but at lower concentrations. Preliminary sulphur isotope data from Grand Duc indicates pyrite, pyrrhotite, and chalcopyrite all have similar delta-34S values (~1.5 � 1 permille) with no core-to-rim variations. Pyrite from Doyon has slightly higher delta-34S values (~2.5 � 1 permille) compared to Grand Duc but similarly does not show much core-to-rim variation. At Grand Duc, the occurrence of Au concentrating along the rim of pyrite grains and associated with an enrichment in As and other metals (Sb-Ag-Bi-Te) shares similarities with porphyry and epithermal deposits, and the overall metal association of Au with Te and Bi is a hallmark of other intrusion-related gold systems. The occurrence of the ore metal-rich rims on pyrite from Grand Duc could be related to fluid boiling which results in the destabilization of gold-bearing aqueous complexes. Pyrite from Doyon does not show this inferred boiling texture but shares characteristics of dissolution-reprecipitation processes, where metals in the pyrite lattice are dissolved and then reconcentrated into discrete mineral phases that commonly precipitate in voids and fractures created during pyrite dissolution.

Laser ablation ICP MS trace element composition of native gold from the Abitibi Greenstone belt, Timmins Ontario.

2021 ◽  
Author(s):  
John D. Greenough ◽  
Alejandro Velasquez ◽  
Mohamed Shaheen ◽  
Joel Gagnon ◽  
Brian J. Fryer ◽  
...  
Keyword(s):  
Trace Elements ◽  
Laser Ablation ◽  
Trace Element ◽  
Greenstone Belt ◽  
Native Gold ◽  
Internal Standard ◽  
Gold Deposits ◽  
Ore Deposits ◽  
Abitibi Greenstone Belt ◽  
Icp Ms

Trace elements in native gold provide a “fingerprint” that tends to be unique to individual gold deposits. Fingerprinting can distinguish gold sources and potentially yield insights into geochemical processes operating during gold deposit formation. Native gold grains come from three historical gold ore deposits; Hollinger, McIntyre (quartz-vein ore), and Aunor near Timmins, Ontario, at the western end of the Porcupine gold camp and the south-western part of the Abitibi greenstone belt. Laser-ablation, inductively-coupled plasma mass spectrometry (LA ICP MS) trace element concentrations were determined on 20 to 25 µm wide, 300 µm long rastor trails in ~ 60 native gold grains. Analyses used Ag as an internal standard with Ag and Au determined by a scanning electron microscope with an energy dispersive spectrometer. The London Bullion Market AuRM2 reference material served as the external standard for 21 trace element analytes (Al, As, Bi, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Pd, Pt, Rh, Sb, Se, Si, Sn, Te, Ti, Zn; Se generally below detection in samples). Trace elements in native gold associate according to Goldschmidt’s classification of elements strongly suggesting that element behavior in native Au is not random. Such element behavior suggests that samples from each Timmins deposit formed under similar but slightly variable geochemical conditions. Chalcophile and siderophile elements provide the most compelling fingerprints of the three ore deposits and appear to be mostly in solid solution in Au. Lithophile elements are not very useful for distinguishing these deposits and element ABSTRACT CUT OFF BY SOFTWARE

The Westwood Deposit, Southern Abitibi Greenstone Belt, Canada: An Archean Au-Rich Polymetallic Magmatic-Hydrothermal System—Part II. Hydrothermal Alteration, Mineralization, and Geologic Model

2021 ◽  
Author(s):  
D. Yergeau ◽  
P. Mercier-Langevin ◽  
B. Dubé ◽  
V. McNicoll ◽  
S. E. Jackson ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Greenstone Belt ◽  
Massive Sulfide ◽  
Alteration Zone ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Abitibi Greenstone Belt ◽  
The North ◽  
Vms Deposits ◽  
Ore Zones

Abstract The Westwood deposit, located in the Archean Doyon-Bousquet-LaRonde mining camp in the southern Archean Abitibi greenstone belt, contains 4.5 Moz (140 metric t) of gold. The deposit is hosted in the 2699–2695 Ma submarine, tholeiitic to calc-alkaline volcanic, volcaniclastic, and intrusive rocks of the Bousquet Formation. The deposit is located near the synvolcanic (ca. 2699–2696 Ma) Mooshla Intrusive Complex that hosts the Doyon epizonal intrusion-related Au ± Cu deposit, whereas several Au-rich volcanogenic massive sulfide (VMS) deposits are present east of the Westwood deposit. The Westwood deposit consists of stratigraphically stacked, contrasting, and overprinting mineralization styles that share analogies with both the intrusion-related and VMS deposits of the camp. The ore zones form three distinct, slightly discordant to stratabound corridors that are, from north (base) to south (top), the Zone 2 Extension, the North Corridor, and the Westwood Corridor. Syn- to late-main regional deformation and upper greenschist to lower amphibolite facies regional metamorphism affect the ore zones, alteration assemblages, and host rocks. The Zone 2 Extension consists of Au ± Cu sulfide (pyrite-chalcopyrite)-quartz veins and zones of disseminated to semimassive sulfides. The ore zones are spatially associated with a series of calc-alkaline felsic sills and dikes that crosscut the mafic to intermediate, tholeiitic to transitional, lower Bousquet Formation volcanic rocks. The metamorphosed proximal alteration consists of muscovite-quartz-pyrite ± gypsum-andalusite-kyanite-pyrophyllite argillic to advanced argillic-style tabular envelope that is up to a few tens of meters thick. The North Corridor consists of auriferous semimassive to massive sulfide veins, zones of sulfide stringers, and disseminated sulfides that are hosted in intermediate volcaniclastic rocks at the base of the upper Bousquet Formation. The Westwood Corridor consists of semimassive to massive sulfide lenses, veins, zones of sulfide stringers, and disseminated sulfides that are located higher in the stratigraphic sequence, at or near the contact between calc-alkaline dacite domes and overlying calc-alkaline rhyodacite of the upper Bousquet Formation. A large, semiconformable distal alteration zone that encompasses the North Corridor is present in the footwall and vicinity of the Westwood Corridor. This metamorphosed alteration zone consists of an assemblage of biotite-Mn garnet-chlorite-carbonate ± muscovite-albite. A proximal muscovite-quartz-chlorite-pyrite argillic-style alteration assemblage is associated with both corridors. The Zone 2 Extension ore zones and associated alteration are considered synvolcanic based on crosscutting relationships and U-Pb geochronology and are interpreted as being the distal expression of an epizonal magmatic-hydrothermal system that is centered on the upper part of the synvolcanic Mooshla Intrusive Complex. The North and Westwood corridors consist of bimodal-felsic Au-rich VMS-type mineralization and alteration produced by the convective circulation of modified seawater that included a magmatic contribution from the coeval epizonal Zone 2 Extension magmatic-hydrothermal system. The Westwood Au deposit represents one of the very few documented examples of an Archean magmatic-hydrothermal system—or at least of such systems formed in a subaqueous environment. The study of the Westwood deposit resulted in a better understanding of the critical role of magmatic fluid input toward the formation of Archean epizonal intrusion-related Au ± Cu and seafloor/subseafloor Au-rich VMS-type mineralization.

Two-stage evolution in an Archean tonalite suite: the Taschereau stock, Abitibi (Quebec, Canada)

1991 ◽  
Vol 28 (2) ◽  
pp. 172-183 ◽  
Author(s):  
Michel Jébrak ◽  
Luc Harnois
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Trace Element ◽  
Greenstone Belt ◽  
Shear Zones ◽  
Granitic Rocks ◽  
Element Abundances ◽  
Abitibi Greenstone Belt ◽  
Rock Types ◽  
End Members

The Taschereau stock occurs north of Timmins and Val-d'Or, Quebec, in the Abitibi greenstone belt of the Superior Province. This late Archean composite pluton is composed mainly of diorite–tonalite–trondhjemite cut by granitic rocks. Gold–molybdenum occurrences are associated with a zone of albite-rich rocks surrounding the granitic rocks. Diabase dykes and shear zones postdate all rock units. Field and geochemical evidence suggests that the Taschereau stock was emplaced diachronously. Trace-element geochemical modelling shows that trace-element abundances (rare-earth elements, Ti, Zr) of Taschereau granitic rocks are consistent with partial melting of preexisting Taschereau tonalitic rocks and implies that these two rock types are not end members of a single magma that evolved through fractional crystallization.

The Westwood Deposit, Southern Abitibi Greenstone Belt, Canada: An Archean Au-Rich Polymetallic Magmatic-Hydrothermal System—Part I. Volcanic Architecture, Deformation, and Metamorphism

2021 ◽  
Author(s):  
D. Yergeau ◽  
P. Mercier-Langevin ◽  
B. Dubé ◽  
M. Malo ◽  
A. Savoie
Keyword(s):  
Fractional Crystallization ◽  
Greenstone Belt ◽  
Massive Sulfide ◽  
Hydrothermal Systems ◽  
Lava Flows ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Abitibi Greenstone Belt ◽  
Intrusive Rocks ◽  
Ore Zones

Abstract The Westwood deposit (4.5 Moz Au) is hosted in the 2699–2695 Ma Bousquet Formation volcanic and intrusive rocks, in the eastern part of the Blake River Group, southern Abitibi greenstone belt. The Bousquet Formation is divided in two geochemically distinct members: a mafic to intermediate, tholeiitic to transitional lower member and an intermediate to felsic, transitional to calc-alkaline upper member. The Bousquet Formation is cut by the synvolcanic (2699–2696 Ma) polyphase Mooshla Intrusive Complex, which is cogenetic with the Bousquet Formation. The deposit contains three strongly deformed (D2 flattening and stretching), steeply S-dipping mineralized corridors that are stacked from north to south: Zone 2 Extension, North Corridor, and Westwood Corridor. The North and Westwood corridors are composed of Au-rich polymetallic sulfide veins and stratabound to stratiform disseminated to massive sulfide ore zones that are spatially and genetically associated with the calcalkaline, intermediate to felsic volcanic rocks of the upper Bousquet Formation. The formation of the disseminated to semimassive ore zones is interpreted as strongly controlled by the replacement of porous volcaniclastic rocks at the contact with more impermeable massive cap rocks that helped confine the upflow of mineralizing fluids. The massive sulfide lenses are spatially associated with dacitic to rhyolitic domes and are interpreted as being formed, at least in part, on the paleoseafloor. The epizonal, sulfide-quartz vein-type ore zones of the Zone 2 Extension are associated with the injection of subvolcanic, calc-alkaline felsic sills and dikes within the lower Bousquet Formation. These subvolcanic intrusive rocks, previously interpreted as lava flows, are cogenetic and coeval with the intermediate to felsic lava flows and domes of the upper Bousquet Formation. The change from fractional crystallization to assimilation- and fractional crystallization-dominated processes and transitional to calc-alkaline magmatism is interpreted to be responsible for the development of the auriferous ore-forming system. The Westwood deposit is similar to some Phanerozoic Au ± base metal-rich magmatic-hydrothermal systems, both in terms of local volcano-plutonic architecture and inferred petrogenetic context. The complex volcanic evolution of the host sequence at Westwood, combined with its proximity to a polyphase synvolcanic intrusive complex, led to the development of one of the few known large Archean subaqueous Au-rich magmatic-hydrothermal systems.

Hydrothermal Alteration Mineralogy and Geochemistry of the Archean World-Class Canadian Malartic Disseminated-Stockwork Gold Deposit, Southern Abitibi Greenstone Belt, Quebec, Canada

2019 ◽  
Vol 114 (6) ◽  
pp. 1057-1094 ◽  
Author(s):  
Stéphane De Souza ◽  
Benoît Dubé ◽  
Patrick Mercier-Langevin ◽  
Vicki McNicoll ◽  
Céline Dupuis ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Fault Zone ◽  
Hydrothermal Alteration ◽  
Greenstone Belt ◽  
Gold Mineralization ◽  
Amphibolite Facies ◽  
Alteration Zone ◽  
Gold Deposition ◽  
Abitibi Greenstone Belt ◽  
World Class

Abstract The Canadian Malartic stockwork-disseminated gold deposit is an Archean world-class deposit located in the southern Abitibi greenstone belt. It contains over 332.8 tonnes (t; 10.7 Moz) of Au at a grade of 0.97 ppm, in addition to 160 t (5.14 Moz) of past production (1935–1981). Although the deposit is partly situated within the Larder Lake-Cadillac fault zone, most of the ore occurs up to ~1.5 km to the south of the fault zone. The main hosts of the mineralized zones are greenschist facies turbiditic graywacke and mudstone of the Pontiac Group (~2685–2682 Ma) and predominantly subalkaline ~2678 Ma porphyritic quartz monzodiorite and granodiorite. These intrusions were emplaced during an episode of clastic sedimentation and alkaline to subalkaline magmatism known as the Timiskaming assemblage (<2680–2670 Ma in the southern Abitibi). The orebodies define two main mineralized trends, which are oriented subparallel to the NW-striking S2 cleavage and the E-striking, S-dipping Sladen fault zone. This syn- to post-D2 ductile-brittle to brittle Sladen fault zone is mineralized for more than 3 km along strike. The ore mainly consists of disseminated pyrite in stockworks and replacement zones, with subordinate auriferous quartz veins and breccia. Gold is associated with pyrite and traces of tellurides defining an Au-Te-W ± Ag-Bi-Mo-Pb signature. The orebodies are zoned outward, and most of the higher-grade (>1 ppm Au) ore was deposited as a result of iron sulfidation from silicates and oxides and Na-K metasomatism in carbonatized rocks. The alteration footprint comprises a proximal alteration envelope (K- or Na-feldspar-dolomite-calcite-pyrite ± phlogopite). This proximal alteration zone transitions to an outer shell of altered rocks (biotite-calcite-phengitic white mica), which hosts sub-ppm gold grades and reflects decreasing carbonatization, sulfidation, and aNa+/aH+ or aK+/aH+ of the ore fluid. Gold mineralization, with an inferred age of ~2664 Ma (Re-Os molybdenite), was contemporaneous with syn- to late-D2 peak metamorphism in the Pontiac Group; it postdates sedimentation of the Timiskaming assemblage along the Larder Lake-Cadillac fault zone (~2680–2669 Ma) and crystallization of the quartz monzodiorite. These chronological relationships agree with a model of CO2-rich auriferous fluid generation in amphibolite facies rocks of the Pontiac Group and gold deposition in syn- to late-D2 structures in the upper greenschist to amphibolite facies. The variable geometry, rheology, and composition of the various intrusive and sedimentary rocks have provided strain heterogeneities and chemical gradients for the formation of structural and chemical traps that host the gold. The Canadian Malartic deposit corresponds to a mesozonal stockwork-disseminated replacement-type deposit formed within an orogenic setting. The predominance of disseminated replacement ore over fault-fill and extensional quartz-carbonate vein systems suggests that the mineralized fracture networks remained relatively permeable and that fluids circulated at a near-constant hydraulic gradient during the main phase of auriferous hydrothermal alteration.

Pontiac metavolcanic rocks within the Cadillac tectonic zone, McWatters, Abitibi Belt, Quebec

1993 ◽  
Vol 30 (7) ◽  
pp. 1521-1531 ◽  
Author(s):  
David Morin ◽  
Michel Jébrak ◽  
Marc Bardoux ◽  
Normand Goulet
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Rare Earth Element ◽  
Greenstone Belt ◽  
Earth Element ◽  
Calc Alkaline ◽  
Tectonic Zone ◽  
Southern Boundary ◽  
Abitibi Greenstone Belt ◽  
Metavolcanic Rocks

The McWatters metavolcanic rocks are structurally bounded lenses within the Cadillac tectonic zone on the southern boundary of the Abitibi greenstone belt. They comprise komatiite, tholeiitic basalt and gabbro, and calc-alkaline andesitic lavas and volcaniclastic rocks cut by calc-alkaline dioritic and lamprophyric dykes. The McWatters basalts are mid-ocean-ridge basalt type tholeiites exhibiting low incompatible trace element contents and [La/Yb]N < 1. They may have formed via relatively high degree partial melting of a rare-earth element depleted mantle source. The andesites exhibit chondrite-normalized trace-element patterns with light-rare-earth and large-ion lithophile element enrichments and negative Nb and Ti anomalies, comparable to those of subduction-related calc-alkaline andesites. McWatters units are distinct from nearby Blake River Group rocks, despite comparable lithological assemblages and some common geochemical characteristics. The McWatters basalts exhibit lower Ti/Y, Zr/Y, and La/Yb than the Blake River tholeiites, whereas the McWatters andesites display lower Ti/Zr and higher Zr/Y than the Blake River calc-alkaline units. The McWatters tholeiites can be correlated with northern Pontiac Group tholeiitic units based on similar trace-element ratios and parallel rare-earth-element patterns. Thus, the McWatters tholeiites represent Pontiac rocks, underthrust beneath the southern Abitibi belt and appearing as isolated and retrograded lenses in the Cadillac tectonic zone. They may represent the remnants of an ocean basin that once separated the southern Abitibi greenstone belt from the Pontiac Subprovince.

scholarly journals (Day 5 - part I) Geology and disseminated-stockwork gold mineralization at the world-class Canadian Malartic mine, Abitibi greenstone belt, Canada

2017 ◽  
Author(s):  
S De Souza ◽  
B Dubé ◽  
V McNicoll ◽  
P Mercier-Langevin ◽  
R A Creaser ◽  
...  
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Abitibi Greenstone Belt ◽  
The World ◽  
World Class
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