Vein topology, structures, and distribution during the prograde formation of an Archean gold stockwork

2021 ◽  
Author(s):  
François Turlin ◽  
Stéphane De Souza ◽  
Michel Jébrak ◽  
Pierre-Arthur Groulier ◽  
Jordi Turcotte
Keyword(s):  
Gold Mineralization ◽  
Network Connectivity ◽  
Gold Concentration ◽  
Prograde Metamorphism ◽  
James Bay ◽  
Vein Density ◽  
Bay Area ◽  
Regional Deformation ◽  
Peak Metamorphism ◽  
Superior Craton

The Archean Cheechoo stockwork gold deposit is hosted by a felsic intrusion of tonalitic-granodioritic composition and crosscutting pegmatite dikes in the Eeyou Istchee James Bay area of Quebec, Canada (Archean Superior craton). The evolution of the stockwork is characterized herein using field relationships, vein density, and connectivity measurements on drill core and outcrop zones. The statistical distribution of gold is used to highlight mechanisms of stockwork emplacement and gold mineralization and remobilization. Two statistical populations of gold concentration are present. Population A is represented by gold grades below 1 g/t with a lognormal cumulative frequency. It is widespread in the hydrothermally altered (albite and quartz) and mineralized facies of the pluton. It is controlled by the development of quartz-feldspar-diopside veins as shown by the similar lognormal distribution of grades and vein density and by the correspondence of grades with network connectivity. Diopside and actinolite porphyroblasts in deformed veins within sodic and calcsilicate alteration zones are evidence for auriferous vein emplacement prior to the amphibolite facies peak of metamorphism. Population B (>1 g/t) is erratic and exhibits a strong nugget effect. It is present throughout the mineralized portion of the pluton and in pegmatites. This population is interpreted as the result of gold remobilization during prograde metamorphism and pegmatite emplacement following the metamorphic peak. The pegmatites are interpreted to have scavenged gold emplaced prior to peak metamorphism. These results show the isotropic behavior of the investigated stockwork during regional deformation and its development during the early stages of regional prograde metamorphism.

The timing of prograde metamorphism in the Pontiac Subprovince, Superior craton; implications for Archean geodynamics and gold mineralization

2019 ◽  
Vol 320 ◽  
pp. 111-136 ◽  
Author(s):  
Nicolas Piette-Lauzière ◽  
Carl Guilmette ◽  
Audrey Bouvier ◽  
Stéphane Perrouty ◽  
Pierre Pilote ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Prograde Metamorphism ◽  
Superior Craton

Predictive geochemistry of ore gold in Eastern Transbaikalia

2020 ◽  
Vol 26 (10) ◽  
pp. 6-14
Author(s):  
Yu. Pavlenko ◽  
Keyword(s):  
Gold Mineralization ◽  
Geological Mapping ◽  
Earth’S Crust ◽  
Natural Environments ◽  
Gold Concentration ◽  
Gold Ore ◽  
Natural Concentration ◽  
Eastern Transbaikalia ◽  
Earth's Crust ◽  
Gold Bearing

The subject of the research is the methods of forecasting the Eastern Transbaikalia - a large mining region of Russia, in which the main internal and external criteria for ore content are established by modern geological mapping at a scale of 1:1,000,000. The article considers endogenous geochemical criteria for gold concentration in the Earth’s crust of the region, which constitute a mandatory methodological method for predicting gold ore objects at any scale. The aim of the work is to clarify the achieved level of knowledge about the mineralogical and geochemical criteria for gold concentration in the course of the evolution of the Earth’s crust up to the formation of industrial deposits and the isolation of ore formations. The methodology of the study is to systematize a huge amount of factual material concerning the processes of natural concentration of gold, to analyze its representativeness, to assess the completeness and reliability of published and stock information used to clarify the mineralogical and geochemical criteria for predicting ore gold. Using the chemical properties of gold, the forms of finding gold, amount of it in the forming geological complexes and natural environments, their evolution, distribution in structural and tectonic zones, some causes of concentration and mineralogical and geochemical prediction criteria are considered. Special attention is paid to the need to study and account for nanoscale (dispersed) gold. As the main ore-formation units of gold mineralization, standardized ore formations are defined with a division into gold ore proper, complex gold-bearing and gold-bearing and geological and industrial types of deposits. There are 15 geological and industrial types, of which 13 are transbaikal deposits standards and two are attracted from other regions. These types of deposits differ in the number of objects related to them. Due to some similarity in the composition of ore matter, geological and industrial types differ in the most important classification characteristics for the forecast. Areas of distribution of direct and indirect mineralogical and geochemical features grouped into mineralogical and geochemical forecast criteria are promising for endogenous concentration of gold mineralization

Timing of Paleoproterozoic granitoid magmatism along the northwestern Superior Province margin: implications for the tectonic evolution of the Thompson Nickel BeltThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 325-346 ◽  
Author(s):  
N. Machado ◽  
L. M. Heaman ◽  
T. E. Krogh ◽  
W. Weber ◽  
M. T. Corkery
Keyword(s):  
Sensu Stricto ◽  
Crustal Thickening ◽  
Superior Province ◽  
Granitoid Magmatism ◽  
Continental Block ◽  
Granitic Magmatism ◽  
Peak Metamorphism ◽  
Granite Magmatism ◽  
Superior Craton ◽  
Superior Margin

The U–Pb geochronology of three granitoid plutons and three granitic pegmatite dykes, largely from the Thompson Nickel Belt located along the northwestern Superior craton margin, was investigated to place constraints on the timing of felsic magmatism associated with closure of the Manikewan Ocean and final continent–continent collision to form the Trans-Hudson Orogen. These data indicate that 1840–1820 Ma granite magmatism along the Superior margin was more active than previously thought and that some magmatism extended beyond the Thompson Nickel Belt sensu stricto, including the 1836 ± 3 Ma Mystery Lake granodiorite, 1822 ± 5 Ma Wintering Lake granodiorite, and the 1825 ± 8 Ma Fox Lake granite located in the Split Lake Block. Granitic pegmatites within the Thompson Nickel Belt were emplaced late in the collisional history in the period 1.79–1.75 Ga and include a 1770 ± 2 Ma dyke exposed at the Thompson pit, a 1767 ± 6 Ma dyke at the Pipe Pit, and a 1786 ± 2 Ma dyke located at Paint Lake. The final stage of crustal amalgamation in the eastern Trans-Hudson Orogen involved Superior Province crustal thickening and partial melting forming 1.84–1.82 Ga granite magmas and then final collision at ∼1.8 Ga between the Superior Province and a continental block to the west consisting of the previously amalgamated Sask and Hearne cratons. Heating of the Superior craton margin and granitic magmatism continued past peak metamorphism (1790–1750 Ma); this thermal event is represented by the emplacement of numerous late pegmatite dykes and evidenced by cooling dates recorded by metamorphic minerals (e.g., titanite) in reworked Archean gneisses and Proterozoic intrusions.

scholarly journals The Coulon deposit: quantifying alteration in volcanogenic massive sulphide systems modified by amphibolite-facies metamorphism

2016 ◽  
Vol 53 (12) ◽  
pp. 1443-1457 ◽  
Author(s):  
Lucie Mathieu ◽  
Rose-Anne Bouchard ◽  
Vital Pearson ◽  
Réal Daigneault
Keyword(s):  
Mass Balance ◽  
Massive Sulphide ◽  
Amphibolite Facies ◽  
High Grade ◽  
Bay Area ◽  
Volcanogenic Massive Sulphide ◽  
High Grade Metamorphism ◽  
And Performance ◽  
Superior Craton ◽  
Ore Zones

The Coulon deposit is a volcanogenic massive sulphide (VMS) system in the James Bay area, Superior craton, Quebec, that was metamorphosed to amphibolite-facies conditions. The chemistry and mineralogy of the VMS-related alteration halo proximal to the mineralized sulphide lenses are investigated, using samples collected in the field and 5583 chemical analyses provided by Osisko Ltd. Alteration is quantified using mass balance and normative calculations, and the application and performance of these methods in an exploration context are investigated. In VMS systems, altered rocks proximal to the ore zones are characterized by multi-element metasomatism, which is best quantified by mass balance methods that have been successfully applied in the study area. However, mass balance calculations necessitate the documentation of a precursor, which is not always possible in an exploration context; therefore, an alternative method (i.e., alteration indices) was also evaluated. In most VMS systems, proximal alteration is characterized by chlorite (chloritization), muscovite (sericitization), and quartz (silicification), while at the Coulon deposit, altered rocks contain mostly cordierite, biotite, sillimanite, and quartz. Alteration indices were calculated using observed and normative minerals, and provide satisfactory results similar to those obtained with mass balance calculations. Using these results, recommendations are made to estimate the intensity of alteration in the core shack using the proportions of observed minerals. Alteration indices are sensitive to the composition of precursors; and because of high-grade metamorphism, chloritization and sericitization are not precisely quantified. Recognizing these limitations is essential to successful quantification of alteration in areas metamorphosed to high-grade conditions.

The James Bay H.E.P. Complex

1983 ◽  
Vol 2 (2) ◽  
pp. 123-131 ◽  
Author(s):  
W. Hamley
Keyword(s):  
North America ◽  
Economic Recession ◽  
The Other ◽  
Energy Market ◽  
James Bay ◽  
Bay Area ◽  
Planning Decisions ◽  
Major Producer ◽  
The Right ◽  
Installed Capacity

Québec is a major producer of hydro-electricity in North America. In 1971 a massive undertaking was announced to add to this output by tapping the power of the rivers in the James Bay area of the province. There were to be five complexes—La Grande I, La Grande II, NBR, Baleine and Caniapiscau which, when completed in the 1990s, would add nearly 40 000 MW to installed capacity. Work is just reaching completion on La Grande I, the largest of the complexes, but in 1982 it was decided not to proceed with the other four, at least for the immediate future. Such a situation has arisen largely as a consequence of a very volatile period in the energy market coinciding with economic recession which has been very severe in Quebec. It is suggested that part of the solution to the province's problems could come about by utilizing James Bay H.E.P to stimulate local electricity intensive industries as well as earning income through electricity exports. However present uncertainties make planning decisions very difficult and the halting of construction, despite there being no problems of funding currently, seems a correct policy under prevailing conditions. It could be that the James Bay developments are the right scheme at the wrong time.

BIOLOGICAL AND OCEANOGRAPHIC CONDITIONS IN HUDSON BAY: 6. THE GENERAL HYDROGRAPHY AND HYDRODYNAMICS OF THE WATERS OF THE HUDSON BAY REGION

1932 ◽  
Vol 7 (1) ◽  
pp. 91-118 ◽  
Author(s):  
H. B. HACHEY
Keyword(s):  
Fresh Water ◽  
Water Movement ◽  
Open Ocean ◽  
Hudson Bay ◽  
Water Drainage ◽  
James Bay ◽  
Bay Area ◽  
Hydrographic Conditions ◽  
The Many ◽  
Oceanographic Conditions

The waters of Hudson bay differ markedly from the waters of Hudson strait and the waters of the open ocean. Intense stratification in the upper twenty-five metres, decreasing as the waters of the open ocean are approached, gives Hudson bay the character of a large estuary. Below fifty metres the waters are for all purposes dynamically dead, thus resulting in a cold saline body of water which probably undergoes very little change from season to season. The movements of the waters at various levels are dealt with to show that the inflow of waters from Fox channel and the many fresh-water drainage areas control the hydrographic conditions as found. The main water movement is from the James bay area to Hudson strait and thence to the open ocean.

An Archean ultramafic turbidite from Lac Guyer, James Bay Area, Quebec, Canada

1980 ◽  
Vol 17 (11) ◽  
pp. 1576-1582 ◽  
Author(s):  
Karen Stamatelopoulou-Seymour ◽  
Donald M. Francis
Keyword(s):  
Greenstone Belt ◽  
Sedimentary Rock ◽  
Turbidity Current ◽  
Soft Sediment ◽  
James Bay ◽  
Deformation Structures ◽  
Bay Area ◽  
Volcanic Sequence ◽  
Sediment Deformation ◽  
Soft Sediment Deformation

A sedimentary rock of ultrabasic composition (MgO 28%, SiO2 48%) has been identified in an Archean volcanic sequence ranging from basaltic to peridotitic komatiite in composition, in the Lac Guyer greenstone belt, James Bay region of New Quebec. The ultramafic sedimentary rock is cyclically layered with an internal stratigraphy indicative of deposition from an aqueous turbidity current. Layers which are interpreted to correlate with the arenaceous A, B, and C divisions of turbidites are pyroxene-rich and display sedimentary features such as grading, parallel and cross-laminations, and climbing ripples. Foliated layers with higher normative olivine contents preserve loading and soft sediment deformation structures indicating a pelitic nature when deposited and are interpreted as Bouma E divisions. These features combined with a sympathetic variation of Al2O3 with normative olivine content in successive Bouma divisions suggest that a Mg-chlorite with subordinate serpentine rather than olivine was present, together with pyroxenes and opaques, in the initial sediment. This sediment may have been derived from the degradation of the associated komatiitic volcanics or may represent a contemporaneous reworked ultramafic tuff or ash flow.

First in-situ Rb-Sr dating of metasedimentary rocks from the Pontiac subprovince, Superior Craton, Canada. Implications towards the regional metamorphic evolution of the sequence.

2020 ◽  
Author(s):  
Nicholas Leventis ◽  
Thomas Zack ◽  
Iain Pitcairn ◽  
Johan Högmalm
Keyword(s):  
Accretionary Prism ◽  
Metasedimentary Rocks ◽  
Metamorphic History ◽  
Accuracy And Precision ◽  
Icp Ms ◽  
Age Variations ◽  
History Of ◽  
Peak Metamorphism ◽  
Superior Craton

<p>The Pontiac subprovince consists of metaturbidites, plutons and thin ultramafic rock layers of Archean age and lies south of the Cadillac-Larder Lake (C-LL) fault zone which is the boundary between the Pontiac and the extensively mineralized Abitibi Greenstone Belt. The sediments show a Barrovian metamorphic gradient which increases southwards, away from the C-LL fault. The most likely tectonic provenance for the Pontiac sedimentary rocks is that they represent a relic accretionary prism with material derived from both the Abitibi and an older terrane. Zircon U-Pb dating shows that deposition occurred not later than 2685±3 Ma ago and recent, robust Lu-Hf dating of garnets bracketed Pontiac's peak metamorphic conditions at 2658±4 Ma. For this study we used a recently developed LA-ICP-MS/MS method for in-situ Rb-Sr dating of biotite and plagioclase in samples ranging in metamorphic grade (biotite to sillimanite zones) from the Pontiac subprovince. Calibration of the instrument was achieved by repeated ablations on several reference materials (see Hogmalm et al. 2017) which also provided the monitoring of accuracy and precision throughout the analyses. Results show a range in dates between 2550 Ma and 2200 Ma with an average of 2440±50 Ma (2σ). Samples from the staurolite and kyanite zones have a larger range with respect to the other zones, but no significant differences are observed in the data with any method of data handing. These dates are ≈300Ma younger than the peak metamorphism in the area and this is attributed to either overgrowth and re-setting of the Rb-Sr system by a second metamorphic/hydrothermal event, or diffusional resetting with core-rim age variations. Possible influence from the adjacent late syntectonic to post-tectonic monzodiorite-monzonite-granodiorite-syenite (MMGS) plutons dated 2671±4 Ma and the garnet-muscovite-granite series (GMG) dated ≈2650 Ma cannot be ruled out. This study provides insights about the metamorphic history of the sequence and supports previous findings regarding resetting of some isotopic systems with relatively low closure temperatures (≈350-400°C) by later thermal events.</p>

Metallogeny of the Marco zone, Corvet Est, disseminated gold deposit, James Bay, Quebec, Canada

2012 ◽  
Vol 49 (10) ◽  
pp. 1154-1176
Author(s):  
Martin Aucoin ◽  
Georges Beaudoin ◽  
Robert A. Creaser ◽  
Paul Archer
Keyword(s):  
Gold Deposit ◽  
Basaltic Andesite ◽  
Native Gold ◽  
Gold Mineralization ◽  
Isotope Composition ◽  
Hanging Wall ◽  
Volcanic Rocks ◽  
Weighted Average ◽  
James Bay ◽  
Host Rocks

The Corvet Est gold deposit is hosted by Archean rocks of the Superior Province in the James Bay region, northern Quebec, Canada. The Marco zone is hosted by amphibolite-grade, strongly foliated volcanic rocks and consists of disseminated gold, with an apparent thickness ranging from 1.8 to 39.5 m and gold grades up to 23 g·t–1 over 1 m, that is continuous along strike for ∼1.3 km. The lithotectonic sequence comprises footwall basaltic andesite amphibolite overlain by a lenticular unit of metadacite and then by hanging-wall basaltic andesite amphibolite, all intruded by quartz–feldspar porphyry dikes. Dacite, basaltic andesite amphibolite, and quartz–feldspar porphyry show a calc-alkaline to transitional affinity and plot in the plate margin arc basalt field, with typical volcanic arc trace element patterns. Mineralization consists of pyrite, arsenopyrite, pyrrhotite, chalcopyrite, and gold, disseminated in deformed dacite, in andesite amphibolite, and in quartz–feldspar porphyry dikes. Dacite and andesite display weak alteration characterized by silicification. Native gold forms inclusions in metamorphic quartz, garnet, feldspar, arsenopyrite, and pyrite or free grains interstitial to quartz, feldspar, pyrite, chalcopyrite, and arsenopyrite. Free gold in late quartz veins cut the sericitized metamorphic fabric. Inclusion and interstitial native gold within minerals annealed during metamorphism shows that gold mineralization is pre- to syn-metamorphic, with some gold remobilized in later veins. Rhenium–osmium dating of arsenopyrite yields an isochron age of 2663 ± 13 Ma for mineralization and a weighted average model age of 2632 ± 7 Ma for arsenopyrite formed during peak metamorphism. The ∼2663 Ma arsenopyrite has a low initial 187Os/188Os of 0.19 ± 0.10, suggesting a juvenile crust or a mantle Os source. The sulfur isotope composition of Marco zone pyrite and arsenopyrite shows that sulfur could have been leached from its volcanic host rocks or from reduction of Archean seawater. The Corvet Est deposit is interpreted to be an orogenic gold deposit (2663 Ma) deformed and recrystallized during amphibolite-grade metamorphism (2632 Ma).

scholarly journals The Kill of Wild Geese by the Natives of the Hudson-James Bay Region

ARCTIC ◽  
1957 ◽  
Vol 10 (4) ◽  
pp. 211 ◽  
Author(s):  
Harold C. Hanson ◽  
Campbell Currie
Keyword(s):  
James Bay ◽  
Wintering Grounds ◽  
Bay Area ◽  
Breeding Grounds ◽  
Safe Limit

The economic plight of Indians and Eskimos in the Hudson-James Bay area is partly dependent on the numbers of wild geese nesting in or migrating through their territory. The information presented on kills indicates that the number taken by native hunters is within a safe limit of what the nesting populations of that area can withstand. Expansion of wintering grounds and inaccessibility of breeding grounds assure that wild geese will continue to be an important source of food for the northern natives.

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