scholarly journals Geology, structural evolution, and hydrothermal alteration of the Island gold deposit, Michipicoten greenstone belt, Ontario

2020 ◽  
Author(s):  
T J Ciufo ◽  
K Jellicoe ◽  
C Yakymchuk ◽  
S Lin ◽  
P Mercier-Langevin ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Hydrothermal Alteration ◽  
Greenstone Belt ◽  
Structural Evolution

Structural evolution of the Hemlo greenstone belt in the vicinity of the world-class Hemlo gold deposit

2003 ◽  
Vol 40 (3) ◽  
pp. 395-430 ◽  
Author(s):  
T L Muir
Keyword(s):  
Gold Deposit ◽  
Greenstone Belt ◽  
Structural Evolution ◽  
Small Scale ◽  
Structural Elements ◽  
Shear Sense ◽  
History Of ◽  
Brittle Fractures ◽  
World Class ◽  
Dextral Shear

A complex history of volcano-sedimentary deposition, polyphase strain, multiple intrusive events, and various stages of porphyroblastesis is indicated for the Hemlo gold deposit area within the Hemlo greenstone belt. Structural elements can be assigned to at least six stages of development (D1–D6). D1 generated small-scale folds and low-angle faults (thrusts?) with no planar fabric, except within strain aureoles around the earliest intrusions. D2 was a progressive event resulting from northeast-directed compression, which generated regional, predominantly S-shaped folds (early D2); penetrative planar and linear fabrics, overturned stratigraphy, and formation of an inflection in the strike of the greenstone belt (mid-D2); and development of high-strain zones with dominant sinistral and local dextral shear sense (late D2). D3 was a distinctly separate progressive event resulting from northwest-directed transpression, which generated variably penetrative east- to northeast-striking foliation (S3), ductile dextral shear fabrics, and small-scale Z-shaped folds (early D3), followed by brittle–ductile to brittle development of cataclasite and pseudotachylite in layer-parallel zones (late D3). D4 resulted in contractional kinks and brittle fractures, locally in conjugate sets. D5 and D6 are represented by brittle to brittle–ductile faults, which overprint Paleoproterozoic and Mesoproterozoic dikes, respectively. Four granitoid magmatic events span the interval 2720–2677 Ma, with emplacement mainly during D2, between ca. 2690 and ca. 2684 Ma. A protracted period of regional medium-grade metamorphism likely spanned the D2–D3 stages. The Hemlo gold deposit was emplaced during mid-D2 and was largely controlled by D2 structural elements and competency contrast between rock units.

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.

scholarly journals Hydrothermal alteration and vectors at the orogenic Island Gold deposit, Michipicoten Greenstone Belt, Wawa, Ontario

2018 ◽  
Author(s):  
T J Ciufo ◽  
C Yakymchuk ◽  
S Lin ◽  
K Jellicoe ◽  
P Mercier-Langevin
Keyword(s):  
Gold Deposit ◽  
Hydrothermal Alteration ◽  
Greenstone Belt

Mineralization and hydrothermal alteration in the Mamão orogenic gold deposit, Andorinhas greenstone belt, Carajás Province, Brazil

2021 ◽  
pp. 103548
Author(s):  
Sebastião Rodrigo Cortez de Souza ◽  
Nilson Francisquini Botelho ◽  
Federico Alberto Cuadros Jiménez ◽  
Elton Luiz Dantas ◽  
Mateus Andrade Reis ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Hydrothermal Alteration ◽  
Greenstone Belt ◽  
Orogenic Gold ◽  
Orogenic Gold Deposit ◽  
Carajás Province

The Yatela gold deposit in Mali, West Africa: The final product of a long-lived history of hydrothermal alteration and weathering

2016 ◽  
Vol 113 ◽  
pp. 73-87 ◽  
Author(s):  
Quentin Masurel ◽  
John Miller ◽  
Kim A.A. Hein ◽  
Eric Hanssen ◽  
Nicolas Thébaud ◽  
...  
Keyword(s):  
West Africa ◽  
Gold Deposit ◽  
Hydrothermal Alteration ◽  
History Of

The Karouni Gold Deposit, Guyana, South America: Part II. Hydrothermal Alteration and Mineralization

2018 ◽  
Vol 113 (8) ◽  
pp. 1705-1732 ◽  
Author(s):  
Michael Tedeschi ◽  
Steffen G. Hagemann ◽  
Malcolm P. Roberts ◽  
Noreen J. Evans
Keyword(s):  
South America ◽  
Gold Deposit ◽  
Hydrothermal Alteration
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