Gold distribution in the Val-d'Or Formation and a model for the formation of the Lamaque–Sigma mines, Val-d'Or, Quebec

1991 ◽  
Vol 28 (5) ◽  
pp. 706-720 ◽  
Author(s):  
Mehmet F. Taner ◽  
Pierre Trudel
Keyword(s):  
Gold Mineralization ◽  
Regional Metamorphism ◽  
Analytical Techniques ◽  
Shear Zones ◽  
Gold Deposits ◽  
Mining District ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Gold Mines ◽  
Geothermal Activity

Recent lithogeochemical studies by accurate analytical techniques (e.g., instrumental and radiochemical neutron-activation analyses) have been used to explore the possibility of using gold distribution in the research for new gold deposits; these show that anomalous gold distribution occurs in some parts of the Val-d'Or Formation in the Val-d'Or mining district of Quebec. Gold lithogeochemistry in the Val-d'Or Formation has shown that it is possible to distinguish: (i) background values (1.4–3.5 ppb Au); (ii) zones of primarily anomalous gold values around the Lamaque–Sigma mines (median: 15 ppb Au); (iii) enrichment halos around gold orebodies (median: 70 ppb Au); and (iv) secondary gold enrichment in shear zones. We conclude that the Val-d'Or Formation is auriferous, i.e., anomalously rich in gold at least in some of its parts and contains the Lamaque – Sigma gold mines, representing 68% of the total gold production in the district. The Val-d'Or Formation is part of a central volcanic complex within an island-arc system. The centre of this complex is located in the main Lamaque plug, and this environment may be compared to high-temperature active geothermal systems that are commonly responsible for the formation of epithermal gold deposits. Gold mineralization at Sigma and Lamaque is considered to be related to a late hydrothermal phase or a retrograde phase of regional metamorphism. For the formation of the gold deposits, two distinct and successive events are postulated: (i) a gold-rich synvolcanic geothermal activity and (ii) a late remobilisation from the host rocks followed by deposition of gold ore within favourable structures.

A structural reappraisal of the Beardmore–Geraldton Belt at the southern boundary of the Wabigoon subprovince, Ontario, and implications for gold mineralization

2004 ◽  
Vol 41 (2) ◽  
pp. 217-235 ◽  
Author(s):  
Bruno Lafrance ◽  
Jerry C DeWolfe ◽  
Greg M Stott
Keyword(s):  
Gold Mineralization ◽  
Shear Zones ◽  
Axial Plane ◽  
Superior Province ◽  
Southern Boundary ◽  
Gold Mines ◽  
Southern Margin ◽  
Ore Zones

The Beardmore–Geraldton Belt occurs along the southern margin of the Archean Wabigoon subprovince, Superior Province, Ontario. The belt consists of shear-bounded interleaved metasedimentary and metavolcanic units. The units were imbricated from 2696 to 2691 Ma during D1 thrusting and accretion of the Wabigoon, Quetico, and Wawa subprovinces. Post-accretion D2 deformation produced regional F2 folds that transposed lithological units parallel to the axial plane S2 cleavage of the folds. During D3 deformation, the folds were overprinted by a regional S3 cleavage oriented anticlockwise of F2 axial planes, and lithological contacts and S2 cleavage were reactivated as planes of shear within dextral regional shear zones that generally conform to the trend of the belt. D3 is a regional dextral transpression event that also affected the Quetico and Wawa subprovinces, south of the Beardmore–Geraldton Belt. Gold mineralization at the Leitch and MacLeod-Cockshutt mines, the two richest past-producing gold mines in the Beardmore–Geraldton Belt, is associated with D3 shear zones and folds, overprinting regional F2 folds. The plunge of the ore zones is parallel to F3 fold axes and to the intersection of D3 shear zones with F2 and F3 folds.

Gold-bismuth-telluride-sulphide assemblages at the Viceroy Mine, Harare-Bindura-Shamva greenstone belt, Zimbabwe

2008 ◽  
Vol 72 (4) ◽  
pp. 953-970 ◽  
Author(s):  
T. Oberthür ◽  
T. W. Weiser
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Close Association ◽  
Shear Zones ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Main Stage ◽  
Melting Temperatures ◽  
Native Bismuth ◽  
Gold Bearing

AbstractGold mineralization at the Viceroy Mine is hosted in extensional veins in steep shear zones that transect metabasalts of the Archaean Arcturus Formation. The gold mineralization is generally made up of banded or massive quartz carrying abundant coarse arsenopyrite. However, most striking is a distinct suite of Au-Bi-Te-S minerals, namely joseite-A (Bi4TeS2), joseite-B (Bi4Te2S), hedleyite (Bi7Te3), ikunolite (Bi4S3), ‘protojoseite’ (Bi3TeS), an unnamed mineral (Bi6Te2S), bismuthinite (Bi2S3), native Bi, native gold, maldonite (Au2Bi), and jonassonite (AuBi5S4). The majority of the Bi-Te-S phases is characterized by Bi/(Se+Te) ratios of >1. Accordingly, this assemblage formed at reduced conditions at relatively low fS2 and fTe2. Fluid-inclusion thermometry indicates depositional temperatures of the main stage of mineralization of up to 342°C, in the normal range of mesothermal, orogenic gold deposits worldwide. However, melting temperatures of Au-Bi-Te phases down to at least 235°C (assemblage (Au2Bi + Bi + Bi7Te3)) imply that the Au-Bi-Te phases have been present as liquids or melt droplets. Furthermore, the close association of native gold, native bismuth and other Bi-Te-S phases suggests that gold was scavenged from the hydrothermal fluids by Bi-Te-S liquids or melts. It is concluded that a liquid/melt-collecting mechanism was probably active at Viceroy Mine, where the distinct Au-Bi-Te-S assemblage either formed late as part of the main, arsenopyrite-dominated mineralization, or it represents a different mineralization event, related to rejuvenation of the shear system. In either case, some of the gold may have been extracted from pre-existing, gold-bearing arsenopyrite by Bi-Te-S melts, thus leading to an upgrade of the gold ores at Viceroy. The Au-Bi-Te-S assemblage represents an epithermal-style mineralization overprinted on an otherwise mesothermal (orogenic) gold mineralization.

Gold Deposits of the ~15-Moz Ahafo South Camp, Sefwi Granite-Greenstone Belt, Ghana: Insights into the Anatomy of an Orogenic Gold Plumbing System

2021 ◽  
Author(s):  
Quentin Masurel ◽  
Paul Morley ◽  
Nicolas Thébaud ◽  
Helen McFarlane
Keyword(s):  
Rock Mass ◽  
Shear Zone ◽  
Gold Mineralization ◽  
Hanging Wall ◽  
Spatial Association ◽  
Sedimentary Rocks ◽  
Shear Zones ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Plutonic Rocks

Abstract The ~15-Moz Ahafo South gold camp is located in southwest Ghana, the world’s premier Paleoproterozoic gold subprovince. Major orogenic gold deposits in the camp include Subika, Apensu, Awonsu, and Amoma. These deposits occur along an ~15-km strike length of the Kenyase-Yamfo shear zone, a major tectonostratigraphic boundary juxtaposing metamorphosed volcano-plutonic rocks of the Sefwi belt against metamorphosed volcano-sedimentary rocks of the Sunyani-Comoé basin. In this study, we document the geologic setting, structural geometry, and rheological architecture of the Ahafo South gold deposits based on the integration of field mapping, diamond drill core logging, 3-D geologic modeling, and the geologic interpretation of aeromagnetic data. At the camp scale, the Awonsu, Apensu, and Amoma deposits lie along strike from one another and share similar hanging-wall plutonic rocks and footwall volcano-sedimentary rocks. In contrast, the Subika gold deposit is hosted entirely in hanging-wall plutonic rocks. Steeper-dipping segments (e.g., Apensu, Awonsu, Subika) and right-hand flexures (e.g., Amoma, Apensu) in the Kenyase-Yamfo shear zone and subsidiary structures appear to have represented sites of enhanced damage and fluid flux (i.e., restraining bends). All gold deposits occur within structural domains bounded by discontinuous, low-displacement, sinistral N-striking tear faults oblique to the orogen-parallel Kenyase-Yamfo shear zone. At the deposit scale, ore-related hydrothermal alteration is zoned, with distal chlorite-sericite grading into proximal silica-albite-Fe-carbonate mineral assemblages. Alteration halos are restricted to narrow selvages around quartz-carbonate vein arrays in multiple stacked ore shoots at Subika, whereas these halos extend 30 to 100 m away from the ore zones at Apensu and Awonsu. There is a clear spatial association between shallow-dipping mafic dikes, mafic chonoliths, shear zones, and economic gold mineralization. The abundance of mafic dikes and chonoliths within intermediate to felsic hanging-wall plutonic host rocks provided rheological heterogeneity that favored the formation of enhanced fracture permeability, promoting the tapping of ore fluid(s). Our interpretation is that these stacked shallow-dipping mafic dike arrays also acted as aquitards, impeding upward fluid flow within the wider intrusive rock mass until a failure threshold was episodically reached due to fluid overpressure, resulting in transient fracture-controlled upward propagation of the ore-fluid(s). Our results indicate that high-grade ore shoots at Ahafo South form part of vertically extensive fluid conduit systems that are primarily controlled by the rheological architecture of the rock mass.

Porphyry intrusions and albitites in the Bardoc–Kalgoorlie area, Western Australia, and their role in Archean epigenetic gold mineralization

1992 ◽  
Vol 29 (8) ◽  
pp. 1609-1622 ◽  
Author(s):  
W. K. Witt
Keyword(s):  
Western Australia ◽  
Gold Mineralization ◽  
Shear Zones ◽  
Rock Composition ◽  
Gold Mines ◽  
Mid Ocean Ridge ◽  
History Of ◽  
Compatible Elements ◽  
Ocean Ridge ◽  
Textural Evidence

Minor intrusions in the Menzies – Kambalda greenstone belt of the Archean Eastern Goldfields Province, Western Australia, range from quartz–feldspar porphyry to plagioclase–hornblende porphyry. The porphyries display enrichment of mobile and incompatible elements (K to Zr) and depletion of relatively compatible elements, with negative Nb, P, and Ti anomalies, on mid-ocean-ridge basalt-normalized spidergrams. The composition and timing of emplacement of the porphyries are consistent with a genetic relationship with spatially related granitoids. Porphyries occur in 30% of gold mines in the Menzies–Kambalda belt. The association appears to be largely structural, since both the intrusions and the mineralizing fluids exploit zones of weaknesses, such as lithological contacts and shear zones. Porphyries have been modified to varying degrees by hydrothermal alteration, especially pervasive albitization. Textural evidence indicates that secondary albite and associated sodic amphibole formed late in the deformation history of the greenstones and were broadly contemporaneous with secondary phyllosilicate, carbonate and sulphide minerals related to gold mineralization. Recent studies in the Alleghany district of California suggest the initial rock composition may critically influence the nature of alteration associated with gold mineralization. Therefore, albitization of porphyries may be caused by the same hydrothermal fluids that deposit gold and produce potassic alteration in mafic rocks.

scholarly journals Virtual Structural Analysis of Jokisivu Open Pit Using ‘Structure-from-Motion’ Unmanned Aerial Vehicles (UAV) Photogrammetry: Implications for Structurally-Controlled Gold Deposits in Southwest Finland

2018 ◽  
Vol 10 (8) ◽  
pp. 1296 ◽  
Author(s):  
Mohammad Sayab ◽  
Domingo Aerden ◽  
Markku Paananen ◽  
Petri Saarela
Keyword(s):  
High Resolution ◽  
Unmanned Aerial Vehicles ◽  
Gold Mineralization ◽  
Regional Scale ◽  
Shear Zones ◽  
Gold Deposits ◽  
Open Pit ◽  
Conjugate System ◽  
Aerial Vehicles ◽  
D Model

Unmanned aerial vehicles (UAVs) are rapidly growing remote sensing platforms for capturing high-resolution images of exposed rock surfaces. We used a DJI Phantom 3 Professional (P3P) quadcopter to capture aerial images that were used to generate a high-resolution three-dimensional (3-D) model of the Jokisivu open-pit gold deposit that is located in southwestern Finland. 158 overlapping oblique and nadir images were taken and processed with Agisoft Photoscan Pro to generate textured 3-D surface models. In addition, 69 overlapping images were taken from the steep faces of the open pit. We assessed the precision of the 3-D model by deploying ground control points (GCPs) and the average errors were found minimal along X (2.0 cm), Y (1.2 cm), and Z (5.0 cm) axes. The steep faces of the open pit were used for virtual structural measurements and kinematic analyses in CloudCompare and ArcGIS to distinguish the orientation of different fracture sets and statistical categorization, respectively. Three distinct fracture sets were observed. The NW-SE and NE-SW striking fractures form a conjugate geometry, whereas the NNW-SSE striking fractures cut the conjugate fracture set. The orientation of conjugate fractures match well with the resource model of the deposit and NW- and NE-trending segments of regional-scale anastomosing shear zones. Based on the conjugate geometry of fracture sets I and II, and the regional pattern of anastomosing shear system lead us to interpret an origin of gold mineralization in two stages. An early N-S or NNW-SSE crustal shortening, corresponding to the regional D4 (ca. 1.83–1.81 Ga) or pre-D4 (ca. 1.87–1.86 Ga) Svecofennian tectonic event(s) that produced anastomosing shear zones. Subsequent E-W directed D5 contraction (ca. 1.79–1.77 Ga) partly reactivated the anastomosing shear zones with the formation of conjugate system, which controlled the migration of fluids and gold mineralization in SW Finland.

IN SITU DATING OF HYDROTHERMAL MONAZITE AND IMPLICATIONS FOR THE GEODYNAMIC CONTROLS ON ORE FORMATION IN THE JIAODONG GOLD PROVINCE, EASTERN CHINA

2020 ◽  
Vol 115 (3) ◽  
pp. 671-685 ◽  
Author(s):  
Jun Deng ◽  
Kun-Feng Qiu ◽  
Qing-Fei Wang ◽  
Richard Goldfarb ◽  
Li-Qiang Yang ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Eastern China ◽  
Analytical Techniques ◽  
Gold Deposits ◽  
Ore Formation ◽  
Transient Event ◽  
Late Mesozoic ◽  
Gold Producer

Abstract The Jiaodong gold province, the largest gold producer in China, formed in a setting dominated by a 30-m.y. episode of Izanagi plate rollback and widespread extension, concomitant with late Mesozoic craton destruction. This study presents new high precision in situ sensitive high-resolution ion microprobe (SHRIMP) U-Th-Pb and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb ages for hydrothermal monazite from the largest of the Jiaodong gold deposits, which were previously dated as indicating ore formation over a few tens of millions of years when applying sericite Ar-Ar, zircon U-Pb, and less robust analytical techniques. Our U-Pb dating on monazite from the Jiaojia and Linglong deposits in western Jiaodong yielded consistent ages at ca. 120 Ma. The new geochronologic results, coupled with recently reported in situ monazite dates from smaller deposits in western Jiaodong, reveal that the deposits that host most of the ≥4,000-t Au resource formed during a relatively brief period at ca. 120 Ma. In eastern Jiaodong, the much smaller resource may have formed about 5 m.y. later, recorded by 114.2 ± 1.5 Ma gold mineralization at the Rushan deposit. The postsubduction opening of a slab gap at ca. 120 Ma is the most likely cause of the extensive gold mineralization in Jiaodong. The gap induced a local and rapid devolatilization of the hydrated mantle wedge at submelt temperatures. The transient event included release of a major volume of gold-transporting aqueous-carbonic fluid that was stored in the wedge into major NNE-trending structures in the overlying lithosphere.

Structural control of gold mineralization at the Bousquet mine, Abitibi, Quebec

1989 ◽  
Vol 26 (1) ◽  
pp. 157-175 ◽  
Author(s):  
Ghislain Tourigny ◽  
Claude Hubert ◽  
Alex C. Brown ◽  
Robert Crépeau
Keyword(s):  
Deformation Zone ◽  
Structural Control ◽  
Gold Mineralization ◽  
Shear Zones ◽  
Hydrothermal Activity ◽  
Gold Deposits ◽  
Ductile Deformation ◽  
Tectonic Deformation ◽  
Progressive Deformation ◽  
Initial Development

The Bousquet gold deposits are structurally controlled, disseminated and vein type lodes located within a 500 m wide anastomosing deformation zone. Ore is located within narrow zones of high strain surrounded by lozenge-shaped panels of less-deformed rock. Strain characteristics are those of the bulk inhomogeneous flattening style. Ore lenses are spatially related to highly sheared, fractured, and altered mafic and felsic volcanic and volcaniclastic rocks of contrasting rheologic properties. Deformation features can be ascribed to multistage progressive ductile → brittle deformation. Strain markers and kinematic indicators show that the principal displacement within the deformation zone was reverse faulting with a minor sinistral throw. A structural analysis demonstrates that the deformation responsible for the development of a pervasive regional foliation, brittle fractures, and oblique reverse faults can be attributed to a north–south compression.Metamorphic minerals such as andalusite, kyanite, garnet, biotite, chlorite, chloritoid, and calcic plagioclases indicate that upper greenschist metamorphism was attained locally within the ductile deformation zones. Subsequent pervasive retrograde alteration, including carbonatization and hydration of silicates to white mica and chlorite, suggests an important period of hydrothermal activity after peak metamorphism. Native gold is typically closely associated with pyrite and with these hydrothermal assemblages and was probably channelled into ductile and brittle structural zones prior to and after peak metamorphism.Two principal types of steeply dipping auriferous sulphide veins are present in the mine: foliation-oblique veins and foliation-parallel veins. Foliation-oblique veins occur within steeply dipping conjugate shear fractures spatially related to competent protoliths. The main set was emplaced during late stages of the regional tectonic deformation, after the initial development of a pervasive regional foliation and before the end of the progressive deformation. Foliation-parallel veins are located within openings created by decoupling schistosity laminae or by overriding of irregular surfaces such as fault planes and shear zones. These veins are relatively younger and less deformed than the foliation-oblique veins.Pervasive pyritic disseminations along foliation surfaces are earliest and synchronous with the development of foliation and probably continued throughout the progressive deformation. Early disseminated sulphides may also have been remobilized by pressure solution into later vein systems.

Structural controls on hypozonal orogenic gold mineralization in the La Ronge Domain, Trans-Hudson Orogen, Saskatchewan

2004 ◽  
Vol 41 (12) ◽  
pp. 1453-1471
Author(s):  
Bruno Lafrance ◽  
Larry M Heaman
Keyword(s):  
Gold Mineralization ◽  
Shear Zones ◽  
Oceanic Lithosphere ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Lake Area ◽  
Structural Controls ◽  
Quartz Veins ◽  
Metavolcanic Rocks ◽  
Orogenic Gold Mineralization

The La Ronge Domain is a granite–greenstone belt in the Saskatchewan segment of the ca. 1.9–1.8 Ga Trans-Hudson Orogen. The La Ronge volcanic arc was accreted to the Archean Hearne craton from ca. 1.87 to 1.86 Ga. Subduction of oceanic lithosphere beneath the accreted La Ronge – Hearne margin produced a voluminous suite of continental-arc intrusions. In the Waddy Lake area, the 1852.6 ± 1.5 Ma Corner Lake stock and 1859 ± 4 Ma and 1861 ± 2 Ma feldspar porphyry dykes crystallized from magmas generated from melting of the subducted oceanic slab. During the ca. 1.83–1.80 Trans-Hudson collision of the Hearne craton with the Archean Sask and Superior cratons, a penetrative regional foliation and a steeply plunging lineation formed within the La Ronge Domain. During further contraction across the domain, the deformation became localized in dextral and oblique-slip shear zones that generally follow contacts between more competent and less competent rock units. Orogenic gold mineralization is associated with quartz veins that are surrounded by hypozonal potassic and sulfidic alteration zones. The Komis gold deposit, the only past-producing gold mine in the Waddy Lake area, formed in the strain shadow of the Round Lake stock during the development of the regional foliation and lineation. Mineralization is associated with quartz veins that cut through tonalite dykes that behaved more brittlely than the surrounding metavolcanic rocks. The Golden Heart and Corner Lake gold deposits are hosted by south-side-up oblique-slip shear zones, which belong to a regional system of structures that extend from Saskatchewan to Manitoba.

scholarly journals Mapping Main Structures and Related Mineralization of the Arabian Shield (Saudi Arabia) Using Sharp Edge Detector of Transformed Gravity Data

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 71
Author(s):  
Ahmed M. Eldosouky ◽  
Reda A. Y. El-Qassas ◽  
Luan Thanh Pham ◽  
Kamal Abdelrahman ◽  
Mansour S. Alhumimidi ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Gold Mineralization ◽  
Gravity Data ◽  
Shear Zones ◽  
Fault Zones ◽  
Gold Deposits ◽  
Fault System ◽  
Arabian Shield ◽  
Potential Field Data ◽  
Najd Fault System

Saudi Arabia covers most of the Arabian Peninsula and is characterized by tectonic regimes ranging from Precambrian to Recent. Using gravity data to produce the lateral boundaries of subsurface density bodies, and edge detection of potential field data, a new subsurface structural map was created to decipher the structural framework controls on the distribution of gold deposits in Saudi Arabia. Moreover, we detected the relationships between major structures and mineral accumulations, thereby simultaneously solving the problem of edge detectors over complex tectonic patterns for both deeper and shallower origins. Analytic signal (ASg), theta map (TM), TDX, and softsign function (SF) filters were applied to gravity data of Saudi Arabia. The results unveil low connectivity along the Najd fault system (NFS) with depth, except perhaps for the central zones along each segment. The central zones are the location of significant gold mineralization, i.e., Fawarah, Gariat Avala, Hamdah, and Ghadarah. Moreover, major fault zones parallel to the Red Sea extend northward from the south, and their connectivity increases with depth and controls numerous gold mines, i.e., Jadmah, Wadi Bidah, Mamilah, and Wadi Leif. These fault zones intersect the NFS in the Midyan Terrane at the northern part of the AS, and their conjugation is suggested to be favorable for gold mineralization. The SF maps revealed the boundary between the Arabian Shield and Arabian Shelf, which comprises major shear zones, implying that most known mineralization sites are linked to post-accretionary structures and are not limited to the Najd fault system (NFS).

scholarly journals Petrographic Characterization of Hydrothermal Gold Deposits in Adi Gozomo Area, Northwestern Tigray, Ethiopia

2019 ◽  
Vol 9 (2) ◽  
pp. 801-807
Keyword(s):  
Gold Mineralization ◽  
Tectonic Setting ◽  
Shear Zones ◽  
Gold Deposits ◽  
Sulfide Deposit ◽  
Alteration Zone ◽  
Petrographic Analysis ◽  
Metasedimentary Rocks ◽  
Quartz Veins ◽  
Basement Rocks

Gold mineralization in Adi Gozomo area in northwestern Ethiopia was studied through petrographic analysis from both surface and core rock samples. Mineralization is associated with Neoproterozoic basement rocks comprised of metavolcanic, metasedimentary rocks and intrusives. Four phases of deformation and development of NE-SW foliation and shear zones were some of the common geological structures. The hydrothermal gold deposit s cramped to shear zones, 2nd generation quartz veins, 4th phase of deformation, silisifed and carbonatized alteration zone. Based on decreasing order of abundance the ore assemblage of the area includes pyrite, chalcopyrite, sphalerite, pyrrhotite, arsenopyrite and gold. The petrographic data indicates that the deposit is hydrothermal vein related type and an island arc tectonic setting. The mineralization is comparable with other known orogenic sulfide deposit types of the country in particular and Arabian-Nubian Shield in general.

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