Contexte structural et minéralisations aurifères des gîtes Casa-Berardi, Abitibi, Québec

1990 ◽  
Vol 27 (12) ◽  
pp. 1672-1685 ◽  
Author(s):  
P. Pilote ◽  
J. Guha ◽  
R. Daigneault ◽  
F. Robert ◽  
J. P. Golightly
Keyword(s):  
Deformation Zone ◽  
Gold Mineralization ◽  
Distinct Element ◽  
Relative Length ◽  
Gold Deposits ◽  
The Other ◽  
Ductile Deformation ◽  
Gold Deposition ◽  
Lateral Extent ◽  
East West

The Casa-Berardi gold deposits are located 180 km north of Rouyn-Noranda within Archean rocks of the Abitibi Subprovince. The Casa-Berardi deformation zone (CBDZ), which contains these deposits, is an east–west trending structure that is recognized along a minimum distance of 80 km. Ductile deformation has affected the lithologies in the central portion of the CBDZ. The CBDZ juxtaposes distinct sedimentary and volcanic lithostratigraphic packages which locally display opposite facing directions. Within the CBDZ the Casa-Berardi fault has been recognized; it is a brittle structure with a reverse motion. This fault represents a distinct element associated with the progression of deformation in the CBDZ and appears late in the geodynamical evolution of this deformation zone. Two other deformation zones have been identified in this region: (i) the east–west-trending Boivin-Paradis deformation zone, which has limited lateral extent and is located at the periphery of a granitoid intrusion, and (ii) the Laberge deformation zone, which has a northwest to east–west trend and crosscuts the regional structural grain. Most of the economic gold mineralization in the Casa-Berardi deposits is found in the second set of four recognized vein and fracture sets. The mineralized veins are found within zones of intense deformation which are preferentially developed close to contacts between sedimentary and volcanic units. The geometry of the different sets of quartz veins, their relative chronology, and their respective hydrothermal alterations can be explained by the progression of deformation within the CBDZ and bracket the gold mineralization as syn- to late-tectonic. The CBDZ is distinguished from the other two deformation zones by its greater lateral extent, the juxtaposition of distinct lithological domains, the complexity of its internal fabrics, and the relative length of the deformation event. These features indicate that in contrast with the other two deformation zones, the CBDZ was the site of a major mineralizing event. The recognition of contrasting characteristics between the different deformation zones has repercussions on the understanding of the different criteria that control gold deposition and, ultimately, on gold exploration.

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.

scholarly journals Role of the Environment in the Placement of Apocarbonate Gold Mineralization Chakylkalyan Megablock (Southern Uzbekistan)

2021 ◽  
Vol 7 (6) ◽  
Author(s):  
T. Yarboboev ◽  
Sh. Sultanov ◽  
I. Ochilov
Keyword(s):  
Carbonate Rocks ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Gold Deposition ◽  
Sufficient Detail ◽  
Available Information ◽  
Gold Bearing ◽  
Geochemical Specialization

Analysis of the available information and the results of many years of research on gold deposits in Uzbekistan made it possible to identify the main unconventional types of deposits. Among them, the most interesting are apocarbonate, crustal, sulfide-carbonaceous and apovolcanogenic quartzite (Upper-Kattakashkasai ore occurrence). The apocarbonate type is widespread in Uzbekistan, has been studied in sufficient detail and information is provided on it in this article. The article examines the existence, distribution and genesis of ores of Karlin type gold deposits. The generalizing characteristics of the Karlin type gold mineralization are given. The issues of geochemical specialization of the Paleozoic strata of the Chakylkalyan megablock are considered, the most favorable stratolevel for the localization of mineralized zones is determined, and the features of carbonate rocks in the process of gold deposition during reactions with silicic solutions are characterized. Based on the materials of regional geochemical profiling, the behavior of the main ore-forming elements in the rocks of both carbonate and volcanogenic-terrigenous strata is analyzed. As a result of the analysis, subclarkic contents of the main ore-forming elements (As, Co, Ni, Pb, Cu, Ag, V, Cr, Sc) were revealed, which create increased concentrations in gold-bearing pyrites of both apocarbonate gold mineralization and related formations.

Gold mineralization in Lower Cambrian McNaughton Formation, Athabasca Pass, Canadian Rocky Mountains: structural, mineralogical, and temporal relationships

1990 ◽  
Vol 27 (4) ◽  
pp. 477-493 ◽  
Author(s):  
Robert P. Shaw ◽  
Roger D. Morton
Keyword(s):  
Rocky Mountains ◽  
Lower Cambrian ◽  
Gold Mineralization ◽  
White Mica ◽  
Gold Deposits ◽  
Process Models ◽  
Gold Deposition ◽  
Canadian Rocky Mountains ◽  
Gold Stage ◽  
Gold Bearing

Gold-bearing quartz veins were recently discovered in archimetamorphic quartzite–rudite and quartzite–pelite sequences of the Lower Cambrian McNaughton Formation in the main ranges of the central Canadian Rocky Mountains. There are two distinct vein types: an early syntectonic, syn- to postmetamorphic, auriferous, bedding-parallel type, generated during repeated northeast-directed compressive tectonism; and a late, postpenetrative deformational discordant type, which contains only minor gold (<500 ppb Au). Gold emplacement and discordant veining were confined to the onset of late compression leading to development of the Chatter Creek Fault.The spatial distribution and dimensions of the veins attest to mechanically founded lithologic anisotropy. Bedding-parallel veins are confined to less competent, volumetrically minor pelitic rock types. Discordant veins are confined to competent quartzitic units.Bedding-parallel vein filling took place in two paragenetic stages: a protracted, pre-gold stage (quartz ± minor white mica and pyrite) depositing over 90% of vein material; and a late gold-bearing–post-gold stage (quartz–pyrite–gold–galena ± white mica and Fe carbonate). Gold usually occurs in association with brecciated pelites and penecontemporaneous sulfides. Discordant veins (quartz ± minor pyrite) record a single stage of vein filling broadly coeval with gold deposition. Minor hydrothermal alteration (pyrite ± white mica ± carbonate) of adjacent wall rocks accompanied gold emplacement and is mineralogically congruent with the regional archimetamorphic and bedding-parallel vein assemblages.In terms of their setting and morphology, the Athabasca Pass gold lodes are viewed as a siliciclastic-hosted analogue of the turbidite-hosted class of gold deposits. Principle geochemical differences from published process models for turbidite-hosted gold deposits are a function of the mineralogical maturity of the siliciclastic host strata in the Athabasca Pass.

Geology, lithogeochemistry, and significance of porphyry intrusions associated with gold mineralization within the Timmins–Porcupine gold camp, Canada

2019 ◽  
Vol 56 (4) ◽  
pp. 399-418 ◽  
Author(s):  
Peter J. MacDonald ◽  
Stephen J. Piercey
Keyword(s):  
Partial Melting ◽  
Greenstone Belt ◽  
Deformation Zone ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Crustal Thickening ◽  
Abitibi Greenstone Belt ◽  
Crustal Structures ◽  
Intrusive Rocks ◽  
Intrusive Suite

The Timmins–Porcupine gold camp, Abitibi greenstone belt, is host >60 Moz of Au with many gold deposits spatially associated with porphyry intrusions and the Porcupine–Destor deformation zone (PDDZ). Porphyry intrusions form three suites. The Timmins porphyry suite (TIS) consists of high-Al tonalite–trondjhemite–granodiorite (TTG) with calc–alkalic affinities and high La/Yb ratios and formed during ∼2690 Ma D1-related crustal thickening and hydrous partial melting of mafic crust where garnet and hornblende were stable in the residue. The Carr Township porphyry intrusive suite (CIS) and the granodiorite intrusive suite (GIS) also have high-Al TTG, calc-alkalic affinities, but were generated 10–15 million years after the TIS; the CIS were generated at shallower depths (during postorogenic extension?) with no garnet in the crustal residue, whereas the GIS formed during D2 thrust-related crustal thickening and partial melting where garnet was stable in the residue. Gold mineralization is preferentially associated with the TIS, and to a lesser extent the GIS, proximal to the PDDZ. Intrusions near mineralization have abundant sericite, carbonate, and sulphide alteration. These intrusions exhibit low Na2O and Sr, and high Al2O3/Na2O, K2O, K2O/Na2O, Rb, and Cs, (i.e., potassic alteration); sulfide- and carbonate-altered porphyries have high (CaO + MgO + Fe2O3)/Al2O3 and LOI values. Although porphyries are not genetically related to gold mineralization, they are spatially related and are interpreted to reflect the emplacement of intrusions and subsequent Au-bearing fluids along the same crustal structures. The intrusive rocks also served as structural traps, where gold mineralization precipitated in dilatant structures along the margins of intrusions during regional (D3?) deformation.

Timing and kinematics of post-Timiskaming deformation within the Larder Lake - Cadillac deformation zone, southwest Abitibi greenstone belt, Ontario, Canada

1999 ◽  
Vol 36 (4) ◽  
pp. 627-647 ◽  
Author(s):  
Lori Wilkinson ◽  
Alexander R Cruden ◽  
Thomas E Krogh
Keyword(s):  
Greenstone Belt ◽  
Deformation Zone ◽  
Greenschist Facies ◽  
Ductile Deformation ◽  
Magmatic Zircon ◽  
Lake Area ◽  
Abitibi Greenstone Belt ◽  
Terrane Accretion ◽  
East West ◽  
Greenschist Facies Metamorphism

The Larder Lake - Cadillac deformation zone is one of several anastomosing zones of high strain within the Abitibi greenstone belt. In the Kirkland Lake area, Ontario, the Larder Lake - Cadillac deformation zone is characterized by extensive carbonate and chlorite alteration, strong south-dipping foliations, and steep lineations. These features formed during two ductile deformation increments, D2 and D3, that occurred after deposition of Timiskaming assemblage sediments. D2 strain accumulation and greenschist facies metamorphism and alteration were localized within the deformation zone, facilitated by channelling of hydrothermal fluids within a preexisting structure, possibly formed during early D1 terrane accretion. During D2 north-south shortening, east-west-trending sectors of the deformation zone accumulated bulk coaxial strains, while southeast- and northeast-trending sectors experienced, respectively, dextral and sinistral transpressive deformations. Preservation of Timiskaming assemblage sediments in the footwall of the deformation zone indicates a component of south-over-north (reverse) displacement that is not recorded by D2 fabrics. Northwest-southeast D3 compression resulted in the formation of a regional, northeast-striking cleavage formed under regional greenschist facies conditions, and local dextral reactivation of suitably oriented sections of the Larder Lake - Cadillac deformation zone. The Murdoch Creek and Lebel stocks abut the Larder Lake - Cadillac deformation zone. Their internal structure and emplacement are interpreted to be a consequence of D2 north-south shortening. Magmatic zircon and titanite in the Murdoch Creek and Lebel stocks yield U-Pb geochronology ages of 2672 ± 2 and 2673 ± 2 Ma, providing a maximum age for D2 deformation. Hydrothermal titantite associated with S3 foliation in the Murdoch Creek stock gives an U-Pb age of 2665 ± 4 Ma, the maximum age of D3 deformation. Pluton emplacement, deformation, and coincident metamorphism occurred over a span of 1 Ma (from 2670 to 2669 Ma) to over 14 Ma (from 2675 to 2661 Ma), during a regime of north-south, followed by northwest-southeast, regional shortening.

Sulphur isotopic composition of sulphides from the Beaver Dam and other Meguma-Group-hosted gold deposits, Nova Scotia: implications for genetic models

1989 ◽  
Vol 26 (8) ◽  
pp. 1617-1629 ◽  
Author(s):  
Daniel J. Kontak ◽  
Paul K. Smith
Keyword(s):  
Nova Scotia ◽  
Gold Mineralization ◽  
Source Region ◽  
Gold Deposits ◽  
Genetic Models ◽  
Gold Deposition ◽  
Published Data ◽  
Sulphide Mineral ◽  
Beaver Dam ◽  
Wide Range

Sulphur isotopic compositions were determined for sulphide mineral phases in Meguma-Group-hosted gold deposits, Nova Scotia, in order to resolve (i) potential source regions for sulphur in these deposits, (ii) prevailing ambient physiochemical conditions during sulphide (and gold?) deposition, and (iii) possible implications of δ34S values on genetic models. The Beaver Dam deposit was selected as a test case, and results (± 1σ) from 32 sulphides analyzed for δ34S are as follows (‰): pyrite, 9.9 ± 1.1 (n = 16); pyrrhotite, 9.9 ± 0.2 (n = 4); arsenopyrite, 10.5 ± 0.4 (n = 11); and 9.4 for a single galena. The strikingly narrow range for sulphur isotope data and the sulphide mineral assemblage together are interpreted as implying that the prevailing chemical conditions during sulphide deposition remained at or below the H2S-SO4 buffer and constant relative to it, thus δ34Smineral is a good approximation of δ34Sfluid. Considering that the sulphide minerals analyzed represent a wide range in paragenesis and mode of occurrence, the uniform values suggest a homogeneous sulphur composition in the fluid, with little if any influence of local wall rocks during sulphide deposition. This is consistent with extensive alteration zones (i.e., silicification) throughout the deposit, indicating both high fluid/rock ratios and disequilibrium conditions. Data for an additional seven Meguma Group gold deposits (arsenopyrite only) indicate for δ34S a total range of about 9–25‰; however, the intradeposit variation is consistently small (2–3‰). These results are confirmed by previously published data for a variety of sulphide phases from three other deposits.Comparison of the results for Meguma-hosted deposits with a wide range of both similar and dissimilar gold deposits of variable age indicates that the large positive values (i.e., >9–10‰) are unique to the deposits examined. Two possible explanations are offered: first, the δ34S values originally may have been similar to those of other deposits (i.e., around 0‰ or slightly enriched) and then modified during transport to the site of deposition, or second, the source region of the fluids contained sulphur in an oxidized form (e.g., evaporites). The former hypothesis is currently favoured.Potential reservoirs for sulphur in the Meguma Zone include the Meguma Group metasedimentary rocks and younger peraluminous granitoid batholiths. The sulphur isotopic data are inconsistent with an unmodified magmatic source, and if the Meguma Group is favoured, then the dominant contribution was from the greywacke component. In the latter case, results for the Beaver Dam deposit may represent relatively unmodified fluid, whereas deposits characterized by enriched sulphur may reflect increasing amounts of greywacke-derived sulphur.The data somewhat constrain the possible genetic models for Meguma Group gold deposits. Syngenetic and magmatic models are considered unlikely; instead, a metamorphogenic origin is favoured. However, the ultimate source for mineralizing fluids is considered as lying beneath the Meguma Group, with variable amounts of contamination of this fluid during passage through Meguma Group strata. The relationship between gold mineralization and sulphur isotopic signatures of the associated sulphides is unclear, although a metamorphic protolith is probable.

Chapter 16: Giant Carlin-Type Gold Deposits of the Cortez District, Lander and Eureka Counties, Nevada

2020 ◽  
pp. 335-353
Author(s):  
Mark A. Bradley ◽  
L. Page Anderson ◽  
Nathan Eck ◽  
Kevin D. Creel
Keyword(s):  
Great Basin ◽  
Genetic Model ◽  
Gold Mineralization ◽  
Late Eocene ◽  
Gold Deposits ◽  
Gold Deposition ◽  
Lower Paleozoic ◽  
Fine Grained ◽  
Siliciclastic Rocks ◽  
Carlin Type Gold Deposits

Abstract The Cortez district is in one of the four major Carlin-type gold deposit trends in the Great Basin province of Nevada and contains three giant (&gt;10 Moz) gold orebodies: Pipeline, Cortez Hills, and Goldrush, including the recently discovered Fourmile extension of the Goldrush deposit. The district has produced &gt;21 Moz (653 t) of gold and contains an additional 26 Moz (809 t) in reserves and resources. The Carlin-type deposits occur in two large structural windows (Gold Acres and Cortez) of Ordovician through Devonian shelf- and slope-facies carbonate rocks exposed through deformed, time-equivalent lower Paleozoic siliciclastic rocks of the overlying Roberts Mountains thrust plate. Juxtaposition of these contrasting Paleozoic strata occurred during the late Paleozoic Antler orogeny along the Roberts Mountains thrust. Both upper and lower plate sequences were further deformed by Mesozoic compressional events. Regional extension, commencing in the Eocene, opened high- and low-angle structural conduits for mineralizing solutions and resulted in gold deposition in reactive carbonate units in structural traps, including antiforms and fault-propagated folds. The Pipeline and Cortez Hills deposits are located adjacent to the Cretaceous Gold Acres and Jurassic Mill Canyon granodioritic stocks, respectively; although these stocks are genetically unrelated to the later Carlin-type mineralization event, their thermal metamorphic aureoles may have influenced ground preparation for later gold deposition. Widespread decarbonatization, argillization, and silicification of the carbonate host rocks accompanied gold mineralization, with gold precipitated within As-rich rims on fine-grained pyrite. Pipeline and Cortez Hills also display deep supergene oxidation of the hypogene sulfide mineralization. Carlin-type mineralization in the district is believed to have been initiated in the late Eocene (&gt;35 Ma) based on the age of late- to postmineral rhyolite dikes at Cortez Hills. The Carlin-type gold deposits in the district share common structural, stratigraphic, alteration, and ore mineralogic characteristics that reflect common modes of orebody formation. Ore-forming fluids were channeled along both low-angle structures (Pipeline, Goldrush/Fourmile) and high-angle features (Cortez Hills), and gold mineralization was deposited in Late Ordovician through Devonian limestone, limy mudstone, and calcareous siltstone. The Carlin-type gold fluids are interpreted to be low-salinity (2–3 wt % NaCl equiv), low-temperature (220°–270°C), and weakly acidic, analogous to those in other Carlin-type gold deposits in the Great Basin. The observed characteristics of the Cortez Carlin-type gold deposits are consistent with the recently proposed deep magmatic genetic model. Although the deposits occur over a wide geographic area in the district, it is possible that they initially formed in greater proximity to each other and were then spatially separated during Miocene and post-Miocene regional extension.

The Mineralization Age of the Gupao Gold Deposit, Guangxi

2014 ◽  
Vol 501-504 ◽  
pp. 327-330
Author(s):  
Zhi Wu Zhang ◽  
Hui Li ◽  
Bin Yu ◽  
Shang Guo Zhou
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Tectonic Setting ◽  
Gold Deposits ◽  
Multiple Sources ◽  
The North ◽  
Mineralization Age ◽  
The Comparative Study ◽  
East West ◽  
Early Yanshanian

The Dayaoshan, which has nearly 200 gold deposits (or mineralization points), is one of the most important gold deposits distribution areas in Guangxi, and the Gupao gold deposit is an important representative one. Previous researches have carried out numerous works there to guide the gold prospecting work. Due to multiple episodes of gold mineralization and multiple sources materials in ore-forming, there are heated debates on the era of the mine, and the main mineralization age of the Gupao gold deposit is focused on the Caledonian or Early Yanshanian. According to the distribution characteristics of the gold ore body showing in the Zhilong, Gulinao, and Dawangding gold deposit, the discussion of macro-tectonic setting of the area, as well as the comparative study of surrounding gold deposits, we conclude that the main mineralization age of the Dawangding gold deposit is Early Yanshanian, and the main mineralization may be controlled by the nearly east-west trending fold which was caused by the north-south extrusion.

scholarly journals Application of magnetic and induced polarization method for delineating gold-bearing vein zones at Cibaliung, Pandeglang Regency, Banten

2021 ◽  
Vol 24 (1) ◽  
pp. 1-14
Author(s):  
Muhammad Sidiq ◽  
◽  
Yatini Yatini ◽  
Agus Fajrin ◽  
◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Sampling Interval ◽  
Gold Deposits ◽  
Magnetic Data ◽  
Magnetic Survey ◽  
Polarization Method ◽  
Geological Surveys ◽  
Main Vein ◽  
East West ◽  
Gold Bearing

Magmatic processes occurred during the Miocene period caused the formation of epithermal gold deposits in Cibaliung area. The deposit has previously been investigated through geological surveys which basically only covers the surface aspect, so in this study a subsurface analysis was carried out through magnetic and IP surveys to determine the distribution and continuity of the gold deposits. The magnetic survey was conducted over an area of about 3 km2 with sampling interval 20 m east and 100 m north. The magnetic data were processed using Oasis Montaj with magnetic intensity map as an output, which was then interpreted to determine the presence of structures and magnetite destruction zones as mineralization clues. The IP survey was conducted on 20 east-west oriented lines with length of about 1.2 km. The electrode configuration used is Wenner with 25 m spacing. IP data were processed using RES2DINV software to eliminate bad datum points and invert the apparent chargeability values into the true ones. IP data are then interpreted to clearly determine the position, direction, and distribution of gold mineralization body by detecting the presence of sulfide minerals as ligands carrying gold. Magnetic data analysis shows that gold mineralization tends to occur at low magnetic anomaly, ranging from 37 nT to 240 nT and generally associated with northwest-oriented structures. The mineralization zone is found in four main vein zones with resistivity and chargeability values < 51 Ωm and > 50 ms.

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