Geochronological constraints on late Archean magmatism deformation and gold–quartz vein mineralization in the northwestern Anialik River greenstone belt and igneous complex, Slave Province, N.W.T.

1994 ◽  
Vol 31 (8) ◽  
pp. 1365-1383 ◽  
Author(s):  
A. P. G. Abraham ◽  
D. W. Davis ◽  
S. L. Kamo ◽  
E. T. C. Spooner
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Shear Zones ◽  
Temporal Variations ◽  
Crustal Material ◽  
The West ◽  
Igneous Complex ◽  
Slave Province ◽  
Minimum Age ◽  
Geochronological Constraints

Three phases of the Anialik River igneous complex (ARIC) give U–Pb zircon ages in the range −2705–2683 Ma, and three units from the adjacent northwestern Anialik River greenstone belt (ARGB) give ca. 2678 Ma ages. Titanite from unsheared ARIC rocks crystallized during localized metamorphism and deuteric alteration between 2693 and 2683 Ma. Hydrothermal titanite in wall rocks to gold-mineralized shear zones crystallized during early shear zone development (2670 ± 1 Ma) and was subsequently locally altered to rutile, with gold occurring within the rutile-bearing assemblage. Unaltered second-generation hydrothermal titanite, overgrowing the rutile assemblage, crystallized during later brittle–ductile movement (2656 ± 2 Ma) and provides a minimum age for gold mineralization. Relatively high 207Pb/204Pb ratios of Pb in gold-associated galena suggest that it was partly derived from significantly older crustal material, possibly underlying the igneous complex and greenstone belt. This interpretation is consistent with other evidence for the existence of > 3.0 Ga crustal rocks to the west of the study area. A late crosscutting granite gives an age of [Formula: see text] and is therefore part of the Pan-Slave tectono-thermal event. These results, and other data for the Slave Province, indicate temporal variations in the development and deformation of predeformational greenstone belts. The new ages show that regional deformation and metamorphism in the northwestern Slave Province followed shortly after major magmatism, and that gold mineralization might have occurred during the late Archean accretion of the greenstone belt and igneous complex to an older crustal domain to the west.

Geochronological constraints on the timing of magmatism, deformation, and gold mineralization in the Red Lake greenstone belt, northwestern Ontario

1987 ◽  
Vol 24 (7) ◽  
pp. 1302-1320 ◽  
Author(s):  
F. Corfu ◽  
A. J. Andrews
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Time Frame ◽  
Time Interval ◽  
Major Activity ◽  
Red Lake ◽  
Sequence Of Events ◽  
Volcanic Sequence ◽  
Two Phases ◽  
Geochronological Constraints

The paper presents U–Pb ages on zircon, baddeleyite, titanite, rutile, and monazite from volcanic and plutonic rocks of the Red Lake greenstone belt in the northern Superior Province. The purpose of the study was to refine a previously outlined time frame for the volcanic evolution of the belt, define the time of major plutonism and deformation, and constrain the age of formation of gold deposits.Volcanism spanned at least 270 Ma between 3000 and 2730 Ma. New ages of 2989 ± 3 and 2894 ± 2 Ma for units of a lower volcanic sequence and [Formula: see text] and 2744 ± 1 Ma for units of an upper volcanic sequence corroborate and refine the previously established relationships. Local gabbroic and felsic intrusions cutting through the lower sequence yield ages of 2870 ± 15 and [Formula: see text], respectively.Volcanism was succeeded by major plutonism, deformation, alteration, and metamorphism between about 2730 and 2700 Ma. These processes were interrelated and progressed as a relatively continuous sequence of events accentuated by major activity during two phases at about 2720–2715 and 2705–2700 Ma. Early plutonism recorded at 2731 ± 3 Ma in the northern batholith complex was succeeded in the eastern part of the belt by a major tectonic – plutonic phase that includes intrusion of the McKenzie Stock at 2720 ± 2 Ma, the Dome Stock at 2718 ± 1 Ma, alteration and deformation of the Abino dyke at [Formula: see text], and emplacement of a late tectonic dyke at 2714 ± 4 Ma. A subsequent phase is recorded at 2701 ± 1.5 Ma in the Wilmar dyke. Major deformation and metamorphism in the western part of the belt is constrained by an age of 2729 ± 1.5 Ma for the deformed Red Crest Stock and a titanite age of 2705 ± 8 Ma for an undeformed crosscutting mafic dyke at Rowan Lake. Peak activity was probably coeval with emplacement of the adjacent batholithic phases at 2717 Ma. In the central part of the belt the deformation is constrained by ages of 2718 ± 1 Ma for the Dome Stock and 2699 ± 4 Ma for titanite of a crosscutting, undeformed diorite dyke and probably peaked during intrusion of the main phase of the Killala–Baird batholith at 2704 ± 1.5 Ma.Gold mineralization, which is spatially related to zones of intense shear deformation and alteration, is constrained within the time interval of 2720–2700 Ma by U–Pb ages on several felsic to mafic intrusive rocks that both pre- and post-date deformation and mineralization in different sections of the belt. These data indicate that mineralization occurred significantly later than the termination of volcanism.

scholarly journals Structural Evolution of the Rio das Velhas Greenstone Belt, Quadrilátero Ferrífero, Brazil: Influence of Proterozoic Orogenies on Its Western Archean Gold Deposits

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 983
Author(s):  
Orivaldo Ferreira Baltazar ◽  
Lydia Maria Lobato
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Structural Evolution ◽  
Shear Zones ◽  
Gold Deposits ◽  
Normal Faults ◽  
Small Scale ◽  
Crenulation Cleavage ◽  
Quadrilátero Ferrífero ◽  
Tectonic Transport

The Quadrilátero Ferrífero region is located in the extreme southeast of the Brasiliano São Francisco craton, Minas Gerais state, Brazil. It is composed of (i) Archean TTG granite-gneaissic terranes; (ii) the Archean Rio das Velhas greenstone belt; (iii) the Proterozoic metasedimentary and metavolcano-sedimentary covers. The Rio das Velhas rocks were deposited in the synformal NW–SE-directed Nova Lima basin. The Archean deformation converted the Nova Lima basin into an ample synclinorium with an eastern inverted flank. Archean orogenic gold mineralization within the Rio das Velhas greenstone belt rocks is controlled by NNW–SSE-directed, Archean regional shear zones subparallel to the strata of the Nova Lima synclinorium borders. Transamazonian and Brasiliano orogenies are superposed onto the Archean structures that control gold mineralization. In the eastern domain, Brasiliano fold-and-fault belts prevail, whereas in the western domain Archean and Transamazonian structures abound. The present study focus mainly is the western domain where the Cuiabá, Morro Velho, Raposos, Lamego and Faria deposits are located. Gold orebodies plunge to the E–NE and are tectonically controlled by the Archean D1–D2 deformation. The D3 Transamazonian compression—Which had a SE–NW vector sub-parallel to the regional mineralized Archean foliation/bedding—Buckled these structures, resulting in commonly open, synformal and antiformal regional folds. These are well documented near the gold deposits, with NE–SW axial traces and fold axes plunging to E–NE. Such folds are normal to inverted, NW-verging, with an axial planar foliation dipping moderately to the SE. The Transamazonian compression has only been responsible for the reorientation of the mineralized Archean gold ores, due to coaxial refolding characterized by an opposite tectonic transport. It has therefore not caused any other significant changes. Thrust shear zones, sub-parallel to the strong Transamazonian foliation, have given rise to localized metric segmentation and to the dislocation of gold orebodies. Throughout the region, along the towns of Nova Lima to Sabará, structures pertaining to the Brasiliano Araçuaí orogeny are represented only by gentle folding and by a discrete, non-pervasive crenulation cleavage. Thrust-shear zones and small-scale normal faults have caused, at most, metric dislocations along N–S-oriented planes.

Products of 2.65–2.58 Ga orogenesis in the Slave Province correlated with Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) seismic reflection patterns

2002 ◽  
Vol 39 (8) ◽  
pp. 1189-1200 ◽  
Author(s):  
Arie J van der Velden ◽  
Frederick A Cook
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
Seismic Reflection ◽  
Imaging Techniques ◽  
Shear Zones ◽  
Accretionary Wedge ◽  
The West ◽  
Crust And Upper Mantle ◽  
Slave Province ◽  
Lithospheric Evolution

Reflection patterns along Lithoprobe Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) seismic reflection line 1 in the southwestern Slave Province are interpreted as products of tectonic wedging during late Archean lithospheric convergence. The interpretation is aided by application of new seismic imaging techniques, by correlation of upper crustal reflection patterns to known geology, and by a comparison of lithospheric reflection patterns to similar convergent zones elsewhere. In the Yellowknife area, reflection patterns consist of (1) east-dipping reflections at 12–14 s that project into the upper mantle, (2) a wedge-shaped body in the lower crust with an east-dipping reflection fabric that is truncated on the west by (3) a series of west-dipping reflections that outline thrust-and-fold structures in the upper crust. The similarity of these reflection patterns to those of the Proterozoic Fort Simpson – Hottah collision zone ~300 km to the west provides support for the interpretation that reflection patterns beneath the Slave Province are also products of collisional tectonics. Rocks within the Slave Province preserve evidence of a ~2.65–2.58 Ga pan-Slave orogenic event, in which the >2.9 Ga Central Slave Basement collided with the ~2.7 Ga juvenile eastern Slave Province. Their suture is interpreted to be a west-dipping surface at 4–5 s (12–15 km) beneath Yellowknife and to project to the surface east of the profile. In the lower crust and upper mantle, east-dipping reflections are interpreted to delineate a coeval subduction zone and accretionary wedge. The upper crustal thrust-and-fold structures are likely linked to gold-bearing shear zones at Yellowknife. These results provide tantalizing evidence that processes similar to those of modern convergent zones were operational at 2.65–2.58 Ga.

Geochronology and structural relationships of mesothermal gold mineralization in the Palaeoproterozoic Jokisivu prospect, southern Finland

2010 ◽  
Vol 147 (4) ◽  
pp. 551-569 ◽  
Author(s):  
K. SAALMANN ◽  
I. MÄNTTÄRI ◽  
P. PELTONEN ◽  
M. J. WHITEHOUSE ◽  
P. GRÖNHOLM ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Regional Scale ◽  
Shear Zones ◽  
Quartz Veins ◽  
Structural Framework ◽  
Structural Relationships ◽  
Three Samples ◽  
Minimum Age ◽  
Zone Development ◽  
Granite Magmatism

AbstractThe palaeoproterozoic Svecofennian orogen in southern Finland contains a number of orogenic gold occurrences. The Jokisivu gold deposit, comprising auriferous quartz veins, is hosted by syn-tectonic quartz diorites to gabbros. Mineralization occurs in approximately WNW–ESE- and WSW–ENE-trending shear zones, which probably branch from regional-scale NW–SE-trending shears. Ore zone fabrics post-date regional-scale folding and the metamorphic peak, and can be correlated with late Svecofennian regional shear tectonics (D6; 1.83–1.78 Ga), indicating that mineralization formed during the late stages of orogenic evolution. SIMS and TIMS U–Pb dating of three samples place tight constraints on the age of gold mineralization. Zircons from both unaltered and altered quartz diorites have ages of 1884±4 Ma and 1881±3 Ma, respectively. These are interpreted as the crystallization age of the rock and as providing the maximum age for mineralization. Zircon rims from an altered quartz diorite from the ore zone give ages of c. 1802±15 Ma, which overlap with the 1801±18 Ma titanite (mean Pb–Pb) age from the ore zone. The ages are similar to the age of the pegmatite dyke that cuts the ore zone and whose zircon age of 1807±3 Ma is approximately the same as the 1791±2 Ma monazite age (TIMS) giving the minimum age of the gold mineralization. The mineralization and its structural framework can be correlated with coeval late Svecofennian shear tectonics related to WNW–ESE-oriented shortening in southern Finland. Extensive c. 1.8 Ga granite magmatism, shear zone development and associated gold mineralization are of regional importance also in the northern and western Fennoscandian Shield (Finnish Lapand and Sweden). A Cordilleran-type setting can explain the widespread distribution of magmatism and gold mineralization associated with shortening, as well as the required heat source triggering hydrothermal fluid flow along shear zones.

scholarly journals CLASSIFICAÇÃO DOS VEIOS QUARTZO-CARBONÁTICOS DE DEPÓSITOS AURÍFEROS NO LINEAMENTO CÓRREGO DO SÍTIO, QF, MG

2013 ◽  
Author(s):  
Marco Aurélio Sequetto Pereira ◽  
Lydia Maria Lobato ◽  
Carlos Alberto Rosière ◽  
Rosaline C. Figueiredo e Silva
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Mineralogical Composition ◽  
Shear Zones ◽  
Gold Deposits ◽  
Lode Gold ◽  
Free Gold ◽  
Quadrilátero Ferrífero ◽  
Lode Gold Deposits ◽  
Mineral Replacement

Os depósitos tipo lode-gold orogênicos Cachorro Bravo, Laranjeiras e Carvoaria, associados ao lineamento regional Córrego doSítio (CdS), estão localizados na porção leste do Quadrilátero Ferrífero, sudeste do cráton São Francisco. São hospedados em rochasmetassedimentares turbidíticas arqueanas do greenstone belt Rio das Velhas e controlados por zonas de cisalhamento NE-SW. Diques esoleiras metamáficos pré- a pós-deformacionais ocorrem intimamente associados à mineralização aurífera e constituem excelentes guiasprospectivos em lineamentos regionais como CdS. Cinco sistemas de veios, V1 a V5, são classificados de acordo com a composiçãomineralógica, textura, orientação, distribuição espacial e geometria. Dois tipos de quartzo ocorrem nestes veios, sendo o tipo 1predominantemente fumê, cedo-hidrotermal, e o tipo 2 leitoso, recristalizado. Apenas os veios V1 (fault-fill veins) são relacionados àmineralização aurífera através da paragênese arsenopirita+pirita+pirrotita+berthierita+ ouro livre; se desenvolvem concordantes à foliaçãomilonítica, S1m, e estão deformados. Veios V2 (oblique-extension veins) são associados temporalmente aos V1 e, embora não estejammineralizados nos depósitos estudados, são contemporâneos ao estágio mineralizador. Estes dois sistemas foram formados em regimedúctil-rúptil. Veios V3 (extension e breccia veins) são tardios à mineralização e representam um estágio posterior do fluido em regimedúctil-rúptil a rúptil; podem estar relacionados à mudança do campo de tensão regional e colocação dos diques tardios Db1. Os veios V4(extension veins) possuem reações de substituição mineral que marcam a hidratação do sistema e podem se associar ao relaxamento dasforças compressivas. Já os veios V5 (vein stockworks) ocorrem apenas em diques e soleiras metamáficos Db1 e estudos de inclusões fluidasindicam que esses contêm fluido diferente dos outros sistemas.Palavras Chave: Classificação de veios quartzo-carbonáticos, ouro orogênico, zonas de cisalhamento, diques e soleiras. ABSTRACTQUARTZ-CARBONATE VEIN CLASSIFICATION OF AURIFEROUS DEPOSITS IN CÓRREGO DO SÍTIO LINEAMENT, QF, MG. Theorogenic-type, lode-gold deposits Cachorro Bravo, Laranjeiras and Carvoaria, associated with the Córrego do Sítio (CdS) regional lineamentare located in the eastern portion of the Quadrilátero Ferrífero region, southern São Francisco craton, Brazil. They are hosted in Archeanmetaturbiditic rocks of the Rio das Velhas greenstone belt and controlled by NE-SW shear zones. Pre- to post-deformational dikes/sills areclosely related to gold mineralization and constitute excellent prospective guides in these regional lineaments such as CdS. Five veinsystems have been classified, V1 to V5, in accordance to their mineralogical composition, texture, orientation, spatial distribution andgeometry. Two types of quartz occur in these veins, with type 1 being predominantly smoky, early hydrothermal, and type 2 a milky,recrystallized quartz. Only V1 veins (fault-fill vein) are related to gold and have a paragenesis with arsenopyrite+pyrite+pyrrhotite+berthierite+ free gold; they develop along the mylonitic foliation S1m, and have been deformed. The V2 veins (oblique-extension veins) areassociated temporally with V1 and although non-mineralized, in the studied deposits they are contemporaneous to the gold stage. Thesetwo systems are formed under a ductile-brittle regime. The V3 veins (extension and breccias veins) are post gold and represent a late-stagehydrothermal fluid under ductile-brittle to brittle regime; they may be related to changes in the stress field and to the emplacement oflate-stage Db1 dikes. The V4 veins (extension veins) have mineral replacement reactions that represent hydration of the system associatedwith the relaxation of the compressive field. The V5 veins (stockwork style) are limited to metamafic Db1 dykes/sills and fluid inclusionstudies indicate that they contain a different fluid from the others systems.Keywords: Quartz-carbonate vein classification, orogenic gold, shear zones, dikes/sills

Source requirements for the Golden Mile, Kalgoorlie: significance to the metamorphic replacement model for Archean gold deposits

1987 ◽  
Vol 24 (8) ◽  
pp. 1643-1651 ◽  
Author(s):  
G. Neil Phillips ◽  
David I. Groves ◽  
Isobel J. Brown
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Source Area ◽  
Shear Zones ◽  
Gold Deposits ◽  
Source Rocks ◽  
Critical Parameters ◽  
Alteration Zones ◽  
Replacement Model ◽  
Golden Mile

The Golden Mile at Kalgoorlie represents a giant Archean hydrothermal gold system localized by ductile shear zones and hosted mainly by a differentiated tholeiitic sill. Chlorite, carbonate, and pyrite alteration zones cover the whole mineralized area (1 km × 3 km), and calculations suggest that for the Golden Mile (production around 1200 t Au), the amounts of components added to these alteration zones are 340 Mt CO2, 20 Mt K, and 5 Mt S. If one adopts a metamorphic-replacement model for gold mineralization in which all ore components derive from devolatilization of greenstones at amphibolite facies or above, these data suggest that a source area involving a 5 km thick greenstone slab of area 8 km × 8 km could produce the necessary CO2, K, S, H2O, and Au. This is considered a reasonable volume of greenstone belt, and under such a model the minimum spacing of large gold deposits would be approximately 20 km along strike.Neither special Au-enriched source rocks nor unreasonably large volumes of greenstone belt are required to produce a giant gold deposit. Instead, the most critical parameters are suitable structural environments providing focussing of fluids and multiple channelways through specific Fe-rich, low-tensile-strength host rocks to ensure efficient depositional mechanisms.

scholarly journals Rheological Contrast between Quartz and Coesite Generates Strain Localization in Deeply Subducted Continental Crust

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 842
Author(s):  
Kouhei Asano ◽  
Katsuyoshi Michibayashi ◽  
Tomohiro Takebayashi
Keyword(s):  
Rheological Behavior ◽  
Strain Localization ◽  
Shear Zones ◽  
Ultrahigh Pressure ◽  
Ultramafic Rocks ◽  
Crustal Material ◽  
Orientation Data ◽  
Crystallographic Preferred Orientation ◽  
Dabie Shan ◽  
Felsic Rocks

Deformation microstructures of peak metamorphic conditions in ultrahigh-pressure (UHP) metamorphic rocks constrain the rheological behavior of deeply subducted crustal material within a subduction channel. However, studies of such rocks are limited by the overprinting effects of retrograde metamorphism during exhumation. Here, we present the deformation microstructures and crystallographic-preferred orientation data of minerals in UHP rocks from the Dabie–Shan to study the rheological behavior of deeply subducted continental material under UHP conditions. The studied samples preserve deformation microstructures that formed under UHP conditions and can be distinguished into two types: high-strain mafic–ultramafic samples (eclogite and garnet-clinopyroxenite) and low-strain felsic samples (jadeite quartzite). This distinction suggests that felsic rocks are less strained than mafic–ultramafic rocks under UHP conditions. We argue that the phase transition from quartz to coesite in the felsic rocks may explain the microstructural differences between the studied mafic–ultramafic and felsic rock samples. The presence of coesite, which has a higher strength than quartz, may result in an increase in the bulk strength of felsic rocks, leading to strain localization in nearby mafic–ultramafic rocks. The formation of shear zones associated with strain localization under HP/UHP conditions can induce the detachment of subducted crustal material from subducting lithosphere, which is a prerequisite for the exhumation of UHP rocks. These findings suggest that coesite has an important influence on the rheological behavior of crustal material that is subducted to coesite-stable depths.

scholarly journals Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 966
Author(s):  
Baptiste Madon ◽  
Lucie Mathieu ◽  
Jeffrey H. Marsh
Keyword(s):  
Oxygen Fugacity ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Chemical Diversity ◽  
Temporal Association ◽  
Volatile Content ◽  
Abitibi Subprovince

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.

scholarly journals Metal source and fluid–rock interaction in the Archean BIF-hosted Lamego gold mineralization: Microthermometric and LA-ICP-MS analyses of fluid inclusions in quartz veins, Rio das Velhas greenstone belt, Brazil

2016 ◽  
Vol 72 ◽  
pp. 510-531 ◽  
Author(s):  
Milton J. Morales ◽  
Rosaline C. Figueiredo e Silva ◽  
Lydia M. Lobato ◽  
Sylvio D. Gomes ◽  
Caio C.C.O. Gomes ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Greenstone Belt ◽  
Gold Mineralization ◽  
Rock Interaction ◽  
Metal Source ◽  
Quartz Veins ◽  
Icp Ms
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