An integrated exploration approach to map bif-hosted gold deposits in the Rio das Velhas greenstone belt, Quadrilátero Ferrífero, Brazil

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.

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U–Pb SHRIMP monazite ages of the giant Morro Velho and Cuiabá gold deposits, Rio das Velhas greenstone belt, Quadrilátero Ferrífero, Minas Gerais, Brazil

Ore Geology Reviews ◽

10.1016/j.oregeorev.2006.11.007 ◽

2007 ◽

Vol 32 (3-4) ◽

pp. 674-680 ◽

Cited By ~ 28

Author(s):

L.M. Lobato ◽

J.O.S. Santos ◽

N.J. McNaughton ◽

I.R. Fletcher ◽

C.M. Noce

Keyword(s):

Greenstone Belt ◽

Minas Gerais ◽

Gold Deposits ◽

Quadrilátero Ferrífero

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Erratum to Brazil's premier gold province. Part II: geology and genesis of gold deposits in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero

Mineralium Deposita ◽

10.1007/s00126-001-0215-x ◽

2001 ◽

Vol 36 (8) ◽

pp. 808-809 ◽

Cited By ~ 3

Author(s):

Lydia Lobato ◽

Luiz Ribeiro-Rodrigues ◽

Frederico Vieira

Keyword(s):

Greenstone Belt ◽

Gold Deposits ◽

Quadrilátero Ferrífero

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

Revista Geonomos ◽

10.18285/geonomos.v21i2.272 ◽

2013 ◽

Cited By ~ 1

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

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

Minerals ◽

10.3390/min10110966 ◽

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.

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