Origin of lode-gold deposits of the Juneau gold belt, southeastern Alaska

Goldfarb, Richard J.; Leach, D. L.; Pickthorn, W.J.; Paterson, Colin J.

doi:10.1130/0091-7613(1988)016<0440:oolgdo>2.3.co;2

Cited by 102 publications

(23 citation statements)

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“…This is consistent with the conclusions of other studies directed at lode-gold deposits of Archean to Phanerozoic age (e.g. Goldfarb et al 1988Goldfarb et al , 1991.…”

Section: Discussionsupporting

confidence: 82%

Metaturbidite-hosted gold deposits, Córrego do Sítio lineament, Quadrilátero Ferrífero, Brazil

Júnior

Lobato

Lima³

et al. 2015

Braz. J. Geol.

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A study of geology and rocks paragenesis has been conducted at the Córrego do Sítio auriferous lineament, containing the Cachorro Bravo, Laranjeiras and Carvoaria metaturbidite-hosted lode-gold deposits located in the Quadrilátero Ferrífero Region, Minas Gerais, Brazil. These representative deposits are described to illustrate the essentially similar general character of all the deposits of lineament as well as the wide compositional and mineralogical differences in the ore of the different deposits, where, for the Cachorro Bravo deposit, a geological mapping included two underground mine galleries. The Córrego do Sítio unit is a metamorphosed turbidite in an alternating sequence of metagraywackes and phyllites, with parallel to discordant metamafic dikes and sills. The ore zone is predominantly hosted at the stratigraphic break between metasedimentary and metamafic rocks. Four deformation events affected the mine sequence. Mineralized veins and veinlets are considered to have formed within a brittle-ductile shear-zone environment and occurred in multiple episodes. Different vein types are recognized, but the most important volumetrically is a S 1 -concordant type characterized by smoky and milky quartz-carbonate-sulfide ± sulfosalts veins. Veins are dominated by quartz, but locally they are characterized by carbonate and a large variety of sulfide and sulfosalt minerals. Pyrite is the commonest associated sulfide mineral, followed by arsenopyrite and pyrrhotite. An extensive mineralogical study of polished sections has confirmed different generations of sulfide minerals. The sulfides and sulfosalt minerals are interrelated in the veins and disseminated on wall rocks. The data are consistent with a genetic models related to other Archean lode-gold deposits.KEYWORDS: lode-gold deposits; orogenic gold; metaturbidite gold deposit Metaturbidite-hosted gold deposits, RESUMO: O estudo da geologia e paragênese do lineamento aurífero Córrego do Sítio foi conduzido, contendo os depósitos Cachorro Bravo, Laranjeiras e Carvoaria. Esses depósitos auríferos, do tipo lode, hospedados em sequência metaturbidítica ocorrem na região do Quadriláte-ro Ferrífero, Minas Gerais, Brasil. Esses três importantes depósitos são descritos para ilustrar as características semelhantes, composição mineralógica e diferenças no tipo de minério ao longo do lineamento. Para o depósito de Cachorro Bravo, o mapeamento geológico inclui duas galerias subterrâneas. A unidade Córrego do Sítio é composta por uma sequência turbidítica com alternância de metagrauvacas e filitos, associada a diques e sills metamáficos, paralelos a discordantes. A zona de

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“…This is consistent with the conclusions of other studies directed at lode-gold deposits of Archean to Phanerozoic age (e.g. Goldfarb et al 1988Goldfarb et al , 1991.…”

Section: Discussionsupporting

confidence: 82%

Metaturbidite-hosted gold deposits, Córrego do Sítio lineament, Quadrilátero Ferrífero, Brazil

Júnior

Lobato

Lima³

et al. 2015

Braz. J. Geol.

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“…In fact, such vertical, extensional fault-fracture systems of different scales were reported from ancient accretionary prisms where fluid percolation along the fractures was exemplified by the formation of mineral veins precipitated from the solution. Sibson (2013) argued that different scales of extensional fault-fracture systems exist, which depend on the degree of release of seismic energy, and for example, one can refer to the large-scale Alsaska-Juneau Au deposit hosted by quartz veins (Goldfarb et al 1988;Miller et al 1994) and the small-scale quartz-carbonate veins in the Nobeoka thrust zone in the Shimanto accretionary complex in Kyushu, Japan (Yamaguchi et al 2011). The forearc horizontal extension immediately after the earthquakes is again succeeded by horizontal compression when the fractures along the megathrust are sealed by mineral veins and the strength is recovered.…”

Section: Discussionmentioning

confidence: 99%

Stress reversal recorded in calcite vein cuttings from the Nankai accretionary prism, southwest Japan

2014

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The Nankai Trough subduction zone in southwest Japan is a typical convergent margin where the Philippine Sea plate subducts in the northwest direction beneath the Eurasian plate, and devastating earthquakes have repeatedly occurred in this region in the past. In order to investigate the evolution of the stress state in the subduction zone, we analyzed deformation microstructures and the preferred orientation of calcite grains in two cuttings of calcite veins from Hole C0002F that was drilled through the inner wedge of the Nankai accretionary prism during the Integrated Ocean Discovery Program (IODP) Expedition 338 in 2012. For both samples collected at depths of 1,085.5 and 1,885.5 meters below the sea floor (mbsf), the c-axes of calcite grains are preferentially oriented perpendicular to the vein wall, which is indicative of competitive growth of calcite during the vein opening caused by a vein normal extension. Also, mechanical e-twins were developed in both samples, and these are inferred to have been developed under the same stress field as that responsible for the formation of calcite veins based on the paleostress analyses in grains with e-twins. For the calcite vein retrieved at the depth of 1,885.5 mbsf, kink bands were also developed by the compression in the direction perpendicular to the vein wall, which is indicative of stress reversal after the formation of mechanical e-twins. Although we could not reach a definite conclusion for the cause of the stress reversal, it could have occurred during either fold development or seismic cycles in the Nankai accretionary prism.

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“…Leurs origines sont typiquement de sources métamorphiques (Phillips et Groves 1983;Goldfarb et al 1988) ou associées au magmatisme profond (Wood et al 1986;Spooner 1993). La paragenèse est dominée par le quartz, les carbonates, les micas blancs ou la fuschite, l'albite, la chlorite, et plus rarement la scheelite et la tourmaline avec un contenu en sulfures variant de < 3 -5% dominé par les sulfures de fer et d'arsenic (Groves et al 1998;Groves et al 2000).…”

Section: Généralitésunclassified

Contrôles structuraux de la minéralisation aurifère de la veine Consuelo, Pataz, La Libertad, Pérou /

Tremblay¹

2012

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Origin of lode-gold deposits of the Juneau gold belt, southeastern Alaska

Cited by 102 publications

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Metaturbidite-hosted gold deposits, Córrego do Sítio lineament, Quadrilátero Ferrífero, Brazil

Metaturbidite-hosted gold deposits, Córrego do Sítio lineament, Quadrilátero Ferrífero, Brazil

Stress reversal recorded in calcite vein cuttings from the Nankai accretionary prism, southwest Japan

Contrôles structuraux de la minéralisation aurifère de la veine Consuelo, Pataz, La Libertad, Pérou /

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