A diatreme-hosted gold deposit at Montana Tunnels, Montana

Sillitoe, Richard H.; Grauberger, Gary L.; Elliott, James E.

doi:10.2113/gsecongeo.80.6.1707

Cited by 25 publications

(8 citation statements)

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“…Based on diamond drill core, the vent breccia cuts the quartz monzonite basement beneath the rhyolite domes. This vent breccia is interpreted as analogous to those described by Sillitoe et al (1985) at Montana Tunnels. Since fragments in the vent breccia contain truncated quartz veinlets, some hydrothermal activity took place before emplacement of the vent breccia.…”

Section: Shumake Depositsupporting

confidence: 72%

The Shumake volcanic dome-hosted epithermal, precious metal deposit, western Mojave Desert, California

Blaske

Bornhorst²,

Brady³

et al. 1991

Economic Geology

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Several Tertiary volcanic-hosted precious metal deposits occur in the Mojave block in southern California which is bounded on the north by the Garlock fault and on the southwest by the San Andreas fault. The Middle Buttes volcanic dome complex hosts several low-grade gold and silver orebodies and is comprised of Miocene-age coalescing lava domes, flows, vent breccias, and pyroclastic deposits lying unconformably on Cretaceous basement of the Sierra Nevada batholith. The volcanic rocks range in composition from andesite through rhyolite and are cut by numerous faults.The Shumake deposit, over 5 million tons of ore with an average grade of 0.043 oz per ton (1.5 ppm) Au and 0.4 oz per ton (14 ppm) Ag, is centered around two large quartz veins and the intervening altered rhyolites. The large veins are characterized by pyrite, arsenopyrite, and silver sulfosalts, with minor base metal sulfides and gold. Gold in the altered rhyolite occurs with stockwork quartz veinlets and an oxidation assemblage of iron oxides, scorodite, and red kaolinite. Alteration of the rhyolites is best characterized by sericite, composed of fine-grained illite and muscovite, and stockwork quartz veinlets with associated adularia. Fluid inclusions indicate that the stockwork quartz formed around 210øC. The quartz, sericite, and minor adularia assemblage is underlain by propylitic alteration and overlain in one part of the deposit by alunite and white kaolinite alteration. These main-stage alterations were followed by an oxidation assemblage which is interpreted to be related to collapse of the hydrothermal system. The deposit is dominated by anomalous abundances ofAu, Ag, Hg, As, and Sb. Spatial geochemical variations suggest that the two massive quartz veins were dominant components of the hydrothermal plumbing system.The paleohydrologic system at the Shumake deposit is analogous to the adularia-sericite type of volcanic-hosted epithermal precious metal deposits. Faults and fractures provided the pathways for hydrothermal fluid movement. Vein textures suggest episodic mineralization that can be explained by seismic pumping of hydrothermal fluids. Since a close temporal relationship exists between volcanism and ore deposition, magmas probably provided heat to the hydrothermal system. Thus, for the Shumake deposit, faulting provided both the pathways and driving mechanism for the hydrothermal system while heat was provided by magmas.

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Section: Shumake Depositsupporting

confidence: 72%

The Shumake volcanic dome-hosted epithermal, precious metal deposit, western Mojave Desert, California

Blaske

Bornhorst²,

Brady³

et al. 1991

Economic Geology

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“…Plusieurs brèches magmatiqueshydrothermales sont aussi associées à une forte altération en carbonates et en séricite. À l'intérieur de ceux-ci on retrouve les gisements Montana Tunnels, Montana (Sillitoe et al, 1985), Colosseum, Californie (Sharp, 1984) et Kidston, Australie (Baker et Andrew, 1991).…”

Section: Classification Des Gisementsunclassified

Environnement métallogénique du couloir de Fancamp avec emphase sur les gisements aurifères de Chevrier, région de Chibougamau, Québec /

Legault¹

2003

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IV REMERCIEMENTSCe partenariat a généré trois rapports ministériels qui traitent sur certaines problématiques du secteur (Legault et al., 1995(Legault et al., , 1997(Legault et al., , 2000. Étant donné que certaines informations ont été recueillies après la rédaction de ces rapports, certaines sections de la thèse sont présentées de façon intégrale afin d'incorporer tous les travaux effectués dans le cadre de ce projet. LOCALISATION ET ACCÈSLa région à l'étude est située à environ 30 km au sud de la ville de Chibougamau et 30 km au sud-est de la ville de Chapais dans la province de Québec ( Fig. 1.1). Elle recoupe la partie sud-ouest du feuillet SNRC 32G/09, la partie sud-est du feuillet SNRC 32G/10 et la partie nord du feuillet 32G/07, soit une superficie de plus de 300 km 2 .Le chemin forestier L-209S, accessible à partir de la route régionale 113 entre Chapais et Chibougamau, offre un excellent accès à la partie sud-ouest de la région à l'étude. Un chemin forestier, praticable avec un véhicule à quatre roues motrices, relie la partie nord-est de la région à l'étude au kilomètre 206 de la route régionale 167 qui joint Chibougamau à St-Félicien. La partie centrale n'est accessible qu'en bateau à partir d'une multitude de lacs inter-reliés. Les forages sur les gisements de Chevrier et de Chevrier Sud permettaient à la CMI de croire à un gros gisement aurifère à faible teneur localisé dans un schiste à séricite. HISTORIQUE DE L'EXPLORATION MINIÈRE DANS LA RÉGION DE FANCAMPCertaines similitudes (association de la minéralisation avec des intrusions felsiques, sulfures disséminés, altération en potassium) avec le gisement du lac Troilus (Fraser, 1993), qui appartient également à la CMI, ont mené à proposer un modèle de porphyre aurifère pour expliquer la formation de ces gisements. Ceci a eu pour effet de fortement influencer l'évaluation de la propriété et les travaux d'exploration effectués par la compagnie.Cependant, les forages de 1993 à 1995 n'ont pas donné les résultats escomptés.Depuis 1995, GéoNova Explorations Inc. a optionné les propriétés contenant les a Les travaux exécutés par la CMI dans le secteur ont été faits sous les noms suivants : Corporation Falconbridge Copper ), Minnova Inc. (1987) et Corporation Minière Métall (1993-1995 Barley et Groves, 1992). Par exemple, la ceinture de feu du Pacifique est l'hôte de nombreux gisements aurifères (Panteleyev, 1986;Berger et Bonham, 1990;Carlile et Mitchell, 1994;White et al., 1995;Goldfarb et al., 1998). Les gisements aurifères se forment soit dans des orogènes intérieurs (d'après la nomenclature de Murphy et Nance, 1991) développés lors de collision entre continent et/ou arc (Kerrich et Cassidy, 1994;Goldfarb et al., 1998) ou dans des orogènes périphériques lors de subduction de croûte océanique le long de marge continentale ou insulaire (Sillitoe, 1989;Kesler, 1997 (Taylor, 1996;Kirkham et Sinclair, 1996), tandis que les gisements aurifères de type filons de quartz-carbonates sont spatialement associés à des failles à mouvement inverse (Robert, 1996).Les ...

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“…Among the biggest values for horizontal dimensions of phreatomagmatic breccias we may quote several extreme examples like Wau (Papua New Guinea) -1.4 x 1.4 km (Sillitoe et al, 1984), and Montana Tunnels (Montana, USA) -2.1 x 0.6 km . Obviously, the most impressive one is the amazing Guinaoang breccia pipe from Philippine (Sillitoe and Angels, fide Sillitoe et al, 1985) …”

Section: Dimensionsmentioning

confidence: 99%

“…Fragments up to hundreds of meters in diameter were cited by Sillitoe (1985), Sillitoe et al (1985). The common fragment size ranges from several meters to tens of centimetres or even less.…”

Section: Fragmentsmentioning

confidence: 99%

Hydrovolcanic Breccia Pipe Structures-General Features and Genetic Criteria. I. Phreatomagmatic Breccias

Tămaş¹,

Milési²

2002

Studia UBB Geologia

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ABSTRACT. Two types of hydrovolcanic breccias are generally accepted: phreatomagmatic and phreatic. Due to their specific characteristics generated during the brecciation, characteristics that control the ore deposition, these breccias represent favourable hosts for mineralization. The depth of formation, the general form and dimensions, the breccia -host rock contact, as well as fragments, matrix, and open spaces altogether control the position and the size of the breccia hosted ore bodies and contribute in different degrees to the rise of the ore grades in phreatomagmatic and phreatic structures. Consequently, the recognition of the genetic type of breccia allows an appropriate strategy in mineral exploration.Describing a breccia necessarily implies a check of its general features, such as environment/depth of formation, general form/geometry, dimensions, brecciahost rock contact, fragments, matrix, alteration, mineralization, surface connection, as well as of its additional features, namely fluidization and facies changes (see Table 2). There are several characteristics with high genetic significance among the abundant descriptive features regarding breccia structures. To point out such evidences means to find out the keys for the genetic intrepretation. A complete list of genetic criteria is proposed for phreatomagmatic breccias (see Table 3).

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A diatreme-hosted gold deposit at Montana Tunnels, Montana

Cited by 25 publications

References 0 publications

The Shumake volcanic dome-hosted epithermal, precious metal deposit, western Mojave Desert, California

The Shumake volcanic dome-hosted epithermal, precious metal deposit, western Mojave Desert, California

Environnement métallogénique du couloir de Fancamp avec emphase sur les gisements aurifères de Chevrier, région de Chibougamau, Québec /

Hydrovolcanic Breccia Pipe Structures-General Features and Genetic Criteria. I. Phreatomagmatic Breccias

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