Walk-rock mineralization along Ontario gold deposits

Bain, George W.

doi:10.2113/gsecongeo.28.8.705

Cited by 9 publications

(5 citation statements)

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“…The geology of the Timmins district and its prodigiously rich gold deposits has been described by numerous authors (Bain 1933;Ferguson et al 1968;Pyke 1982;Hodgson 1984). For this study, samples were collected from the Hollinger-McIntyre, Dome, and Buffalo Ankerite deposits and from felsic intrusive rocks that host, or are peripheral to, some of the vein arrays.…”

Section: Geological Setting Timmins Districtmentioning

confidence: 96%

“…For this study, samples were collected from the Hollinger-McIntyre, Dome, and Buffalo Ankerite deposits and from felsic intrusive rocks that host, or are peripheral to, some of the vein arrays. The Hollinger and McIntyre gold deposits have been described as a whole, or in part, by Bain (1933), Ferguson et al (1968), Griffis (1968), Mason and Melnik (1986), and . Representative samples were collected from underground on the 1500 and 3600 ft levels of the McIntyre mine and from the 11, 44, 55, and 400 pits of the Hollinger surface workings.…”

Section: Geological Setting Timmins Districtmentioning

confidence: 99%

“…In veins, quartz and carbonate constitute the principal gangue minerals where they are associated with variable modal proportions of pyrite, albite, tourmaline, mucovite, chlorite, and gold. This mineral assemblage is also typically developed in the extensive domains of alteration that envelop vein systems (Bain 1933;Boyle 1979;Kerrich and Fyfe 1981;Davies et al 1982;Kerrich 1983;Fyon et al 1983). Chemical analyses of the carbonates reveal that ferroan dolomite is the most abundant carbonate species, but magnesite, calcite, and siderite are found in veins hosted by ultramafic or felsic igneous rocks and in iron formation, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Carbon-isotope systematics of Archean Au–Ag vein deposits in the Superior Province

Kerrich¹

1990

Can. J. Earth Sci.

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Abundant carbonate is a characteristic feature of most Archean mesothermal Au-Ag vein deposits, but the source of the C is controversial. For Superior Province deposits collectively, the maximum variation of average SI3c values is from -9.0 2 0 . 7 %~ ( l a , n = 19; Darius) to -0.6 + 1 . 6 %~ ( l u , n = 7; Cochenour-Willians), and limiting SI3c values are -13.6 and + 1.3%0. At the deposit scale, Fe dolomites in nongraphitic lithologies are for the most part isotopically uniform, where S13c .2 2 0.3 (Bousquet), -5.4 ? 0.9 (Lamaque), and -5.3 + 0 . 5 %~ (Hasaga): the restricted individual ranges of SI3C values imply a corresponding uniformity to the ambient temperature and s~~c~~ of the ore-forming fluids.Within individual deposits, small systematic variations of S '~C carbonate arise from (i) interaction of hydrothermal fluids with carbonaceous rocks, (ii) immiscible separation of COz + CH,, or (iii) Rayleigh fractionation effects. Positive shifts in 613c result from buffering of the fluid to lower Eh by reaction with reduced C, whereas negative shifts reflect partial isotopic equilibration between I3C-depleted C (613c = -26%0) and aqueous hydrothermal C species. Transient immiscibility of C 0 2 + CH4 acts to precipitate carbonates enriched relative to the main population of Fe dolomites. The SI3c values of carbonates in unmineralized alteration halos (-2.2 2 I .~% G , n = 42) at the McIntyre deposit are enriched in 13c relative to the main gold-bearing vein systems (SI3c = -3.2 + 0.3%~): the enrichment is attributed to a Rayleigh fractionation accompanying progressive consumption of C 0 2 as hydrothermal fluids infiltrate laterally from veins into wall rocks. Fe dolomite and calcite are variably enriched in "0 with respect to equilibrium quartz-carbonate fractionations for ambient temperatures of 270"-340°C. Carbonate 6180 values diminish in an irregular manner with depth, converging on values of -1 1 %~ (Fe dolomite, 6800 ft (2073 m), McIntyre). Variable degrees of oxygen-isotope disequilibrium represent overprinting of carbonates by post-Archean brines in the Canadian Shield. Synvolcanic vesicle calcite in three groups of metabasalts (SI3c = -4.3 f 2.1; -2.8 2 1.5; -2.7 2 1.3%0) and calcite in two groups of clastic sediments (-6.4 + 1.8; -4.6 ? 2.5%0) remote from deposits are systematically depleted of 13C relative to average Precambrian limestones (-0 & I%o), owing to the involvement of COz derived from I3c-depleted organic matter. Consequently, calcite in greenstone belt supracrustal rocks is not restricted to approximately 0 %~. The total spread of average SI3C~, dol values (-9.0 2 0.7 to -0.6 + 0 . 6 %~) in the Au deposits, which goes in hand with a geographical provinciality in 0 -,Sr-, and Pb-isotope compositions of the ore-forming fluids, is too large to be accounted for by mantle C 0 2 (-6 2 2%0) or magmatic C 0 2 (-6 * 2 %~) alone but rather is interpreted as reflecting generation of hydrothermal fluids in crustal or subcreted rocks heterogeneous in terms of the distribution of 13c-enriched (carbonat...

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Section: Geological Setting Timmins Districtmentioning

confidence: 96%

Section: Geological Setting Timmins Districtmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Carbon-isotope systematics of Archean Au–Ag vein deposits in the Superior Province

Kerrich¹

1990

Can. J. Earth Sci.

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“…The genetic scheme stems from three principal lines of evidence: (1) lithophile element (K, Rb, etc.) enrichments characteristic of the deposits (Bain, 1933;Kerrich and Fyfe, 1981;Davies et al, 1982) are considered to be directly complementary to the 'depletion' of these elements in granulites, ( 2) the existence of a secular conjunction of 'depleted' Archean granulites with Archean mesothermal Au deposits, and ( 3) calculated & 13C values of the hydrothermal fluids carrying Au and LJLE, many of which average -4 per mil, are equated with a juvenile mantle CO2 reservoir (-7±2 per mil) that is presumed to have induced the granulitization and concurrent LJLE depletion. Tarney and Weaver, (1987) proposed that 'depleted' tonalitic Archean granulites are formed in a two-stage process, in which TJTP, are first extracted, followed by partial melting of the 'depleted' residue to generate tonalitic magmas.…”

Section: Mantle Co2 -Granulitizationmentioning

confidence: 99%

Proceedings of workshop LXIII; USGS Red-Book conference on the Mechanical involvement of fluids in faulting

Jacobson¹,

Hickman²,

Sibson³

et al. 1994

Open-File Report

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The Wattle Gully Fault is a high-angle reverse fault zone that developed at depths around 10km late during mid-Devonian regional crustal shortening in central Victoria. The fault has a length around 800m and a maximum displacement of 40m. The widespread development of steeply-dipping fault-fill quartz veins and associated sub-horizontal extension veins within the fault zone indicate that faulting occurred at low stress differences in a transiently supralithostatic fluid pressure regime. The structure was the site of focussed fluid migration during vein formation.The internal structures of veins indicate vein development was intimately associated with faulting and involved thousands of increments of hydraulic fracturing, fault slip and vein sealing. Fault slip and vein opening is interpreted to have been strongly influenced by repeated fluid pressure fluctuations associated with fault-valve behavior.The geometries and internal structures of veins in the Wattle Gully Fault Zone are interpreted in terms of cyclic changes in shear stresses, fluid pressures, and near-field principal stress orientations during fault-valve behavior. Substantial fluctuations in fluid pressure have played a key role in controlling fault strength, as well as nucleation and recurrence of slip events. There is evidence that faulting in supralithostatic fluid pressure regimes can result in near-total stress relief and local dynamic overshoot.Fault-valve behavior is shown to have important implications for coupling between fault dynamics and the dynamics of fluid circulation around active faults that are sites of focussed fluid migration. In particular, fault-valve action is expected to lead to distinctly different fluid migration patterns adjacent to the fault zone before, and immediately after fault rupture. geometries of extension veins in the fault zone indicate that some failure events have been associated with near-total relief of shear stress and transient re-orientation of near-field stresses.Repeated fluctuations in fluid pressure associated with fault-valve behavior are expected to lead to distinctly different fluid migration patterns adjacent to faults before, and immediately after rupture events. References

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“…'Pressure fringes' are generally found on pyrite or magnetite crystals and have been described quite extensively (e.g. Pabst, 1931;Bain, 1933;Magnee, 1935;Miles, 1945;Fairbairn, 1950a;Frankel, 1957;Hills, 1963;Joplin, 1968). 'Pressure shadows' are generally associated with other types of porphyroblast or clastic material and are less well described.…”

Section: Introductionmentioning

confidence: 99%

‘Pressure shadow’ structures in foliated rocks from Bermagui, New South Wales

Williams

1972

Journal of the Geological Society of Australia

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Walk-rock mineralization along Ontario gold deposits

Cited by 9 publications

References 0 publications

Carbon-isotope systematics of Archean Au–Ag vein deposits in the Superior Province

Carbon-isotope systematics of Archean Au–Ag vein deposits in the Superior Province

Proceedings of workshop LXIII; USGS Red-Book conference on the Mechanical involvement of fluids in faulting

‘Pressure shadow’ structures in foliated rocks from Bermagui, New South Wales

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