Fluid inclusion geochemistry of high-grade, vein-hosted gold ore at the Pamour Mine, Porcupine Camp, Ontario

Walsh, James F.; Kesler, Stephen E.; Duff, Damien; Cloke, Paul

doi:10.2113/gsecongeo.83.7.1347

Cited by 50 publications

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“…The volume (and overall grade of ore shoots) in the Sigma mine is superior to that in Norbeau. A similar correlation between extensive unmixing and high-grade ore exists at the Pamour mine (Walsh et al, 1988). A blind test was carried out on a rich ore shoot in the Doyon mine within the Abitibi belt.…”

Section: Show That Although Inclusions May Have High Cos or Hso All mentioning

confidence: 85%

Fluid characteristics of vein and altered wall rock in Archean mesothermal gold deposits

Guha

Huanzhang²,

Dubé³

et al. 1991

Economic Geology

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Certain trends in alteration are commonly observed near Archcan mesothermal gold deposits. This study was designed to monitor the changes in composition of fluid inclusions using solid probe mass spectrometry by: (1) establishing and verifying systematic changes in the composition of the fluid during fluid-rock interaction, (2) characterizing the composition and behavior of fluids in the vein and the wall rock in order to establish a link between them, (3) elucidating new insights on the role of fluid immiscibility in gold deposition, and (4) scrutinizing the results for potential use in exploration. Three representative sites of gold mineralization were chosen: a large deposit with appreciable amounts of free gold (Sigma mine in Val d'Or), a second deposit with a smaller amount of free gold (Norbeau mine in Chibougamau), and a third area of gold mineralization with altered wall rock and little veining (Tadd prospect in Chibougamau). Fluid inclusions were carefully selected to sample different alteration zones and the gold mineralization at each site. In most of the cases, varying degrees of unmixing of CO2-H20 were noted. Mass spectra results show that during alteration all generations of inclusions at all sites contained CO2 and H•O. For the alteration-hosted deposit a decrease in Xco2 could be mapped outward from the mineralized zone. The most striking result was that fluid inclusions associated with the main mineralizing episode at Sigma showed a nearly complete segregation into CO• and H•O end members. This can be interpreted as the result of extreme fluid pressure fluctuations. This characteristic was absent from the Norbeau veins where free gold exists in very limited amounts. A test on a high-grade ore shoot from the Doyon mine resulted in a pattern similar to Sigma. We suggest extreme pressure fluctuations were limited in vein-hosted deposits like Norbeau and gold was precipitated essentially from fluid-rock mineral interaction. Unmixing was the most likely cause of free gold deposition. Mineralizing systems may have undergone major fracturing events at time of free gold deposition.This study suggests high CO•/H20 ratios are related to gold mineralization in altered rockhosted deposits but that the ratio may be an unreliable guide in vein-hosted deposits because of the variable unmixing pattern of CO2-H20 fluids. Decrepitometry may prove a useful and rapid method for identifying CO•-H•O unmixing and bonanza gold potential.

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Section: Show That Although Inclusions May Have High Cos or Hso All mentioning

confidence: 85%

Fluid characteristics of vein and altered wall rock in Archean mesothermal gold deposits

Guha

Huanzhang²,

Dubé³

et al. 1991

Economic Geology

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“…These show that the formation temperatures of such deposits generally fall within the range of 200 to 350° C, salinities are low, and the fluid inclusions do not contain NaCl daughter crystals (e.g., Roedder, 1984). CO 2 is present in the fluid inclusions of many Au-quartz vein deposits (Kerrich and Fyfe, 1981;Roedder, 1984) and the occurrence of CH 4 and other gases also has been reported frequently (e.g., Robert and Kelly, 1987;Spooner et al, 1987;Bottrell et al, 1988;Walsh et al, 1988;Naden and Shepherd, 1989;Ortega et al, 1991). Immiscibility and boiling hypotheses have been developed on the basis of the coexistence of gas-rich and liquid-rich inclusions (e.g., Ramboz et al, 1982).…”

Section: Introductionmentioning

confidence: 90%

“…A variable degree of unmixing is indicated by the wide range of CO 2 content (trace to 60 mole%) and ubiquitous coexistence of H 2 O-NaCl-CO 2 ±CH 4 inclusions and aqueous inclusions, within and among different samples. Evidence of fluid immiscibility for gold-bearing veins and its effects on gold deposition has been demon strated by a number of researchers-e.g., Kamilli and Ohmoto (1977), Lyakhov and Popivnyak (1978), Robert and Kelly (1987), Spooner et al (1987), Walsh et al (1988), McKeag and Craw (1989), Naden and Shepherd (1989), Diamond (1990), and Lynch et al (1990). Bowers andHelgeson (1983, 1983b) and Bowers (1991) show that the loss of gases results in oxidation of the fluids and destabilization of the Au-bisulfide complexes; however, above log f(O 2 ) of -31, gold precipitation ceases.…”

Section: Fluid Immiscibility and Implications For Gold Precipitationmentioning

confidence: 98%

Turbidite-Hosted Gold Deposits in the Bendigo-Ballarat and Melbourne Zones, Australia. II. Nature of Ore Fluids

Gao

Kwak

1995

International Geology Review

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Fluids in mesothermal, turbidite-hosted, gold vein deposits in central Victoria, Australia are characterized by temperatures ranging from 180 to 310° C and salinities of less than 10 wt% NaCl equivalent. From west to east there is a general decrease in temperatures, averaging near 300° C in the western Bendigo-Ballarat Zone (BBZ), 270° C in the eastern BBZ, and 230° C in the Melbourne Zone (MZ). Pre-mineralization veins generally are lower in temperature than those hosting mineralization, whereas post-mineralization veins have the lowest average temperatures. Salinities are low, <10 wt% NaCl equivalent; those in deposits in the MZ are slightly lower than those in the BBZ. Salinities are variable in a given deposit or even a single vein period, but there is a weak trend of dilution toward late mineralization and post-mineralization stages. Some pre-mineralization veins have higher salinities (to 9 wt%) than mineralized veins.Fluids in the BBZ have C-O-H compositions, whereas those in the MZ are C-O-H-N. In the BBZ, the CH 4 :CO 2 ratio in the gas phase of fluid inclusions varied from 74:26 to 1:99. In the MZ, similar values occurred, as well as high N 2 , to 69% of the gas phase. Minor hydrocarbons (such as C 3 H 6 ) occur, suggesting low values of H. For most of the deposits there is a trend of increasing concentration of CH 4 and CO 2 during mineralization. Average CH 4 :CO 2 ratios for the western BBZ (Maxwells and Cambrian deposits) are 0.56 and 0.33, and for the eastern BBZ (Wattle Gully), 0.23.One or more periods of immiscibility occurred, especially in BBZ deposits during mineralization, but not in pre-or post-mineralization veins. Average pressures present during mineralization were as follows: western BBZ (Maxwells deposit and New Cambrian deposit), 1200 and 1400 bars; eastern BBZ (Wattle Gully deposit), 800 bars; and MZ (Brunswick and Bailieston deposits), 300 and 900 bars. Oxygen fugacities between the HM and QFM buffers varied from 10 -43

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“…This textural evidence points to different precipitation mechanisms having been active at Navachab. Free gold grains in contact with quartz occurring in veins or at other sites of dilation are rather indicative of gold being precipitated by phase separation (Guha et al, 1991;Walsh et al, 1988). A phase separation is induced by a drop in the fluid pressure when the fluid enters an opening volume.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

The Relationship between the Structural Orientation and the Gold Mineralisation of Quartz-Sulphide Veins in the Navachab Gold Deposit, Namibia

Wulff

Steven

Hein

et al. 2017

Ore Geology Reviews

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Fluid inclusion geochemistry of high-grade, vein-hosted gold ore at the Pamour Mine, Porcupine Camp, Ontario

Cited by 50 publications

References 0 publications

Fluid characteristics of vein and altered wall rock in Archean mesothermal gold deposits

Fluid characteristics of vein and altered wall rock in Archean mesothermal gold deposits

Turbidite-Hosted Gold Deposits in the Bendigo-Ballarat and Melbourne Zones, Australia. II. Nature of Ore Fluids

The Relationship between the Structural Orientation and the Gold Mineralisation of Quartz-Sulphide Veins in the Navachab Gold Deposit, Namibia

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