Two sulphur isotope provinces deduced from ores in the Mount Isa Eastern Succession, Australia

Davidson, Garry J.; Dixon, Grant

doi:10.1007/bf00196078

Cited by 29 publications

(7 citation statements)

References 21 publications

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“…An oxidized magmatie sulfur soume was discounted on the basis that the sulfur isotope range (-7 to +4.0%0) was not large enough and was suggested to be more consistent with a reduced hydrothermal system. Davidson (1989) and Davidson and Dixon (1992) interpreted other possible sulfur sources at Starra to be leached biogenie sedimentary sulfur; inorganically reduced seawater sulfate; and thermally degraded organic sulfur (as organic earbon was believed to have been contributed to the Starra earbonares during volcanic exhalation). This final point is questioned, as the calcite at Starra was deposited late in the paragenesis (post-metamorphic, post-ironstone formation) from very oxidized fluid.…”

Section: Origin Of the Starra Ironstones And Mineralizationmentioning

confidence: 96%

“…Inorganically reduced seawater sulfate is also disputed, due to the large, positive isotopic range (-5 to +20%0) that is not consistent with isotopic signatures of Starra sulfides, and the significantly depleted 834S sulfate values (1.1-2.4%o; see below), which compare to 20 per mil for Proterozoie seawater-derived anhydrite (Ohmoto, 1986). The Starra sulfur must have had a significantly different isotopic composition to sulfur that Davidson and Dixon (1992) interpreted to be derived from metasedimentary host rocks at two nearby localities (Answer mine: 834Spyrite 8.4-9.1%o; Mount Cobalt: 834Spyrite 4.2-4.9%0). 8a4S in Starra bornitc, chalcocite, and anhydrite falls within the pyrite-chalcopyrite 8a4S range and supports a single sulfur source.…”

Section: Origin Of the Starra Ironstones And Mineralizationmentioning

confidence: 99%

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Stable isotope evidence for the origin of the Mesoproterozoic Starra Au-Cu deposit, Cloncurry District, Northwest Queensland

Rotherham

Blake

Cartwright³

et al. 1998

Economic Geology

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New stable isotope data are consistent with a metasomatic origin for the controversial Mesoproterozoic ironstone-hosted Au-Cu deposit at Starra in the Cloncurry district of northwest Queensland. This supports textural and mineralogical evidence that the ore-bearing ironstones formed after the peak of metamorphism and were strongly controlled by brittle-ductile deformation. Three dominant paragenetic stages are recognized. These are: (1) early, widespread Na-Ca metasomatism (quartz-albite-scapolite-actinolite), (2) localized K-Fe metasomatism (biotite-magnetite-hematite-quartz-pyrite), and (3) mineralization (quartz-anhydrite-baritehematite-ca•cite-g••d-•yrite-cha•c••yrite-b•rnite-cha•c•cite-ch••rite-musc•vite).Crosscutting anhydrite veins associated with carbonate + hematite are rare in the upper parts of the system but more common at depths greater than 700 m. Stage 3 minerals demonstrate that the ore fluid was highly oxidized.A restricted range of Fe oxide •1sO implies isotopically similar fluids were responsible for the magnetite ironstones and later hematite alteration associated with gold and sulfides (between -0.2 to +3.3%0 except for one magnetite at 5.4%0). Sulfur isotope compositions suggest that pyrite (-0.2 to +3.9%0), chalcopyrite (-5.8 to -0.7 and -14.6%o), bornRe (-4.7%o), chalcocite (-0.1%o), and anhydrite (1.1-2.4%o) all formed from the same sulfur source. Anhydrite •a4S falls within the sulfide range, suggesting that the sulfate inherited its •a4S through hydrolytic processes similar to those of some porphyry environments. •i13C of ore-stage carbonates range from -7.3 to -2.2 per mil. Temperatures based on stage 2 quartz-magnetite pairs imply 400 ø to 500øC for ironstone formation and stage 3 calcite-hematite pairs indicate 180 ø to 330øC for mineralization. Stage 2 fluid inclusions have homogenization temperatures between 345 ø and 615øC and salinities of 34 to 52 wt percent NaC1 equiv. Stage 3 fluid inclusions homogenized between 225 ø and 360øC and have salinities of 30 to 42 wt percent NaC1 equiv. Calculated •ilsO fluid compositions for magnetite-quartz and hematite-calcite average 7.8 per mil and 9.5 per mil, respectively. Fluid compositions (for stages 2 and 3) fall within the range for a magmatic or metamorphic fluid. However, combined stable isotope and fluid inclusion data and thermodynamic considerations suggest a magmatic-metasomatic origin for both the magnetite ironstones and the highly oxidized mineral assemblage associated with high-grade gold deposition.

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Section: Origin Of the Starra Ironstones And Mineralizationmentioning

confidence: 96%

Section: Origin Of the Starra Ironstones And Mineralizationmentioning

confidence: 99%

Stable isotope evidence for the origin of the Mesoproterozoic Starra Au-Cu deposit, Cloncurry District, Northwest Queensland

Rotherham

Blake

Cartwright³

et al. 1998

Economic Geology

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“…Data represent pyrite and the full range of base metal sulfi des present, as well as disseminated sulfi des within the host sediments. References and location information are as follows: Aberfeldy, Scotland (Willan and Coleman, 1983); Balmat-Edwards, United States (Whelan et al, 1984); Jianshengpan, Dongshengmiao, and Tanyaokou, China (Ding and Jiang, 2000); Sullivan, Canada (Campbell et al, 1978(Campbell et al, , 1980; Belt Supergroup, United States (Lyons et al, 2000;Luepke and Lyons, 2001); Amjhore, India (Guha, 1971;Pandalai et al, 1991); McArthur River, Australia (Smith and Croxford, 1975;Rye and Williams, 1981;Eldridge et al, 1993;Shen et al, 2002); Mount Isa, Australia (Solomon, 1965;Smith et al, 1978;Andrew et al, 1989;Davidson and Dixon, 1992;Painter et al, 1999;McShane, 1996); Dugald River, Australia (Dixon and Davidson, 1996;Davidson and Dixon, 1992); Lady Loretta, Australia, (Carr and Smith, 1977;Scott et al, 1985). With the exception of the Chinese deposits, the histograms are stacked in a generally correct stratigraphic order.…”

Section: Implications Stratigraphic Isotope Trendsmentioning

confidence: 99%

Proterozoic sedimentary exhalative (SEDEX) deposits and links to evolving global ocean chemistry

Lyons¹,

Gellatly²,

McGoldrick³

et al. 2006

Evolution of Early Earth's Atmosphere, Hydrosphere, and Biosphere - Constraints From Ore Deposits

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Sedimentary exhalative (SEDEX) Zn-Pb-sulfi de mineralization fi rst occurred on a large scale during the late Paleoproterozoic. Metal sulfi des in most Proterozoic deposits have yielded broad ranges of predominantly positive δ 34 S values traditionally attributed to bacterial sulfate reduction. Heavy isotopic signatures are often ascribed to fractionation within closed or partly closed local reservoirs isolated from the global ocean by rifting before, during, and after the formation of Rodinia. Although such conditions likely played a central role, we argue here that the fi rst appearance of signifi cant SEDEX mineralization during the Proterozoic and the isotopic properties of those deposits are also strongly coupled to temporal evolution of the amount of sulfate in seawater.The ubiquity of 34 S-enriched sulfi de in ore bodies and shales and the widespread stratigraphic patterns of rapid δ 34 S variability expressed in both sulfate and sulfi de data are among the principal evidence for global seawater sulfate that was increasing during the Proterozoic but remained substantially lower than today. Because sulfate is produced mostly through weathering of the continents in the presence of oxygen, low Proterozoic concentrations imply that levels of atmospheric oxygen fell between the abundances of the Phanerozoic and the defi ciencies of the Archean, which are also indicated by the Precambrian sulfur isotope record. Given the limited availability of atmospheric oxygen, deep-water anoxia may have persisted well into the Proterozoic in the presence of a growing sulfate reservoir, which promoted prevalent euxinia. Collectively, these observations suggest that the mid-Proterozoic maximum in SEDEX mineralization and the absence of Archean deposits refl ect a critical threshold in the accumulation of oceanic sulfate and thus sulfi de within anoxic bottom waters and pore fl uids-conditions that favored both the production and preservation of sulfi de mineralization at or just below the seafl oor. Consistent with these evolving global conditions, the appearance of voluminous SEDEX mineralization ca. 1800 Ma coincides generally with the disappearance of banded iron formations-marking the transition from an early iron-dominated ocean to one more strongly infl uenced by sulfi de availability. 170 T.W. Lyons et al.

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“…Light sulphur signatures δ 34 S values (>−3‰) are found in sulphide from Dubarpeth that probably reflect the relatively high oxidation state of the ore stage and magmatic in origin. However, δ 34 S value (−10.85‰) observed in one chalcopyrite grain could also imply other sulphur sources besides the magmatic one (Davidson & Dixon, ).…”

Section: Discussionmentioning

confidence: 99%

Characterization of copper ± (gold) vein‐type mineralization along terrain boundary fault, Dubarpeth in Central India: Constraints from fluid inclusion, stable isotope, and in situ trace element geochemistry of sulphides

et al. 2019

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We present the findings on in situ trace element geochemistry of sulphides by LA-ICPMS, sulphur isotope, and hydrothermal fluid evolution of copper ± gold mineralization at Dubarpeth, Central India. Mineralization is associated with chloritizedsilicified alteration zones, structurally localized along the terrain boundary fault between Archean TTG quartz diorite (2.5 Ga) of Western Bastar Craton and Paleo-Mesoproterozoic cover sediments of Pranhita-Godavari (PG) Valley. Studies reveal that the Cu ± Au mineralization occurs in the form of dissemination, stringers, and veins along the microfaults and fractures. We infer three stages of mineralization based on the field observations and petrography studies. The early stage is characterized by the quartz-pyrite-chalcopyrite assemblage, while the middle stage is represented by quartz-chlorite-chalcopyrite ± pyrite. Calcite ± epidote is conspicuous in the late stage. Fluid inclusion microthermometry and Raman spectroscopy studies indicate that the early-stage veins are mainly aqueous rich, mixed carbonicaqueous, and minor vapour-rich aqueous inclusions. FIs in the early stage displayed evidence of vein formation during episode of fluid immiscibility with the homogenization temperatures and salinities up to 259°C and 27 wt.% NaCl equiv., respectively, indicating initial ore-forming fluids of moderate temperature, moderate to high salinity in H 2 O-CO 2 -NaCl systems. Copper mineralization stage is liquid-and vapour-rich (H 2 O-CO 2 -CH 4 + N 2 ) aqueous inclusions, with homogenization temperatures of 174-221°C and salinities of 6.37 to 13.9 wt.% NaCl equiv. This temperature range has been further supported by empirical chlorite thermometry based on Fe/Mg, Al IV , and Al V . The sulphur isotope values of pyrite and chalcopyrite showed δ 34 S interval of 2.29‰ to −10.85‰, characteristic of highly oxidized nature of the fluids and attributing sulphur source to magmatic origin. The ore-forming fluids gradually became SO 2− 4 enriched and relatively oxidized during Cu mineralization. High Co-Ni trace element signatures of pyrite by LA-ICPMS substantiate this observation, further indicating remobilization from a magmatic-hydrothermal fluid. The presence of CH 4 favours either a source of deep crustal nature or a mantle for the ore-

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Two sulphur isotope provinces deduced from ores in the Mount Isa Eastern Succession, Australia

Cited by 29 publications

References 21 publications

Stable isotope evidence for the origin of the Mesoproterozoic Starra Au-Cu deposit, Cloncurry District, Northwest Queensland

Stable isotope evidence for the origin of the Mesoproterozoic Starra Au-Cu deposit, Cloncurry District, Northwest Queensland

Proterozoic sedimentary exhalative (SEDEX) deposits and links to evolving global ocean chemistry

Characterization of copper ± (gold) vein‐type mineralization along terrain boundary fault, Dubarpeth in Central India: Constraints from fluid inclusion, stable isotope, and in situ trace element geochemistry of sulphides

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