Sulphur‐isotope study of the massive sulphide orebody at Woodlawn, New South Wales

Ayres, D. E.; Burns, M.S.; Smith, J. W.

doi:10.1080/00167617908729081

Cited by 12 publications

(3 citation statements)

References 15 publications

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“…Similar results were obtained from Woodlawn ore by Ayres et al (1979). Both cases contrast with the "apparent" equilibrium values obtained from the Shakanai No.…”

Section: Isotopic Fractionation Between Coexisting Mineralssupporting

confidence: 50%

The formation of the volcanic-hosted massive sulfide ore deposit at Rosebery, Tasmania

Green¹,

Solomon²,

Walshe³

1981

Economic Geology

110

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The Rosebery pyritic zinc-lead-copper-silver-gold orebody occurs in dominantly felsic volcanic rocks of Cambrian age in western Tasmania. Ore formation occurred in a marine environment following eruption of a thick pyroclastic unit consisting mainly of welded, ashflow tuffs, and subsequent subsidence. The main orebody consists of a discontinuous massive sulfide horizon and in the southern part of the mine there is a generalized metal zonation with a lower and central Cu-Fe-rich zone surrounded and overlain by Zn-Pb-Ag-rich ore. Barite-sulfide ore occurs as separate lenses higher in the sequence separated from the sulfide orebody by unmineralized, cleaved siltstone. The orebody is underlain by an extensive zone of alteration marked by depletion of Na and Sr and enrichment in Rb, K, Mg, Mn, and H20. The pyrite and chalcopyrite content of the altered footwall tuff and the Co content of the pyrite is highest beneath the Fe-and Cu-rich zones in the sulfide orebody and a feeder is inferred in this area.The •a4S values for sulfides in the sulfide orebody are higher in the richest Zn-Pb-Ag ore (>14.1%0) than the Fe-Cu ore (>7.8•), a pattern paralleled by a decrease in the Fe/Fe + Mg + Mn ratio of chlorite and a decrease in the FeS content of sphalerite. The •$48 values for sulfides in the barite ore are even higher (14.5 to 19.8%0) and the FeS content of sphalerite lower. Barite throughout the barite and sulfide orebodies is fairly constant between 84.6 and 41.2 per mil, but that in the sulfide ore appears to be epigenetic. The/i34S values for baritesulfide pairs indicate a temperature range of 255 ø to 298øC for the barite orebody, but the temperature of barite ore formation was probably about 250øC.The use of $a4S values for sulfides as stratigraphic markers indicates that the sulfide orebody is diachronous. It is possible to account for the metal and $a4S distribution by assuming that the ore solutions are buoyant on reaching the sea floor during the Fe-and Cu-rich phases but show reversing buoyancy during the PboZn-rich phase.The coexisting arsenopyrite-pyrite-chlorite-quartz assemblage in the sulfide orebody defines a range of aO2-T conditions using the six-component solid solution chlorite model of Walshe and Solomon (1981). The maximum indicated temperature of $00øC is consistent with the minimum temperature required by iron and copper solubilities. However, the chlorite compositions may be postdepositional, as seems to be the case for the FeS contents of sphalerite. The $a4Szs for the sulfide orebody is probably derived by almost complete reduction of Cambrian seawater sulfate mixed with sulfur leached from underlying rocks. The/ia4S values for the barite orebody may represent partial reduction of seawater sulfate.The ore fluid is supposed to have been generated by convective circulation of seawater in a rock pile heated by a Cambrian granitoid pluton.

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“…Similar results were obtained from Woodlawn ore by Ayres et al (1979). Both cases contrast with the "apparent" equilibrium values obtained from the Shakanai No.…”

Section: Isotopic Fractionation Between Coexisting Mineralssupporting

confidence: 50%

The formation of the volcanic-hosted massive sulfide ore deposit at Rosebery, Tasmania

Green¹,

Solomon²,

Walshe³

1981

Economic Geology

110

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“…The average 634S = 8.1%0 for the Elura sulphide minerals is quite consistent with that for other metamorphic gold and base metal vein deposits in the Cobar area (CSA mine: 7.5%0; Central Cobar deposits: 7.9%o; Seccombe and Brill 1989). The 634S values are also similar to those found for pyrite from metamorphic gold deposits elsewhere in the Lachlan Fold Belt of New South Wales (Ayres et al 1979;Seccombe and Hicks 1989).…”

Section: Discussionsupporting

confidence: 73%

Fluid inclusion and sulphur isotope evidence for syntectonic mineralisation at the Elura mine, southeastern Australia

Seccombe

1990

Mineral. Deposita

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Abstract. Fluid inclusion and sulphur isotope data for the discordant, metasediment-hosted massive sulphide deposit at Elura are consistent with a syntectonic origin of the orebodies. Thermometric and laser Raman microprobe analyses indicate that two-phase, primary fluid inclusions are low salinity and HzO-CO2-CH 4 types. Inclusion fluids from quartz in ore yield homogenisation temperatures (T0 ranging from 298 ~ to 354~ (mean 320 ~ They are likely to have been trapped close to the solvus of the H20-COz-(CH4-NaC1 ) system and thus should give temperatures of the mineralising fluid. An additional, low T h population of later fluid inclusions is recognised in quartz from ore and syntectonic extension veins in the adjacent wallrock. Th'S for these low CO2-bearing inclusions range from 150 to 231~ (mean 190 c~C), and should be considerably lower than true trapping temperatures. Sulphur isotopic composition (~34S) of pyrite, sphalerite, pyrrhotite and galena ranges from 4.7 to 12.6%o and indicates a sulphur source from underlying Cobar Supergroup metasediments. An average temperature of 275 ~ from the sphalerite-galena sulphur isotopic thermometer suggests isotopic re-equilibration below peak metamorphic temperatures.

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“…The narrow range of d 34 S values at Lewis Ponds (0.1 and 7.4&) compares with Silurian VHMS deposits in the Hill End and Captains Flat-Goulburn troughs, New South Wales. Sulphides from Woodlawn have d 34 S values of 2.8-9.2& (Ayres et al 1979). d 34 S values from Mt.…”

Section: Temperature and Chemistry Of The Mineralizing Fluidsmentioning

confidence: 99%

Lewis Ponds, a hybrid carbonate and volcanic-hosted polymetallic massive sulphide deposit, New South Wales, Australia

2005

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The Lewis Ponds Zn-Pb-Cu-Ag-Au deposit, located in the eastern Lachlan Fold Belt, central western New South Wales, exhibits the characteristics of both volcanic-hosted massive sulphide and carbonate-hosted replacement deposits. Two stratabound massive to disseminated sulphide zones, Main and Toms, occur in a tightly folded Upper Silurian sequence of marine felsic volcanic and sedimentary rocks. They have a combined indicated resource of 5.7 Mt grading 3.5% Zn, 2.0% Pb, 0.19% Cu, 97 g/t Ag and 1.9 g/t Au. Main Zone is hosted by a thick unit of poorly sorted mixed provenance breccia, limestone-clast breccia and quartz crystal-rich sandstone, whereas Toms Zone occurs in the overlying siltstone. Pretectonic carbonate-chalcopyrite-pyrite and quartz-pyrite stringer veins occur in the footwall porphyritic dacite, south of Toms Zone. Strongly sheared dolomite-chalcopyrite-pyrrhotite veins directly underlie the Toms massive sulphide lens. The mineralized zones consist predominantly of pyrite, sphalerite and galena. Paragenetically early framboidal, dendritic and botryoidal pyrite aggregates and tabular pyrrhotite pseudomorphs of sulphate occur throughout the breccia and sandstone beds that host Main Zone, but are rarely preserved in the annealed massive sulphide in Toms Zone. Main and Toms zones are associated with a semi-conformable hydrothermal alteration envelope, characterized by texturally destructive chlorite-, dolomite-and quartz-rich assemblages. Dolomite, chlorite, quartz, calcite and sulphides have selectively replaced breccia and sandstone beds in the Main Zone host sequence, whereas the underlying porphyritic dacite is weakly sericite altered. Vuggy and Editorial handling: D. Lentz

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Sulphur‐isotope study of the massive sulphide orebody at Woodlawn, New South Wales

Cited by 12 publications

References 15 publications

The formation of the volcanic-hosted massive sulfide ore deposit at Rosebery, Tasmania

The formation of the volcanic-hosted massive sulfide ore deposit at Rosebery, Tasmania

Fluid inclusion and sulphur isotope evidence for syntectonic mineralisation at the Elura mine, southeastern Australia

Lewis Ponds, a hybrid carbonate and volcanic-hosted polymetallic massive sulphide deposit, New South Wales, Australia

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