The Willyama Supergroup in the Broken Hill and Euriowie Blocks, New South Wales

Stevens, B. P. J.; Barnes, Robert G.; Brown, R. E.; Stroud, W. J.; Willis, I. L.

doi:10.1016/0301-9268(88)90073-3

Cited by 79 publications

(59 citation statements)

References 51 publications

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“…Textures indicative of proximal hydrothermal vents have not been previously recorded for Broken Hill-type deposits in the Willyama Supergroup and the lack of any evidence has previously been ascribed to the intense deformation and metamorphism (Plimer, 1984;Stevens et al, 1988). The evidence presented here, however, indicates that, although the vein stockwork itself may have been destroyed, textural data can survive which can be used to infer its existence.…”

Section: Sphalerite Chemistrymentioning

confidence: 63%

“…The lower part of the supergroup comprises felsic gneiss together with lesser volumes of mafic gneiss which represent bimodal magmatism. In contrast, the upper part of the stratigraphic sequence is dominated by metasedimentary rocks which represent elastic deposition in an increasingly deep, subaqueous environment (Stevens et al, , 1988Willis et al, 1983). Stratabound base metal sulphide mineralisation is concentrated, although not exclusively located, at the transition from volcanic to sedimentary derived sequences, which is a characteristic of Broken Hill-type mineralisation (Parr and Plimer, 1994).…”

Section: Geological Settingmentioning

confidence: 99%

“…The mineralisation is associated with a suite of chemically unusual rocks such as garnetites, quartz-garnet, quartz-gahnite, quartz-magnetite, magnetite-garnet and tourmaline-quartz rocks all of which have been interpreted as the metamorphic equivalent of exhalites (Stanton, 1972;Barnes, 1980;Lottermoser, 1989;Parr, 1992a). Although alternative tectonic models have been proposed Wright et al, 1987), the overall stratigraphic sequence of the Willyama Supergroup is believed to represent deposition in an evolving intracontinental rift environment which formed as the result of extensional tectonism of young Proterozoic crust Stevens et al, 1988).…”

Section: Geological Settingmentioning

confidence: 99%

“…1). The deposit lies in the Proterozoic rocks of the Broken Hill Block which forms part of the Willyama Supergroup Willis et al, 1983) and is the second largest Broken Hill-type orebody in the area after the Broken Hill deposit itself (Stevens et al, 1988). Of the estimated ore reserves of 6 x 105 tonnes at the Pinnacles (Department of Mineral Resources 1981), approximately 2 x 105 tonnes have been extracted.…”

Section: Geological Settingmentioning

confidence: 99%

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The preservation of pre-metamorphic colloform banding in pyrite from the Broken Hill-type Pinnacles deposit, New South Wales, Australia

Parr

1994

Mineral. mag.

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Two distinct generations of pyrite, with different morphologies, are described from the Proterozoic Broken Hill-type Pinnacles deposit in western NSW. The earlier, pyl, forms concentric layers interpreted as colloform banding. Although the textures are somewhat similar to those observed in supergene alteration zones, textural relationships in fresh rocks suggest that these are pre-metamorphic and that the pyrite formed as the result of precipitation from hydrothermal fluids in open veins, vugs and fissures. The second generation, py2, post-dates pyl and forms euhedral overgrowths on it. It is interpreted as being synchronous with the main phase of base metal sulphide mineralisation. The textures reported here are previously unrecorded for Broken Hill-type mineralisation, and have implications for the regional identification of feeder zones to the Broken Hill deposit. The evidence supports a model in which mineralising conditions at the Pinnacles were characterised by slightly higher oxygen and lower sulphur fugacity (further constrained by Fe contents of sphalerite) than at Broken Hill, where pyrrhotite is the major Fe sulphide.The pre-metamorphic textures observed in the pyrite at the Pinnacles deposit are also unusual because they have survived granulite facies metamorphism and five phases of deformation, whereas previously the preservation of such textures has not been recognised at metamorphic grades greater than amphibolite facies.

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Section: Sphalerite Chemistrymentioning

confidence: 63%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

See 2 more Smart Citations

The preservation of pre-metamorphic colloform banding in pyrite from the Broken Hill-type Pinnacles deposit, New South Wales, Australia

Parr

1994

Mineral. mag.

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“…Because D 1 occurred near the peak of metamorphism, the age constraints for D 1 are the same Figure 3; C: Champion, LBH: Little Broken Hill. After Phillips (1980) and Stevens et al (1988 as those for the peak metamorphism (1606-1593 Ma). Ar-Ar ages in hornblende indicate that the ambient temperature of the area had cooled below ca.…”

Section: Timing Of the Metamorphism And Deformationmentioning

confidence: 99%

Prolonged Existence of Sulfide Melt in the Broken Hill Orebody, New South Wales, Australia

Frost¹,

Swapp²,

Gregory³

2005

The Canadian Mineralogist

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The Broken Hill orebody, in Australia, is hosted in pelitic and psammitic gneisses that underwent metamorphism in the granulite facies. Peak metamorphism in the area occurred around 1600 Ma and exceeded temperatures of 850°C at pressures of 5-7 kilobars. The orebody is located in an area of intense deformation that occurred 5 to 15 million years after the peak metamorphism. Highly foliated pelitic schist directly adjacent to the Broken Hill orebody contains assemblages ranging from quartz -K-feldspar -biotite -garnet -sillimanite to quartz -muscovite -biotite -staurolite -garnet -chlorite. The latter assemblage equilibrated at temperatures as low as 600°C. Silicates in the low-temperature assemblages are intimately associated with galena that, in places contains clusters rich in Ag and Sb alloys, sulfides, and sulfosalts. One-bar experiments in the system Ag-Sb-S indicate that the assemblages seen in these rocks would have been molten at 500°C. These relations suggest that a polymetallic melt persisted at Broken Hill for up to twenty million years after peak metamorphism.Keywords: metamorphism, orebody, massive sulfides, melting, Broken Hill, Australia. SOMMAIRELe gisement de Broken Hill, en Australie, est situé dans un hôte gneissique métapélitique et métapsammitique qui a subi un métamorphisme au faciès granulite. Le paroxysme métamorphique dans la région a eu lieu il y a environ 1600 millions d'années, et a impliqué une température au delà de 850°C à une pression entre 5 et 7 kilobars. Le gisement est situé dans une zone de déformation intense active de 5 à 15 million d'années après la culmination métamorphique. Des schistes pélitiques fortement foliés directement adjacents au gisement de Broken Hill contiennent des assemblages allant de quartz -feldspath potassiquebiotite -grenat -sillimanite à quartz -muscovite -biotite -staurolite -grenat -chlorite. Ce deuxième assemblage s'est équilibré à une température aussi basse que 600°C. Les silicates des assemblages de plus faible température sont intimement associés à la galène qui, par endroits, contient des amas riches en alliages, sulfures et sulfosels d'argent et d'antimoine. Des expériences à un bar dans le système Ag-Sb-S indiquent que les assemblages de ces roches pourraient avoir été à l'état fondu à 500°C. Ces relations font penser qu'un liquide polymétallique a persisté à Broken Hill jusqu'à vingt millions d'années après la culmination métamorphique.(Traduit par la Rédaction)

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