Precious metals in volcanic peridotite-associated nickel sulfide deposits in Western Australia; II, Distribution within the ores and host rocks at Kambalda

Keays, Reid R.; Ross, J. R.; Woolrich, Paul

doi:10.2113/gsecongeo.76.6.1645

Cited by 63 publications

(18 citation statements)

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“…In detail, ore profiles are commonly more complex than the stereotype (Lesher, 2007;Houle et al, 2012). In a number of cases the composition of the sulfide fraction is not homogeneous, but shows a systematic variation from Cu-and Pt-Pd poor, Ir-Ru-Os-Rh enriched massive ore, indicative of an origin as MSS cumulate, to net textured ores with the opposite characteristics (Keays et al, 1981;Barnes and Naldrett, 1986;Barnes et al, 1988;Heggie et al, 2012). These complexities could still be accommodated within the basic theory, but the presence of leopard-textured poikilitic matrix ores as well as patchy net-textured ores, especially patchy net-texture with sulfide globules as described above from Alexo and the South Raglan deposits, become very hard to explain.…”

Section: The Billiard-ball Model Reconsidered -Origins Of Net-texturementioning

confidence: 99%

Sulfide-silicate textures in magmatic Ni-Cu-PGE sulfide ore deposits: Disseminated and net-textured ores

Barnes

Mungall

Godel

et al. 2017

American Mineralogist

123

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A large proportion of ores in magmatic sulfide deposits consist of mixtures of cumulus silicate minerals, sulfide liquid and silicate melt, with characteristic textural relationships that provide essential clues to their origin. Within silicate-sulfide cumulates, there is a range of sulfide abundance in magmatic-textured silicate-sulfide ores between ores with up to about five modal percent sulfides, called "disseminated ores", and "net-textured" (or "matrix") ores containing about 30 to 70 modal percent sulfide forming continuous networks enclosing cumulus silicates. Disseminated ores in cumulates have a variety of textural types relating to the presence or absence of trapped interstitial silicate melt and (rarely) vapour bubbles. Spherical or oblate spherical globules with smooth menisci, as in the Black Swan disseminated ores, are associated with silicate-filled cavities interpreted as amygdales or segregation vesicles. More irregular globules lacking internal differentiation and having partially facetted margins are interpreted as entrainment of previously segregated, partially solidified sulfide. There is a textural continuum between various types of disseminated and net-textured ores, intermediate types commonly taking the form of "patchy net-textured ores" containing sulfide-rich and sulfide-poor domains at cm to dm scale. These textures are ascribed primarily to the process of sulfide percolation, itself triggered by the process of competitive wetting whereby the silicate melt preferentially wets silicate crystal surfaces. The process is self-reinforcing as sulfide migration causes sulfide networks to grow by coalescence, with a larger rise height and hence a greater gravitational driving force for percolation and silicate melt displacement. Many of the textural variants catalogued here, including poikilitic or leopard-textured ores, can be explained in these terms. Additional complexity is added by factors such as the presence of oikocrysts and segregation of sulfide liquid during strain-rate dependent thixotropic behaviour of partially consolidated cumulates. Integrated textural and geochemical studies are critical to full understanding of ore-forming systems.

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Section: The Billiard-ball Model Reconsidered -Origins Of Net-texturementioning

confidence: 99%

Sulfide-silicate textures in magmatic Ni-Cu-PGE sulfide ore deposits: Disseminated and net-textured ores

Barnes

Mungall

Godel

et al. 2017

American Mineralogist

123

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“…Similar arguments have been made for komatiite-hosted PGE-enriched Ni-Cu sulfide deposits. Naldrett (1986, 1987) favored immiscible sulfide liquid fractionation to explain the compositional variations in the Alexo deposit in Canada, whereas at Kambalda in Western Australia, Keays et al (1981) and Lesher and Keays (1984) proposed a later remobilization and hydrothermal transport of ores into the footwall.…”

Section: Origin Of the Volatiles And Bi Te And Sb In Pge-enriched Nmentioning

confidence: 99%

Petrology and Crystallization History of Multiphase Sulfide Droplets in a Mafic Dike from Uruguay: Implications for the Origin of Cu-Ni-PGE Sulfide Deposits

Prichard¹,

Hutchinson²,

Fisher³

2004

Economic Geology

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Sulfide blebs in a mafic dike belonging to the Uruguayan dike swarm replicate, at a small scale, many features observed in larger platinum-group element-enriched nickel-copper sulfide deposits, such as in Sudbury and Noril'sk. These blebs, formed by the crystallization of droplets of immiscible sulfide liquid, form ~1-cmsized ovoid geopetal structures with pyrrhotite and pentlandite at the base, chalcopyrite and cubanite at the top, and titaniferous magnetite at the margins. Magnetite crystallized first followed by nickel-and iron-rich monosulfide solid solution, which sank to the bottom of the droplets and from which pyrrhotite and pentlandite subsequently exsolved. The remaining copper-rich liquid in the upper part of the droplets crystallized to form an intermediate solid solution from which chalcopyrite and cubanite subsequently exsolved. The final extremely evolved Cu-, Fe-, S-rich, Pd-, Sn-, Pb-, Mo-,Ag-, Bi-, Te, and Sb-bearing liquid crystallized as 10-to 20-µm-sized veinlets filling fractures in the magnetite and adjacent silicate minerals. The veinlets crossing the magnetite often terminate in 100-µm-sized subrounded globules at the contact of the magnetite and the surrounding silicate minerals, indicating a direction of veinlet filling away from the center of the blebs. Textural evidence in the blebs illustrates that as crystallization proceeded and the immiscible sulfide liquid droplets within the dike sank (a distance of less than 1 mm relative to the adjacent silicate) onto already partially crystallized silicate minerals, the sulfide liquid surrounded and resorbed the already-solid magnetite grains. At the top of the blebs magnetite grains were isolated above the sulfide liquid and partially surrounded by quartz, plagioclase, and amphibole, an assemblage representing a late-stage magma that had been drawn into the space created above the droplets as they sank and which is more evolved than that of the surrounding host dike. The location of the blebs within the dike, isolated from influences external to the dike, indicates both that the fracture filling by evolved immiscible Cu-rich sulfide liquid is related to crystallization processes rather than later tectonic events and that the bismuth, tellurium, and antimony have a late magmatic origin associated with crystallization of the immiscible sulfide liquid.

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“…values (Rajamani and Naldrett 1978, Duke and Naldrett 1978, Ross and Keays 1979, Keays et al 1981, Seccombe et al 1981, Donaldson 1984a). 4.…”

Section: Aspects Of Genesis Of Volcanic Peridotite-associated Depositsmentioning

confidence: 98%

“…Ni/Cu varies between 10-16 and NilCo between 40-65 and both vary systematically with nickel grade. Platinum group element concentrations generally show a strong positive correlation with nickel grade with typical concentrations in 100070 sulphides being, platinum 1000-2500 ppb, palladium 1500-3500 ppb, iridium 150-200 ppb, osmium 200-1000 ppb, ruthenium 800-1500 ppb and rhodium 250-800 ppb (Ross and Keays 1979, Keays et al 1981, Donaldson 1984a. S/Se values of 5000-15000 and 6 3 4s values from 0 to + 3.5% for all deposits except Windarra are typical of values for magmatic sulphides.…”

Section: Geological Features Of Western Australian Volcanic Peridotitmentioning

confidence: 99%

Depositional Environments of Volcanic Peridotite-Associated Nickel Sulphide Deposits with Special Reference to the Kambalda Dome

Gresham

1986

Special Publication No. 4 of the Society for Geology Applied to Mineral Deposits

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Volcanic peridotite-associated Fe -Ni sulphide deposits in the Archaean Yilgarn Block of Western Australia display a strong volcanological control on the distribution of individual ore shoots. Although considerably modified by tectonism and amphibolite facies metamorphism, there are distinctive stratigraphic relationships within the host ultramafic komatiite sequence that distinguish ore environments from adjacent areas barren of Fe -Ni sulphides.At the well documented Kambalda Dome deposits, contact ores which occur at the base of the lowermost flow of the ultramafic sequence are commonly confined within narrow (100 -300 m), elongate embayments or troughs in the underlying tholeiitic footwall metabasalt. Hangingwall ores occur at the base of immediately overlying flows and generally directly overlie the troughs and contact ores.Compared to adjacent barren areas, ore environments are characterized by thicker more-magnesian basal ultramafic flows, fewer interflow metasediments and better textural development and compositional differentiation in overlying thin flow units. The ultramafic sequence overlying ore environments is generally less ordered than that in adjacent non-ore environments where there is a more consistent trend of diminishing magnesium content upward through the ultramafic sequence.The major ore-confining troughs are interpreted as original elongate linear depressions within the footwall metabasalt, and some of the local ore-confining structures probably represent original topographic or volcanological features. Ore deposition in an active rift environment may account for the close spatial relationship of contact and hangingwall ores, and the development of the distinctive stratigraphic features of the ore environment. Analogies are drawn with oceanic rift systems and recent submarine volcanism.

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Precious metals in volcanic peridotite-associated nickel sulfide deposits in Western Australia; II, Distribution within the ores and host rocks at Kambalda

Cited by 63 publications

References 0 publications

Sulfide-silicate textures in magmatic Ni-Cu-PGE sulfide ore deposits: Disseminated and net-textured ores

Sulfide-silicate textures in magmatic Ni-Cu-PGE sulfide ore deposits: Disseminated and net-textured ores

Petrology and Crystallization History of Multiphase Sulfide Droplets in a Mafic Dike from Uruguay: Implications for the Origin of Cu-Ni-PGE Sulfide Deposits

Depositional Environments of Volcanic Peridotite-Associated Nickel Sulphide Deposits with Special Reference to the Kambalda Dome

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