Crystal features of supergene gold at Hannan South, Western Australia

Lawrance, L. M.; Griffin, Brendan

doi:10.1007/bf01886956

Cited by 41 publications

(22 citation statements)

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“…The degree to which authigenic gold contributes to a population of gold grains is governed by the prevailing climate and geomorphology of the location (Nichol et al, 1994). Studies of gold from lateritic environments in Australia (e.g., Lawrance and Griffin, 1994) and Ghana (Bowell, 1992;Bowell et al, 1993) have identified the mechanisms of gold mobility and describe some internal textures exhibited by authigenic gold grains. Alteration of placer gold can also occur in placer gold in temperate climates.…”

Section: Discrimination Between Epithermal and Authigenic Goldmentioning

confidence: 98%

Application of microchemical characterization of placer gold grains to exploration for epithermal gold mineralization in regions of poor exposure

Chapman

Mortensen

2006

Journal of Geochemical Exploration

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Section: Discrimination Between Epithermal and Authigenic Goldmentioning

confidence: 98%

Application of microchemical characterization of placer gold grains to exploration for epithermal gold mineralization in regions of poor exposure

Chapman

Mortensen

2006

Journal of Geochemical Exploration

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“…Sorption of gold complexes and colloids to organic matter, clays, Fe and Mn minerals as well as bioaccumulation and biomineralization may lead to the formation of secondary gold particles, which are often observed close to primary deposits (see below; Boyle, 1979;Goldhaber, 1983, Webster andMann, 1984;Webster, 1986;Lawrance and Griffin, 1994;Gray, 1998). Secondary gold is generally much finer (up to 99 wt% of gold) compared to primary gold, and the individual gold aggregates are often larger than in potential source rocks (Wilson, 1984;Watterson, 1992;Mossman et al, 1999).…”

Section: The Geochemical Characteristics Of Goldmentioning

confidence: 99%

“…These morphologies include wire, dendritic, octahedral, porous and sponge gold (Figure 5b; Kampf and Keller, 1982;Leicht, 1982;Lieber, 1982;Wilson, 1984;Watterson, 1992;Márquez-Zavalía et al, 2004). Hence, many authors have provided fieldbased evidence that secondary processes are responsible for their formation that occur mainly in soils or shallow regolith (Webster and Mann, 1984;Wilson, 1984;Clough and Craw, 1989;Watterson, 1992;Craw and Youngson, 1993;Lawrance and Griffin, 1994). Previous sections have shown that microbial gold solubilization and precipitation may occur in surficial environments.…”

Section: The Geomicrobiology Of Gold F Reith Et Almentioning

confidence: 99%

“…Octahedral plate-like secondary gold platelets are common in oxidized zones surrounding primary deposits (Figure 5b; Wilson, 1984;Lawrance and Griffin, 1994;Gray, 1998). Beveridge (1994, 1996) demonstrated the formation of metallic gold with octahedral habit by organic phosphate and sulphur compounds derived from bacteria at pH B2.6.…”

Section: Possible Bacterial Textures In Secondary Goldmentioning

confidence: 99%

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The geomicrobiology of gold

et al. 2007

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Microorganisms capable of actively solubilizing and precipitating gold appear to play a larger role in the biogeochemical cycling of gold than previously believed. Recent research suggests that bacteria and archaea are involved in every step of the biogeochemical cycle of gold, from the formation of primary mineralization in hydrothermal and deep subsurface systems to its solubilization, dispersion and re-concentration as secondary gold under surface conditions. Enzymatically catalysed precipitation of gold has been observed in thermophilic and hyperthermophilic bacteria and archaea (for example, Thermotoga maritime, Pyrobaculum islandicum), and their activity led to the formation of gold-and silver-bearing sinters in New Zealand's hot spring systems. Sulphatereducing bacteria (SRB), for example, Desulfovibrio sp., may be involved in the formation of goldbearing sulphide minerals in deep subsurface environments; over geological timescales this may contribute to the formation of economic deposits. Iron-and sulphur-oxidizing bacteria (for example, Acidothiobacillus ferrooxidans, A. thiooxidans) are known to breakdown gold-hosting sulphide minerals in zones of primary mineralization, and release associated gold in the process. These and other bacteria (for example, actinobacteria) produce thiosulphate, which is known to oxidize gold and form stable, transportable complexes. Other microbial processes, for example, excretion of amino acids and cyanide, may control gold solubilization in auriferous top-and rhizosphere soils. A number of bacteria and archaea are capable of actively catalysing the precipitation of toxic gold(I/ III) complexes. Reductive precipitation of these complexes may improve survival rates of bacterial populations that are capable of (1) detoxifying the immediate cell environment by detecting, excreting and reducing gold complexes, possibly using P-type ATPase efflux pumps as well as membrane vesicles (for example, Salmonella enterica, Cupriavidus (Ralstonia) metallidurans, Plectonema boryanum); (2) gaining metabolic energy by utilizing gold-complexing ligands (for example, thiosulphate by A. ferrooxidans) or (3) using gold as metal centre in enzymes (Micrococcus luteus). C. metallidurans containing biofilms were detected on gold grains from two Australian sites, indicating that gold bioaccumulation may lead to gold biomineralization by forming secondary 'bacterioform' gold. Formation of secondary octahedral gold crystals from gold(III) chloride solution, was promoted by a cyanobacterium (P. boryanum) via an amorphous gold(I) sulphide intermediate. 'Bacterioform' gold and secondary gold crystals are common in quartz pebble conglomerates (QPC), where they are often associated with bituminous organic matter possibly derived from cyanobacteria. This may suggest that cyanobacteria have played a role in the formation of the Witwatersrand QPC, the world's largest gold deposit.

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“…The weathering of gold particles under lateritic conditions leads to the development of an Au-rich, Ag-depleted halo (e.g., Mann 1984, Colin & Vieillard 1991, Freyssinet et al 1989, Minko et al 1992, Colin et al 1997, and ultimately, to the formation of grains of com-positionally pure, supergene gold (e.g., Boyle 1979, Mann 1984, Oliveira & Campos 1991, Santosh & Omana 1991, Lawrance & Griffin 1994. Like silver, palladium also is leached from gold alloy during weathering (Varajão et al 2000).…”

Section: Dendrites Of Palladian Goldmentioning

confidence: 99%

PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL

Cabral

Lehmann

Kwitko-Ribeiro

et al. 2002

The Canadian Mineralogist

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The Serra Pelada garimpo (1980)(1981)(1982)(1983)(1984) was the site of the most spectacular gold rush in recent history, but the mineralogy of the bonanza-style mineralization has not so far been documented in detail. Rediscovery of an early drill-core, recovered in 1982 from the near-surface lateritic portion of the garimpo area, has provided coarse-grained gold aggregates for this study. The centimeter-long aggregates of gold occur in powdery, earthy material. They exhibit a delicate arborescent fabric and are coated by goethite. Four compositional types of gold are recognized: palladian gold with an atomic ratio Au:Pd of 7:1 ("Au 7 Pd"), Hgbearing palladian gold (Au-Pd-Hg), Pd-bearing gold with up to 3 wt.% Pd (Pd-poor gold) and pure gold. A number of platinumgroup minerals (PGM) are included in, or attached to the surface of, palladian gold: "guanglinite", Sb-bearing "guanglinite", atheneite and isomertieite, including the noteworthy presence of Se-bearing PGM (Pd-Pt-Se, Pd-Se, Pd-Hg-Se and Pd-Bi-Se phases, and sudovikovite and palladseite). They define an As-Sb-Hg-Se mineral assemblage typical of hydrothermal vein-type deposits formed at relatively low temperatures. Native palladium, characteristically situated in the goethite coating, is intimately associated with a Pd-O phase. The remarkable occurrence of native platinum associated with Pd-bearing gold, PGM (compositionally close to mertieite-II and isomertieite) and berzelianite from a nearby prospect (Elefante prospect) is also recorded.

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Crystal features of supergene gold at Hannan South, Western Australia

Cited by 41 publications

References 6 publications

Application of microchemical characterization of placer gold grains to exploration for epithermal gold mineralization in regions of poor exposure

Application of microchemical characterization of placer gold grains to exploration for epithermal gold mineralization in regions of poor exposure

The geomicrobiology of gold

PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL

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