Gold and sulphide minerals in Tertiary quartz pebble conglomerate gold placers, Southland, New Zealand

Falconer, Donna; Craw, D.; Youngson, J. H.; Faure, Kevin

doi:10.1016/j.oregeorev.2005.03.009

Cited by 57 publications

(40 citation statements)

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“…Numerous specimens from different locations in Australia, South America and Canada have been studied, and many of the crevices in gold grains were covered by Pedomicrobium-like pseudomorphs similar to those described from the Alaskan specimens (Figures 5e and f; Bischoff et al, 1992;Mann, 1992;Keeling, 1993;Bischoff, 1994Bischoff, , 1997Reith, 2005;. Bud-like gold growths are common on the surfaces of authigenic gold from low-redox placer settings in southern New Zealand (Figures 5g and h; Falconer et al, 2006). These latter examples show a range of textures in a transition, with increasing mineralization, from isolated buds to coalesced buds to chains of buds and ultimately to infilled cavities .…”

Section: The Geomicrobiology Of Gold F Reith Et Almentioning

confidence: 68%

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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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Section: The Geomicrobiology Of Gold F Reith Et Almentioning

confidence: 68%

“…Most QPC sequences contain detrital and authigenic sulphide minerals Falconer et al, 2006). Authigenic sulphide and gold textures are well preserved in New Zealand QPCs, and also in the regionally metamorphosed Witwatersrand .…”

Section: Bacteria To Transform Goldmentioning

confidence: 97%

The geomicrobiology of gold

et al. 2007

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“…Our studies in combination with works of other authors led to the understanding that the detrital and aggregation models for gold grain and nugget formation need to be combined into a unified formation model that covers all alluvial and lateritic gold ( Figure 5; e.g., [11,13,14,24,[32][33][34][35][36][37][38][39]. Hence, the more than 100 year lasting debate concerning the formation of gold grains and nuggets in surface environments was finally resolved.…”

Section: A Unified Model For Gold Grain Formation and Implications Fomentioning

confidence: 73%

“…Here gold is commonly associated with bituminous organic matter of putative microbial origin. Falconer et al [32] and Falconer and Craw [33] provided further evidence that geobiological processes play an important role for the formation of QPC-deposits by showing that carbonaceous mudstones within a QPC sequence in New Zealand contain fine gold grains of detrital origin as well as gold of secondary (authigenic) origin displaying bacteriomorphic and sheet-like morphologies. The porous, sheet-like authigenic gold is morphologically similar to gold associated with carbonaceous material in the Witwatersrand QPC.…”

Section: Figurementioning

confidence: 99%

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Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions

et al. 2013

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Microbial communities mediating gold cycling occur on gold grains from (sub)-tropical, (semi)-arid, temperate and subarctic environments. The majority of identified species comprising these biofilms are β-Proteobacteria. Some bacteria, e.g., Cupriavidus metallidurans, Delftia acidovorans and Salmonella typhimurium, have developed biochemical responses to deal with highly toxic gold complexes. These include gold specific sensing and efflux, co-utilization of resistance mechanisms for other metals, and excretion of gold-complex-reducing siderophores that ultimately catalyze the biomineralization of nano-particulate, spheroidal and/or bacteriomorphic gold. In turn, the toxicity of gold complexes fosters the development of specialized biofilms on gold grains, and hence the cycling of gold in surface environments. This was not reported on isoferroplatinum grains under most near-surface environments, due to the lower toxicity of mobile platinum complexes. The discovery of gold-specific microbial responses can now drive the development of geobiological exploration tools, e.g., gold bioindicators and biosensors. Bioindicators employ genetic markers from soils and groundwaters to provide information about gold mineralization processes, while biosensors will allow in-field analyses of gold concentrations in complex sampling media.

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Economic Geology Principles and Practice

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Gold and sulphide minerals in Tertiary quartz pebble conglomerate gold placers, Southland, New Zealand

Cited by 57 publications

References 48 publications

The geomicrobiology of gold

The geomicrobiology of gold

Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions

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