The Biogeochemistry of Gold

Southam, Gordon; Lengke, Maggy F.; Fairbrother, Lintern; Reith, Frank

doi:10.2113/gselements.5.5.303

Cited by 105 publications

(62 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This indicates selective addition of high-purity gold and copper. Biogenic and secondary gold deposition is known to generally be of high purity [9,37]. The conditions consistent with biogenic or secondary gold growth are also consistent with conditions of secondary copper mineralization [38,39], which is often associated with manganese known as "copper wad".…”

Section: Abundances Of Silver and Coppermentioning

confidence: 92%

“…This abiological process of "depletion gilding" or recrystallization is suggested by some [10,13,51] to account for the gold-rich rim effects observed in many placer gold districts. Conversely, others suggest that gold-rich rims result from the addition of high-purity gold to the outer surface of gold by geochemical and biological processes [6,9]. Direct resolution of this long-debated issue is not the immediate goal of this paper.…”

Section: Rim Enrichments and Elemental Abundancesmentioning

confidence: 94%

“…In the most established theory of primary placer formation, a gold mass forms as a lode deposit during a hydrothermal event and survives physical and chemical weathering as native gold grains due to the low chemical reactivity and malleability of gold [1,4]. However, a secondary, accretionary origin for some placer gold has been suggested by observations of bacterioform gold, high-purity gold overgrowths and nanoparticulate gold in biomats [3,[5][6][7][8][9]. Other authors have rejected low-temperature or biogeochemical nugget growth and suggested an abiological, high-temperature origin within lode deposits [10].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Biological and Geochemical Development of Placer Gold Deposits at Rich Hill, Arizona, USA

et al. 2018

View full text Add to dashboard Cite

Placer gold from the Devils Nest deposits at Rich Hill, Arizona, USA, was studied using a range of micro-analytical and microbiological techniques to assess if differences in (paleo)-environmental conditions of three stratigraphically-adjacent placer units are recorded by the gold particles themselves. High-angle basin and range faulting at 5-17 Ma produced a shallow basin that preserved three placer units. The stratigraphically-oldest unit is thin gold-rich gravel within bedrock gravity traps, hosting elongated and flattened placer gold particles coated with manganese-, iron-, barium-(Mn-Fe-Ba) oxide crusts. These crusts host abundant nano-particulate and microcrystalline secondary gold, as well as thick biomats. Gold surfaces display unusual plumate-dendritic structures of putative secondary gold. A new micro-aerophilic Betaproteobacterium, identified as a strain of Comamonas testosteroni, was isolated from these biomats. Significantly, this "black" placer gold is the radiogenically youngest of the gold from the three placer units. The middle unit has well-rounded gold nuggets with deep chemical weathering rims, which likely recorded chemical weathering during a wetter period in Arizona's history. Biomats, nano-particulate gold and secondary gold growths were not observed here. The uppermost unit is a pulse placer deposited by debris flows during a recent drier period. Deep cracks and pits in the rough and angular gold from this unit host biomats and nano-particulate gold. During this late arid period, and continuing to the present, microbial communities established within the wet, oxygen-poor bedrock traps of the lowermost placer unit, which resulted in biological modification of placer gold chemistry, and production of Mn-Fe-Ba oxide biomats, which have coated and cemented both gold and sediments. Similarly, deep cracks and pits in gold from the uppermost unit provided a moist and sheltered micro-environment for additional gold-tolerant biological communities. In conclusion, placer gold from the Devils Nest deposits at Rich Hill, Arizona, USA, preserves a detailed record of physical, chemical and biological modifications.

show abstract

Section: Abundances Of Silver and Coppermentioning

confidence: 92%

Section: Rim Enrichments and Elemental Abundancesmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Biological and Geochemical Development of Placer Gold Deposits at Rich Hill, Arizona, USA

et al. 2018

View full text Add to dashboard Cite

show abstract

“…( Figure 1; [11,12]). In a recent study, Tomkins [16] suggested that microbial processes may have had a far greater influence on the formation of orogenic gold deposits as previously believed.…”

mentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

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.

show abstract

“…The biogeochemical cycling of precious metals and the formation of certain geologic deposits can be attributed to microbial activity [8][9][10][11][12]. In vitro studies have shown that bacteria are able to immobilize and/or precipitate gold from gold-rich solutions [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Immobilisation of Platinum by Cupriavidus metallidurans

et al. 2018

View full text Add to dashboard Cite

Abstract:The metal resistant bacterium Cupriavidus metallidurans CH34, challenged with aqueous platinous and platinic chloride, rapidly immobilized platinum. XANES/EXAFS analysis of these reaction systems demonstrated that platinum binding shifted from chloride to carboxyl functional groups within the bacteria. Pt(IV) was more toxic than Pt(II), presumably due to the oxidative stress imparted by the platinic form. Platinum immobilisation increased with time and with increasing concentrations of platinum. From a bacterial perspective, intracellular platinum concentrations were two to three orders of magnitude greater than the fluid phase, and became saturated at almost molar concentrations in both reaction systems. TEM revealed that C. metallidurans was also able to precipitate nm-scale colloidal platinum, primarily along the cell envelope where energy generation/electron transport occurs. Cells enriched in platinum shed outer membrane vesicles that were enriched in metallic, colloidal platinum, likely representing an important detoxification strategy. The formation of organo-platinum compounds and membrane encapsulated nanophase platinum, supports a role for bacteria in the formation and transport of platinum in natural systems, forming dispersion halos important to metal exploration.

show abstract

The Biogeochemistry of Gold

Cited by 105 publications

References 33 publications

Biological and Geochemical Development of Placer Gold Deposits at Rich Hill, Arizona, USA

Biological and Geochemical Development of Placer Gold Deposits at Rich Hill, Arizona, USA

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

Immobilisation of Platinum by Cupriavidus metallidurans

Contact Info

Product

Resources

About