Gold in Magmatic Hydrothermal Solutions and the Rapid Formation of a Giant Ore Deposit

Simmons, S. W.; Brown, Kevin L.

doi:10.1126/science.1132866

Cited by 182 publications

(68 citation statements)

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“…Finally, our results challenge the existing models of ore deposit formation and offer more perspectives for exploration. The large enhancement by S − 3 of the fluid transport capacities for Au, coupled with the efficient Au precipitation triggered by S − 3 breakdown, implies that far smaller but more concentrated amounts of fluid than previously thought (39,41) are responsible for economic gold deposition at high temperatures. This conclusion offers previously unidentified insights into magmatic and metamorphic ore fluid dynamics that appears to be similar to that for sedimentary rock-hosted base-metal deposits whose formation would occur by periodic injections of anomalously metal-rich batches of fluids during short ore-forming events (40).…”

Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 99%

“…A smaller amount of S − 3 -bearing fluid would imply a smaller volume of the magma source necessary for an economic gold deposit. Furthermore, modern conceptual models of ore deposits require an exceptionally fortuitous combination of Au-rich sources such as Au preconcentration in magmatic sulfides (3,41,42) or sedimentary pyrite (7,8), sustained and focused hydrothermal fluid flow (38,39), and tectonic and other geochemical triggers of an efficient precipitation mechanism (39)(40)(41)(42), all acting in unison to form an economic gold deposit from typically part-per-billion levels of Au concentrations as hydrogen sulfide or chloride complexes in the fluid and silicate melt. The existence of gold-trisulfur ion species with large capacities to extract, transfer, and precipitate gold reduces these requirements and shortens by up to 10-100 times the duration needed to form a given deposit from a much smaller magma or rock source.…”

Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 99%

See 1 more Smart Citation

Sulfur radical species form gold deposits on Earth

Pokrovski

Kokh

Guillaume

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

112

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Current models of the formation and distribution of gold deposits on Earth are based on the long-standing paradigm that hydrogen sulfide and chloride are the ligands responsible for gold mobilization and precipitation by fluids across the lithosphere. Here we challenge this view by demonstrating, using in situ X-ray absorption spectroscopy and solubility measurements, coupled with molecular dynamics and thermodynamic simulations, that sulfur radical species, such as the trisulfur ion S − 3 , form very stable and soluble complexes with Au + in aqueous solution at elevated temperatures (>250°C) and pressures (>100 bar). These species enable extraction, transport, and focused precipitation of gold by sulfur-rich fluids 10-100 times more efficiently than sulfide and chloride only. As a result, S − 3 exerts an important control on the source, concentration, and distribution of gold in its major economic deposits from magmatic, hydrothermal, and metamorphic settings. The growth and decay of S − 3 during the fluid generation and evolution is one of the key factors that determine the fate of gold in the lithosphere.gold | sulfur | ore deposit | hydrothermal fluid | trisulfur ion

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Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 99%

Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 99%

Sulfur radical species form gold deposits on Earth

Pokrovski

Kokh

Guillaume

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

112

View full text Add to dashboard Cite

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“…Moreover, magmatic fluids have long been proposed as an additional source of economically important metals (i.e. Cu, Zn, Ag and Au) in excess of that feasible by rock leaching alone Sun et al, 2004;Simmons and Brown, 2006;. Many large volcanic-hosted massive sulfide deposits (Kuroko-type) are thought to have formed in arc and back-arc magmatichydrothermal settings (Franklin et al, 1981;Herzig and Hannington, 1995).…”

Section: Introductionmentioning

confidence: 99%

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Reeves¹

2010

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This thesis presents the results of four discrete investigations into processes governing the organic and inorganic chemical composition of seafloor hydrothermal fluids in a variety of geologic settings. Though Chapters 2 through 5 of this thesis are disparate in focus, each represents a novel investigation aimed at furthering our understanding of subsurface geochemical processes affecting hydrothermal fluid compositions. Chapters 2 and 3 concern the abiotic (nonbiological) formation of organic compounds in high temperature vent fluids, a process which has direct implications for the emergence of life in early Earth settings and sustainment of present day microbial populations in hydrothermal environments. Chapter 2 represents an experimental investigation of methane (CH 4 ) formation under hydrothermal conditions. The overall reduction of carbon dioxide (CO 2 ) to CH 4 , previously assumed to be kinetically inhibited in the absence of mineral catalysts, is shown to proceed on timescales pertinent to crustal residence times of hydrothermal fluids. In Chapter 3, the abundance of methanethiol (CH 3 SH), considered to be a crucial precursor for the emergence of primitive chemoautotrophic life, is characterized in vent fluids from ultramafic-, basalt-and sediment-hosted hydrothermal systems. Previous assumptions that CH 3 SH forms by reduction of CO 2 are not supported by the observed distribution in natural systems. Chapter 4 investigates factors regulating the hydrogen isotope composition of hydrocarbons under hydrothermal conditions. Isotopic exchange between low molecular weight n-alkanes and water is shown to be facilitated by metastable equilibrium reactions between alkanes and their corresponding alkenes, which are feasible in natural systems. In Chapter 5, the controls on vent fluid composition in a backarc hydrothermal system are investigated. A comprehensive survey of the inorganic geochemistry of fluids from sites of hydrothermal activity in the eastern Manus Basin indicates that fluids there are influenced by input of acidic magmatic solutions at depth, and subsequently modified by variable extents of seawater entrainment and mixing-related secondary acidity production. CHAPTER 1 IntroductionSeafloor hydrothermal systems associated with the generation of oceanic crust represent a dramatic expression of heat and mass transfer from the interior of the Earth. In addition to profound effects on ocean chemistry, convective circulation of seawater through volcanically active oceanic crust leads to the formation of metal sulfide deposits. In addition, seafloor hot springs are often invoked as ideal settings from which early microbial life could have emerged.Since the initial discovery of low temperature venting at the Galápagos Spreading Center in 1977 (CORLISS et al., 1979), our understanding of the composition and diversity of hydrothermal solutions has expanded greatly. During convection through oceanic crust of basaltic composition, O 2 -replete seawater reacts with crustal rock, typically producin...

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“…More recently, Saunders [29] discussed one implication of the 100 s of episodes of gold deposition at Sleeper, suggesting that each perhaps represented a discrete (short) time interval for each gold layer formation, and further suggested that perhaps the entire bonanza ore-forming event might have been much shorter than previously thought (a possibility also suggested by Heinrich et al [23] Simmons and Brown [30], and Heinrich [31]). …”

Section: Ore Texturesmentioning

confidence: 96%

“…Previously, Saunders [2] proposed that the formation of 100 s of gold-rich bands at the Sleeper deposit was a function of episodic boiling in that system. It has been demonstrated [30,35] that boiling is an effective gold-depositional process in geothermal fluids significantly under-saturated with respect to gold prior to boiling. But does this conclusion hold for gold-rich ore forming fluids such as interpreted by Saunders and Schoenly [18] for deposits such as Sleeper?…”

Section: Discussionmentioning

confidence: 99%

Textural Evidence of Episodic Introduction of Metallic Nanoparticles into Bonanza Epithermal Ores

Saunders

2012

Minerals

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Tertiary low sulfidation (LS) epithermal deposits in the western USA often show evidence of the former presence of nanoparticle-sized precious-metal and silica phases in the highest grade (bonanza) ores. Here, nanoparticles are defined to have a size less than ~10 −7 m. The ore-mineral textures that formed from aggregation of nanoparticles (or colloids) observed to date in these ores include electrum and naumannite (Ag 2 Se). Here it is proposed that chalcopyrite also forms nanoparticles in these ores, but sulfide nanoparticles apparently have significantly different physical (surface) properties than the precious-metal phases, and thus exhibit different mineral textures (e.g., no textural evidence of previous chalcopyrite nanoparticles). Textures described here show that nanoparticles of precious-metal phases and silica were episodically and often repeatedly deposited to form the banded bonanza veins typical of many western USA epithermal deposits. Chalcopyrite is the most abundant metal-sulfide mineral in these bonanza ores, and it was also deposited episodically as well, and it appears to replace earlier formed naumannite dendrites. However, this apparent "replacement" texture may just be the result of naumannite dendrite limbs trapping chalcopyrite nanoparticles that later recrystallized to the apparent replacement texture. The episodic and repetitive nature of the metal-depositing events may record periodic "degassing" of magma chambers at depth, where metals are repeatedly delivered to the shallow epithermal environment by "vapor-phase" metal (loid) transport.

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Gold in Magmatic Hydrothermal Solutions and the Rapid Formation of a Giant Ore Deposit

Cited by 182 publications

References 14 publications

Sulfur radical species form gold deposits on Earth

Sulfur radical species form gold deposits on Earth

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Textural Evidence of Episodic Introduction of Metallic Nanoparticles into Bonanza Epithermal Ores

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