Fluid pressure and hydraulic fracturing in hydrothermal ore formation at gold deposits

Ostapenko, N. S.; Neroda, O. N.

doi:10.1134/s1819714007030074

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…Epizonal orogenic gold mineralization (<6 km) in metamorphic belts, especially high-grade breccia ore shoots, has been proposed to record a history of incremental extensional opening and hydrothermal recementation (Hagemann et al, 1992;Gebre-Mariam et al, 1995). Mineral deposition in the extensional zones is thought to be triggered by fluid fluctuations and boiling revealed by fluid inclusion microthermometry and critical stress analyses (e.g., Phillips, 1972;Sibson, 1987;Li et al, 2002;Ostapenko and Neroda, 2007). Thermodynamic modelling reveals that removal of H2S from ore fluids into vapor phase during boiling lowers the total activity of sulfur in ore fluids, which destabilizes gold-bisulphide complexes and leads to gold deposition (Williams-Jones et al, 2009).…”

Section: Implications For Gold Redistribution In Fault-valve Regimementioning

confidence: 99%

Metal remobilization and ore-fluid perturbation during episodic replacement of auriferous pyrite from an epizonal orogenic gold deposit

Evans

et al. 2019

Geochimica et Cosmochimica Acta

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Mineral-scale episodic replacement of auriferous pyrite by texturally-complex pyrite, marcasite and minor arsenopyrite occurred in breccia ores from the Daqiao epizonal orogenic gold deposit, West Qinling Orogen, China. This study uses a novel combination of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), Nanoscale secondary ion mass spectrometry (NanoSIMS), and secondary ion mass spectrometry (SIMS) to investigate the remobilization and re-concentration of gold and other trace elements during this complex replacement process and the probable mechanism. Several lines of evidence including some degree of preservation of external morphology, sharp contacts and compositional differences between the parent pyrite and product pyrite and marcasite, and reaction-induced porosity suggest that the replacement of parent pyrite proceeds via a two-step replacement via a dissolution and reprecipitation mechanism, plus an additional marcasite overgrowth. During the replacement of euhedral pyrite, depletion of gold and other trace elements (Te, Se, Zn, Co, Tl, Ni, W, and As) in porous product pyrite relative to its precursor indicate exsolution and remobilization of these metals from crystal lattice of the original pyrite. In the subsequent replacement of porous pyrite by two types of marcasite and minor arsenopyrite, euhedral product marcasite contains low contents of trace elements, possibly due to high metal solubility in the acidic fluids favorable for marcasite precipitation. The complex-zoned marcasite significantly enriched in gold and other metals relative to porous pyrite (W, Tl, As, Sb, Ag, Se, and Zn) is thought to have formed via precipitation triggered by further oxidation and/or immediate reduction in threshold supersaturation. Dissolution of the impurity-rich pyrite and precipitation of new pyrite and marcasite generations could have occurred at low pH plus high concentrations of dissolved Fe 2+ condition caused by partial oxidation of aqueous H2S and/or S 2in ore fluids. The fluid oxidation is evidenced by a general decreasing trend of δ 34 S values from the parent euhedral pyrite, to product porous pyrite, euhedral marcasite, and complex-zoned marcasite. The isotopic results are consistent with ore fluid oxidation controlled by pressure fluctuations during multistage hydraulic fracturing in a fault-valve regime at Daqiao deposit. This quantitative study emphasizes that the pressure-driven hydrothermal process plays a key role in the micron-to nano-scale redistribution and re-enrichment of gold and other trace metals during episodic replacement of auriferous pyrite in brittle rheological zones from epizonal orogenic gold systems.

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Section: Implications For Gold Redistribution In Fault-valve Regimementioning

confidence: 99%

Metal remobilization and ore-fluid perturbation during episodic replacement of auriferous pyrite from an epizonal orogenic gold deposit

Evans

et al. 2019

Geochimica et Cosmochimica Acta

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“…1,2). The geology of this deposit and mineralogy of ore were described in detail by Eirish (2002), Eirish et al (2002), and Ostapenko and Neroda (2007). The deposit is located in the Tokur lithotectonic zone, or the terrane of accretionary wedge (Sorokin, 2001).…”

Section: Geology Of the Depositmentioning

confidence: 97%

“…The gold mineralization comprises metasomatic and stringer-disseminated orebodies localized in the ore controlling fault zone and gently dipping dilation quartz veins in splays of the hanging wall of this zone (Eirish et al, 2002;Ostapenko and Neroda, 2007). The veins are conformable or nearly conformable to the bedding in host rocks.…”

Section: Geology Of the Depositmentioning

confidence: 97%

40Ar/39Ar age of adularia from veins of the Tokur gold deposit, the Mongolian-Okhotsk Orogenic Belt, Russia

et al. 2011

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The 40 Ar/ 39 Ar age of the productive stage of the ore forming hydrothermal process at the large Tokur gold deposit is 122.4 ± 2.0 Ma. This estimate suggests a paragenetic relationship of this deposit with the nearly exposed Karaurak subvolcanic trachyrhyodacite intrusion, the U-Pb zircon age of which was pre viously estimated at 120 ± 5 Ma. The age of mineralization at the Tokur deposit is close to the time of forma tion of some other deposits in the Russian Far East localized in various structural units.

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Deposition conditions and distribution features of native gold individuals in the veins of the Tokur mesothermal deposit, Russia

Ostapenko

Neroda

2016

Geol. Ore Deposits

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Fluid pressure and hydraulic fracturing in hydrothermal ore formation at gold deposits

Cited by 5 publications

References 5 publications

Metal remobilization and ore-fluid perturbation during episodic replacement of auriferous pyrite from an epizonal orogenic gold deposit

Metal remobilization and ore-fluid perturbation during episodic replacement of auriferous pyrite from an epizonal orogenic gold deposit

40Ar/39Ar age of adularia from veins of the Tokur gold deposit, the Mongolian-Okhotsk Orogenic Belt, Russia

Deposition conditions and distribution features of native gold individuals in the veins of the Tokur mesothermal deposit, Russia

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