Gold remobilisation and formation of high grade ore shoots driven by dissolution-reprecipitation replacement and Ni substitution into auriferous arsenopyrite

Fougerouse, Denis; Micklethwaite, Steven; Tomkins, Andrew G.; Mei, Yuan; Kilburn, Matt R.; Guagliardo, Paul; Fisher, Louise; Halfpenny, Angela; Gee, Mary; Paterson, David L.; Howard, Daryl L.

doi:10.1016/j.gca.2016.01.040

Cited by 168 publications

(47 citation statements)

References 80 publications

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“…). B‐rims are characterised by higher arsenic concentrations (~46 wt% as opposed to ~44 wt% in A‐rims; Fougerouse et al ., ; Fougerouse et al ., in press) and preserve the original shape of the crystals. The B‐rim contacts are sharp, planar to curvilinear (bulbous) and penetrate in from microcracks and grain boundaries (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The mineralised arsenopyrites are hosted in Palaeoproterozoic sheared phyllites (2155 Ma, zircon U/Pb maximum age of deposition; Oberthür et al ., ) composed of micas, quartz, carbonates (ankerite and siderite), chlorites, rutile and graphite. Arsenopyrite growth and mineralisation occurred during continuous cleavage development and peak upper greenschist metamorphism at 340°–460° and 2 kbar as shown by the development of strain shadows parallel with the continuous cleavage surrounding the arsenopyrites (the Eburnean orogeny: Schwartz et al ., ; Oberthür et al ., ; Fougerouse et al ., ; Fougerouse et al ., in press). A large sample suite (>200 samples) was collected and studied from mineralised exposures of the Obuasi mine to provide representative petrographical and geochemical results across the deposit.…”

Section: Samples and Methodsmentioning

confidence: 99%

“…The arsenopyrites have been subject to two strain events (Fougerouse et al ., in press), mostly accommodating pure shear. The first event is high strain, at the peak of metamorphism, which occurred during the Eburnean orogeny (D2 Ob ; Fougerouse et al ., ; Fougerouse et al ., in press). A pervasive continuous cleavage developed while the quartz veins underwent boudinage and strain shadows developed around the arsenopyrite grains (Fig.…”

Section: Samples and Methodsmentioning

confidence: 99%

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The golden ark: arsenopyrite crystal plasticity and the retention of gold through high strain and metamorphism

et al. 2016

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Quantitative electron backscatter diffraction analysis and ion microprobe imaging of gold-rich arsenopyrites provide the first insights into the crystal plasticity and element mobility behaviour of arsenopyrites through metamorphism (340°-460°and 2 kbar). Remarkably, the gold-rich arsenopyrites remained structurally and chemically robust during high strain deformation. It was only during a superimposed lower strain deformation event, at a high angle to the preferred orientation of the arsenopyrites, that small amounts of crystal plasticity affected the arsenopyrites. During the low strain event, a dissolution-reprecipitation reaction resulted in loss of gold from the crystal lattice, facilitated by localised domains of recrystallisation, most likely due to fluid percolation along sub-and new grain boundaries. We suggest that the abundance and rheologically robust nature of gold-rich arsenopyrite in giant gold deposits, affected by greenschistamphibolite metamorphism, is actually critical in the preservation of those deposits.

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Section: Resultsmentioning

confidence: 99%

Section: Samples and Methodsmentioning

confidence: 99%

Section: Samples and Methodsmentioning

confidence: 99%

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The golden ark: arsenopyrite crystal plasticity and the retention of gold through high strain and metamorphism

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“…However, in some geological systems grains can align due to mineralization and deformation processes producing a crystallographic preferred orientation (CPO) (Halfpenny, 2011;Halfpenny and Prior, 2009). If a CPO is identified it may be used to interpret the underlying processes which caused grain alignment (Fougerouse et al, 2016a;Fougerouse et al, 2016b).…”

Section: Texture Analysismentioning

confidence: 99%

Actively forming Kuroko-type volcanic-hosted massive sulfide (VHMS) mineralization at Iheya North, Okinawa Trough, Japan

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et al. 2017

Ore Geology Reviews

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“…There are currently~40 nanoSIMS instruments worldwide, and the technique is proving extraordinarily valuable for understanding the internal structure and composition of ore minerals. Among ore minerals, pyrite and arsenopyrite have been a major focus in published work, particularly with respect to their capacity for hosting both nanoparticulate and solid solution gold [95][96][97]. Opportunity exists to use nanoSIMS to address other outstanding issues in the mineralogy of compositionally-zoned minerals, trace element partitioning, and in mineral processing.…”

Section: Nanoscale Secondary Ion Mass Spectrometry (Nanosims)mentioning

confidence: 99%

Advances and Opportunities in Ore Mineralogy

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Abstract:The study of ore minerals is rapidly transforming due to an explosion of new microand nano-analytical technologies. These advanced microbeam techniques can expose the physical and chemical character of ore minerals at ever-better spatial resolution and analytical precision. The insights that can be obtained from ten of today's most important, or emerging, techniques and methodologies are reviewed: laser-ablation inductively-coupled plasma mass spectrometry; focussed ion beam-scanning electron microscopy; high-angle annular dark field scanning transmission electron microscopy; electron back-scatter diffraction; synchrotron X-ray fluorescence mapping; automated mineral analysis (Quantitative Evaluation of Mineralogy via Scanning Electron Microscopy and Mineral Liberation Analysis); nanoscale secondary ion mass spectrometry; atom probe tomography; radioisotope geochronology using ore minerals; and, non-traditional stable isotopes. Many of these technical advances cut across conceptual boundaries between mineralogy and geochemistry and require an in-depth knowledge of the material that is being analysed. These technological advances are accompanied by changing approaches to ore mineralogy: the increased focus on trace element distributions; the challenges offered by nanoscale characterisation; and the recognition of the critical petrogenetic information in gangue minerals, and, thus the need to for a holistic approach to the characterization of mineral assemblages. Using original examples, with an emphasis on iron oxide-copper-gold deposits, we show how increased analytical capabilities, particularly imaging and chemical mapping at the nanoscale, offer the potential to resolve outstanding questions in ore mineralogy. Broad regional or deposit-scale genetic models can be validated or refuted by careful analysis at the smallest scales of observation. As the volume of information at different scales of observation expands, the level of complexity that is revealed will increase, in turn generating additional research questions. Topics that are likely to be a focus of breakthrough research over the coming decades include, understanding atomic-scale distributions of metals and the role of nanoparticles, as well how minerals adapt, at the lattice-scale, to changing physicochemical conditions. Most importantly, the complementary use of advanced microbeam techniques allows for information of different types and levels of quantification on the same materials to be correlated.

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Gold remobilisation and formation of high grade ore shoots driven by dissolution-reprecipitation replacement and Ni substitution into auriferous arsenopyrite

Cited by 168 publications

References 80 publications

The golden ark: arsenopyrite crystal plasticity and the retention of gold through high strain and metamorphism

The golden ark: arsenopyrite crystal plasticity and the retention of gold through high strain and metamorphism

Actively forming Kuroko-type volcanic-hosted massive sulfide (VHMS) mineralization at Iheya North, Okinawa Trough, Japan

Advances and Opportunities in Ore Mineralogy

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