Ore minerals down to the nanoscale: Cu-(Fe)-sulphides from the iron oxide copper gold deposit at Olympic Dam, South Australia

Ciobanu, Cristiana L.; Cook, Nigel J.; Ehrig, Kathy

doi:10.1016/j.oregeorev.2016.08.015

Cited by 42 publications

(25 citation statements)

References 47 publications

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“…The present study also confirms the widespread presence of lamellar low-temperature djurleite, formed via cooling of bornite solid solutions, as documented elsewhere [24]. The typical basket-weave appearance of bornite containing djurleite in foils prepared for TEM (Figure 6i,k,l) is a characteristic induced by FIB-milling [24].…”

Section: Evolution Of Sulphide Assemblagessupporting

confidence: 89%

“…The presence of bornite superstructures indicates that the minimum temperatures of formation above 265 • C can be inferred [29]. The co-existence of different bornite superstructure domains at the nanoscale in the same sample ( Figure 10) is also reported in natural samples [24,31]. The present study also confirms the widespread presence of lamellar low-temperature djurleite, formed via cooling of bornite solid solutions, as documented elsewhere [24].…”

Section: Evolution Of Sulphide Assemblagessupporting

confidence: 87%

“…This is attributed to the presence of nanoscale intergrowths of other mineral species such chalcopyrite (or more rarely djurleite) in bornite (Figure 3c,d) and digenite in chalcocite. A similar non-stoichiometry is reported for Cu-(Fe)-sulphides from the Olympic Dam [24]. …”

Section: Compositional Data For Pb-chalcogenides and Host Cu-(fe)-sulsupporting

confidence: 81%

“…Both "chalcocite" and bornite show evidence of high-temperature phases that undergo phase transformation and restructuring upon cooling. Bornite solid solutions [44], resulting in bornite-chalcocite and bornite-chalcopyrite assemblages, are comparable to those seen elsewhere [24,45]. The presence of bornite superstructures indicates that the minimum temperatures of formation above 265 • C can be inferred [29].…”

Section: Evolution Of Sulphide Assemblagessupporting

confidence: 71%

“…The intimate relationships between Cu-(Fe)-sulphides that extend down to the nanoscale (Figures 1-3 and 5) account for the non-stoichiometry observed here ( Figure 4) and are common in these type of ores [24].…”

Section: Evolution Of Sulphide Assemblagesmentioning

confidence: 57%

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Nanoscale Study of Clausthalite-Bearing Symplectites in Cu-Au-(U) Ores: Implications for Ore Genesis

et al. 2018

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Symplectites comprising clausthalite (PbSe) and host Cu-(Fe)-sulphides (chalcocite, bornite, and chalcopyrite) are instructive for constraining the genesis of Cu-Au-(U) ores if adequately addressed at the nanoscale. The present study is carried out on samples representative of all three Cu-(Fe)-sulphides displaying clausthalite inclusions that vary in size, from a few µm down to the nm-scale (<5 nm), as well as in morphology and inclusion density. A Transmission Electron Microscopy (TEM) study was undertaken on foils prepared by Focussed Ion Beam and included atom-scale High-Angle Annular Dark-Field Scanning TEM (HAADF-STEM) imaging. Emphasis is placed on phase relationships and their changes in speciation during cooling, as well as on boundaries between inclusions and host sulphide. Three species from the chalcocite group (Cu 2-x S) are identified as 6a digenite superstructure, monoclinic chalcocite, and djurleite. Bornite is represented by superstructures, of which 2a and 4a are discussed here, placing constraints for ore formation at T > 265 • C. A minimum temperature of 165 • C is considered for clausthalite-bearing symplectites from the relationships with antiphase boundaries in 6a digenite. The results show that alongside rods, blebs, and needle-like grains of clausthalite within the chalcocite that likely formed via exsolution, a second, overprinting set of replacement textures, extending down to the nanoscale, occurs and affects the primary symplectites. In addition, other reactions between pre-existing Se, present in solid solution within the Cu-(Fe)-sulphides, and Pb, transported within a fluid phase, account for the formation of composite, commonly pore-attached PbSe and Bi-bearing nanoparticles within the chalcopyrite. The inferred reorganisation of PbSe nanoparticles into larger tetragonal superlattices represents a link between the solid solution and the symplectite formation and represents the first such example in natural materials. Epitaxial growth between clausthalite and monazite is further evidence for the interaction between pre-existing Cu ores and fluids carrying REE, P, and most likely Pb. In U-bearing ores, such Pb can form via decay of uranium within the ore, implying hydrothermal activity after the initial ore deposition. The U-Pb ages obtained for such ores therefore need to be carefully assessed as to whether they represent primary ore deposition or, more likely, an overprinting event. A latest phase of fluid infiltration is the recognised formation of Cu-selenide bellidoite (Cu 2 Se), as well as Fe oxides.

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Section: Evolution Of Sulphide Assemblagessupporting

confidence: 89%