The use of electron backscatter diffraction and orientation contrast imaging as tools for sulphide textural studies: example from the Greens Creek deposit (Alaska)

Freitag, Katja; Boyle, Alan P.; Nelson, Eric P.; Hitzman, Murray W.; Churchill, James M.; Lopez‐Pedrosa, M.

doi:10.1007/s00126-003-0386-8

Cited by 37 publications

(6 citation statements)

References 23 publications

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“…[16] There are several volcanogenic massive sulfide deposits of various sizes in British Columbia and southeastern Alaska located in the Alexander Terrane [Taylor et al, 2008] and along the same geographic trend as the Alaskan-type complexes, including Duke Island. The two biggest deposits are the Windy Craggy Cu-Au-Zn [Peter and Scott, 1999] deposit in British Columbia and the Greens Creek Ag-Au-Zn [Taylor et al, 2000;Freitag et al, 2004] deposit in southeastern Alaska. Lowgrade Cu-Ni-PGE mineralization (e.g., the Wellgreen deposit) has also been reported from the intrusions that are associated with flood-basalt volcanism in the Wrangellia terrane in British Columbia [Hulbert and Stone, 2006;Greene et al, 2004].…”

Section: Geological Setting Of the Duke Island Complexmentioning

confidence: 99%

Geochemical constraints on the origin of sulfide mineralization in the Duke Island Complex, southeastern Alaska

Thakurta

Ripley

2008

Geochem Geophys Geosyst

130

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[1] Magmatic Cu-Ni-PGE sulfide mineralization associated with mafic to ultramafic igneous rocks is rare in convergent plate settings. However, recent exploration in the Duke Island Complex of southeastern Alaska has detected horizons of sulfide mineralization primarily in the olivine clinopyroxenite unit. The composition of the sulfides, recalculated to 100% sulfide, averages 0.48% Ni and 1.4% Cu. The Duke Island Complex was generated by the emplacement of multiple pulses of variably fractionated magma ranging in composition from picrite to ankaramite that originated in deeper staging chambers. The presence of sulfides in the complex indicates that fO 2 conditions were more reduced than those commonly ascribed to arc-related magmas. The mass of sulfide mineralization together with the sulfur isotopic values indicates that external sulfur was added to the parent magmas at staging chambers. Os isotopic data from sulfides and C isotopic compositions of graphite in the olivine clinopyroxenites also indicate that the parental magmas were contaminated by crustal material. However, oxygen isotopic values of clinopyroxene together with the REE data suggest that bulk assimilation of country rocks has not occurred and the contamination was selective, involving C-and S-bearing fluids or graphitic sulfides. The observed enrichment in Cu and S isotopic values of the sulfides is best explained by assimilation of sulfides from metal-bearing rock types such as black shales or volcanogenic massive sulfide deposits that occur in terranes above the mantle wedge.

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Section: Geological Setting Of the Duke Island Complexmentioning

confidence: 99%

Geochemical constraints on the origin of sulfide mineralization in the Duke Island Complex, southeastern Alaska

Thakurta

Ripley

2008

Geochem Geophys Geosyst

130

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“…In the absence of a rigid matrix, 'bottlenecking' of a developing dislocation glide system also led to dislocation creep (Figure 6B) in pyrite from siderite-rich breccia (Figures 3B and 4D). EBSD studies of both natural and experimentally deformed pyrite have shown that dislocation creep is common down to the brittle/ductile transition at ~260 • C [3,11,13].…”

Section: Pyrite Deformation Texturesmentioning

confidence: 99%

“…It is sufficiently refractory to allow the preservation of microstructures that are typically erased in more ductile ore minerals, meaning it can be used to fingerprint sequential stages in the deformational history of a mineral deposit [1]. Pyrite is therefore a valuable indicator of deformation in sulfide ore deposits [2], and it has been widely used to characterise metamorphosed ores and successfully constrain the impact of regional metamorphism and associated deformation on mineralization [3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…The application of electron backscatter diffraction (EBSD) techniques to pyrite underpinned major improvements in understanding pyrite deformation mechanisms [5,[10][11][12]. This research culminated in construction of a new deformation mechanism map for pyrite [13] that indicates ductile behavior down to temperatures as low as ~260 • C. Ductile deformation in pyrite is commonly accommodated through low-angle subgrain boundary formation by dislocation creep during dislocation glide with a climb recovery step operated through slip on {100} and, less commonly, {110} systems [3,10,11]. However, deformation style largely depends on the mineralogy and fabric of the surrounding groundmass, whereby a ductile or very fine matrix can allow uninterrupted dislocation glide without grain locking or formation of low-angle boundaries [5].…”

Section: Introductionmentioning

confidence: 99%

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Coupled Microstructural EBSD and LA-ICP-MS Trace Element Mapping of Pyrite Constrains the Deformation History of Breccia-Hosted IOCG Ore Systems

King,

Cook,

Ciobanu

et al. 2024

Minerals

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Electron backscatter diffraction (EBSD) methods are used to investigate the presence of microstructures in pyrite from the giant breccia-hosted Olympic Dam iron–oxide copper gold (IOCG) deposit, South Australia. Results include the first evidence for ductile deformation in pyrite from a brecciated deposit. Two stages of ductile behavior are observed, although extensive replacement and recrystallization driven by coupled dissolution–reprecipitation reaction have prevented widespread preservation of the earlier event. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) element maps of pyrite confirm that many pyrite grains display compositional zoning with respect to As, Co, and Ni, but that the zoning is often irregular, patchy, or otherwise disrupted and are readily correlated with observed microstructures. The formation of ductile microstructures in pyrite requires temperatures above ~260 °C, which could potentially be related to heat from radioactive decay and fault displacements during tectonothermal events. Coupling EBSD methods with LA-ICP-MS element mapping allows a comprehensive characterization of pyrite textures and microstructures that are otherwise invisible to conventional reflected light or BSE imaging. Beyond providing new insights into ore genesis and superimposed events, the two techniques enable a detailed understanding of the grain-scale distribution of minor elements. Such information is pivotal for efforts intended to develop new ways to recover value components (precious and critical metals), as well as remove deleterious components of the ore using low-energy, low-waste ore processing methods.

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“…Halfpenny et al, 2013;Grimshaw et al, 2017), (ii) the textural investigation of the ore and integration to the regional metamorphismdeformation history (e.g. Boyle et al, 2004;Barrie et al, 2010b;Sayab et al, 2020) as well as (iii) the study of ore formation and remobilisation processes related to microdeformation (e.g. Kolb et al, 2003;Mateen et al, 2013;Reddy and Hough, 2013;Rosière et al, 2013;Vukmanovic et al, 2013;Fougerouse et al, 2016a;Dubosq et al, 2018;Cugerone et al, 2020;Spinks et al, 2021b).…”

Section: Electron Back-scattered Diffractionmentioning

confidence: 99%

Structural and geochemical ore-forming processes in deformed gold deposits: towards a multiscale and multimethod approach

Perret

André-Mayer

Eglinger

et al. 2021

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Integrating structural control on mineralisation and geochemical ore-forming processes is crucial when studying deformed ore deposits. Yet, structural and geochemical data are rarely acquired at the same scale: structural control on mineralisation is typically investigated from the district to the deposit and macroscopic scales whereas geochemical ore processes are described at the microscopic scale. The deciphering of a deformation-mineralisation history valid at every scale thus remains challenging.This study proposes a multi-scale approach that enables the reconciliation of structural and geochemical information collected at every scale, applied to the example of the Galat Sufar South gold deposit, Nubian shield, northeastern Sudan. It gathers field and laboratory information by coupling a classical petrological-structural study with high-resolution X-ray computed tomography, electron back-scattered diffraction and laser ablation inductively-coupled plasma mass spectrometry on mineralised sulphide mineral assemblages.This approach demonstrates that there is a linear control on mineralisation expressed from the district to microscopic scales at the Galat Sufar South gold deposit. We highlight the relationships between Atmur-Delgo suturing tectonics, micro-deformation of sulphide minerals, syn-pyrite recrystallisation metal remobilisation, gold liberation and ore upgrading. Our contribution therefore represents another step forward a holistic field-to-laboratory approach for the study of any other sulphide-bearing, structurally-controlled ore deposit type.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5635726

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The use of electron backscatter diffraction and orientation contrast imaging as tools for sulphide textural studies: example from the Greens Creek deposit (Alaska)

Cited by 37 publications

References 23 publications

Geochemical constraints on the origin of sulfide mineralization in the Duke Island Complex, southeastern Alaska

Geochemical constraints on the origin of sulfide mineralization in the Duke Island Complex, southeastern Alaska

Coupled Microstructural EBSD and LA-ICP-MS Trace Element Mapping of Pyrite Constrains the Deformation History of Breccia-Hosted IOCG Ore Systems

Structural and geochemical ore-forming processes in deformed gold deposits: towards a multiscale and multimethod approach

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