Editorial for Special Issue “Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes”

Ciobanu, Cristiana L.; Utsunomiya, Satoshi; Reich, Martín; Plümper, Oliver; Cook, Nigel J.

doi:10.3390/min9110692

Cited by 2 publications

(2 citation statements)

References 36 publications

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“…One of the main advantages of using HAADF STEM over High Resolution (HR) TEM techniques is that the image is formed from a convergent rather than parallel beam (Van Tendeloo et al 2012) and thus, the displayed 'dots' are directly attributable to atoms, with a distribution that is unaffected by focus and thickness as in conventional HR TEM imaging. This enables an unparalleled route to direct imaging of minerals and their intergrowths at the nanoscale, in turn providing insights into petrological processes that cannot be constrained by other methods (Ciobanu et al 2019a, and references therein). In HAADF STEM mode, the image contrast is correlated with atomic mass, i.e., the atomic number Zdependence of the contrast is ~Z 2 , with application to the smallest U-bearing nanoparticles in environmental studies (e.g., Utsunomiya and Ewing 2003).…”

Section: Introductionmentioning

confidence: 99%

Ferro-tschermakite with polysomatic chain-width disorder identified in silician magnetite from Wirrda Well, South Australia: A HAADF STEM study

Ciobanu

Verdugo-Ihl

Cook

et al. 2022

American Mineralogist

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Silician magnetite within ~1.85 Ga lithologies hosting the ~1.6 Ga Wirrda Well iron oxide copper gold (IOCG) prospect, South Australia, was examined at the nanoscale. The magnetite is oscillatory-zoned with respect to the density and orientation of nanometer-scale inclusions, among which Si-Fe-nanorods and Al-rich amphibole (as much as hundreds of nanometers long and tens of nanometers wide) form swarms along <111> directions in magnetite. The amphibole is identified as ferro-tschermakite (Ftsk) with the crystal-chemical formula: A(K0.06Na0.01)0.07B(Ca1.65Na0.35)2C(Fe2.072+Al1.64Mg1.15Ti0.06Fe0.043+Mn0.04)5T(Si6.48Al1.52)8O22W(OH)2. This contains single and double rows of a triple-chain silicate attributed to clinojimthompsonite (Cjt) as coherently intergrown (010) zippers along the entire length of the grains. High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) imaging and simulation of Ftsk and Cjt on the [001] zone axis provide direct visualization of crystal structures. These are defined by the 7- and 10-atom octahedron strips (B+C sites) and flanked by double- and triple-pairs of Si atoms (T sites). Remarkably, the sites for light cations and/or vacancies are clearly imaged as single and double, darkest, diamond-shaped motifs separating the octahedron strips showing that A cavities known in amphibole are readily depicted in the wider-chain silicate. I-beam models show that nanoscale intergrowths among the two silicates are coherent along zigzag chains of cations at the edges of the octahedron strips, with single and double rows of the triple-chain silicate corresponding to 1 and 1.5 unit cells of Cjt (27 and 41 Å intervals along the b axis). This type of polysomatic chain-width disorder is widely reported in Mg-rich pyriboles but is shown here in an Al-Fe-rich amphibole. The lack of planar defects and/or reaction fronts at mutual contacts between three-chain zippers and host amphibole indicates primary co-crystallization growth, promoted by the formation of the Si-Fe-nanorods. Co-crystallizing plagioclase is also preserved in close vicinity to the amphibole hosted by magnetite (from a few nanometers to micrometers apart). In contrast, the replacement of amphibole by phyllosilicates is recognizable as irregular swells along the (010) zippers and results in extensive chloritization of the amphibole during an overprinting event. Pressures of ~11.5 kbar are estimated using Al-in-hornblende nano-geobarometry and calculated Al content in Ftsk (3.16 apfu). Assuming the amphibole-plagioclase association buffered by host magnetite fulfills the textural equilibration criteria required for application of this barometer, we interpret the Ftsk nanoinclusions in magnetite as preserved evidence for amphibolite facies metamorphism affecting host lithologies at Wirrda Well with subsequent retrograde alteration during the ~1.6 Ga IOCG mineralizing event. Magnetite records petrogenetic processes by accommodating variable ranges of nanomineral inclusions and preserving them over geological time scales. HAADF STEM imaging is ideally suited to the depiction of crystal-structural modularity and also provides insights into the evolution of geological terranes with protracted histories.

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Section: Introductionmentioning

confidence: 99%

Ferro-tschermakite with polysomatic chain-width disorder identified in silician magnetite from Wirrda Well, South Australia: A HAADF STEM study

Ciobanu

Verdugo-Ihl

Cook

et al. 2022

American Mineralogist

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“…Here, we derive the characteristics of ore‐forming fluids through gangue minerals with volatile components, that is, CO 2 , SO 2 , etc. Additionally, trace elements in ore minerals are the optimal record of ore‐forming fluids (Ciobanu, Utsunomiya, Reich, Plümper, & Cook, 2019; Reich et al, 2011; Tang et al, 2021). In this study, representative end members concerning sulphide–gangue mineral assemblages collected from the advanced argillic zone (AAZ) and the phyllic zone (PZ) are selected, and LA–ICPMS mapping and spot analyses plus SEM‐EDS are used to detect trace element distribution, concentration, and occurrence of trace minerals in the selected copper sulphides, respectively.…”

Section: Introductionmentioning

confidence: 99%

Sulphide geochemistry of the superlarge Tiegelongnan Cu (Au) deposit in Tibet, China: Implication for the mineralization process

Lin

Wang

et al. 2021

Geological Journal

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The Tiegelongnan deposit in central Tibet presents a typical high‐sulfidation porphyry Cu (Au) mineralization system. Optical microscopy, scanning electron microscopy–energy dispersive spectrometry (SEM–EDS), and laser ablation inductively coupled plasma mass spectrometry (LA–ICPMS) were used to understand the mineralization processes. The advanced argillic alteration zone directly contacts the phyllic alteration zone, which is linked to the Early Cretaceous porphyritic intrusions. In this study, the spatial distributions of chief copper sulphides with variable gangue minerals are illustrated. The deep inner phyllic zone typically produced an end‐member assemblage of chalcopyrite–sericite (±dolomite), which trended upwards to produce more bornite–sericite (±siderite ± magnesite), and subsequently, the advanced argillic alteration yielded the representative end‐member assemblage of tennantite–alunite ± (aluminium‐phosphate‐sulphate, namely, APS, ±kaolinite). In the phyllic–advanced argillic transition zone, intensive covellite precipitation with the widespread occurrence of sericite–kaolinite (±APS) assemblage is proposed as an important feature in this study, which is mainly produced on the southwest side of the ore‐body centre. The typical co‐occurrence of chalcopyrite with dolomite at great depths indicates that it was related to a gently acidic fluid containing CO2; however, the pervasive tennantite–alunite association present at shallower levels suggests that fluids with SO2 were mainly involved and produced stronger acidic conditions. Acidic fluids are demonstrated to highly accelerate water‐rock alteration. Trace element analyses of the copper sulphides reflect that Au concentrations of bornite and tennantite are higher than chalcopyrite and covellite and present small signal variations. Moreover, comparing the presence of micron‐sized Au‐telluride in tennantite under advanced argillic alteration with the nano‐sized native gold in bornite resulting from phyllic alteration suggests that to a certain extent, Au enrichment is affected by the shift of more Te contents in fluid towards shallower levels, which could promote Au precipitation. Additionally, the Se contents of the selected samples were typically concentrated in chalcopyrite, bornite, and covellite, which yielded contents an order of magnitude greater than those in tennantite, indicating the intimate hydrothermal origin of the first three sulphides. Overall, the sulphide–gangue mineral associations and their copper sulphide geochemistry indicate that the hypogene–chalcopyrite of low Au contents from the phyllic zone closely corresponds to the action of gentle acidic fluids with CO2, while more acidic fluids with SO2 are involved in the formation of supergene tennantite with relatively high values of Au and Te in the advanced argillic alteration.

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Editorial for Special Issue “Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes”

Abstract: Minerals form in all types of chemical and physical environments [...]

Cited by 2 publications

References 36 publications

Ferro-tschermakite with polysomatic chain-width disorder identified in silician magnetite from Wirrda Well, South Australia: A HAADF STEM study

Ferro-tschermakite with polysomatic chain-width disorder identified in silician magnetite from Wirrda Well, South Australia: A HAADF STEM study

Sulphide geochemistry of the superlarge Tiegelongnan Cu (Au) deposit in Tibet, China: Implication for the mineralization process

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