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Minerals of the tetrahedrite isotypic series are widespread components of base metal ores, where they co-exist with common base metal sulphides (BMS) such as sphalerite, galena, and chalcopyrite. We used electron probe microanalysis and laser-ablation inductively-coupled plasma mass spectrometry to obtain quantitative multi-trace element data on tetrahedrite-tennantite in a suite of 37 samples from different deposits with the objective of understanding which trace elements can be incorporated, at what levels of concentration, and how the presence of tetrahedrite-tennantite influences patterns of trace element partitioning in base metal ores. Apart from Fe and Zn, Hg and Pb are the two most abundant divalent cations present in the analysed tetrahedrite-tennantite (up to 10.6 wt % Hg and 4 wt % Pb). Cadmium, Co and Mn are also often present at concentrations exceeding 1000 ppm. Apart from one particularly Te-rich tetrahedrite, most contained very little Te (around 1 ppm), irrespective of prevailing assemblage. Bismuth is a common minor component of tetrahedrite-tennantite (commonly > 1000 ppm). Tetrahedrite-tennantite typically hosts between 0.1 and 1000 ppm Se, while Sn concentrations are typically between 0.01 and 100 ppm. Concentrations of Ni, Ga, Mo, In, Au, and Tl are rarely, if ever, greater than 10 ppm in tetrahedrite-tennantite and measured W concentrations are consistently <1 ppm. Taking into account the trace element concentrations in co-crystallizing BMS, the results presented allow the partitioning trends between co-crystallized sphalerite, galena, chalcopyrite, and tetrahedrite-tennantite to be defined. In co-crystallizing BMS assemblages, tetrahedrite-tennantite will always be the primary host of Ag, Fe, Cu, Zn, As, and Sb, and will be the secondary host of Cd, Hg, and Bi. In contrast, tetrahedrite-tennantite is a poor host for the critical metals Ga, In, and Sn, all of which prefer to partition to co-crystallizing BMS. This study shows that tetrahedrite-tennantite is a significant carrier of a range of trace elements at concentrations measurable using contemporary instrumentation. This should be recognized when establishing protocols for trace element analysis of tetrahedrite-tennantite, and when assessing the main hosts of trace elements in any given assemblage, e.g., for geometallurgical purposes. [ABSTRACT FROM AUTHOR]

This paper comprises a review of the rapidly expanding application of nanoscale mineral characterization methodology to the study of ore deposits. Utilising bismuth sulphosalt minerals from a reaction front in a skarn assemblage as an example, we illustrate how a complex problem in ore petrology, can be approached at scales down to that of single atoms. We demonstrate the interpretive opportunities that can be realised by doing this for other minerals within their petrogenetic contexts. From an area defined as Au-rich within a sulphosalt-sulphide assemblage, and using samples prepared on a Focused Ion Beam-Scanning Electron Microscopy (SEM) platform, we identify mineral species and trace the evolution of their intergrowths down to the atomic scale. Our approach progresses from a petrographic and trace element study of a larger polished block, to high-resolution Transmission Electron Microscopy (TEM) and High Angle Annular Dark Field (HAADF) Scanning-TEM (STEM) studies. Lattice-scale heterogeneity imaged in HAADF STEM mode is expressed by changes in composition of unit cell slabs followed by nanoparticle formation and their growth into "veins". We report a progressive transition from sulphosalt species which host lattice-bound Au (neyite, lillianite homologues; Pb-Bi-sulphosalts), to those that cannot accept Au (aikinite). This transition acts as a crystal structural barrier for Au. Fine particles of native gold track this progression over the scale of several hundred microns, leading to Au enrichment at the reaction front defined by an increase in the Cu gradient (several wt %), and abrupt changes in sulphosalt speciation from Pb-Bi-sulphosalts to aikinite. Atom-scale resolution imaging in HAADF STEM mode allows for the direct visualisation of the three component slabs in the neyite crystal structure, one of the largest and complex sulphosalts of boxwork-type. We show for the first time the presence of aikinite nanoparticles a few nanometres in size, occurring on distinct (111)PbS slabs in the neyite. This directly explains the non-stoichiometry of this phase, particularly with respect to Cu. Such non-stoichiometry is discussed elsewhere as defining distinct mineral species. The interplay between modular crystal structures and trace element behaviour, as discussed here for Au and Cu, has applications for other mineral systems. These include the incorporation and release of critical metals in sulphides, heavy elements (U, Pb, W) in iron oxides, the distribution of rare earth elements (REE), Y, and chalcophile elements (Mo, As) in calcic garnets, and the identification of nanometre-sized particles containing daughter products of radioactive decay in ores, concentrates, and tailings. [ABSTRACT FROM AUTHOR]

Laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) has rapidly established itself as the method of choice for generation of multi-element datasets for specific minerals, with broad applications in Earth science. Variation in absolute concentrations of different trace elements within common, widely distributed phases, such as pyrite, iron-oxides (magnetite and hematite), and key accessory minerals, such as apatite and titanite, can be particularly valuable for understanding processes of ore formation, and when trace element distributions vary systematically within a mineral system, for a vector approach in mineral exploration. LA-ICP-MS trace element data can assist in element deportment and geometallurgical studies, providing proof of which minerals host key elements of economic relevance, or elements that are deleterious to various metallurgical processes. This contribution reviews recent advances in LA-ICP-MS methodology, reference standards, the application of the method to new mineral matrices, outstanding analytical uncertainties that impact on the quality and usefulness of trace element data, and future applications of the technique. We illustrate how data interpretation is highly dependent on an adequate understanding of prevailing mineral textures, geological history, and in some cases, crystal structure. [ABSTRACT FROM AUTHOR]

Constraints on accurate quantitative trace element and sulfur (S) isotope analysis of sulfide minerals, especially pyrite, by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remain imperfectly understood at the present time. Mapping of S isotope distributions within a complex sample containing several minerals requires an evaluation of the matrix effects and accuracy. Here, we apply LA-Q(quadrupole)-ICP-MS and LA-MC(multiple collector)-ICP-MS methods to analyze trace elements and S isotopes in sulfides. Spot analysis of S isotopes was conducted to evaluate the influence of matrix effects. The matrix effects from siderite and magnetite are deemed to be negligible in mapping analysis at the precision of this study. Both Fe and S were used as internal standard elements to normalize trace element concentrations in pyrite. Fe proved to be the better choice because the normalized counts per second ratio of trace elements with Fe is much more stable than if using S. A case study of a sulfide sample from the Chengmenshan Cu deposit, Jiangxi Province, South China, demonstrates the potential of combined S isotope and trace element mapping by LA-(MC)-ICP-MS. The results suggest that this deposit underwent multi-stage ore formation. Elements, including Au and Ag, were hosted in early-stage pyrite but were re-concentrated into multi-component sulfide assemblages during a late-stage hydrothermal event, which also led to crosscutting veins containing pyrite largely devoid of trace elements, except Se. Combining in situ S isotope and trace element analysis on the same sample represents a powerful tool for understanding ore-forming processes. [ABSTRACT FROM AUTHOR]

U–Pb dating of the common iron-oxide hematite (α-Fe2O3), using laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS), provides unparalleled insight into the timing and processes of mineral deposit formation. Until now, the full potential of this method has been negatively impacted by the lack of suitable matrix-matched standards. To achieve matrix-matching, we report an approach in which a U–Pb solution and ablated material from 99.99% synthetic hematite are simultaneously mixed in a nebulizer chamber and introduced to the ICP-MS. The standard solution contains fixed U- and Pb-isotope ratios, calibrated independently, and aspiration of the isotopically homogeneous solution negates the need for a matrix-matched, isotopically homogenous natural iron-oxide standard. An additional advantage of using the solution is that the individual U–Pb concentrations and isotope ratios can be adjusted to approximate that in the unknown, making the method efficient for dating hematite containing low (~10 ppm) to high (>1 wt %) U concentrations. The above-mentioned advantage to this solution method results in reliable datasets, with arguably-better accuracy in measuring U–Pb ratios than using GJ-1 Zircon as the primary standard, which cannot be employed for such low U concentrations. Statistical overlaps between 207Pb/206Pb weighted average ages (using GJ-1 Zircon) and U–Pb upper intercept ages (using the U–Pb mixed solution method) of two samples from iron-oxide copper-gold (IOCG) deposits in South Australia demonstrate that, although fractionation associated with a non-matrix matched standard does occur when using GJ-1 Zircon as the primary standard, it does not impact the 207Pb/206Pb or upper intercept age. Thus, GJ-1 Zircon can be considered reliable for dating hematite using LA-ICP-MS. Downhole fractionation of 206Pb/238U is observed to occur in spot analyses of hematite. The use of rasters in future studies will hopefully minimize this problem, allowing for matrix-matched data. Using the mixed-solution method in this study, we have validated a published hematite Pb–Pb age for Olympic Dam, and provide a new age (1604 ± 11 Ma) for a second deposit in the same province. These ages are further evidence that the IOCG mineralizing event is tied to large igneous province (LIP) magmatism in the region at ~1.6 Ga. [ABSTRACT FROM AUTHOR]

The distribution and substitution mechanism of Ge in the Ge-rich sphalerite from the Tres Marias Zn deposit, Mexico, was studied using a combination of techniques at µm- to atomic scales. Trace element mapping by Laser Ablation Inductively Coupled Mass Spectrometry shows that Ge is enriched in the same bands as Fe, and that Ge-rich sphalerite also contains measurable levels of several other minor elements, including As, Pb and Tl. Micron- to nanoscale heterogeneity in the sample, both textural and compositional, is revealed by investigation using Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) combined with Synchrotron X-ray Fluorescence mapping and High-Resolution Transmission Electron Microscopy imaging of FIB-prepared samples. Results show that Ge is preferentially incorporated within Fe-rich sphalerite with textural complexity finer than that of the microbeam used for the X-ray Absorption Near Edge Structure (XANES) measurements. Such heterogeneity, expressed as intergrowths between 3C sphalerite and 2H wurtzite on zones, could be the result of either a primary growth process, or alternatively, polystage crystallization, in which early Fe-Ge-rich sphalerite is partially replaced by Fe-Ge-poor wurtzite. FIB-SEM imaging shows evidence for replacement supporting the latter. Transformation of sphalerite into wurtzite is promoted by (111)* twinning or lattice-scale defects, leading to a heterogeneous ZnS sample, in which the dominant component, sphalerite, can host up to ~20% wurtzite. Ge K-edge XANES spectra for this sphalerite are identical to those of the germanite and argyrodite standards and the synthetic chalcogenide glasses GeS2 and GeSe2, indicating the Ge formally exists in the tetravalent form in this sphalerite. Fe K-edge XANES spectra for the same sample indicate that Fe is present mainly as Fe2+, and Cu K-edge XANES spectra are characteristic for Cu+. Since there is no evidence for coupled substitution involving a monovalent element, we propose that Ge4+ substitutes for (Zn2+, Fe2+) with vacancies in the structure to compensate for charge balance. This study shows the utility of synchrotron radiation combined with electron beam micro-analysis in investigating low-level concentrations of minor metals in common sulfides. [ABSTRACT FROM AUTHOR]

Minor and trace elements can substitute into the crystal lattice of galena at various concentrations. In situ LA-ICP-MS analysis and trace element mapping of a range of galena specimens from different deposit types are used to obtain minor/trace element data, aimed at achieving insight into factors that control minor/trace element partitioning. The previously recognized coupled substitution Ag++(Bi,Sb)3+ ↔ 2Pb2+ is confirmed. However, the poorer correlation between Ag and (Bi+Sb) when the latter elements are present at high concentrations (~>2000 ppm), suggests that site vacancies may come into play: [2(Bi,Sb)3++ ↔ 3Pb2+]. Galena is the primary host of Tl in all mapped mineral assemblages. Along with Cu, Tl is likely incorporated into galena via the coupled substitution: (Ag,Cu,Tl)++(Bi,Sb)3+ ↔ 2Pb2+. Tin can reach significant concentrations in galena (>500 ppm). Cd and minor Hg can be incorporated into galena; the simple isovalent substitution (Cd,Hg)2+ ↔ Pb2+ is inferred. This paper shows for the first time, oscillatory and sector compositional zoning of minor/trace elements (Ag, Sb, Bi, Se, Te, Tl) in galena from two epithermal ores. Zoning is attributed to slow crystal growth into open spaces within the vein at relatively low temperatures. The present data show that galena can host a broader range of elements than previously recognized. For many measured elements, the data sets generated display predictable partitioning patterns between galena and coexisting minerals, which may be dependent on temperature or other factors. Trace element concentrations in galena and their grain-scale distributions may also have potential in the identification of spatial and/or temporal trends within individual metallogenic belts, and as markers of ore formation processes in deposits that have undergone superimposed metamorphism and deformation. Galena trace element geochemistry may also display potential to be used as a trace/minor element vector approach in mineral exploration, notably for recognition of proximal-to-distal trends within a given ore system. [ABSTRACT FROM AUTHOR]

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) spot analysis and element mapping coupled with high-resolution focused ion beam-scanning electron microscopy (FIB-SEM) imaging has been performed on Au-hosting sulfides from a Proterozoic orogenic gold deposit, Tanami gold province, north-central Australia. Gold distribution patterns in the arsenopyrite-pyrite assemblage, which probably crystallized toward the end of the Au-forming event, suggest a process of initial scavenging of Au into arsenopyrite and subsequent remobilization of that An following brittle fracture. Gold expelled from the sulfide lattice during the remobilization event is reconcentrated around the margins of the same arsenopyrite grains and within swarms of crosscutting microfractures. The distribution of Pb, Bi, and Ag closely mimic Au, indicating that these elements were also reconcentrated. Preservation of oscillatory zonation patterns for Co, Ni, Sb, Se, and Te in arsenopyrite imply, however, that no significant degree of sulfide reciystallization took place. Residual concentrations of invisible gold (in grain centers) are <5 ppm in arsenopyrite and <1 ppm in coexisting pyrite. The presence of submicron-sized pores is suggestive of a fluid-driven process rather than solid state diffusion. Micron-scale (2-10 µm) remobilized gold is accompanied by fine particles (200 nm-2 µm) and nanoparticles (<200 nm) of gold. The extensive variation of Au concentrations within single arsenopyrite grains underlines the significance of textures when using trace element data to understand how gold ores evolved. [ABSTRACT FROM AUTHOR]

Pyrite, the most abundant sulfide on Earth and a common component of gold deposits, can be a significant host for refractory gold. This is the first documentation of pore-attached, composite Au-telluride nanoparticles in "arsenic-free" pyrite. Trace elements mapping in pyrite from an intrusion-hosted Au deposit with orogenic overprint (Dongping, China) shows trails of tellurides overlapping Co-Ni-zonation. Intragranular microfracturing, anomalous anisotropy, and high porosity are all features consistent with devolatilization attributable to the orogenic event. The pyrite-hosted nanoparticles are likely the "frozen," solid expression of Te-rich, Au-Ag-Pb-bearing vapors discharged at this stage. Nanoparticle formation, as presented here, provides the "smallest-scale" tool to fingerprint Au-trapping during crustal metamorphism [ABSTRACT FROM AUTHOR]

In situ spatially resolved X-ray absorption near edge structure (m-XANES) spectra are obtained for natural Cu-In-bearing sphalerite. Copper K-edge spectral data show that, in Cu-In-bearing sphalerite, in which an excellent correlation between the Cu and In contents is noted, Cu is present in the Cu+ state. This offers indirect proof for the coupled substitution 2 Zn2+ ↔ Cu+ + In3+, which allows indium to enter the sphalerite structure. The study clearly demonstrates the utility of synchrotron radiation to accurately determine oxidation state in small volumes of mineral in which the concentration of the element of interest is low or very low. The study also demonstrates that good quality m-XANES spectra can be collected on TEM foils prepared in situ at a chosen position on the surface of a polished sample using the focused ion beam-scanning electron microscope method. [ABSTRACT FROM AUTHOR]

Bi8Te3 is a member of the tetradymite homologous series, previously shown to be compositionally and structurally distinct from hedleyite, Bi7Te3, yet inadequately characterized structurally. The phase is identified in a sample from the Hedley district, British Columbia, Canada. Compositions are documented by electron probe microanalysis and structures are directly imaged using high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Results confirm that Bi8Te3 has an 11-atom layer structure, in which three Bi-Bi pairs are placed adjacent to the five-atom sequence (Te-Bi-Te-Bi-Te). Bi8Te3 has trigonal symmetry (space group R 3 ¯ m) with unit cell dimensions of a = ~4.4 Å and c = ~63 Å calculated from measurements on representative electron diffraction patterns. The model is assessed by STEM simulations and EDS mapping, all displaying good agreement with the HAADF STEM imaging. Lattice-scale intergrowths are documented in phases replacing Bi8Te3, accounting for the rarity of this phase in nature. These results support prior predictions of crystal structures in the tetradymite homologous series from theoretical modeling and indicate that other phases are likely to exist for future discovery. Tetradymite homologues are mixed-layer compounds derived as one-dimensional superstructures of a basic rhombohedral sub-cell. Each member of the series has a discrete stoichiometric composition and unique crystal structure. [ABSTRACT FROM AUTHOR]

The incorporation of impurity elements into minerals impacts their physical properties (e.g., reflectance, hardness, and electrical conductivity), but the quantitative relationships between these features and compositional variation remain inadequately constrained. Prior work has shown that gamma-enhancement of reflected light images represents a simple yet powerful tool to assess the compositional heterogeneity of single pyrite crystals, as it can enhance subtle differences in reflectance between distinct domains with different minor element concentrations. This study extends the gamma correction method to several other common Fe-bearing minerals, magnetite, garnet, wolframite, and tetrahedrite-tennantite, which all have far lower reflectance than pyrite. Gamma-enhanced optical images reveal clear variations in reflectance that are either systematic with increased minor element concentration, as the change in gray value on backscatter electron (BSE) images (in the case of magnetite, garnet, and tetrahedrite-tennantite) or contrasting (as in pyrite), yielding a convincing linkage between reflectance variation and compositional heterogeneity. Reflectance variation is an expression of the distribution of the average effective number of free electrons on the mineral surface that can re-emit light when excited by visible light. Gamma-enhanced images can reveal compositional heterogeneity in minerals such as wolframite where small atomic mass differences between substituting elements (Mn and Fe, in the case of wolframite) are virtually impossible to observe as a variation of gray values on BSE images. Results also demonstrate that Fe-rich domains in these minerals can be expected to have higher reflectance than Fe-poor domains whenever Fe is a major constituent. The greater reflectance is attributed to Fe ions having a greater effective number of free electrons than many other elements (e.g., Co, Ni, Si, Ca, Al, Mg, Mn, and As). This research highlights the utility of gamma correction as an inexpensive tool for routine evaluation of compositional heterogeneity in common Fe-bearing minerals, potentially obviating the necessity of a microbeam platform to correlate textures and composition. [ABSTRACT FROM AUTHOR]

• U-bearing magnetite is characterised from the outer shell of the Olympic Dam deposit. • LA-ICP-MS U-Pb dating of magnetite generates reproducible ~1760 Ma 207Pb206Pb dates. • First recognition of incorporated protoliths predating deposit formation at ~1590 Ma. • U-rich iron formations may provide additional sources of U and Fe to IOCG systems. Spatial associations between banded iron formation and iron-oxide Cu-Au (IOCG) style mineralization are well documented in the Gawler Craton (South Australia), but the possible genetic relationships between these two distinct types of mineralization are hitherto unclear. A texturally conspicuous generation of coarse-grained silician magnetite, intergrown with carbonates and quartz, is observed in drillholes intersecting the 'outer shell' of the Olympic Dam IOCG-type deposit. This magnetite is characterised by high U-content (~50 ppm), siliceous chemistry, and unusual zonal textures with respect to Si-Fe-nanoprecipitates. Direct dating of this magnetite by laser ablation inductively coupled plasma mass spectrometry yields reproducible 207Pb/206Pb dates (1761 ± 16 Ma) that are significantly older than the granite hosting the deposit (1593 Ma), or the mineralized breccias constituting the Cu-U-Au-Ag resource (~1592–1589 Ma). The older, Fe-rich crustal material can be correlated with the ~1.76–1.74 Ga (meta)sedimentary Wallaroo Group, host to Fe-rich horizons across the Gawler Craton, including locations ~15 km NW of Olympic Dam. A generation of granitic rocks, which intruded bedrock at ~1.75 Ga are present ~30 km NE of Olympic Dam, and likely exsolved hydrothermal fluids that enriched pre-existing magnetite-bearing protoliths in both U and REE. Such material was physically, and likely chemically, incorporated into the 'outer shell' at Olympic Dam some ~150 Ma later, during granite uplift along faults. The coincidence between Fe-rich horizons/BIF and ~1750 Ma granitoids may have provided IOCG systems with an additional source of both Fe and U that predates the ~1.59 Ga craton-scale metallogenic event. The uranium concentrations in some South Australian IOCG systems represent major global anomalies in the element. A combination of the fortuitous geological circumstances outlined here, may help explain the highly anomalous accumulation of uranium found at Olympic Dam. [ABSTRACT FROM AUTHOR]

• BIF-associated mafic magmatism constrained by petrography and U-Pb geochronology. • ~2.5 Ga mafic sills interbedded with BIFs are metamorphosed to amphibolites. • First confirmation of Gairdner LIP dolerites in Middleback Ranges. • Second burial and ore upgrading constrained from U-Pb hematite age at ~680 Ma. Banded iron formation (BIF)-derived iron ore deposits of the Middleback Ranges, Eyre Peninsula, South Australia, are hosted within Archean to Paleoproterozoic basement in the southeastern Gawler Craton. Mafic sills and dikes are associated with the orebodies throughout the belt and although described previously, have never been studied in detail. Two main types of mafic rocks, amphibolites and dolerites, are distinguishable from field occurrence and mineralogy. Amphibolites interbedded with BIFs from the southern Iron Magnet deposit are characterized by extensive overprinting. These amphibolites contain metamorphic assemblages of coexisting Mg-Fe- and Ca-amphiboles, garnet, corundum, biotite and relict titaniferous magnetite displaying ilmenite exsolution. Amphibolite petrography and geochemistry in the southern part of the belt indicate formation in a complex BIF depositional environment, with possible detrital input of titaniferous magnetite from igneous rocks. In contrast, NW-trending dolerite dikes occur throughout the belt and contain assemblages consisting of igneous magnesiohornblende and plagioclase. SHRIMP U–Pb zircon ages for amphibolites and dolerites yield two age groups. Amphibolite from Iron Magnet yields a 207Pb/206Pb weighted mean age of 2542 ± 15 Ma. The most robust 206Pb/238U weighted mean age of 782 ± 23 Ma for dolerites comes from the Iron Queen deposit in the central part of the Middleback Ranges. LA-ICP-MS U–Pb geochronology of U-bearing hematite from the Iron Knight South deposit yields ages of ~680 Ma. Taken together, these results suggest mafic magmatism contemporaneous with Archean BIF deposition followed by a high-grade metamorphic event (~2.47–2.41 Ga Sleafordian Orogeny). Dikes from Cape Donington, the southernmost point on the Eyre Peninsula are, instead, associated with the 1.73–1.69 Ga Kimban Orogeny, as evidenced by zircon from a pyroxene-rich dolerite, which yields a 206Pb/238U weighted mean age of 1711 ± 14 Ma. The dolerite ages from the Iron Queen deposit provide the first evidence for the presence of the ~800 Ma craton-scale Gairdner Large Igneous Province in the Middleback Ranges. The young U–Pb hematite age from Iron Knight South and post-emplacement alteration of dikes of Gairdner age from the central part of the Middleback Ranges belt provide additional support for multiple events leading to upgrading of iron ores. [ABSTRACT FROM AUTHOR]

The Acropolis prospect, 20 km southwest from the Olympic Dam Cu-U-Au-Ag deposit, South Australia, is a vein-style magnetite (±apatite ±hematite) system. A whole-rock dataset comprising 4864 core samples from 14 drillholes was analysed using multivariate statistical analyses to understand and identify geochemical signatures of mineralization, as well as the expressions and extents of hydrothermal alteration. Statistical analysis included unsupervised (principal component analysis, hierarchical and k -means clustering) and supervised (random forests) machine learning algorithms. The geology of the Acropolis prospect is presented as a 3D geological model complemented by cross-sections. The results of statistical analyses are overlaid and interpreted relative to the geological model, and encompass a projection of sodic and propylitic alteration as PC3, and mineralization signature as PC1. Although the mineralization footprint of the Acropolis prospect partially overlaps with a Hiltaba Suite granite, it is not centred on the granite body. A distinct 'magnetite' signature of Fe-V-Ni-Co is developed in the southwestern part of Acropolis and represents samples containing >60 wt% Fe. In contrast, the 'hematite' signature displays an association of REE, W, Sn, Sb, U, Th, Ca and P, and is present throughout the Acropolis prospect with the exception of drillhole ACD5, which is non-mineralized. Interpolated values of Cu (> 200 ppm) indicate an offset from Fe-rich veins, thus supporting a genetic model in which Cu-bearing mineralization overprints Cu-Au-deficient magnetite-dominant veins. The results obtained provide insights into the evolution from magnetite to hematite-dominant IOCG systems and may provide a proxy for exploration of shallow and economically significant IOCG deposits in the eastern Gawler Craton. Unlabelled Image • k -means clustering is appropriate to define geochemically meaningful domains • W-Sn-Mo-U, Sb, Bi and REE are characteristic for the hematite-dominant assemblage • Cu Au deficient magnetite veins are overprinted by Cu-bearing hematite assemblage • Fe-V-Ni-Co-bearing magnetite in veins typifies early IOCG mineralization in Acropolis • The 'hematite' signature unequivocally correlates Acropolis with Olympic Dam [ABSTRACT FROM AUTHOR]

• Compositional data for copper anodes from Olympic Dam (Australia) are given. • Trace element impurities are homogeneously distributed at the scale of the anode. • LA-ICP-MS analysis allows quantification of trace elements in solid solution. • Impurities also occur as micron-scale impurity inclusions containing multiple phases. • Nanoscale particles containing impurity elements are also present in copper. Anode copper is the intermediate product between copper smelting and electrorefining. Anodes are typically 98.5 to 99.8 % pure and require electrorefining to high-purity copper cathode that can be sold to customers. Impurity elements, including Ag, Au, As, Sb, Bi, Se, Te, Sn, Pb, Co, and Ni (alongside minor Fe, Al, and Si), are either dissolved within anode copper, or contained within micron-scale inclusions. To better understand the distribution of these impurities, a study of anode copper was undertaken on representative samples from the Olympic Dam anode plant, South Australia. Bulk assay for 61 elements of 269 sub-samples collected on a grid across a single anode, including the 'ears', shows homogeneity irrespective of location. The five most abundant impurity elements are As (mean 1279 ± 41 ppm), Se (218 ± 11 ppm), Sb (211 ± 8 ppm), Bi (202 ± 9 ppm), and Ni (195 ± 6 ppm). The assay data demonstrate that reliable, representative compositional data on the anode can be obtained from sampling and assay of only a limited part of the whole, including the 'ears'. Trace element analysis of copper metal by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) allows quantification of dissolved minor components. Some metals, notably Ni, occur almost completely dissolved in copper. Other elements occur only partially in dissolved form, but the proportions measured in copper metal relative to bulk assay vary significantly from only ∼ 9 % for Pb, 13 % for Bi and Te, 25 % for Se, 29 % for Sn, 34 % for Sb, 55 % for As, and 60–70 % for Au, Ag, and Co. These results are consistent with the observation of a diverse suite of 1–10 µm-sized, rounded impurity inclusions containing Pb, Bi, As, Sb, Te, Se etc. that are associated with cuprite, Cu 2 O, and largely follow copper grain boundaries. The inclusions, each containing one or more crystalline (e.g., Cu-selenides, some Cu-Bi-arsenates, Sn-oxides and cuprite) and/or glassy phases (e.g., Cu-Pb-As-Sb-Bi-oxides), represents a trapped melt droplet, leading to the observed broad range of compositions. [ABSTRACT FROM AUTHOR]

Titanite textures and chemistry have been investigated from the Roxby Downs Granite, host to the Olympic Dam Cu–U–Au–Ag deposit, South Australia. Three textural subtypes of titanite are documented: primary magmatic (cores and rims); deuteric; and hydrothermal (low T recrystallisation). Magmatic cores are defined by enrichment in LREE (~ 3 wt%), Nb (up to 1 wt%) and Zr relative to rims, which typically contain < 1 wt% LREE and Nb, as well as greater concentrations of Al, Ca, Fe and F. Deuteric titanite occurs as overgrowths on pre-existing titanite and other magmatic accessory minerals (magnetite and ilmenite), and is depleted in HFSE compared to magmatic rims, showing geochemical trends consistent with substitution of Ca2+ + Ti4+ ↔ REE3+ + (Al, Fe)3+. Hydrothermal titanite forms as a low-temperature hydrothermal overprint on primary titanite as well as an alteration product of chloritised phlogopite. Applying Zr-in-titanite geothermometry, three temperature ranges are obtained for titanite crystallisation: magmatic cores ~ 765 to 780 °C; rims ~ 705 to 740 °C; and deuteric ~ 680 to 690 °C. Titanite breakdown is a ubiquitous feature of the Roxby Downs Granite, and occurs through interaction with CO2- and F-rich fluids, forming pseudomorphs characterised by the presence of REE-fluorocarbonates, which are subsequently overprinted by REE-phosphates with increased proximity to the Olympic Dam Breccia Complex. This change is related to interaction with fluids containing appreciable PO42− liberated from local dissolution of fluorapatite. Such observations are consistent with and linked to later/retrograde stages in the formation of the Olympic Dam deposit. [ABSTRACT FROM AUTHOR]

The petrography and geochemistry of zircon offers an exciting opportunity to better understand the genesis of, as well as identify pathfinders for, large magmatic–hydrothermal ore systems. Electron probe microanalysis, laser ablation inductively coupled plasma mass spectrometry, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging, and energy-dispersive X-ray spectrometry STEM mapping/spot analysis were combined to characterize Proterozoic granitic zircon in the eastern Gawler Craton, South Australia. Granites from the ~1.85 Ga Donington Suite and ~1.6 Ga Hiltaba Suite were selected from locations that are either mineralized or not, with the same style of iron-oxide copper gold (IOCG) mineralization. Although Donington Suite granites are host to mineralization in several prospects, only Hiltaba Suite granites are considered "fertile" in that their emplacement at ~1.6 Ga is associated with generation of one of the best metal-endowed IOCG provinces on Earth. Crystal oscillatory zoning with respect to non-formula elements, notably Fe and Cl, are textural and chemical features preserved in zircon, with no evidence for U or Pb accumulation relating to amorphization effects. Bands with Fe and Ca show mottling with respect to chloro–hydroxy–zircon nanoprecipitates. Lattice defects occur along fractures crosscutting such nanoprecipitates indicating fluid infiltration post-mottling. Lattice stretching and screw dislocations leading to expansion of the zircon structure are the only nanoscale structures attributable to self-induced irradiation damage. These features increase in abundance in zircons from granites hosting IOCG mineralization, including from the world-class Olympic Dam Cu–U–Au–Ag deposit. The nano- to micron-scale features documented reflect interaction between magmatic zircon and corrosive Fe–Cl-bearing fluids in an initial metasomatic event that follows magmatic crystallization and immediately precedes deposition of IOCG mineralization. Quantification of α-decay damage that could relate zircon alteration to the first percolation point in zircon gives ~100 Ma, a time interval that cannot be reconciled with the 2–4 Ma period between magmatic crystallization and onset of hydrothermal fluid flow. Crystal oscillatory zoning and nanoprecipitate mottling in zircon intensify with proximity to mineralization and represent a potential pathfinder to locate fertile granites associated with Cu–Au mineralization. [ABSTRACT FROM AUTHOR]

Zirconium is an element of considerable petrogenetic significance but is rarely found in hematite at concentrations higher than a few parts-per-million (ppm). Coarse-grained hematite ore from the metamorphosed Peculiar Knob iron deposit, South Australia, contains anomalous concentrations of Zr and has been investigated using microanalytical techniques that can bridge the micron- to nanoscales to understand the distribution of Zr in the ore. Hematite displays textures attributable to annealing under conditions of high-grade metamorphism, deformation twins (r~85° to hematite elongation), relict magnetite and fields of sub-micron-wide inclusions of baddeleyite as conjugate needles with orientation at ~110°/70°. Skeletal and granoblastic zircon, containing only a few ppm U, are both present interstitial to hematite. Using laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) spot analysis and mapping, the concentration of Zr in hematite is determined to be ~260 ppm on average (up to 680 ppm). The Zr content is, however, directly attributable to nm-scale inclusions of baddeleyite pervasively distributed throughout the hematite rather than Zr in solid solution. Distinction between nm-scale inclusions and lattice-bound trace element substitutions cannot be made from LA-ICP-MS data alone and requires nanoscale characterization. Scandium-rich (up to 0.18 wt. % Sc2O3) cores in zircon are documented by microprobe analysis and mapping. Using high-angle annular dark field scanning transmission electron microscopy imaging (HAADF-STEM) and energy-dispersive spectrometry STEM mapping of foils prepared in-situ by focused ion beam methods, we identify [ 0 1 ¯ 1 ]baddeleyite epitaxially intergrown with [ 2 2 ¯.1 ]hematite. Lattice vectors at 84–86° underpinning the epitaxial intergrowth orientation correspond to directions of r-twins but not to the orientation of the needles, which display a ~15° misfit. This is attributable to directions of trellis exsolutions in a precursor titanomagnetite. U–Pb dating of zircon gives a 206Pb/238U weighted mean age of 1741 ± 49 Ma (sensitive high-resolution ion microprobe U–Pb method). Based on the findings presented here, detrital titanomagnetite from erosion of mafic rocks is considered the most likely source for Zr, Ti, Cr and Sc. Whether such detrital horizons accumulated in a basin with chemical precipitation of Fe-minerals (banded iron formation) is debatable, but such Fe-rich sediments clearly included detrital horizons. Martitization during the diagenesis-supergene enrichment cycle was followed by high-grade metamorphism during the ~1.73–1.69 Ga Kimban Orogeny during which martite recrystallized as granoblastic hematite. Later interaction with hydrothermal fluids associated with ~1.6 Ga Hiltaba-granitoids led to W, Sn and Sb enrichment in the hematite. By reconstructing the evolution of the massive orebody at Peculiar Knob, we show how application of complimentary advanced microanalytical techniques, in-situ and on the same material but at different scales, provides critical constraints on ore-forming processes. [ABSTRACT FROM AUTHOR]

• The chemistry of anode slimes from the Olympic Dam electrorefinery is described. • Decopperisation results in replacement and redistribution of Sb, Se and Te. • Gold occurs dissolved in Cu-Ag- and Ag-selenides and microgranular Ag 3 Au(Se,Te) 2. • Nanoscale imaging confirms α-BiAsO 4 , corresponding to the mineral rooseveltite. • EBSD methods enable rapid assessment of crystallinity in individual particles. Together with silver (Ag) and gold (Au), which are almost always recovered, the impurity elements, arsenic (As), antimony (Sb), bismuth (Bi), tin (Sn), lead (Pb), selenium (Se) and tellurium (Te) are major components of anode slimes, a by-product of the electrorefining of impure copper. The Olympic Dam electrorefinery, South Australia, generates raw slimes (∼30 % Cu, 5–10 % Ag, 0.5–1 % Au, 3–4 % Bi, ∼2–3 % Sb, and 5–6 % As), which subsequently undergo decopperisation and then pH-neutralisation. Decopperisation involves treatment with steam and acid at 90 °C, giving a slime that contains ∼ 1 % Cu, 8–17 % Ag, ∼2% Au, ∼7% Bi, ∼4–5 % Sb, and ∼ 3 % As. pH-neutralisation is achieved by addition of NaOH and is the final step prior to cyanidation and precious metal recovery. Bulk chemical compositions, gross morphology and particle size distributions are complemented by high-magnification backscatter imaging and energy-dispersive X-ray analysis of individual particles in raw, decopperised, and pH-neutralised anode slimes. In a first micron-to-nanoscale approach, we use electron backscatter diffraction mapping to assess the crystallinity of individual component phases and a scanning transmission electron microscopy study on micron-sized slices extracted in-situ to confirm the crystal structure of a conspicuous BiAsO 4 phase as rooseveltite. The results establish an in-depth understanding of element deportments in slimes and their evolution during sequential stages of treatment. Characterisation studies for Te, Se, Sb, Bi, and As are essential prerequisites for any design of metallurgical circuits for by-product recovery from anode slimes and/or electrolyte. This study aims to demonstrate that complementary cutting-edge microanalytical techniques widely used in mineralogy provide a level of detail essential when considering refinery slimes as a new source of critical commodities. [ABSTRACT FROM AUTHOR]

The distributions of 210Pb and 210Po, short half-life products of 238U decay, in geological and related anthropogenic materials are reviewed, with emphasis on their geochemical behaviours and likely mineral hosts. Concentrations of natural 210Pb and 210Po in igneous and related hydrothermal environments are governed by release from crustal reservoirs. 210Po may undergo volatilisation, inducing disequilibrium in magmatic systems. In sedimentary environments (marine, lacustrine, deltaic and fluvial), as in soils, concentrations of 210Pb and 210Po are commonly derived from a combination of natural and anthropogenic sources. Enhanced concentrations of both radionuclides are reported in media from a variety of industrial operations, including uranium mill tailings, waste from phosphoric acid production, oil and gas exploitation and energy production from coals, as well as in residues from the mining and smelting of uranium-bearing copper ores. Although the mineral hosts of the two radionuclides in most solid media are readily defined as those containing parent 238U and 226Ra, their distributions in some hydrothermal U-bearing ores and the products of processing those ores are much less well constrained. Much of the present understanding of these radionuclides is based on indirect data rather than direct observation and potential hosts are likely to be diverse, with deportments depending on the local geochemical environment. Some predictions can nevertheless be made based on the geochemical properties of 210Pb and 210Po and those of the intermediate products of 238U decay, including isotopes of Ra and Rn. Alongside all U-bearing minerals, the potential hosts of 210Pb and 210Po may include Pb-bearing chalcogenides such as galena, as well as a range of sulphates, carbonates, and Fe-oxides. 210Pb and 210Po are also likely to occur as nanoparticles adsorbed onto the surface of other minerals, such as clays, Fe-(hydr)oxides and possibly also carbonates. In rocks, unsupported 210Pb- and/or 210Po-bearing nanoparticles may also be present within micro-fractures in minerals and at the interfaces of mineral grains. Despite forming under very limited and special conditions, the local-scale isotopic disequilibrium they infer is highly relevant for understanding their distributions in mineralized rocks and processing products. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe 2 O 3) is a common iron-oxide mineral known to incorporate U into its crystal lattice at up to wt% concentrations and has been previously used to date ore formation within iron-oxide copper gold and banded iron formation deposits. However, there has been no detailed evaluation of the potential challenges this novel mineral geochronometer may present for accurate temporal interpretation. We report a multi-technique U Pb geochronological study comprising laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), sensitive high-resolution ion microprobe (SHRIMP) and the first isotope dilution-thermal ionization mass spectrometry (ID-TIMS) procedure and analyses using an in-situ grain micro-sampling technique. We assess intra- and inter-sample data reproducibility, and examine the compatibility of spatial and analytical resolutions to texturally and compositionally diverse samples. Five samples of hydrothermal, primary, oscillatory-zoned hematite were analysed from distinct lithologies throughout the ~1.59 Ga Olympic Dam Cu-U-Au-Ag deposit, with typical U concentrations ranging between ~20 and 1000 ppm. LA-ICP-MS mapping of isotope distributions across mm-sized grains allows pinpointing of U-rich and relatively U/Pb isotopically 'homogeneous' domains. Micro-domains were extracted via laser-cut square shaped trenches (100 × 100 μm). U Pb datum range in complexity, with concordant age domains measured by ID-TIMS indicating that hematite can retain a near-closed U Pb system over ~1.6 Ga, while also demonstrating that younger Pb-loss events may be recorded. Significant reverse discordance is common in the data, likely to be a real feature due to both internal decoupling and mobility of Pb within a single grain and U Pb fractionation during microbeam analysis. These effects will obscure the interpretation of real ages for Proterozoic samples where non-zero age Pb-loss events occur, and restricts the evaluation of common Pb mixing components. As a result, microbeam analyses may be biased younger or older in terms of 207Pb/206Pb dates in samples with complex histories. Microbeam datum compare favourably with high precision ID-TIMS ages. Although reproducible ID-TIMS U Pb dates were generally not obtained, in the best-case example, a 207Pb/206Pb weighted mean age of 1589.91 ± 0.91 Ma (MSWD = 1.3, n = 5), within 0.2% of the Olympic Dam granite host rock age (1593.87 ± 0.21 Ma) was generated. All five hematite samples dated by LA-ICP-MS and SHRIMP yield weighted mean 207Pb/206Pb dates within 2% of the host granite age after small degrees of data rejection. The results demonstrate that with careful sample petrography, screening and data interpretation, hematite can be considered a very useful U Pb mineral geochronometer, with potential application to all U-bearing Fe-oxide rich mineral systems. • New methodology for ID-TIMS, SHRIMP and LA-ICP-MS hematite U-Pb geochronology, isotope mapping and in-situ grain extraction • The U-Pb systematics of compositionally and morphologically distinct samples from Olympic Dam are evaluated • Hematite is a remarkably robust mineral for constraining ore forming processes [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First definition of geochemical IOCG mineralisation signature in the Olympic Dam. • The IOCG signature is formed by associations of Cu-U 3 O 8 -Se-S and Au-W-Mo-As-Sb. • Au-W-Mo-Sb-As forms a ∼1800 m deep corridor in the south-eastern lobe of the deposit. • The PCA allows delineation of ore body within a disseminated ore deposit. Abstract The Olympic Dam Cu-U-Au-Ag deposit is dominantly composed of mineralised hematite-breccias and occurs entirely within the Roxby Downs Granite. Multivariate statistical analysis of a large whole-rock, 15 m-interval geochemical dataset (10,565 samples) was undertaken to identify geochemical signatures characteristic of iron-oxide copper gold (IOCG)-style mineralization and constrain the conspicuous lithogeochemical zonation observed at Olympic Dam. Statistical analyses include principal component analysis on centred logratio (clr)-transformed data coupled with hierarchical clustering. Certain groups of elements that can be interpreted in terms of an evolving hydrothermal system relative to host lithologies are derived from data analysis: granitophile (U-W-Sn-Mo); siderophile (Ni-Co); chalcophile (Ag-Bi) and related elements (As-Sb and Au-Te). The distributions of elements within each group are investigated through three vertical cross-sections and are compared with known lithological and Cu-(Fe)-sulphide zonation. Throughout the Olympic Dam Breccia Complex, the IOCG signature is defined by multi-element combinations of the commodity metals Cu, U, Au, and Ag, coupled with a range of trace elements. Overall, the IOCG signature overlaps well with Fe-metasomatism despite mismatch which is likely due to discrete styles of mineralisation found only on the margins of the deposit and also to the presence of mineralised domains within Fe-poor zones. The IOCG signature is composed of two geochemical associations, which exhibit distinct spatial distributions. The first group, Cu-U 3 O 8 -Se-S, shows concentric zonation whereas the second group, Au-W-Mo-Sb-As, forms a vertical ∼1800 m deep corridor in the southeastern lobe of the deposit. The specific Au-W-Mo-As-Sb signature could potentially be generic within IOCG systems across the Olympic Cu-Au province and if so, would provide a proxy model for near-mine exploration. [ABSTRACT FROM AUTHOR]

The Wirrda Well and Acropolis prospects are located ~ 25 km SSE and SW, respectively, from the giant Olympic Dam Cu-U-Au-Ag deposit within the Olympic Cu-Au Province of South Australia. Mineralisation in the two prospects displays a temporal and spatial zonation characteristic of other IOCG-type deposits and prospects within the province, including Olympic Dam, in which an early high-temperature, magnetite-dominant mineralisation is transitional to a hematite-dominant mineralisation style, accompanied by subordinate and often localised carbonate alteration. Both prospects contain conspicuous hydrothermal apatite which is characteristic in terms of host assemblage and geochemical signature. Chondrite-normalised rare earth element (REE) fractionation patterns for apatite depict the evolution of hydrothermal fluids during ore formation. An early generation of apatite is abundant within magnetite-dominant mineralisation in both prospects, and displays a characteristic light-REE enriched fractionation trend. Overprinting of this initial high-temperature assemblage results in the loss of REE and Y (REY), as well as Cl, along fractures within this apatite, as well as the formation of new generations of apatite that are also depleted in these elements. The transition from early reduced, to later oxidised assemblages within both prospects is accompanied by an evolution of the REY signature of apatite in which LREE-enriched patters with negative Eu-anomalies are replaced by convex middle-REE (MREE)-enriched patterns, positive Eu-anomalies and the development of a conspicuous negative Y-anomaly. Comparable trends are recognised elsewhere within the district and are interpreted as the hallmark of productive mineralised IOCG ore systems. The evolution of chondrite-normalised REY patterns can be explained in terms of changes in fluid parameters, speciation of REY in ore-forming fluids, and the capacity of REY to precipitate and partition into apatite in ways that contrast with those expected by simple consideration of crystal structure. Results are concordant with modelling of REY-speciation, which show that, under hydrothermal conditions typical of IOCG mineralisation, a decrease in salinity, pH and temperature is associated with hematite-sericite alteration sufficient to produce MREE-enriched apatite. These data offer encouragement for the use of apatite geochemistry in mineral exploration within the Olympic Cu-Au Province, and potentially in analogous terranes elsewhere, given the clear association between MREE-enriched apatite and often well-mineralised, hematite-dominant domains within these large IOCG systems. [ABSTRACT FROM AUTHOR]

The new mineral grațianite, MnBi2S4, is described from the Băița Bihor skarn deposit, Bihor County. Romania. Grațianite occurs as thin lamellae, intimately intergrown with cosalite and bismuthinite, or as flower-shaped blebs within chalcopyrite, where it is associated with cosalite and tetradymite. Grațianite displays weak to modest bireflectance in air and oil, respectively, and strong anisotropy. The mean empirical composition based on 20 electron probe microanalyses is: (Mn0.541Fe0.319Pb0.070Cu0.040 Cd0.009Ag0.001)Σ0.980(Bi1.975Sb0.018)Σ1.993(S4.008Se0.012Te0.007)Σ4.027, corresponding to the ideal formula MnBi2S4. Grațianite crystallizes in the monoclinic system (space group Cllm). Single-crystal X-ray studies of material extracted by the focused ion beam-scanning electron microscopy (FIB-SEM) technique, and carried out on the MX2 macromolecular beamline of the Australian Synchrotron determined the following cell dimensions: α = 12.6774(25) Å, b = 3.9140(8) Å, c = 14.7581(30) Å, β = 115.31(3)°, V= 662.0(2) ų, and Z = 4. The six strongest X-ray reflections and their relative intensities are: 3.448 Å (100), 2.731 Å (77), 2.855 Å (64), 3.637 Å (55), 3.644 Å (54), and 3.062 Å (51). Grațianite is the monoclinic analog of berthierite (FeSb2S4), garavellite [Fe(Bi,Sb)2S4] and clerite [Mn(SbAs)2S4] (Nickel-Strunz class 02.HA.20). It is isostructural with synthetic sulfides and selenides in the MnBi2S4-MnSb2S4 and MnBi2Se4-MnSb2Se4 series, and with grumiplucite (HgBi2S4) and ku-driavite, [(Cd,Pb)Bi2S4], ³P members of the pavonite homologous series. The mineral is named for Grațian Cioflica (1927-2002), formerly Professor in Mineralogy and Ore Deposits at the University of Bucharest, Romania. The Băița Bihor skarn, like others within the same belt, is geochemically complex. The availability of Cu, Zn, and Pb, but also Ag, Bi, Mo, and B, as well as a wide range of minor elements, has created an environment allowing for crystallization of an unusually diverse range of discrete minerals. Grațianite is part of the peculiar associations of Bi--Pb-sulfosalts and Bi-chalcogenides that are genetically related to Au-enrichment. This study demonstrates the versatility of FIB-SEM techniques for in situ extraction of small volumes of well-characterized material, coupled with single-crystal X-ray analysis using synchrotron radiation, for the characterization of new minerals. [ABSTRACT FROM AUTHOR]

This study reports a detailed evaluation of how key parameters of operation influence the measurement of sulfur isotopes using laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Sulfur isotopes are observed to display a fractionation up to 2‰ δ 34 S during analysis of pyrite with different laser parameters using a 193 nm ArF excimer laser. In order to understand why the laser parameters affect S isotope fractionation when measuring S isotopes in pyrite, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques were used to characterize debris formed during the ablation of pyrite, i.e., morphology and speciation of phases. The results show that pyrite decomposes to two phases: ball-like troilite (FeS) and a sulfur-rich floc-like agglomeration surrounding the troilite. The measured δ 34 S values vary due to the different proportions of troilite balls and the floc-like material generated under different laser parameters. The proportion of troilite and S was evaluated with a LA-(Quadrupole)-ICP-MS through direct comparison of the counts per second (CPS) ratio of 56 Fe to 32 S. In contrast to pyrite, natural pyrrhotite shows no decomposition process and the particle size of the debris from pyrrhotite is nearly 10 times larger than that of pyrite (~ 5 μm for pyrrhotite compared to < 1 μm for pyrite). Therefore, a biased analysis of pyrite may happen using laser ablation although this problem can be minimized using high raster velocity. Last but not least, we provide a case study of S isotope mapping using high raster velocity, which extends the application of the in-situ S isotope analysis technique. The results here carry implications for the choice of settings needed to obtain accurate LA-MC-ICP-MS S-isotope maps of pyrite. [ABSTRACT FROM AUTHOR]

The Irish Orefield is characterised by the presence of both Zn-Pb- and Cu-Ni-As-rich deposits, prospects, and orebodies in similar structural and stratigraphic positions. However, the genetic relationships between these mineralisation types are still debated. In this article, we present new mineralogical, paragenetic, and mineral-chemical observations from the Cu-Ni-As-rich ores at the classic Lisheen deposit, County Tipperary. These observations indicate the intimate association and cogenetic nature of these ores with the more abundant Zn-Pb-rich mineralisation. Specifically, both mineralisation types appear to have formed at the same time, under similar physicochemical conditions, and from the same ore fluids. In addition, both types of mineralisation contain elevated Ge contents. The cogenetic nature of the two mineralisation types, the relative absence of Cu-Ni-As-rich ores from most of the larger Irish-type Zn-Pb deposits compared to expectations derived from probable ore fluid compositions, and finally, the known geological characteristics of larger Cu-Ni-As-rich ore bodies, like Gortdrum, indicate that significant Cu-Ni-As-rich mineralisation could be present at lower stratigraphic levels across the Irish Orefield. Areas with extensive known Zn-Pb mineralisation are expected to be particularly prospective for such ores, which may occur at stratigraphic levels as deep as the Old Red Sandstone. This may have additional implications beyond Ireland, and could point to the potential for undiscovered Cu-rich ores in low-temperature carbonate-hosted Zn-Pb districts elsewhere. [ABSTRACT FROM AUTHOR]

• Zircon from Samphire Pluton granites are characterised at micron- to nanoscale. • 207Pb/206Pb weighted average ages are 1586 ± 9.3, 1583.2 ± 8.5 and 1578 ± 9.5 Ma. • Zircon alteration expressed by variation in concentrations of HREE, Y, Th & Pb. • Enrichment in non-formula elements and marked disturbance of U-Th-Pb isotope ratios. • Results confirm open system U-Pb behaviour in Hiltaba Suite zircon. Zircons from three distinct granites within the Samphire Pluton, South Australia, are characterised at the micron- to nanoscale. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon dating generated 207Pb/206Pb weighted average ages of 1586 ± 9.3 Ma, 1583.2 ± 8.5 Ma and 1578 ± 9.5 Ma, respectively. Although zircons from all three granites display evidence of hydrothermal overprinting, this is most strongly expressed in a distinct, red-colored granite referred to here as Granite C. Alteration is expressed as variation in the concentrations of HREE + Y, Th and Pb, whereby grain margins are relatively enriched in these elements and both Zr and Si are depleted. Altered zircon cores have high U contents relative to grain margins, which are appreciably poorer in this element, whereas Th is strongly enriched within crosscutting microfractures. Coupled with the relative enrichment in non-formula elements and marked disturbance of U-Th-Pb isotope ratios, the nanoscale observations of Pb-bearing nanoparticles (galena?) implying mobility of Pb and other elements, nanofractures and structural defects demonstrate that zircon in Granite C has undergone multi-stage alteration impacting upon accurate dating. Importantly, and with implications for analogous systems elsewhere, our results confirm nanoscale open system U-Pb behaviour in Hiltaba Suite zircon. SHRIMP U-Pb zircon geochronology cannot confidently resolve any statistical differences in the age of the three granites, despite their distinct appearance suggesting they might represent temporally distinct phases of a larger magmatic system. Zircons within the most altered Granite (C), directly underlying the Blackbush uranium prospect contain convincing micron- to nanoscale evidence for an alteration event that triggered a remobilisation of uranium from granite into the cover sequence. [ABSTRACT FROM AUTHOR]

• We suggest a near-continuous model of hydrothermal reworking in the Olympic Cu-Au Province resulting in recrystallisation of the Cu-(Fe)-sulfides, and Pb (re)mobilisation at nm- to deposit-scales. • Pb-isotope ratios in galena, clausthalite, altaite hosted within the Cu-(Fe)-sulfides, and the Cu-(Fe)-sulfides themselves, are highly radiogenic and are indistinguishable from one another. • Hydrothermal autoclave experiments showed that the Pb-chalcogenide inclusions likely formed within porous zones of the Cu-(Fe)-sulfides during coupled dissolution reprecipitation reactions. • The data presented here are consistent with other studies in the Olympic Cu-Au Province which record the impact of tectonothermal events younger than the 1600–1585 Ma 'main' mineralisation event. Lead-isotope data were obtained for a population of Pb-chalcogenides (galena, clausthalite and altaite) and Cu-(Fe)-sulfides in Cu-(Fe)-sulfide mineral separates from the Prominent Hill iron-oxide copper gold deposit, Mt Woods Inlier, South Australia. Each mineral displays wide variability in 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios, ranging from moderately radiogenic Pb signatures to strongly radiogenic. Any contribution from non-radiogenic (common) lead at the time of initial deposit formation (1600–1585 Ma) is minor. Lead is overwhelmingly derived from the decay of U, with a minor contribution from the decay of Th also present within the ores. The heterogenous nature of the recorded Pb isotope values suggests a mixing of isotope signatures during repeated cycles of fluid-assisted dissolution, remobilisation and reprecipitation of U- and Pb-bearing phases. Hydrothermal experiments showed that the incorporation of Pb-chalcogenide (galena) occurs rapidly (days) at relatively mild conditions (≤150 °C), via precipitation in reaction-induced porosity formed during coupled dissolution reprecipitation reactions of the host Cu-(Fe)-sulfides. Hence, even minor hydrothermal activity may result in some trapping of radiogenic Pb by pre-existing Cu-(Fe)-sulfides. Construction of Pb-Pb pseudo-isochrons from the data supports these assessments, returning a range of possible (theoretical) ages (0–0.535 Ga) for Pb-chalcogenide formation. An additional (two-stage) Pb evolution model is preserved by the data with separation of each reservoir from the bulk silicate earth at ∼ 830 Ma and mixing of the two reservoirs at ∼ 500 Ma. Although the Pb-isotope data can be interpreted as resulting from a number of discrete events that generated regional-scale fluid flow, near-continuous Pb (re)-mobilisation at the nm- to deposit-scales is an equally valid interpretation, and is also consistent with observations of modern radionuclide mobility in the ores. The observations made within this study should be considered when discussing the mobility of elements within and between mineral phases in ore-forming systems. They show that many mineral phases, particularly the sulphide mineral phases discussed here, should not be considered as closed systems, but potentially, as systems in which chemistry and mineral stoichiometry evolve continuously over geological time. [ABSTRACT FROM AUTHOR]

LA-ICP-MS element maps of zoned enargite from the Zijinshan high-sulphidation Cu-Au deposit reveal often spectacular grain-scale zonation that track changes in fluid composition. Enargite also concentrates several elements of interest, including Ag, Au, Te and Ge, relative to associated minerals. • Enargite hosts Sb, Te, Sn, Zn and Ge at concentrations up to several thousand ppm. • Enargite also concentrates Mo, Cd, Bi, Pb, Fe, Se, Ag, Au, W, Ga and In. • Enargite grains display oscillatory, compositional zoning. • Te-rich enargite may be a prospective guide to high Au grade mineralization. • Measured Au, Ag, Te and Ge make enargite a mineral of potential economic interest. Enargite, Cu 3 AsS 4 , is a relatively common sulphide mineral and is considered diagnostic for deposits of intermediate- to high-sulphidation type. Analysis of enargite-bearing samples from deposits in the Zijinshan porphyry – high-sulphidation epithermal Cu-Au orefield, southeastern China, provides evidence for the diversity of trace elements that may be hosted within enargite and their range of concentrations. Enargite is shown to host Sb, Te, Sn, Zn and Ge at concentrations up to several thousand ppm. The mineral also incorporates measurable concentrations of Mo, Cd, Bi, Pb, Fe, Se, Ag, Au W, Ga and In. Element mapping (electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry) provides evidence for grain-scale heterogeneity in enargite in the form of oscillatory, grain-scale compositional zonation with respect to Sb, Sn, Te and several other trace elements. Element mapping also clearly shows an inverse correlation between the concentrations of As and Te, and between As and Sn. Incorporation of Sn and Te into the enargite structure is achieved by substitution of Sn4+ and Te4+ for As5+. Charge balance is maintained by incorporation of Fe2+, Zn2+ and other divalent cations (potentially including Cu2+) into the Cu+ site. The complex intra-grain zoning results from evolving fluids, multiple phases of growth – in turn leading to an overprinting of primary distribution patterns. Observed patterns are also influenced by equilibrium partitioning between enargite and co-existing minerals. Nevertheless, trace element signatures in enargite from different parts of the Zijinshan ore system show notable differences. Enargite from the high-sulphidation stage typically shows a marked enrichment in Te and Sn whereas enargite from intermediate-sulphidation stage is relatively depleted in Te and Sn, and comparatively enriched in Sb and Se. These differences represent a potential vector for exploration within porphyry – high-sulphidation epithermal systems. Furthermore, the presence of Te-rich enargite may be a prospective guide to high Au-grade mineralization. The notable concentrations of precious metals (Au, Ag) and critical elements (notably Te and Ge) within enargite make this mineral of particular interest from the perspective of potential recovery of these economically important elements. The observed grain-scale zoning and inherent variability within any given sample emphasize that spot analysis of trace elements alone without consideration of such heterogeneity may provide quantitative data of limited use and potentially, lead to misleading interpretations. [ABSTRACT FROM AUTHOR]

Graphical abstract We have described the texture and Au distribution within pyrite, sphalerite and chalcopyrite from Zhengguang gold deposit. Pyrite formed through the ore-deposit evolution from early porphyry mineralization to the followed epithermal mineralization, to latest metamorphism event. Among all the sulfides, pyrite and sphalerite are the two important carriers for gold in Zhengguang. There is no doubt an undiscovered porphyry system below or near the Zhengguang gold deposit. Emplacement of the porphyry will result in the formation of Au-poor group of pyrite in pyrite zone. After the formation of an Au-poor group of pyrite in porphyry system, the later epithermal fluids alter and overprint the early pyrite, and give birth to Au-rich group of pyrite, Bi-rich group of chalcopyrite, and Au-rich group of sphalerites in Zhengguang deposit. This process results in the deposition of gold and base metal sulfides with overprinting, and altering the early formed pyrite. The gold element is most likely derived from magma system. There was a metamorphic event altered and deformed the early formed sulfides, and result in the remobilization of Au. Highlights • Porphyry emplacement results in formation of Au-poor pyrite and Bi-poor chalcopyrite. • Later epithermal fluids replace and overprint early pyrite. • Epithermal pyrite is relatively Au-rich pyrite; chalcopyrite is Bi-enriched. • Gold is most likely sourced from magma; pyrite and sphalerite both carry some gold. • Gold occurs as Au in Au-poor and Sb-rich pyrite, and Au+ and Au0 in Au-rich pyrite. • A metamorphic event led to sulfide deformation and associated Au remobilizations follows. Abstract The Zhengguang gold deposit, a typical intermediate-sulfidation epithermal deposit, is located in the southeastern part of the Duobaoshan orefield, west of the Hegenshan-Heihe suture zone, in the eastern part of the Central Asian Orogenic Belt. The deposit comprises five ore zones with total Au reserves exceeding 35 tonnes, with potential additional resources at depth. All vein-type orebodies are hosted by Paleozoic volcanic rocks and comprise multiple vein sets 1–100 cm in thickness. Although gold generally occurs in native form, or as electrum in epithermal deposits like Zhengguang, both pyrite and sphalerite are known to accommodate modest concentrations of invisible gold. This study employs a combination of petrography and sulfide chemistry to determine the role of invisible gold in the Zhengguang ores and the mechanisms of gold incorporation into epithermal sulfides. Three sulfide stages are identified: an early quartz + pyrite (Py1a, Py1b) ± chalcopyrite (Ccp1) stage; a subsequent quartz + sphalerite (Sph2a, Sph2b) + pyrite (Py2a, Py2b, Py2c, Py2d) + chalcopyrite (Ccp2a, Ccp2b) ± galena ± calcite stage; and a late stage containing deformed quartz + pyrite (Py3a, Py3b) ± sphalerite. Petrography and sulfide chemistry allow three groups of pyrite (Au-poor, Au-rich, and a distinct Sb-rich group) to be distinguished, alongside three groups of chalcopyrite (Bi-rich, intermediate-Bi, and Bi-poor), and two groups of sphalerite (Au-poor, Au-rich). A potential porphyry system is indicated beneath the epithermal system by the appearance of Au-poor pyrite and Bi-poor chalcopyrite. After precipitation of early Au-poor sulfides, inflow of relatively low temperature epithermal fluids led to alteration and replacement of early porphyry-related sulfides, and to precipitation of Au-rich pyrite, Bi-rich and intermediate-Bi chalcopyrite, and sphalerite. Gold-rich pyrite contains up to 140 ppm Au, interpreted as both as lattice-scale substitution (Au1+) and as included particles of native gold (Au0). Epithermal chalcopyrite is an important silver carrier but, although Au is measurable, it is a not a good carrier for gold. A strong positive correlation between Au and Cu in pyrite from the first two stages indicate that gold and other metals were likely sourced from magma-derived hydrothermal fluids. The deposit was formed in the Early Paleozoic but some gold ores appear deformed and partially destroyed by a later metamorphic event during which a distinct Sb-rich pyrite crystallized. This study should catalyze exploration in the orefield as it provides further support for an as-yet undiscovered porphyry system close to the Zhengguang deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] Several Pb–Zn deposits in the Nyainqêntanglha metallogenic belt have unique features whereby either the causative pluton is not exposed, or there is evidence for complex multistage and multi-type ore-forming processes. These scenarios are typified by the Lawu and Yaguila Pb–Zn skarn deposits, respectively. In this contribution, we selected skarn garnets from these two deposits as the research objects and utilized LA–ICP–MS to measure the U–Pb isotope and trace element compositions. Our new garnet U–Pb data, combined with published age constraints on Pb–Zn mineralization in this belt, suggest a magmatic-hydrothermal origin for corresponding mineralization, with the causative magma likely derived from partial melting of ancient continental material due to rollback and subsequent breakoff of the Neo-Tethys oceanic slab during India–Asia continental collision. • The Lawu Pb–Zn skarn mineralization event is constrained at 54.6 ± 2.9 Ma. • Garnet U–Pb ages for the Yaguila Pb–Zn skarn are older: 65.0 ± 4.7 ─ 68.5 ± 3.4 Ma. • Garnet U–Pb geochronology support a magmatic-hydrothermal origin for Pb–Zn skarns. • Reliable garnet U–Pb dating underpins genetic models for Pb–Zn skarns. Lawu and Yaguila are two Pb–Zn skarn deposits in the eastern Nyainqêntanglha metallogenic belt, central Lhasa subterrane, Tibet. The genesis of Pb–Zn deposits in this belt and the crustal processes leading to their formation remain ill-constrained, mostly because of the lack of precise mineralization ages. We integrate textural information, geochemistry, and in-situ garnet U–Pb geochronology to constrain the timing and genesis of Pb–Zn mineralization. Garnets from the two deposits display oscillatory compositional zoning (And 14 Gr 86 to And 100) and contain variable U contents (0.07–5.3 ppm). Aluminum-rich garnet displays a chondrite-normalized rare earth element (REE) fractionation pattern in which LREEs are depleted relative to flattish HREE segments. In contrast, Fe-rich garnet shows LREE-enriched, relatively HREE-poor patterns with positive Eu-anomalies. Uranium concentration is correlated with total REE and Fe components in garnets, implying that U incorporation is largely controlled by coupled substitution mechanisms. The same garnets also contain measurable contents of other metals (up to hundreds of ppm), such as Sn, W, and In. The distribution and fractionation of major and trace elements in zoned garnets record periodic fluid pluses with different compositions during hydraulic fracturing. The new garnet U–Pb data show that the Yaguila deposit formed between 68.5 ± 3.4 and 65.0 ± 4.7 Ma, and the Lawu deposit formed at 54.6 ± 2.9 Ma. Within the geochronological framework of igneous rocks and Pb–Zn mineralization in the Nyainqêntanglha metallogenic belt, the new garnet ages suggest a magmatic-hydrothermal origin for related mineralization, with the causative magma likely derived from partial melting of ancient continental material due to rollback and subsequent breakoff of the Neo-Tethys oceanic slab during India–Asia continental collision. This study highlights the opportunities offered by garnet U–Pb dating for elucidating the formation age and ore genesis of base metal skarn systems. [ABSTRACT FROM AUTHOR]

Mechanisms for Fe isotope fractionation in hydrothermal mineral deposits and in zones of associated K-feldspar alteration remain poorly constrained. We have analyzed a suite of bulk samples consisting of granite displaying K-feldspar alteration, Precambrian metamorphic rocks, and pyrite from gold deposits of the Jiaodong Peninsula, East China, by multi-collector inductively-coupled plasma mass spectrometry. Pyrites from disseminated (J-type) ores show a δ 56 Fe variation from +0.01 to +0.64‰, overlapping with the signature of the host granites (+0.08 to +0.39‰). In contrast, pyrites from quartz veins (L-type ores) show a wide range of Fe-isotopic composition from −0.78 to +0.79‰. Negative values are never seen in the J-type pyrites. The Fe isotope signature of the host granite with K-feldspar alteration is significantly heavier than that of the bulk silicate Earth. The Fe isotopic compositions of Precambrian metamorphic rocks across the district display a narrow range between −0.16‰ and +0.19‰, which is similar to most terrestrial rocks. Concentrations of major and trace elements in bulk samples were also determined, so as to evaluate any correlation between Fe isotope composition and degree of alteration. We note that during progressive K-feldspar alteration to rocks containing >70 wt% SiO 2 , >75 ppm Rb, and <1.2 wt% total Fe 2 O 3 , the Fe isotope composition of the granite changes systematically. The Fe isotope signature becomes heavier as the degree of alteration increases. The extremely light Fe isotopic compositions in L-type gold deposits may be explained by Rayleigh fractionation during pyrite precipitation in an open fracture system. We note that the sulfur isotopic compositions of pyrite in the two types of ores are also different. Pyrite from J-type ores has a systematically 3.5‰-higher δ 34 S value (11.2‰) than those of pyrite from the L-type ores (7.7‰). There is, however, no correlation between Fe and S isotope signatures. The isotopic fractionation of sulfur is used to constrain a change in the f O 2 of the hydrothermal fluids from which pyrite precipitated. This work demonstrates that the Fe isotope composition of pyrite displays a significant response to the process of pyrite precipitation in hydrothermal systems, and that systematic fractionation of iron isotopes occurs during fluid/rock reaction in the K-feldspar alteration zone of the Linglong granite. The implications of the results are that processes of mineralization and associated fluid-rock interaction, which are ubiquitously observed in porphyry-style Cu-Au-Mo and other hydrothermal deposits, may be readily traceable using Fe isotopes. [ABSTRACT FROM AUTHOR]

The Blackbush uranium deposit (JORC Inferred Resource: 12,580 tonnes U), located on the north-eastern Eyre Peninsula, is currently the only sediment-hosted U deposit investigated in detail in the Gawler Craton. Uranium is hosted within Eocene sandstone of the Kanaka Beds, overlying Mesoproterozoic granites of the Samphire pluton, affiliated with the Hiltaba Intrusive Suite (~ 1.6 Ga). These are considered the most probable source rocks for uranium mineralisation. By constraining the petrography and mineralogy of the granites, insights into the post-emplacement evolution can be gained, which may provide an exploration indicator for other sediment-hosted uranium systems. Three geochemically distinct granite types were identified in the Samphire Pluton and correspond to domains interpreted from geophysical data. All granites show complex alteration overprints and textures with increasing intensity closer to the deposit, as well as crosscutting veining. Alkali feldspar has been replaced by porous K-feldspar and albite, and plagioclase is overprinted by an assemblage of porous albite + sericite ± calc-silicates (prehnite, pumpellyite and epidote). This style of feldspar alteration is regionally widespread and known from Hiltaba-aged granites associated with iron-oxide copper‑gold mineralisation at Olympic Dam and in the Moonta-Wallaroo region. In two granite types biotite is replaced by calcic garnet. Calc-silicates are indicative of Ca-metasomatism, sourced from the anorthite component of altered plagioclase. Minor clay alteration of feldspars is present in all samples. Mineral assemblages in veins include quartz + hematite, hematite + coffinite, fluorite + quartz, and clay minerals. Minor chlorite and sericite are found in all vein types. All granite types are anomalously rich in U (concentrations between 10 and 81 ppm). Highly variable Th/U ratios, as well as hydrothermal U minerals (mostly coffinite) in granites and veins, are clear evidence for U mobility. Uranium may have been preconcentrated in veins in the upper parts of the pluton, and was subsequently leached after deposition of the sediment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gaojiangbang is a reduced porphyry-skarn W-Mo metallogenetic system. • The ∼150 Ma mineralization event represents the upper age boundary in the MLYB and JMB. • Crustal materials played a key role in formation of Gaojiabang porphyries. • Ductile deformation at Gaojiabang is related to Qingyang Complex emplacement. The Jiangnan Mo-W-Pb-Zn metallogenic belt hosts more than fifteen W-Mo and Mo deposits and is located at the margin between the Middle-Lower Yangtze metallogenic belt and the South China Continent. The recently discovered Gaojiabang W-Mo deposit, Chizhou district, Anhui Province, is the one of the largest W-Mo deposits in the belt (25.4 Mt at a grade of 0.28% WO 3 , 0.11 g/t Mo, with about 10,000 t of that total at an averarge grade of 6.6 g/t Au). The deposit is associated with Jurassic granite and monzonite porphyries that intruded sedimentary rocks of the Cambrian Huangboling Formation. Alteration displays a zonation from granite porphyry to wall rock. Five distinct alteration zones are recognized: deep-seated K-feldspar-biotite-quartz alteration, a quartz-sericite alteration zone, garnet-diopside-epidote alteration zone, calcite-quartz alteration zone, and zone of thermal metamorphism (hornfels). These features are comparable with porphyry Cu-Au-Mo systems. The first three zones of alteration display a close spatial relationship with W-Mo ores. Three distinct styles of W-Mo mineralization are recognized: minor vein-type W-Mo mineralization within sedimentary units; skarn W-Mo mineralization at the contact between sedimentary rocks and granite porphyry; and disseminated Mo(±W) mineralization hosted within both porphyries. The main ore minerals are scheelite, molybdenite, pyrite, pyrrhotite, and minor chalcopyrite, and display a zoned distribution in which most molybdenite occurs inside deep porphyries and the majority of the scheelite is observed inside shallow skarns and hornfels. Based on the presence of redox-indicative mineral assemblages such as pyrrhotite, molybdenite and pyrite in the absence of sulfates, we consider Gaojiabang to be a relatively reduced W-Mo porphyry-skarn system. Our new U-Pb zircon ages confirm Late Jurassic ages for granite (150.4±1.1 Ma) and monzonite porphyries (149.4±1.6 Ma). A molybdenite Re-Os age of 149.5±1.4 Ma indicates that W-Mo mineralization is closely associated with the two porphyries. This new data makes Gaojiabang the oldest deposit recognised so far in the Middle-Lower Yangtze River area, in turn inferring that the westward subduction of the Pacific Plate commenced at ∼150 Ma. Geochemical data indicate that mineralization in the Gaojiabang deposit derives from multiple sources, dominantly from magmatic rocks and basement strata via mantle-crust interaction, with the single greatest involvment of crustal materials among all deposits in the Middle-Lower Yangtze River area. Sulfides, including pyrite, pyrrhotite and molybdenite, display a wide range of δ34S between +3.8‰ to +12.1‰. The gradual increase of δ34S from inner porphyry to outer wall rock indicates contamination from crustal marine sedimentary facies as the ore-forming fluids evolved. Following the W-Mo mineralization event at Gaojiabang, emplacement of Qingyang-Jiuhua Complex at 144–127 Ma resulted in a previously unrecognized ductile deformation of porphyries, sedimentary rocks, and ores. [ABSTRACT FROM AUTHOR]

The origins of mafic mineral clots and microgranular enclaves in Mesoproterozoic granites were investigated in a case study of felsic A-type Hiltaba Suite granites from the Gawler Craton, South Australia. Mafic mineral clots display interlocked textures comprising plagioclase, amphibole, biotite, apatite and magnetite and occur interstitial to coarse rapakivi feldspar, compositionally zoned plagioclase, and quartz phenocrysts. The microgranular enclaves, which may be partly disaggregated, are rounded, contain partially resorbed K-feldspar xenocrysts and have a similar mineralogy to the clots. Whole-rock geochemistry, mineral chemistry and textural features (e.g., rapakivi and granophyric textures, quartz-amphibole ocelli, multiple generations of biotite, xenocrysts, evidence of undercooling) indicate that mineral clots and enclaves may have similar origins and were sourced via multistage magma mixing. Magma rejuvenation caused mingling with a partially crystalline and ductile mush resulting in the formation of microgranular mafic enclaves which contain numerous xenocrysts. Prolonged input of mafic magma and elevated F within the residual melt promoted partial disaggregation of enclaves and recrystallization of mineral clots. Geochemically distinct biotite generations show this evolution from initially F-poor annite to F-rich phlogopite dispersed throughout mineral clots and as 'free' grains within the Hiltaba Suite granites. Annite-bearing mineral clots formed at higher pressures than phlogopite clots, corresponding to crystallization at greater depths. The abundance of Cu and S in mineral clots and enclaves within Hiltaba Suite granite studied here indicates that repeated magma mixing processes may have provided a source of metals for the formation of the nearby Olympic Dam Fe-oxide Cu-U-Au-Ag deposit. • Multistage magma mixing processes recorded in A-type Hiltaba Suite granites. • Ubiquitous mafic mineral clots and microgranular enclaves reflect timing and source. • Late-stage partial disaggregation and re-equilibration of microgranular enclaves. • Clots and enclaves host Cu and S, provide source for nearby Olympic Dam deposit. [ABSTRACT FROM AUTHOR]