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![Contrasting U-Cu distribution in three samples from the Olympic Dam IOCG deposit, South Australia, illustrated by synchrotron-micro-XRF imaging of selected samples described in detail by Macmillan et al. [15]. Mineralogical and grade data are taken from Macmillan et al. [15]. The RGB maps show Cu (blue), U (green), and Fe (red) distribution (colour scale at the bottom right). In (a) (uraninite-dominated ore), Cu and U distribution mirror each other, suggesting coprecipitation of the two metals. Mineralogy is dominated by uraninite. In (b) and (c), the main U minerals are coffinite and brannerite, and U distribution is diffuse and overprints the ore textures, suggesting a secondary origin. The maps were collected at the XFM beamline, Australian Synchrotron. See Li et al. [40] for details of data collection and processing.](publication/325860001/figure/fig2/AS:1086458014244865@1636043184305/Contrasting-U-Cu-distribution-in-three-samples-from-the-Olympic-Dam-IOCG-deposit-South.jpg)
Contrasting U-Cu distribution in three samples from the Olympic Dam IOCG deposit, South Australia, illustrated by synchrotron-micro-XRF imaging of selected samples described in detail by Macmillan et al. [15]. Mineralogical and grade data are taken from Macmillan et al. [15]. The RGB maps show Cu (blue), U (green), and Fe (red) distribution (colour scale at the bottom right). In (a) (uraninite-dominated ore), Cu and U distribution mirror each other, suggesting coprecipitation of the two metals. Mineralogy is dominated by uraninite. In (b) and (c), the main U minerals are coffinite and brannerite, and U distribution is diffuse and overprints the ore textures, suggesting a secondary origin. The maps were collected at the XFM beamline, Australian Synchrotron. See Li et al. [40] for details of data collection and processing.
Source publication
Uranium mineralization is commonly accompanied by enrichment of fluorite and other F-bearing minerals, leading to the hypothesis that fluoride may play a key role in the hydrothermal transport of U. In this paper, we review the thermodynamics of U(IV) and U(VI) complexing in chloride- and fluoride-bearing hydrothermal fluids, and perform mineral so...
Citations
... Generally, the Raman analysis proves the presence of some uranium salts like Uranophane-alpha (Ca(UO 2 ) 2 (Si 3 OH) 2 ⋅5H 2 O). Also other uranium salts Rutherfordine ((UO)CO 3 ), Kasolite (Pb(UO 2 )(SiO 4 )⋅H 2 O), Soddyite ((UO 2 )2SiO 4 ⋅2H 2 O), and [55]. These salts are believed to play a radiating role in the fluorite sample. ...
... Fluorite is slightly radioactive when the average uranium concentration is 1.4 ppm, as seen in Table 2. U is most commonly found in magma-hydrothermal systems at high temperatures, where it forms complex compounds with F − [55]. ...
Green fluorite samples from Homret Akarem, eastern desert Egypt, were investigated by laser-based Raman spectroscopy to study the effect of rare earth elements (REEs) and natural radiation from the surrounding environment on their physico-chemical properties, taking into consideration the geological setting. Geochemical data of trace elements display fluorite enrichment with Y, Pb, Sr, Sn, and other REEs. XRD showed lattice parameters with values higher than those for synthetic fluorite due to the substitution of Ca by Sr and less likely by radiation from U. A considerable shift in the binding energy (BE) for Ca and F obtained from the XPS spectrum indicates that U carried by the hydrothermal solutions formed a discontinuous thin film on the surface of fluorite. Laser-Raman spectroscopy showed strong peaks below 500 cm−1 and both shallow and weak peaks above 500 cm−1. The strong peaks indicate that the substitution of Ca by Sr, point defects, and natural radiation caused by U have a stronger effect on the crystal structure than REEs. Raman spectroscopy supported the initial reports of uranium minerals like Rutherfordine, Kasolite, Soddyite, and Uranophane-alpha.
Graphical abstract
... Whereas the mobility of U within mineralised rocks is relatively well understood and documented in the literature (e.g., Li et al., 2020;Xing et al., 2018), the comparative behaviour of the intermediate daughter products of uranium decay (i.e., between parent U and the stable daughter isotopes of Pb) during fluid-assisted tectonothermal overprinting is less widely reported due to the difficulty of accurately measuring concentrations of shorter half-life isotopes at extremely low concentrations. Recent studies (Owen et al., 2019;Ram et al., 2021c;Rollog et al., 2019aRollog et al., , 2019bRollog et al., , 2019cSchmandt, 2019) have shown that products of uranium decay, notably but not restricted to stable radiogenic lead ( 206 Pb, 207 Pb, 208 Pb), may migrate from the parent U-mineral over distances ranging from nanometres upwards, and combine with available ligands to form 'new' minerals, or become incorporated into the structures of existing minerals. ...
... Uraninite can retain high levels of radiogenic Pb due to its flexible crystal structure (Syverson et al., 2019). However, due to high U contents, self-oxidation of uranium is significant in uraninite; oxidised U is easily leachable by aqueous fluids (Plášil, 2014;Xing et al., 2018), a process that also drives the creation of porosity and Pb release (Ram et al., 2021c). As a result, radiogenic Pb may be removed from uraninite without its complete dissolution, as shown in samples of Pb-zoned uraninite from Johangeorgenstadt, Saxony, Germany (Ram et al., 2013). ...
... Aside from uraninite, brannerite and coffinite are the two major hosts of U in IOCG ores from the Olympic Cu-Au Province. Brannerite, UTi 2 O 6 , is typically metamict, which allows Pb to freely migrate from its structure; while coffinite, a mineral that reflects late-stage, low temperature (<250 C) U mobility at the neighbouring Olympic Dam deposit (Macmillan et al., 2017;Xing et al., 2018), appears to have little ability to retain radiogenic Pb (Syverson et al., 2019;Rollog 2019c). Hence, late hydrothermal events need not necessarily be intense in order to mobilise significant amounts of Pb. ...
... The iron-manganese ore in the LKR is also characterized by prominent HFSE depletions (especially, Ta) in primitive mantlenormalized patterns and, with the exception of the Kaylan deposit, general enrichment in LILE with respect to the rare earth elements (Figure 8c,f,i). Uranium enrichments in the Fe-Mn mineralization at the Kostenga and Poperechny deposits (Figure 8c,f) are also indicative of their predominantly hydrothermal origin due to the uptake of uranium by phosphates (monazite, xenotime) and Fe-Mn oxides (for example, hematite) under hydrothermal conditions [137][138][139][140]. Monazite, xenotime, and hematite are common mineral phases in the LKR iron-manganese ores (Figure 5a,b,d,e). ...
Iron and iron–manganese deposits form three closely spaced clusters within the Lesser Khingan Range of the Russian Far East. Fe-Mn mineralization is hosted in Vendian–Cambrian carbonates and composed of magnetite, hematite, braunite, haussmanite, rhodochrosite and pyrolusite. The iron–manganese ores are closely associated with explosive intermediate–felsic breccias, magnetite-rich lavas, dolerites and mineralized lithocrystalloclastic tuffs. Magmatic rocks display both concordant and discordant relationships with Fe-Mn mineralization and contain abundant xenoliths of host carbonates. Both magmatic rocks (with the exception of Nb-enriched dolerites) and Fe-Mn ores are characterized by variable enrichments in large-ion lithophile and light rare earth elements and strong depletions in high-field strength elements compatible with the broad subduction setting for explosive volcanism and associated hydrothermal Fe-Mn ore mineralization. Nd-Sr isotope systematics suggest contamination by both ancient and juvenile continental crust and the involvement of recycled pelagic sediment in the formation of Fe-Mn deposits in the Lesser Khingan Range of the Russian Far East.
... Under other conditions, enrichment of trace elements associated with U can be a criterion for determining the type of mineralization [33]. The abundance of F can also indicate the presence of hydrothermal U deposits [34], fluorine in metapelite and metasiltstone was identified as being present in muscovite, biotite, and other mica minerals. At low-medium temperature hydrothermal U deposits in metasedimentary rocks, it is common to find associations between U and Cu, Co, Mo, and V forming sulfide and aluminosilicate bonds [35]. ...
The Rirang River, Kalan, West Kalimantan has U and REE resources in the form of mineralization found at the intercalation of metapelite and metasiltstone. However, there are only a few studies about the characterization of U and REE-bearing host rocks in Indonesia. Determining the geological influence of the metasedimentary rock on the mineralization of U and REE is crucial. Thus, the characterization of metapelite and metasiltstone has been substantiated in this study to reveal the potency of the host rock in hosting the U and REE. Petrographic, micro-XRF, and AMICS methods were used to conduct mineralogical analysis. These two rocks share a mineral composition that includes clay minerals, hydrothermal alteration products, and several minerals that indicate metamorphism processes. The foliation structure with a spotted shale texture further indicates the metamorphism process in metapelite and metasiltstone. REE and trace elements associated with U are constituents of clay minerals such as wonesite, staurolite, montmorillonite, chlorite, illite, and kaolinite. The geochemical properties of metapelite and metasiltstone suggest that REE mineralization and trace elements associated with U come from hydrothermal alteration processes.
... The precise mechanism(s) explaining this causal link remain speculative (Xing et al., 2019). As a hard ligand (Pearson, 1963), fluorine increases the fluid transport of high field strength elements (HFSE) via formation of F-complexes (Brugger et al., 2016;Xing et al., 2018); for example, Ti concentrations are 20-100 times higher in F-rich fluids than in pure H 2 O (Rapp et al., 2010). Alternatively, corrosive hydrofluoric acid (HF(aq)) could facilitate dissolution of silicate minerals, thus enhancing fluid pathways (McPhie et al., 2011). ...
... is much more soluble in the hexavalent (U 6+ ) than in the tetravalent form (U 4+ ) in geofluids at low (near surface) to moderate (~ 300 o C) temperature (Langmuir, 1978;Romberger, 1984;Mernagh et al., 1994;Wersin et al., 1994;Komninou and Sverjensky et al., 1996;Cuney, 2009;Bastrakov et al., 2010;Dargent et al., 2013Dargent et al., , 2015Cuney and Kyser, 2015;Cumberland et al., 2016;Xing et al., 2018Xing et al., , 2019. Based on this general understanding of the aqueous geochemistry of uranium, redox reactions that transform U 6+ to U 4+ have been considered to be a key factor controlling uranium mineralization in a variety of geologic environments (Romberger, 1984;Cuney and Kyser, 2015). ...
... For example, a reassessment of the thermodynamic properties of Fe 2+ -bearing chloride and hydroxy complexes have shown that the Fe 2+ species are stable at fO 2 well above the MH buffer (e.g., log fO 2 <HM+7.2 at pH=3 and T=250°C) (Liu et al., 2006;Scholten et al., 2019;Gammons and Allin, 2022). This finding, taken in conjunction with reassessments of the thermodynamic properties of UO 2 2+ chloride and hydroxy complexes (Dargent et al., 2013;Xing et al., 2018;Migdisov et al., 2019), provides strong support for the notion that U 6+ and Fe 2+ can be transported in the same hydrothermal fluid over a wide interval of physicochemical conditions. ...
... The deposition of hematite began at the start of fluid-rock interaction, and the amount precipitated from the reaction with annite was greater than in the other reactions (Fig.5e). Komninou and Sverjensky, 1996;Richard et al., 2012;Dargent et al., 2015;Xing et al., 2018Xing et al., , 2019 Some studies (Bastrakov et al., 2010. Xing et al., 2018 proposed that H 2 O itself could be a potential reducing agent for uranium precipitation through the reaction below: ...
... These same xenotime grains also show a low Th content and a striking depletion in LREE compared to xenotime from Types (1) and (3) ore (Table 4; Appendix 3). The UO 2 enrichment in xenotime can be explained as the result of the metasomatic addition of U to xenotime under oxidising conditions (Xing et al., 2018), which is supported by the predominance of hematite in Type (4) ore. Grainy xenotime aggregates (Fig. 6l) locally show a very high Ca content (up to 29.0 wt%; Appendix 3) and enrichment in F (up to 0.51 wt%), suggesting the presence of minor amounts of Y-HREE-bearing apatite micro-or nano-inclusions. ...
On Prins Karls Forland, Svalbard Archipelago, a set of small iron oxide-apatite (IOA) ore bodies have been discovered within a crustal shear zone, which deformed the polymetamorphosed Neoproterozoic metasedimentary rocks. The ores have various styles and grades of deformation and distinct mineral assemblages whose compositions record a multi-stage tectonothermal and metasomatic history. These IOA ore bodies can be subdivided into fluorapatite-bearing and predominant low-Th monazite in the upper section of the shear zone and F-Cl apatite-bearing and predominant high Th-monazite in the structurally lower higher-grade deformed part. The first stage of alteration for these ore bodies resulted in metasomatic alteration of the apatite and liberation of REE and P redeposited as monazite and xenotime. The transport of dissolved REE and P was likely enhanced by deformation. The second stage of alteration had a distinct impact on the individual ore bodies, which resulted in the Th-enrichment of a small subset of the monazite grains in the upper section of the shear zone. In the lower section of the shear zone most of the monazite was replaced by high Th monazite. Here the original fluorapatite is enriched in Cl, Mn, and Sr, most probably due to interaction with CaCl2-rich fluids enriched in Sr and Mn that was scavenged from the hosting metasediments and altered metagabbros. Contrasting textures, mineral assemblages, and the geochemistry of the ores from distinct localities reflect involvement of compositionally different fluids from the gabbroic rocks and surrounding metasedimentary rocks during the protracted tectonothermal evolution of Prins Karls Forland. Therefore, it is concluded that the IOA ore bodies most likely resulted due to the fractionation of Fe, P, Ca, and REE from hypersaline fluids associated with the gabbros. Once deposited, these IOA ore bodies were subsequently altered during at least one and perhaps two later metamorphic events.
... Although K-feldspar is a minor component in basalt, the KMQ pH buffer is widely used experimentally or theoretically to cover the range of pH values typical of complex basalt-hosted alteration by adjusting the activity of dissolved K + (Foustoukos and Seyfried, 2005;Scheuermann et al., 2020;Xing et al., 2021), as was the case here. It is also noted that in this modelling, sufficient sphalerite was included as the Zn source to avoid the complexity of fluid/rock ratio that potentially affects metal solubility such as in many natural hydrothermal systems (e.g., Thébaud et al., 2008;Meffre et al., 2016;Xing et al., 2018;Xing et al., 2019a). Calculations were performed using the aliquot-type model as detailed in Xing et al. (2019b); the simulated conditions were 250-450°C, 500 bar, and the fluid salinity range was 0-2 m NaCl. ...
... In natural hydrothermal systems, including the seafloor vents, fluid/rock ratio is also an important factor determining observed fluid chemistry and base metal-bearing mineralization (Bau, 1991;Alt-Epping and Smith, 2001;German and Seyfried, 2014;Xing et al., 2018;Xing et al., 2019a). Hence, temperature, salinity, pH, as well as fluid/rock ratio, should function as a whole, contributing to the observed metal contents. ...
The solubility and speciation of zinc (Zn) in chloride-bearing aqueous fluids at high temperature and pressure are important for understanding Zn transport in natural hydrothermal systems and associated mineralizing processes. Here, we measured sphalerite solubility in NaCl-HCl-H2O fluids using a fixed-volume titanium alloy hydrothermal reactor equipped with a newly designed gas-tight titanium piston sampler. This novel reactor-sampling system is capable of acquiring internally filtered fluids at high temperature and pressure. The experiments were conducted at 300-450 °C, 500 bar, in fluid with 0.5m and 1m NaCl, respectively. The measured sphalerite solubilities are consistent with predicted values using previous thermodynamic data at 300-400 °C, but diverge significantly above 400 °C. To resolve this discrepancy, we adjusted the solubility product of Zn minerals by modifying the heat capacity and Born coefficients that describe the Gibbs Free Energy of formation from the elements of the Zn2+ aqua ion based on the new solubility data. The refined Helgeson-Kirkham-Flowers (HKF) equation of state (EoS) of Zn2+ empirically reproduces the solubility data of Zn minerals from previous experimental studies well over the covered T-P range (25-600 °C, Psat to 2 kbar), but extends accurate predictions to conditions typical of deep sea hydrothermal systems, down to fluid densities of 0.35 g/cm3. Thermodynamic modelling using the revised EoS of Zn2+ shows that higher temperatures, chlorinity and lower pH increase Zn solubility, and that Zn chloride complexes are the predominant species. The influence from salinity on Zn solubility is less significant in fluids with low pH. Applied to seafloor hydrothermal systems, our results suggest that in addition to temperature, pH and total dissolved chloride, fluid/rock ratio may be an important factor contributing to Zn concentrations in vent fluids at Mid Ocean Ridges.
... Temperature estimates obtained using the Ti-in-zircon thermometer are also correlated to La content (Figure 10b), suggesting that Ti is indeed affected by alteration. Uranium is strongly compatible in zircon, as it is incorporated by a simple substitution mechanism (U(IV) = Zr(IV); [49]), and may thus be difficult to remove from zircon during an alteration process; however, U can be mobilized by F-Clbearing fluids [71]. Such fluids may have circulated in the Douay mineralized system, where fluoritization is reported and where base metals-bearing sulfides (chalcopyrite, molybdenite, sphalerite, galena) are observed [11] that are indicative of Cl-bearing fluids. ...
Zircon provides essential information on the age and oxidation state of magmatic systems and can be used to characterize magmatic-hydrothermal Au mineralizing systems. Using the Douay intrusion-related gold system (IRGS) as a type example of Neoarchean syenite-associated mineralization (Abitibi greenstone belt), we demonstrate that zircon from altered quartz-monzonite rocks can also be used to infer the age of a magmatic-hydrothermal event. Here, zircon chemistry is used to identify the following sequence of events at the Douay exploration project: (1) the crystallization of zircon at ~2690 Ma in evolved residual melts with distinct U-contents (quartz-monzonite magma); (2) the extensive radiation damage for the U-rich grains over a period of ~10–15 My; and (3) the alteration of zircon grains at ~2676 Ma by interaction with magmatic-hydrothermal mineralizing fluids derived from syenite and carbonatite intrusive phases. This study also distinguishes extensively altered zircon grains from pristine to least-altered zircon formed in distinct magmatic environments using a Th/U vs. U discrimination diagram.
... It is usually concentrated with Ce in monazite or bastnaesite (Smith and Henderson, 2000). Although LREE are expected to form stronger complexes with fluoride than with chloride with increasing temperature (T > 250°C, Migdisov et al., 2009), chloride is considered to be the main transporter of REE at high T because of its high availability in most geo-fluids, whereas the solubility of F is limited by phases such as fluorapatite and biotite (Migdisov et al., 2009;Xing et al., 2018). A number of experimental and theoretical studies have been conducted to determine the properties of the La(III) aqua ion and La(III)-chloride complexes, mostly at room temperature, i.e. hydration and chlorination numbers, coordination geometry, and thermodynamic properties ( Table 1). ...
Chlorine is the most common ligand in geofluids, and one of the most important complexing agents for rare earth elements. The geometry and thermodynamic properties of La(III)-Cl complexes determined by previous experimental studies show inconsistency especially at temperature over 350 C. Here, ab initio molecular dynamics (MD) simulations were employed to determine the nature and thermodynamic properties of La(III)-Cl complexes at temperature up to 50°C and pressure up to 30 kbar. The simulations were ground proofed by in situ x-ray absorption spectroscopy (XAS) results (400 bar, 25 to 500 C). Both MD and XAS show an increase in the relative stabilities of chloride complexes with increasing temperature. The formation constants of LaCln³⁻ⁿ (n = 1-3) complexes were calculated using thermodynamic integration method that is within ab initio MD. The calculated formation constants of LaCl²⁺ and LaCl2⁺ at temperatures below 400 C agree with Migdisov et al.’s (2009) extrapolations from the Helgeson-Kirkham-Flowers (HKF) equation-of-state. We fitted the HKF equation-of-state parameters of LaCln³⁻ⁿ (n = 1-3) within the Deep Earth Model (DEW, Sverjensky et al., 2014) of LaCln³⁻ⁿ (n = 1-3) to enable the calculations of the formation constants up to 1200 C, 60 kbar, based on the previous experimental data and the new results. The predictions confirm the increased stability of chloride complexes with increasing temperature and further underline the effect of pressure on La speciation: while LaCl3(aq) becomes important in Cl-rich metamorphic and magmatic hydrothermal fluids (T>350C; P<5kbar) circulating in the upper crust, LaCl²⁺ and LaCl2⁺ appear to be the dominant complexes under higher pressure characteristic of the lower crust or subducting slab environments.
