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Advances in the quantification of rare earth elements ( REE) at the micrometric scale in uranium oxides by laser ablation-inductively coupled plasma-mass spectrometry are described. The determination of the best analytical conditions was tested using a uranium oxide ( Mistamisk) the concentrations of REE in which were previously estimated by other techniques. Comparison between the use of U or Pb as an internal standard clearly showed a diameter-dependent fractionation effect related to Pb at small crater diameters (16 and 24 μm), which was not found for U. The quantification of REE contents in uranium oxide samples using both matrix-matched (uranium oxide) and non-matrix-matched ( NIST SRM 610 certified glass) external calibrators displayed no significant difference, demonstrating a limited matrix effect for REE determination by LA- ICP- MS. Moreover, no major interferences on REEs were detected. The proposed methodology ( NIST SRM 610 as external calibrator and U as internal standard) was applied to samples from uranium deposits from around the world. The results showed that LA- ICP- MS is a suitable analytical technique to determine REE down to the μg g−1 level in uranium oxides at the micrometre scale and that this technique can provide significant insights into uranium metallogeny. [ABSTRACT FROM AUTHOR]

In giant unconformity-related U deposits from the Athabasca Basin (Canada), the origin of the ore fluids and the source of elements typically associated with U ore, such as Mg and B, are highly controversial. This paper presents a petrographic and boron isotopic study of Mg-tourmalines (dravites) coeval with U oxides and of primary tourmalines from basement rocks. The heavy B isotopic compositions of dravites (ä11δ = 19.6‰-36.5‰) contrast with the light composition of basement tourmalines (ä11δ= -8.1‰-3.3‰) and clearly show that most of the B was brought to the ore system by basinal brines of marine origin. Because the latter are also typically Mg-rich, a similar origin for Mg is proposed. These results support the idea that marine-derived brines were the only fluids involved in the formation of the deposits, and therefore challenge the previous models in which the B and Mg were leached from sedimentary and/or basement rocks, or carried by a basement-derived fluid. [ABSTRACT FROM AUTHOR]

Abstract: Analyses of halogen concentration and stable chlorine isotope composition of fluid inclusions from hydrothermal quartz and carbonate veins spatially and temporally associated with giant unconformity-related uranium deposits from the Paleoproterozoic Athabasca Basin (Canada) were performed in order to determine the origin of chloride in the ore-forming brines. Microthermometric analyses show that samples contain variable amounts of a NaCl-rich brine (Cl concentration between 120,000 and 180,000ppm) and a CaCl2-rich brine (Cl concentration between 160,000 and 220,000ppm). Molar Cl/Br ratios of fluid inclusion leachates range from ∼100 to ∼900, with most values between 150 and 350. Cl/Br ratios below 650 (seawater value) indicate that the high salinities were acquired by evaporation of seawater. Most δ37Cl values are between −0.6‰ and 0‰ (seawater value) which is also compatible with a common evaporated seawater origin for both NaCl- and CaCl2-rich brines. Slight discrepancies between the Cl concentration, Cl/Br, δ37Cl data and seawater evaporation trends, indicate that the evaporated seawater underwent secondary minor modification of its composition by: (i) mixing with a minor amount of halite-dissolution brine or re-equilibration with halite during burial; (ii) dilution in a maximum of 30% of connate and/or formation waters during its migration towards the base of the Athabasca sandstones; (iii) leaching of chloride from biotites within basement rocks and (iv) water loss by hydration reactions in alteration haloes linked to uranium deposition. The chloride in uranium ore-forming brines of the Athabasca Basin has an unambiguous dominantly marine origin and has required large-scale seawater evaporation and evaporite deposition. Although the direct evidence for evaporative environments in the Athabasca Basin are lacking due to the erosion of ∼80% of the sedimentary pile, Cl/Br ratios and δ37Cl values of brines have behaved conservatively at the basin scale and throughout basin history. [Copyright &y& Elsevier]

Although intersection zones of two or more fault arrays have been identified as favorable loci of unconformity-related basin-basement mineral deposits in previous studies, their roles in controlling fluid flow patterns related to formation of oriented-, and structurally-controlled mineral deposits remain unclear. In this study, 3-D hydromechanical models were conducted to better understand the response of a natural fault intersected by a hydraulic fault under different stress regimes. A comprehensive parametric study was carried out to assess the roles of fluid pressure, burial depth, basin permeability, intersection angle, and horizontal differential stress on the hydromechanical response of a system containing two intersecting faults. Depending on basin sediment permeability, fault intersection angle, and horizontal differential stress, the fluid flow either stops, crosses, or diverts toward natural fault. Among the tested parameters, the intersection angle, and horizontal differential stress have the most noticeable effect on the fluid flow in the system. The critical intersection angle at which the fluid flow diverts toward the natural fault varies between ≈27° in normal faulting regimes, to ≈55°, in both strike-slip and reverse faulting regimes. Conversely, burial depth and fluid pressure have no significant effect on fluid flow diversion in the intersection zone. The results are in agreement with field observations related to the unconformity-related uranium deposits found in northern Canada. [ABSTRACT FROM AUTHOR]

The relative contribution of magmatic and non-magmatic fluids to the metasomatic and ore-forming processes in iron-oxide copper‑gold (IOCG) deposits is still widely debated. In this study, the petrography, detailed composition and U Pb ages of various apatite occurrences from the Nautanen North IOCG deposit, Norrbotten, Sweden, were determined to decipher the evolution of fluid sources in the area. The hydrothermal apatite grains grow over muscovite, intergrow with magnetite, amphibole, K-feldspar, chalcopyrite and sericite, and are replaced by epidote, allanite and/or chlorite along the grain margins. Irregular patterns of the apatite grains were revealed by cathodoluminescence imaging. Fluorine in all apatite occurrences is the dominant halogen (1.62–3.58 wt%), chlorine is depleted (up to 0.34 wt%), while bromine and iodine are found in traces (0.7–72 ppm and 0.15–4.2 ppm respectively). The δ37Cl value of the apatite grains ranges between −0.8 and 3.4‰. Uranium-Pb data yield ages between 1.63 and 1.55 Ga (with one exception at 1.49 Ga showing large age errors). Textural evidences show that the apatite grains have been precipitated during the potassic alteration of the D 2 event (1.81–1.78 Ga), which is considered a regional, IOCG-related, high-temperature event. Cathodoluminescence textures reveal that all the apatite occurrences have been chemically modified by the late-stage metasomatic and ore-forming fluids during the nucleation of epidote ± allanite ± chlorite. The Br/I and δ37Cl values of the apatite grains can be considered representative of the associated fluid values and show a trend between two end-members, which indicates the contribution and progressive mixing of two different fluids during late-stage ore-related hydrothermal circulation. The ore-forming fluids were mainly issued from exsolved magmatic fluids from S-type bodies, as revealed by the strong affinity of the Br/I ratio of the ore zone with the pegmatite-related apatite. The other end-member associated with the apatite occurrences that co-exist with metasomatic assemblages, is consistent with fluids linked to evaporite dissolution. Apatite dating is interpreted to reflect resetting ages. • Halogen and δ37Cl values of apatite give insights about IOCG ore-forming fluids. • Two fluids during ore-forming and metasomatic processes at the Nautanen North deposit. • Apatite U Pb systematics have been reset. • Trace element signatures of apatite are influenced by host-rocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study focuses on apatite in the Niutitang formation. • Petrological and geochemical in-situ study helps deciphering its genesis. • A hydrothermal contribution is evidenced. • Element sources are better constrained. The Early Cambrian Mo-Ni-PGE sulphidic black shale in the Niutitang Formation on the margin of the Yangtze Craton (Southern China) is known for its extremely high metal concentrations. It is also very rich in phosphate that formed contemporaneously with the sulphides. Detailed petrological as well as in-situ trace element and Sr isotope analyses of authigenic apatite revealed new information on the metallogenesis of this enigmatic rock unit. In the ore bed, apatite forms nodules or is found in phosphatic (phoslithoclasts) and sulphide clasts. In the latter, the replacement of organic matter and sulphides by apatite microspherules suggests a microbially mediated phosphogenesis. Enrichment in middle rare earth elements emphasizes the role played by Fe-oxyhydroxides and organic matter in element scavenging. Moderately reducing conditions are supported by a lack of Ce and Eu anomalies. The trace element signature of apatite and its initial 87Sr/86Sr (0.7032–0.7190), which is - for a group of analyses - well below the signature of Lower Cambrian seawater, points to some contribution from mafic rock-sourced hydrothermal brines. This effectively explains the exceptional enrichment of Ni and PGE in the sulphides. Seawater remains, however, the preferred source for other elements such as P and Mo. [ABSTRACT FROM AUTHOR]

The world's lithium demand is currently increasing due to its use in batteries and in green energy technologies. As a consequence, Li has recently been added to the list of critical materials in Europe. Finding new deposits is necessary in order to guarantee a mid- to long-term stable supply. Granites and associated pegmatites are the primary 'hard-rock' source for Li, where it is present in a variety of aluminosilicate minerals. Li is a light element that typically occurs at low concentrations in rocks and minerals, which presents challenges for some analytical techniques (e.g., portable X-ray fluorescence) for exploration. Laser induced breakdown spectroscopy (LIBS) is a powerful analytical technique for the acquisition of simultaneous almost all elements of the periodic table. LIBS has particular sensitivity to the light elements (Z < 13) and, therefore, handheld LIBS has significant potential for the exploration of pegmatite- or granite-related Li mineralization. For this study, a suite of 16 pegmatite-hosted Li ore minerals comprising the three main aluminosilicate species (spodumene, lepidolite and petalite) that contained between 1.36 and 3.54 wt% Li was analyzed using a handheld LIBS instrument. A univariate calibration curve was developed for LIBS quantification of Li in these minerals using the strong Li emission lines at 610.36 nm and 670.79 nm (R2 > 0.9, RMSD = 0.2 wt% Li). Simultaneous quantification of Li contents and measurement of major element ratios (e.g., Si/Al) using portable LIBS permits rapid discrimination between different Li-bearing silicates, such as spodumene and petalite, that can be difficult to identify in the field on the basis of macroscopic criteria. Moreover, the detection of minor/trace elements such as Be, Rb and Cs is possible by handheld LIBS, which can provide useful information for rare metal pegmatite and granite exploration. Thus, qualitative and quantitative analysis by handheld LIBS represents a very promising approach for Li exploration. • Laser induced breakdown spectroscopy (LIBS) is a powerful technique for the analysis of the light elements (Z < 13). • Handheld LIBS provides a capability for rapid multi-element analysis in rocks and minerals. • Several Li rich-minerals were analyzed to obtain a calibration curve for Li at a limit of detection of ~0.1 ppm. • Be, Rb, and Cs were detected at limits of detection of ~20 ppm. • Li minerals can be recognized in the field using handheld LIBS. [ABSTRACT FROM AUTHOR]

Abstract: Isotope analyses (K–Ar, δ 18O and δD) were performed on illite from both the sandstone cover and the underlying basement, close to and distant from Shea Creek, an unconformity-type U deposit (Athabasca Basin, Canada); the illite had previously been characterized crystallographically. In the barren areas away from deposit, illite is mainly of the cis-vacant 1M polytype occurring as relatively coarse-grained lath-shaped particles, while it occurs as fine-grained particles of the trans-vacant 1M type next to and in the U mineralized strata. The tectonic-induced hydrothermal system that favored illite crystallization was multi-episodic 1453±2, 1330±20 and probably about 1235Ma ago. These illite-forming episodes appear to have occurred contemporaneously to those favoring the concentration of the associated U oxides, which were dated independently by the U–Pb method in the Shea Creek deposits and elsewhere in the Athabasca Basin. No relationship was found between the illite polytypes and their crystallization ages, meaning that precipitation of each, either as the cis-vacant or the trans-vacant type, did not relate to a specific event, but to variable physical and chemical crystallization conditions during the same event. The change in the contemporaneous illite polytypes appears to relate to an increase in the δ 18O with distance to the U deposit. Such a change could result from a progressively lower formation temperature with increasing distance to the U deposit, probably combined to a changing δ 18O of the interstitial fluids due to variable water–rock interactions in the rocks. Variable water–rock ratios could have resulted from variable tectonic adjustments of the basement. The authors are inclined to believe that the cis-vacant 1M type crystallized from chemically different fluids, at slightly lower temperatures and away from U concentrations than the equivalent trans-vacant 1M type detected next to the U ores, both precipitating contemporaneously within analytical uncertainty. In addition, comparison of the δD of the hydroxyls from cis-vacant and trans-vacant types suggests that the illite mineral structure was not affected by radiation related to radioactive decay within the deposit or by further natural alteration, as advocated for other occurrences. [Copyright &y& Elsevier]