The large range of Rb and Sr mass fractions in natural micas presents a challenge for LA-ICP-MS/MS Rb-Sr geochronology. Mica with disparately high Rb and low common Sr mass fractions are particularly problematic given the limited linear dynamic range (1-2 & times; 10(6) cps) of ICP-MS/MS systems. Here we quantify sources of uncertainty and inaccuracy associated with the in situ Rb-Sr method, including assessing laser-ICP-MS/MS timing issues, evaluating statistical bias at low count rates and quantifying non-linearity of the electron multiplier between pulse and analogue detection. These considerations are tested on natural mica with high Rb-87/Sr-86 ratios (> 1000), including ca. 92 Ma biotite (Tombstone pluton, Yukon) and ca. 2620 Ma muscovite (Tanco pegmatite, Manitoba), with Rb mass fractions of ca. 2300 and 30000 mu g g(-1), respectively. Our results highlight the importance of: (1) optimising analytical parameters (e.g., laser energy, spot size), (2) potential application of non-linearity corrections for high Rb signals and (3) judicious selection of data reduction methods (e.g., signal integration methods, incorporating all sources of uncertainty, error correlation) for the determination of precise and accurate Rb-Sr ages. With these considerations in mind, in situ Rb-Sr measurements of Tombstone and Tanco mica yielded isochron ages within similar to 1% of their accepted Rb-Sr TIMS ages.

Recovering geological samples from the deep basins and ridges of the central Arctic Ocean presents significant challenges because of remote access and thick ice cover. During the 2016 Canada-Sweden Polar Expedition to the Arctic Ocean, volcaniclastic breccia was dredged from the Alpha Ridge, part of an underwater mountain chain extending from the Canadian polar margin to the Siberian shelf. Argon geochronology of plagioclase crystals within glassy lava fragments dates the sample to 90.4 ± 0.26 Ma. The geochemical composition of basalt clasts in the volcaniclastic breccia closely resembles that of igneous rocks from the High Arctic Large Igneous Province suggesting that the Alpha Ridge was an active volcanic feature within the circum-Arctic in the Late Cretaceous. Our results support lava–water interactions in a littoral environment, driven by the growth and emergence of a central igneous platform and accompanied by eruptive activity at constructional volcanic edifices along its margins. Fresh basaltic glass preserved in a sample of volcanic breccia record a single eruptive event at the Alpha Ridge around 90 Ma, suggesting that parts of the ridge were emergent during the final stages of magmatism in the High Arctic Large Igneous Province, according to geochemical and geochronological analysis of the sample.

This study explores the application of machine learning techniques for an enhanced interpretation of pyrite laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) maps. The Colosseum Au deposit, in southern California, was considered as a case study. Colosseum is genetically related to a rhyolitic breccia-pipe complex, where Au mineralization is associated with two main pyrite generations—early pyrite and late pyrite. Our machine learning workflow involves the detection of distinct compositional zones in individual maps through unsupervised clustering, and a second clustering step where these zones are grouped by compositional similarity, enabling the direct comparison between different maps and providing a compositional overview of pyrite representative of the various styles of mineralization present in the deposit. Clustering of individual maps correctly differentiated between distinct growth zones in early pyrite, fractures that crosscut early pyrite growth, and zones of late pyrite growth, matching petrographic observation. All the zones detected by this first step, in turn, were classified into two compositionally distinct groups and a third transitional group, enabling the direct comparison between maps while keeping petrographic consistency. For Colosseum, our approach revealed that (1) Au is more abundant in late pyrite than early pyrite, but significant amounts can be found in both generations and in both Colosseum mineralized breccia pipes; (2) the transition from early to late pyrite is represented by a change from a Co-Ni-Te–rich end member to a Cu-Ag-Zn-Sb-Tl–rich end member; and (3) Au is directly correlated with As in both pyrite generations.

ABSTRACT Integrated field mapping, phase equilibria modelling and in situ U–Pb monazite geochronology from the northern margin of the Rae craton on Baffin Island document three metamorphic events during the Neoarchean to the middle Paleoproterozoic. The Qimivvik area comprises Neoarchean tonalitic gneiss structurally juxtaposed over Neoarchean metasedimentary rocks along the Paleoproterozoic Qimivvik thrust and associated shear zone. High‐grade metamorphism at ca. 2.56–2.50 Ga supports a footprint for cryptic late Neoarchean metamorphism over a distance of ∼600 km along the northwestern Rae margin from southern Boothia Peninsula to northern Baffin Island. Thermal peak mineral assemblages in the Qimivvik area equilibrated at ca. 1.9 Ga at conditions of ~710°C–790°C and 4.3–5.5 kbar. The dominant Paleoproterozoic foliation is defined by peak metamorphic phases and is reoriented by folds related to the Qimivvik thrust. Peak metamorphism and associated deformation, including the Qimivvik thrust, are interpreted as a manifestation of the Ellesmere‐Inglefield belt of Ellesmere Island and West Greenland, which links with the ca. 1.9 Ga Thelon orogen of western Canada. Partial melting also occurred at ca. 1.8 Ga, possibly resulting from decompression of the Churchill domain following the collisional‐accretionary events related to the late stages of amalgamation of Laurentia and supercontinent Nuna. Quantitative trace element maps (acquired using LA‐ICP‐MS) of monazite reveal distinct trace element signatures associated with each of three growth stages. Ca. 2.5 Ga monazite exhibits complex intragrain compositional zoning, has elevated Y and heavy rare earth elements (HREEs) relative to ca. 1.9 Ga monazite and has higher Th/U overall than both ca. 1.9 Ga and ca. 1.8 Ga monazite. These signatures suggest that ca. 2.5 Ga monazite growth was concomitant with partial melting and preceded the majority of garnet growth. The ca. 1.9 Ga monazite grains are comparatively less zoned and have lower Y + HREE contents than both ca. 2.5 Ga and 1.8 Ga monazite, consistent with the ca. 1.9 Ga monazite forming after most garnet growth. Elevated Y + HREE in the ca. 1.8 Ga monazite imply that it formed after retrograde resorption of garnet rims. In our samples, Y + HREE generally exhibit stronger correlations with monazite age and/or petrographic context than Eu/Eu* and Th/U. As some compositional overlap exists between monazite of different ages and petrographic contexts, quantitative limits (‘cut‐offs’) based on trace element concentrations or ratios (e.g., Th/U, Eu/Eu*, La CN /Yb CN ) are unreliable for distinguishing between monazite populations. In addition to providing important constraints on the early tectonic evolution of northeastern Laurentia, our study offers new insights into trace element behaviour in a key accessory mineral during three metamorphic events occurring over a ~700 Ma time period.

The crystal growth history of an Au-rich sedimentary pyrite nodule from the Timmins-Porcupine Au camp, Ontario, Canada, has been investigated using Electron Backscattered Diffraction and Laser Ablation Inductively Coupled Plasma Mass Spectrometry techniques to study the crystallographic processes controlling metal deportment in the pyrite structure. Results show four distinct growth stages characterized by different pyrite microstructures, crystal forms and trace element compositions. A direct link is observed between the growth of octahedral facets in pyrite and the development of primary (non-tectonic) subgrain boundaries. Furthermore, zones with a high abundance of subgrain boundaries have the highest Au, As, Ag and Cu (and other metals) contents - suggesting metal distribution is linked to the development of microstructures. Finer-grained aggregates are characterized by higher grain boundary density than in coarse areas, making higher trace element concentrations inversely proportional to grain size. Our results indicate that the high Au concentrations (similar to 100 ppm) in pyrite represent a primary feature related to nodule growth, instead of secondary enrichment processes, and highlight the possibility that sediment-hosted pyrite nodules could represent a metal-rich geochemical reservoir for the formation of younger orogenic Au deposits.

The Archean Horne 5 deposit, located in the Rouyn-Noranda district in the southern Abitibi greenstone belt, Canada, contains a total resource of 172.4 t Au (5.6 Moz) from 112.7 Mt of ore grading at 1.53 g/t Au. The deposit is part of the Au-rich Horne volcanogenic massive sulfide (VMS) complex that also includes the past -producing Horne mine (i.e., the Upper and Lower H zones plus small subsidiary lenses) that yielded 325.4 t Au (10.5 Moz Au) from 53.7 Mt of ore grading at 6.06 g/t Au. Combined, the Horne mine and Horne 5 deposit contain similar to 500 t Au (16 Moz), making them the world's single largest accumulation of VMS-related Au. The Horne 5 deposit consists of stacked lenses of massive to semimassive sulfides alternating with extensive zones of disseminated and stringer sulfides. The mineralization is hosted within thick accumulations of steeply dipping dacitic to rhyodacitic volcaniclastic units of transitional to calc-alkaline magmatic affinity. Dacitic-rhyo-dacitic synvolcanic units (lobes, sills, and/or domes) intrude the host succession, which is also crosscut by a series of post-ore mafic and younger intermediate to felsic feldspar +/- quartz porphyry dikes. A broad and diffuse halo of distal sericite-chlorite-epidote alteration extends outboard of intensely sericite-altered zones proximal to the sulfide lenses. Gold is interpreted to be synvolcanic on the basis of Au-rich mas-sive sulfide clasts in the volcaniclastic units, the presence of preserved Au-rich primary pyrite, Au zones limited to the sulfide envelope, crosscutting deformed but unaltered and barren dikes, and the absence of typical syn-deformation, orogenic-style alteration and mineralization despite overprinting high-strain corridors and faults. Gold is spatially associated with pyrite, sphalerite, and chalcopyrite, and its distribution is largely controlled by the higher porosity and permeability of the volcaniclastic host rocks, which are interpreted to have facili-tated hydrothermal fluid circulation in the subseafloor environment. Synvolcanic intrusions and fine-grained tuffs overlying auriferous zones also influenced the distribution of the mineralization by acting as cap rocks to ascending fluids. Evidence suggests that Au enrichment at the Horne 5 deposit is due to efficient transport and precipitation of Au in the subseafloor environment, a favorable geodynamic setting (transitional to calc-alkaline magmatism over thick crust), and possible input of magmatic fluids as suggested by high Te and Cu in the mineralization. Minor and very local remobilization of metals occurred in response to regional deformation and associated greenschist facies metamorphism. The detailed study of the Horne 5 deposit geology and a review of the available information on the Horne mine and recent 3-D modeling indicate that the Horne 5 deposit may have formed higher in the stratigraphy than the Upper and Lower H orebodies of the former Horne mine, which originally formed a single lens. Therefore, the Horne Au-rich VMS complex originally formed as a stacked system in which the Horne 5 deposit was deposited above the Upper and Lower H zones and not in a distal or lateral position as previously proposed, indicating that a robust hydrothermal system was responsible for the formation of the world's largest Au-rich VMS complex.

Cannabis vaping involves the vaporization of a cannabis vaping liquid or solid via a vaping accessory such as a vape pen constructed of various metals or other parts. An increasing number of reports advocate for expansion of the testing and regulation of metal contaminants in cannabis vape liquids beyond the metals typically tested such as arsenic, cadmium, mercury, and lead to reflect the possibility of consumers' exposure to other metal contaminants. Metal contaminants may originate not only from the cannabis itself but also from the vape devices in which the cannabis vape liquid is packaged. However, metal analyses of cannabis vape liquids sampled from cannabis vaping devices are challenged by poor precision and reproducibility. Herein, we present data on the metal content of 12 metals in 20 legal and 21 illegal cannabis vape liquids. The lead mass fraction in several illegal samples reached up to 50 μg g-1. High levels of nickel (max 677 μg g-1) and zinc (max 426 μg g-1) were found in illegal samples, whereas the highest copper content (485 μg g-1) was measured in legal samples. Significant differences in metal mass fractions were observed in the legal cannabis vape liquid taken from two identical devices, even though the liquid was from the same lot of the same cannabis product. Metal particles in the vape liquids were observed by scanning electron microscopy, and laser ablation inductively coupled plasma mass spectrometry confirmed the presence of copper-, zinc-, lead-, and manganese-bearing particles, metals that are in common alloys that may be used to make vape devices. Colocalized particles containing aluminum, silica, and sodium were also detected. These results suggest that metal particles could be a contributing factor to poor measurement precision and for the first time, to the best of our knowledge, provide evidence of metal particles in cannabis vape liquids contained in unused cannabis vape pens.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb dating of hydrothermal calcite associated with the waning stage of mineralization is used to constrain the age of Neoproterozoic-hosted Carlin-type gold deposits in central Yukon, Canada. Samples exhibiting minor textural complexity show low dispersion of individual spot analyses and define Tera-Wasserburg lower intercept ages between 75.1 ± 2.5 and 71.2 ± 4.3 Ma. Samples with U-rich microfractures and/or a second generation of calcite associated with vein reopening record the primary stage of calcite growth related to hydrothermal activity at ca. 74 Ma and a younger ca. 48 Ma event related to fluid-assisted U mobility. The minimum age for mineralization at ca. 74 Ma overlaps with a maximum age based on a zircon U-Pb date of 74.1 ± 1.0 Ma for a gabbro dike that is locally altered and mineralized. These time constraints indicate that mineralization is ca. 74 Ma and penecontemporaneous with dike emplacement. Furthermore, mineralization is contemporaneous with a regional gold-bearing, intrusion-related, metallogenic event in eastern Alaska and central Yukon. This temporal link between Carlin-type mineralization and other mineralization types bears similarities with world-class sedimentary rock-hosted gold deposits of Nevada. This study demonstrates the potential of using LA-ICP-MS U-Pb dating on calcite to constrain the age of mineral deposits lacking synmineralization minerals amenable to classic dating techniques.

The trace element composition of detrital magnetite grains recovered from six local streams around the Casino high-grade porphyry Cu–Au–Mo deposit, west-central Yukon, is compared with igneous and magmatic-hydrothermal magnetite recovered from mineralized and unmineralized host rocks at the deposit. Linear discriminant analysis of 12 elements (Mg, Al, Ti, V, Mn, Co, Cr, Ni, Cu, Zn, Ga and Ge) and plots of Ti v. Ni/Cr are used to discriminate between magmatic-hydrothermal magnetite from the potassic alteration zone and igneous magnetite from granodiorite and quartz monzonite hosting the deposit. Magmatic-hydrothermal magnetite with a trace element composition similar to that from the potassic alteration zone at Casino is identifiable in stream sediments draining the deposit. Copper in magmatic-hydrothermal magnetite, present as minute inclusions of sulfide minerals such as chalcopyrite or substituted within the magnetite crystal lattice, is a strong indicator of Cu mineralization. We show that the chemical compositions of magnetite recovered from stream sediments can be used to explore for porphyry systems. Thematic collection: This article is part of the Applications of Innovations in Geochemical Data Analysis collection available at: https://www.lyellcollection.org/cc/applications-of-innovations-in-geochemical-data-analysis Supplementary material: Laser ablation data for major, minor and trace elements in magnetite from bedrock and stream sediment samples from Casino are available at https://doi.org/10.6084/m9.figshare.c.5896900

The Proterozoic Athabasca Basin hosts a large number of high-grade, large-tonnage unconformity-related uranium (U) deposits, many of which are also enriched in rare earth elements (REE). The basin also contains hydrothermal REE mineralization unassociated with U. Previous studies postulated that U and REE were derived from either the basin or the basement; however, the exact source of the metals remains ambiguous. This study provides evidence of U- and REE-rich fluids throughout the Athabasca Basin through laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) mapping of barren sandstone distal to mineralized areas. The results indicate that elevated U and REE concentrations mainly occur in the matrix; there are strong positive correlations between U and REE, Th, P and Sr, and moderate positive correlations between U and Zr, Ba, Fe, Al, K and Ca, but the few spots with the highest U are unrelated to these elements. Quantitative evaluation of the element correlations, together with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis, suggests that most of the elevated U and REE are hosted in aluminum phosphate sulfate (APS) minerals rather than apatite and monazite. As the APS minerals are of diagenetic-hydrothermal origin, the results testify to the presence of U- and REE-rich fluids within the Athabasca Basin. The elevated Th/U ratio (~10) and REE pattern (strong heavy rare earth element (HREE) depletion) are consistent with a model in which large amounts of U and REE (especially HREE) were leached from the sandstone within the Athabasca Basin and contributed to U and REE mineralization near the unconformity between the sedimentary rocks in the basin and underlying basement rocks. This study demonstrates that LA-ICP-MS mapping can be effectively used to evaluate microscale distribution of elements and their mobility in sedimentary rocks to address mineralization related problems.

The distribution of precious metals in intermediate sulfidation (IS) epithermal systems remains a subject of limited understanding and, as such, contributes a possible metallurgical risk during its processing and recovery. A combination of empirical (field observations, drill core logging, petrography) and quantitative analytical (LA-ICP-MS element mapping of sulfides) methods are used to investigate ore genesis and sulfide modification at the well-preserved Late Cretaceous Klaza deposit in Yukon, Canada. A workflow utilizing unsupervised machine learning methods (K-means clustering and principal component analysis (PCA)) is established to interrogate raster datasets generated from the (often underutilized) laser ablation maps and to quantify and assess elemental relationships in the data. This workflow was successful in: (1) automating the filtration of pixels unrelated to the mineral of interest from the element maps; (2) differentiating between primary growth-related features from secondary late features (PC1); and (3) producing "feature maps" that depict these textural relationships for comparison with the element maps. Results suggest four distinct stages: (1) primary Au was deposited as solid-solution (Au1+) in early arsenopyrite and arsenian pyrite during cooling of a magmatic fluid, whereas Ag was deposited later (with Zn-Pb sulfides) as a result of further cooling and dilution of this fluid with its concentration in sulfosalts and galena; (2) a later, higher temperature, chalcophile element-rich (Ag-Cu-Bi-Pb-Sn-Sb-As), and higher-sulfidation state fluid of likely magmatic origin overprinted the earlier Klaza system; (3) addition of Cu and liberation of earlier lattice-hosted Au (and other impurities) from the arsenian pyrite and arsenopyrite to form particulate Au (Au0); and (4) purification of the sulfides with coupled re-concentration of Au-Ag-Bi-Pb as inclusions during zone refining in the epithermal realm. The results of this study have significant impacts on the understanding of metal deportment, ore formation, and the economics of IS epithermal systems.

The cold, rigid, and melt-depleted mantle underlying Archean cratons plays an important role in the preservation of the overlying continental crust and is one of the main sources of diamonds. However, with the possible exception of rare earth elements (REE) and platinum group-elements (PGE), the concentrations and host mineral phases for many other critical trace elements within lithospheric mantle remain very poorly understood. Here we address that knowledge gap, presenting new electron microprobe and laser-ablation inductively-coupled-plasma mass-spectrometry results for a suite of mantle xenoliths (n = 12) and olivine xenocrysts (n = 376) from the Jericho, Muskox, and Voyageur kimberlites (northern Slave craton, Canada). Low-temperature (<1000 °C) harzburgite xenoliths and olivine xenocrysts suggest that the shallowest portions of the garnet-bearing mantle (≤160 km) underlying the northern Slave craton is chemically depleted and becomes increasing re-fertilized from 160 to 200 km. High-temperature (>1000 °C) garnet and clinopyroxene crystals with Ti/Eu ratios > > 1000, and olivine xenocrysts suggest that interaction with ultramafic silicate melts is the most likely mechanism to re-fertilize melt-depleted peridotite with incompatible elements toward the base of the lithosphere (~200 km). In contrast, lower temperature garnet and clinopyroxene with Ti/Eu ratios <1000 are more likely related to metasomatism by carbonatitic melts and/or fluids. Carbonatitic metasomatism is also interpreted as the preferred explanation for the trend of Nb (4 ppm)- and Ta (185 ppb)-rich concentrations of olivine xenocrysts sampled from mid-lithosphere depths (~140 km). With the exception of a few elements that substitute into the olivine crystal structure during sub-solidus re-equilibration (e.g., Ca, Cr, Cu, Na, Sc, V, Zn), most other olivine-hosted trace elements do not systematically vary with depth. Instead, we interpret olivine-hosted trace element concentrations that are significantly above the analytical detection and/or quantification limits to reflect trapped fluid (e.g., As, Mo, Sb, Sn), base-metal sulphide (e.g., Ag, Au, Bi, Pd, Pt, Se, Te), and other mineral inclusions (e.g., U, Th) rather than enrichments of these elements due to substitution reactions or analytical artefacts. We interpret that these inclusions occur in olivine throughout the garnet stability field, but are relatively rare. As a result, these trapped carbonatitic, proto-kimberlite, and/or other ultramafic silicate melts do not represent a significant source for the suite of trace elements that become enriched to economic levels in the crust.

Garnet crystallization has been simulated in the MnNCKFMASHT model system using a simple nucleation and growth scenario, calibrated with three‐dimensional garnet crystal size distribution data as well as garnet compositional data obtained by electron probe micro‐analysis and laser ablation inductively coupled plasma mass spectrometry. Results indicate wide‐spread Barrovian‐type metamorphism for garnet‐zone rocks from the Snowcap assemblage along a hairpin‐shaped pressure–temperature loop with garnet growth from ~515°C and 4 kbar to metamorphic peak conditions of ~600°C and 6 kbar. Lu–Hf garnet‐whole geochronology points to initial garnet growth at c. 192.2 ± 4.7 Ma. Sm–Nd garnet–whole‐rock geochronology applied to a sample with garnet rims enriched in Sm indicates that the metamorphic peak conditions have been attained at c. 172.9 ± 2.4 Ma. Older garnet growth at c. 245.3 ± 0.8 Ma during a low‐P–high‐T event has been preserved as garnet cores separated from the Jurassic garnet rims by a sharp microstructural and compositional discontinuity. These polyphase garnets are restricted to Mn‐rich metapelitic lithologies. Trace element zoning in the outermost ~50 μm thin segments of the Early Triassic garnet cores reflects a short garnet growth episode in the presence of melt at peak conditions of ~710°C and 2.5 kbar, supported by phase equilibrium and diffusion geospeedometry calculations. Diffusion simulations across the interface between the Early Triassic garnet core and the Jurassic garnet rim indicate that the Barrovian‐type metamorphism during the Jurassic lasted for 20–25 Myr, in line with the radiometric data.

Laser ablation inductively coupled plasma multi-collector mass spectrometry (LA-MC-ICP-MS) allows rapid, in situ, highly precise measurements of Cu isotope ratios of native Cu and Cu-bearing minerals. However, the National Institute of Standards and Technology Cu-metal isotope standard NIST SRM976 that is commonly used to calibrate LA-MC-ICP-MS Cu isotope measurements of native Cu is no longer available. We have investigated the suitability of four Cu metal materials, SSC-1, SSC-3 and SSC-4 (cathode Cu metal rods) and CUPD-1 (Cu anode sawings), originally developed by the Canada Centre for Mineral and Energy Technology (CANMET) as certified reference materials for trace element analysis, as Cu isotope reference materials for LA-MC-ICP-MS analysis and solution nebulization (SN) of Cu. The Cu isotopic composition and homogeneity of these four materials were characterised by SN- and LA-MC-ICP-MS, and are reported for the first time. The bulk Cu isotopic compositions, expressed as δ65CuSRM976 in per mil (‰) relative to NIST SRM976 with combined uncertainties (U, k = 2), of SSC-1, SSC-3 and SSC-4, determined utilizing SN-MC-ICP-MS, are identical within analytical uncertainty at 0.03 ± 0.07‰ (n = 29), 0.04 ± 0.04‰ (n = 28), and 0.05 ± 0.08‰ (n = 29), respectively; the composition of CUPD-1 is 2.14 ± 0.08‰ (n = 28). The compositions are 0.01 ± 0.07‰ (n = 29), 0.04 ± 0.06‰ (n = 29), 0.03 ± 0.06‰ (n = 28) and 2.15 ± 0.06‰ (n = 28), respectively, relative to the European Reference Material ERM®-AE633 Cu isotope standard. The Cu isotope homogeneity of the four new reference materials was assessed by determining whether multiple individual in situ Cu isotope measurements made by LA-MC-ICP-MS analysis (43 µm spot size), using each of the other three reference materials as a calibrator, approximate a single normal distribution. We also investigate whether there are statistically significant differences between the mean δ65Cu values of three independent data sets for each of the Cu isotope reference materials using one-way analysis of variance (ANOVA). Normality tests (graphical assessment of normal distribution quantile-quantile plots, and the Shapiro-Wilk, Jarque-Bera and reduced chi-squared statistic tests) show that: 1) the Cu isotope data acquired on SSC-1, SSC-3, SSC-4 and CUPD-1 do not depart significantly from a normal distribution, 2) the scatter of the Cu isotope data is due to analytical uncertainty with 95% confidence, and 3) there are no other significant sources of scatter; e.g. heterogeneity of the reference materials. The results of one-way ANOVA reveal that the mean difference of the δ65Cu value for each of the reference materials SSC-1, SSC-3, SSC-4 and CUPD-1 is statistically not significant at the 0.05 level. The mean δ65CuSRM976 values with combined uncertainties (U, k = 2) of SSC-1, SSC-3, SSC-4 and CUPD-1, determined by LA-MC-ICP-MS using each of the other three reference materials as a calibration standard, are 0.03 ± 0.09‰ (n = 132), 0.05 ± 0.09‰ (n = 154), 0.03 ± 0.09‰ (n = 144) and 2.14 ± 0.10‰ (n = 106), respectively. These values are in agreement with those determined by SN-MC-ICP-MS analysis at the 95% confidence level and have excellent precision (2 s.d. ≤ 0.10‰). These results suggest that SSC-1, SSC-3, SSC-4 and CUPD-1 can be considered isotopically homogeneous at a spatial resolution of 43 μm, and they are suitable reference materials for calibration and quality control of in situ and solution nebulization Cu isotope analyses of Cu.

There is increasing acceptance of the presence of variable magmatic contributions to the mineralizing fluids in the formation of volcanogenic massive sulfide (VMS) deposits. The world-class Windy Craggy Cu-Co-Au deposit (>300 MT @ 2.12 wt% Cu) in northwestern British Columbia is of interest because, unlike most VMS deposits, fluid inclusions in quartz from within the deposit range from relatively low to intermediate salinity (most 6–16 wt% equivalent). In this study we used an excimer (193 nm) laser ablation system interfaced to a quadrupole inductively coupled plasma mass spectrometer to quantify key metals and metalloids that are considered by many to be indicative of magmatic contributions to hydrothermal ore deposits. Although LA-ICP-MS signals from these low-salinity inclusions are highly transient, we were able to quantify Na, Mg, K, Ca, Mn, Fe, Co, Cu, Zn, Sr, Sn, Ba, Ce, Pb and Bi consistently – of the 34 elements that were monitored. Furthermore, Cl, Sb, Cd, Mo, Rb, Br and As were also measured in a significant number of inclusions. Comparison of the fluid inclusion chemistry with unaltered and altered mafic volcanic and sedimentary rocks and mineralized samples from the deposit indicate that enrichment in the main ore metals (Cu, Zn, Fe, Pb) in the inclusions reflects that of the altered rocks and sulfides. Metals and metalloids that may indicate a magmatic contribution typically show much greater enrichments in the fluid inclusions over the host rocks at the same Cu concentration; in particular Bi, Sn and Sb are significantly elevated when compared to the host rock samples. These data are consistent with the ore-forming fluids at Windy Craggy having a strong magmatic contribution. Supplementary material: fluid inclusion data for temperature of homogenization and salinity, and full analytical results for laser ablation ICP-MS analyses of individual inclusions for the two analytical sessions are available at https://doi.org/10.6084/m9.figshare.c.5443094

The mineralogy and chemical composition of native gold from twenty-seven representative orogenic gold deposits were investigated using optical microscopy, electron probe microanalysis (EPMA), and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Minor elements, such as Ag and Cu, occur in solid solution, while trace elements, such as Fe, As, S, Hg, form impurities or micro inclusions in native gold. Partial least squares-discriminant analysis (PLS-DA) has identified compositional characteristics based on mineral association, gold texture and dominant country rocks. Gold grains are commonly associated with pyrite, arsenopyrite, chalcopyrite, pyrrhotite, and tourmaline in the studied orogenic deposits. Chemical variations in gold with different associated mineral assemblages are related to the partitioning of trace elements between co-crystalizing minerals and gold during precipitation. Gold inclusions in gangue minerals are discriminated from later gold in fractures based on contents of Ag, Fe, Pb, and Bi, which indicates that gold in different paragenetic stages of mineralization can be identified using its trace element signature. Gold hosted in different regional country rocks can be discriminated by Ag, Cu, Pd, Sb, and Hg, likely because of reactions of hydrothermal fluids with the regional country rocks along the fluid flow paths.

This study presents results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) elemental analysis of scattered dolomite crystals in the Upper Ordovician Utica Shale of southern Québec to investigate the geochemical cause(s) of color variation in dolomite fluorescence and its possible relationship to thermal maturity. Utica Shale dolomite crystals show fluorescence zonation under ultraviolet (UV) light, with a shift from higher red/green quotient (R/G) in the crystal core to lower R/G in the crystal rims within dolomite crystal, while the crystal cores and rims R/G consistently increase with increasing thermal maturity.The LA-ICP-MS results show a consistent increase of Fe, Mn, Sr, Pb, and rare earth elements (REE) from crystal cores to rims, while Mg content shows the opposite trend. The decline in Mg content from the core to rim suggests depletion of Mg in the dolomitizing fluids during dolomite growth. Iron and Fe/Mn ratio are the only parameters that varied systematically with Mg content. The negative correlation between the red/green (R/G) quotient and Fe/Mn ratio suggests that temperature likely had an overarching effect on the chemistry of dolomite that ultimately controls the crystal zonation and its optical properties.Our data suggest that dolomite fluorescence can potentially be used as an alternative thermal maturity indicator in mudrocks with low organic content. However, compilation of a larger dataset is required to completely understand the relationship between dolomite R/G quotient and other established thermal maturity indicators.

ABSTRACT The use of zircon in the dating of geological processes and tectonic events has become a standard approach in many aspects of Earth science research. As a result, understanding how zircon interacts with aqueous fluids during metasomatism has become increasingly important. The alteration of natural zircon is driven primarily by coupled dissolution–reprecipitation or by ion-exchange with an aqueous fluid. In this study, whole and intact, euhedral light-brown zircon crystals (100–250 μm in length; 2 mg) from the Oligocene Fish Canyon Tuff (FCT) were experimentally reacted with an alkali-bearing reactive fluid and a REE + P source (0.5 mg CePO4 or 0.5 mg YPO4). Experiments were conducted in sealed Au metal capsules at 350 °C and 100 MPa for 182 days. During the experiment, the zircon became colorless, indicating annealing of the radiation damage in the crystal. Two-dimensional element maps of the outermost 3 μm of unpolished zircon crystal surfaces were produced using a grind of contiguous 7 μm analytical spots via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The chemical maps indicate that the surface of the zircon crystals from each experiment heterogeneously reacted with the fluid, such that the Ce and Y concentration of chemically modified areas increased (by an order of magnitude) in the CePO4-bearing and YPO4-bearing experiments, respectively, when compared with the chemical maps of unaltered zircon grain surfaces. Helium ion microscopy of polished crystals revealed discontinuous micron-scale altered domains at the crystal margin, consistent with the findings of the unpolished mapping technique. Interestingly, the Th and U concentration of the altered zircon grain surfaces were consistent with the unaltered zircon regardless of the experiment. Incorporation of REEs on the zircon grain surface likely occurred via the coupled substitution REE3+ + P5+ ↔ Zr4+ + Si4+. The results from these experiments imply that the surfaces of minimally metamict zircon can be chemically modified by alkali-bearing fluids via ion exchange under lower greenschist pressures and temperatures over relatively short time periods with respect to the geological time scale.

The lithospheric mantle should be depleted in base- and precious-metals as these elements are transferred to the crust during partial melting. However, some melt-depleted mantle peridotites are enriched in these ore-forming elements. This may reflect re-fertilization of the mantle lithosphere and/or sequestering of these elements by residual mantle phase(s). Both processes remain poorly understood because of the low abundances of incompatible elements in peridotite and the nugget-like distribution of digestion-resistant mantle phases that pose analytical challenges for conventional geochemical methods. Herein we report new major and trace element concentrations for a suite of mantle peridotite and pyroxenite samples from the Late Permian to Middle Triassic Nahlin ophiolite (Cache Creek terrane, British Columbia, Canada) using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) analysis of nanoparticulate powders and olivine. Compatible to moderately incompatible element concentrations suggest that Nahlin ophiolite peridotites represent residues after >= 20% melt extraction. Pyroxenite dykes and replacive dunite bands are folded and closely intercalated with residual harzburgite. These field relationships, coupled with the presence of intergranular base metal sulphide, clinopyroxene and Cr-spinel at the microscale, point to percolating melts that variably re-fertilized melt-depleted mantle peridotite. Radiogenic Pb (Pb-206/Pb-204 = 15.402-19.050; Pb-207/Pb-204 = 15.127-15.633; Pb-208/Pb-204 = 34.980-38.434; n = 45) and Os (Os-187/Os-188 0.1143-0.5745; n = 58) isotope compositions for a subset of melt-depleted peridotite samples further support metasomatic re-fertilization of these elements. Other ore-forming elements are also implicated in these metasomatic reactions because some melt-depleted peridotite samples are enriched relative to the primitive mantle, opposite to their expected behaviour during partial melting. New LA-ICPMS analysis of fresh olivine further demonstrates that a significant proportion of the highly incompatible element budget for the most melt-depleted rocks is either hosted by, and/or occurs as trapped inclusions within, the olivine-rich residues. Trapped phases from past melting and/or re-fertilization events are the preferred explanation for unradiogenic Pb isotope compositions and Paleozoic to Paleoproterozoic Re-depletion model ages, which predate the Nahlin ophiolite by over one billion years.

Measurement of ng g−1 amounts of Rh and Pd in Cu-rich minerals by LA single quadrupole and tandem MS ICP-MS, using He collision gas and (NH3)/He (10%/90%) reaction gas, respectively, to attenuate CuAr interferences on 103Rh and 105Pd.