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This study aimed to synthesise and interpret stable isotopic data (δ2H and δ18O) from various sources to understand the isotope hydrology around coal mine operations in Elk Valley, B.C., Canada. The data, including precipitation, groundwaters, seeps, and mine rock drains, were used to construct a local meteoric water line (LMWL) for the Elk Valley, evaluate the spatiotemporal isotopic composition of its groundwater, and assess mine seepage and mine rock drain discharge. The study revealed a robust LMWL relation (δ2H = 7.4 ± 0.2 · δ18O – 4.3 ± 4.1). The groundwater and seep data indicated a winter season bias and a north–south latitudinal gradient, suggesting rapid near-surface groundwater flow without significant post-precipitation evaporation. Porewater isotope samples from unsaturated mine rock piles (MRPs) showed site-specific evaporation patterns, potentially due to convective air flows or exothermic sulphide oxidation. This research revealed the influence of groundwater and meltwater on rock drain discharge. Based on evaporative mass balance calculations, MRPs seasonally contributed ca. 5 %(December base flow) and 22 % (snowmelt) to drain discharge. The findings underscore the value of stable isotope data collections in the Elk Valley to help better define and quantify the hydrology–hydrogeology, including a better understanding of evaporative conditions in MRPs. [ABSTRACT FROM AUTHOR]

The package PbIso is a free and open R toolbox for commonly used calculations and plots of Pb–Pb isotope data and for generating Pb evolution models. In this paper, we review Pb isotope systematics and the calculations that are commonly used, such as model age, model source μ (238U/204Pb), time-integrated κ (232Th/238U), and initial Pb isotope ratios. These equations are implemented into R functions in the package PbIso. In addition, functions are provided for generating Pb evolution models, paleoisochrons, and isochrons. This allows users to apply calculations to their data in a straightforward way while providing transparency and flexibility of the calculations used. We have implemented some basic features of the PbIso package into an online shiny R application (see https://shereearmistead.github.io/software/pbiso), which makes it easy for users without any R experience to use these calculations with their own data and to generate plots. We have provided a case study from the Superior Province in Canada, showing how different Pb evolution models can be generated in PbIso and compared to Pb isotope data. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Water Resources Journal / Revue Canadienne des Ressources Hydriques is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Current deposit is hosted by serpentinized peridotite that intruded rocks of the Quetico Subprovince in the Midcontinent Rift, and is subdivided into three morphologically distinct regions — the shallow and thin Current–Bridge Zone in the northwest, the deep and thick 437–Southeast Anomaly (SEA) Zone in the southeast, and the thick Beaver–Cloud Zone in the middle. The magma parental to the Current deposit became saturated in sulfide as a result of the addition of external S from at least two sources — a deep source characterized by high Δ33S (< 3‰) values, and a shallow source, potentially the Archean metasedimentary country rocks, characterized by low Δ33S (< 0.3‰). Variations in Δ33S–S/Se–Cu/Pd values indicate that the contamination signatures were largely destroyed by interaction of the sulfide liquid with large volumes of uncontaminated silicate melt. The intrusion crystallized sequentially, with the Current–Bridge Zone crystallizing first, followed by the Beaver–Cloud Zone, and lastly by the 437–SEA Zone. This, along with the elevated Cu/Pd ratios in the 437–SEA Zone, which formed as a result of sulfide segregation during an earlier saturation event, and development of igneous layering in this zone, suggests that it represents the feeder channel to the Current deposit. After the intrusion crystallized, the base-metal sulfide mineralogy was modified by circulation of late-stage hydrothermal fluids, with pyrrhotite and pentlandite being replaced by pyrite and millerite, respectively. This fluid activity mobilized metals and semi-metals, including Fe, Ni, S, Se, Co, Cu, Ag, and As, but did not affect the PGE. This contribution highlights the importance of the interplay between magma dynamics and magmatic–hydrothermal processes in the formation of Ni–Cu–PGE-mineralized deposits. [ABSTRACT FROM AUTHOR]

We report the discovery of one of the largest ancient (>3.0 Ga) crustal terranes on Earth. Granitoids with crystallization ages >3.0 Ga and/or Sm-Nd depleted mantle model ages ≥3.2 Ga define a -1000 x 100 km belt on the western margin of the Rae craton, Canada, referred to herein as the Perry River terrane (PRT). Zircon U-Pb-Hf-O isotope and whole-rock geochemical data from granitoids show that the PRT is a predominantly juvenile 3.3--3.2 Ga terrane that was partially reworked by more evolved ca. 3.1 Ga magmatism. These findings call for a reassessment of the timing and extent of ancient continental growth on Earth. A global compilation of zircon Hf isotope data from 3.6 to 3.0 Ga igneous rocks reveals clusters of relatively juvenile (initial εHf -2 to +3) rocks at ca. 3.31 and ca. 3.23 Ga, which include samples from the PRT and 13 other terranes worldwide. Other global zircon data sets also document age peaks between 3.3 and 3.2 Ga, and a cluster of broadly chondritic initial εHf values around 3.2 Ga. The 3.3--3.2 Ga period may therefore have been a time of enhanced net continental growth on Earth, and the PRT is one of the largest terranes preserved from that time. Furthermore, zircon Hf isotope data from 3.3--3.1 Ga PRT granitoids and 3.5--3.0 Ga igneous rocks worldwide yield little evidence for parent magmas that interacted with or derived from pre--3.6 Ga continental material. Contrary to some continental-growth models, this latter observation suggests that the volume of continental crust established by 3.6 Ga was relatively small. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

New data on the C and O isotope composition in the Neoproterozoic carbonates of the Ballaganakh and Dal'nyaya Taiga regional stages (southeastern margin of the Patom paleobasin (hereafter, Basin) are presented. The negative δ13С anomaly, established in the upper part of the Ballaganakh regional stage, is comparable (in amplitude and stratigraphic position) to the Trezona anomaly, which preceded the Marinoan glaciation. The carbonate layers in glacial deposits of the Nichatka Formation of the Dal'nyaya Taiga regional stage have moderately positive δ13С values. The dolomite unit at the postglacial sequence base is characterized by moderately negative δ13С values that are typical for the cap carbonate sequence associated with the end-Marinoan glaciation. The lower part of the postglacial sequence (Barakun Formation) is characterized by a gradual increase of calcite in the carbonate component of rocks and a shift in the isotope composition corresponding to the difference in the fractionation coefficient of stable C and O isotopes for dolomite and calcite. This phenomenon, recorded in the postglacial sequences of Namibia and Canada as well, indicates that the carbonate mineral composition was governed by a global change in water chemistry rather than postsedimentary alteration. The overlying carbonate rocks of the Dal'nyaya Taiga regional stage in the epicontinental part of the Patom Basin (Sen Formation) are depleted in 13С compared to their shelf analogs in the Ura Uplift. Probably, the carbonates were accumulated asynchronously in the epicontinental and shelf facies of the Patom Basin. The reconstructed trend of variations in the carbon isotope composition for the Dal'nyaya Taiga regional stage is characterized by positive and low-amplitude negative δ13С anomalies similar to those in the Doushantuo Formation (China). [ABSTRACT FROM AUTHOR]

Wood Buffalo National Park (WBNP), the largest national park of Canada, has unique and complex ecosystems that depend on specific water quantity and quality. We characterize groundwaters and surface waters in WBNP by determining their chemical compositions and water types, the dominant hydrochemical processes affecting their compositions, and their hydrochemical characteristics in relation to interpreted groundwater flow systems. Total Dissolved Solid concentrations in groundwaters and surface waters range from ≤10 mg/L to ≥300,000 mg/L. Four distinct water type groups are found: (1) Ca-SO4-type waters occur in multiple clusters across the area in outcrop areas of Devonian evaporites; (2) Na-Cl-type waters predominantly occur in the Salt plains region along the central eastern boundary, overlapping evaporite and carbonate-dominated bedrock formations; (3) Ca-HCO3-type waters dominate the Peace-Athabasca Delta-region in the south and most of the central region; and (4) "mixed" waters. Solutes in the waters originate from three main processes: dissolution of halite, dissolution of sulphate minerals, and dissolution of carbonates. The spatial occurrence of hydrochemical characteristics correlate with hypothesized groundwater flow systems, i.e., Ca-SO4 and Na-Cl-type waters coincide with discharge areas of intermediate to regional groundwater flow paths, and Ca-HCO3-type waters overlap with recharge areas. The findings of this study contribute to advancing knowledge on the hydrochemical characteristics of this remote and highly protected region of Alberta, Canada, and are important components of any further, comprehensive assessment of the natural water conditions. [ABSTRACT FROM AUTHOR]

The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost 1 km below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation, which is only observed in shallow samples from the Triple R deposit (Tur 1), contain the heaviest isotopic signature (δ 11B ≈ 19–26‰), whereas subsequent generations (Tur 2 and Tur 3) yield lighter and more homogeneous isotopic signatures (δ 11B ≈ 17.5–19.9‰). These results are consistent with precipitation from low-temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ 11B values). The lower δ 11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time, whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ 11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact. Supplementary material: Complete analytical dataset including reference materials are available at https://doi.org/10.6084/m9.figshare.c.5727555 Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways [ABSTRACT FROM AUTHOR]

This article analyzes how US nonproliferation policies that sought to curtail US exports of highly enriched uranium (HEU) affected Canada's medical-isotope industry and, particularly, the Canadian MAPLE (Multipurpose Applied Physics Lattice Experiment) reactors project. US HEU-export policies established between 1978 and 2012 highlight the "nuclear ambivalence" of the Canadian isotope industry's flagship product, molybdenum-99 (Mo-99)—a life-saving commodity widely used by US hospitals but also a material whose production process, based on HEU, came to be perceived as a potential threat to US and world security. The ambivalent status of Mo-99 production was reinforced by a state of mutual dependence between the two countries: On the one hand, Canada depended entirely on US HEU exports to maintain its dominant position in the Mo-99 world market and could not turn to other sources of HEU supply. On the other hand, US hospitals relied mainly on Mo-99 of Canadian origin, which limited the US government's ability to enforce its policy by suspending its HEU exports to Canada. As a result, US and Canadian efforts to convert the Canadian isotope facilities to low-enriched uranium were thwarted by tensions between global security, public health, and commercial stakes, which led ultimately to ending Canada's Mo-99 production. [ABSTRACT FROM AUTHOR]

The Isotrace CNRS workgroup in collaboration with National Research Council of Canada has characterized a number of trace element mass fractions and isotope ratios currently not certified in AQUA-1 natural drinking water reference material (NRC Canada). This survey further expands the use of this material as a tool for environmental quality control, method validation, and method development tool for the international community. Simultaneously, the SLRS-6 river water was analyzed as quality control and also in order to compare both water characteristics, which were sampled in the same area but having undergone different treatment. Mass fractions for B, Cs, Li, Ga, Ge, Hf, Nb, P, Rb, Rh, Re, S, Sc, Se, Si, Sn, Th, Ti, Tl, W, Y, Zr, REEs, and six isotopic ratios are proposed for Sr and Pb. Measurements were mostly performed using ICP-MS with various calibration approaches. The results are reported as consensus or indicative values depending on the number of available datasets, with their associated uncertainties. [ABSTRACT FROM AUTHOR]

A freeze-dried bovine muscle-certified reference material (CRM), known as BOTS-1 (DOI: https://doi.org/10.4224/crm.2018.bots-1 ), containing incurred residues of commonly used veterinary drugs was produced and certified for the mass fraction of eight veterinary drug residues. Value assignment was carried out using liquid chromatography tandem mass spectrometry (LC-MS/MS) methods in conjunction with isotope dilution and standard addition approaches involving stable isotope internal standards. Data from the National Research Council of Canada (NRC), Canadian Food Inspection Agency (CFIA), United States Department of Agriculture (USDA), and the Federal Office of Consumer Protection and Food Safety in Germany (BVL) were used for value assignment. Results for two drug residues were also obtained through an international inter-laboratory comparison CCQM-K141/P178 organized under the auspices of the International Bureau of Weights and Measures (BIPM). Quantitative NMR ( 1 H-qNMR) was used to characterize primary standards of all veterinary drugs certified. The certified mass fractions of the veterinary drug residues were 490 ± 100 µg/kg for chlorpromazine, 44 ± 4.4 µg/kg for ciprofloxacin, 3.3 ± 1.4 µg/kg for clenbuterol, 9.5 ± 0.8 µg/kg for dexamethasone, 57 ± 4.8 µg/kg for enrofloxacin, 3.0 ± 0.4 µg/kg for meloxicam, 12.4 ± 1.2 µg/kg for ractopamine, and 2290 ± 120 µg/kg for sulfadiazine with expanded uncertainties quoted (95% confidence) which include the effects due to between-bottle inhomogeneity, instability during long-term storage and transportation, and characterization., (© 2023. Crown.)

Featured Application: Use of fiber optics to monitor a target on a medical cyclotron. Many medical isotopes can be produced on a small cyclotron. The alignment and profiles of low-energy proton beams from cyclotrons used for medical radioisotope production, such as the TR13 cyclotron at TRIUMF, Canada, cannot be directly quantified during dose delivery with simultaneous constant feedback and sharp spatial resolutions. Doped silica fibers are a potential solution that has been tested at TRIUMF. To measure the effects of irradiation inside an isotope production target, we attached fibers to the outside of an 18O gas target and measured the light output during irradiation. Different dopants, fiber diameters, and target materials were investigated. It was found that 200 µm diameter Ce- and B-doped fibers produce signals linearly proportional to the beam current. This only deviated when the target was moved such that the beam was steered into the target wall, increasing the production of prompt radiation and causing the beam current to decrease but the fiber signal to increase. With the technique described here, the beam can be monitored on the target, including its steering and its overall alignment with the target. [ABSTRACT FROM AUTHOR]

Kimberlite-borne granulite xenoliths provide rare insights into the age, chemical composition and tectonothermal evolution of the otherwise largely inaccessible deep cratonic crust. The formation and transformation of the lower continental crust (LCC) beneath the central Slave craton (Canada) is here illuminated using whole-rock trace-element and Sr-Nd isotope compositions of nine metabasaltic (MBG), one gabbroic (MGG) and two metasedimentary/hybrid (MSG) granulite xenoliths. On the one hand, published sulphide Re-Os and a few zircon U-Pb data indicate that at least a portion of the LCC beneath the central Slave craton has a Palaeoarchaean origin (∼3.3 Ga), which apparently coincides with a period of juvenile crust and deep lithospheric mantle formation during plume impingement beneath the pre-existing cratonic nucleus. On the other hand, enrichment in Li, Sr, LREE, Pb and Th, but relative depletion in Ti, Hf and HREE, suggest formation of (picro)basaltic protoliths by partial melting of a subduction-modified garnet-bearing source, Crystallisation in the crust after fractionation of plagioclase is inidicated by their Sr and Eu negative anomalies, which are complementary to the positive anomalies in the MGG. Samarium-Nd isotopes in MBG and MGG show large scatter, but fall on Neo- or Mesoarchaean age arrays. These elemental systematics are suggested to fingerprint deserpentinisation fluids plus small amounts of sedimentary melt as the main contaminants of the mantle source, supporting the operation of at least regional and transient subduction at 3.3 Ga. Evidence for quasi-coeval plume impingement and subduction beneath the central Slave craton in the Mesoarchaean is reconcilable in a dynamic regime where vertical tectonics, though waning, was still active and plate interactions became increasingly important. Unradiogenic 87Sr/86Sr (down to 0.7017) is consistent with significant loss of Rb and probably other heat-producing elements (K, Th, U) plus H 2 O during Neoarchaean metamorphism, which helped to enhance LCC viscosity and stabilise the cratonic lithosphere. [ABSTRACT FROM AUTHOR]

The Proterozoic evolution of Laurentia involved intermittent orogens and arc-related crustal growth along a modern-style convergent margin, termed the Great Proterozoic Accretionary Orogen (GPAO). The major lithotectonic provinces of the GPAO in the United States are exposed as telescoped equivalents within the thrust stack of the Grenville Province in Canada. We report zircon U Pb and Lu Hf isotope analyses for two orthogneisses and one quartzite from Archean and Paleoproterozoic domains in the gneiss belt of the SW Grenville Province, Canada. The data constrains Paleoproterozoic crustal growth and sedimentation for this part of the Laurentian margin. The orthogneisses have similar zircon U Pb and Lu Hf isotope systematics that reflect igneous reworking (ca. 1700–1660 Ma) of a Penokean aged (ca. 1.9 Ga) depleted mantle derived source, along with metamorphic reactivation at both ca. 1.45 Ga and during the Grenville Orogeny (1.2–1.0 Ga). The quartzite has a bimodal Paleoproterozoic (2.1–1.8 Ga) and Archean (> 2.5 Ga) detrital zircon age spectrum. The Paleoproterozoic detrital zircon grains have a wide range of Hf(t) compositions (εHf(t) = −12.5 to 10) reflecting co-eval interaction of Archean and depleted Paleoproterozoic sources, contrasted by a more restricted range for the Archean population (εHf(t) = −7 to 4). The new data support the presence of reworked ca. 1.9 Ga depleted mantle sources in the Paleoproterozoic Parautochthon, which extend further east than previously thought. They also identify correlations amongst detrital zircon age spectra and Hf isotope compositions in quartzites from different locations of the Archean Parautochthon. • Juvenile Penokean sources (∼1.9 Ga) extend into the SW Grenville Province. • Penokean (∼1.9 Ga) crust-mantle mixing recorded by detrital zircon Lu Hf isotopes. • Erosion and redeposition of sedimentary sinks can mask orogen detrital systematics. [ABSTRACT FROM AUTHOR]

Canada is one of the most important diamonds producers in the world despite the first diamond mine opening relatively recently in 1998 in the Slave craton. Given the increasing economic and scientific interest towards Canadian diamonds, an investigation of their geochemical and petrological properties was needed to better understand their genesis. A detailed review is given of all available petrological and geochemical data from >3000 Canadian diamonds and their silicate, oxide and sulfide inclusions from published literature and unpublished datasets, compared with data from worldwide datasets. Based on the available published data, different abundances of peridotites and eclogites in the lithosphere of the Canadian cratons are indicated by mineral inclusions, with the Slave craton exhibiting a high amount of eclogitic diamonds, and the Superior craton exhibiting a strong prevalence of peridotitic diamonds. Diamond formation from extremely 13C-depleted subducted organic matter is necessary to explain the extremely low δ13C observed in some samples from the Canadian lithosphere, which, as of today, are the lowest values ever recorded in mantle diamonds. Core-to-rim δ13C analyses revealed progressive rimward enrichment in 13C for some of the samples, a behavior which is associated to the crystallization of diamonds from oxidized C species (e.g., CO 2). Using the available data geothermobarometric calculations were performed on both single inclusions and inclusion pairs and provide a formation window for Canadian lithospheric diamonds from ∼140 to ∼210 km, with temperatures ranging from 900 to 1400 °C, which are generally higher than mantle residence temperature given by N aggregation geothermometry. Sub-lithospheric diamonds are sampled from ∼240 km to >660 km based on geobarometry on majoritic garnets and observations of inclusion assemblages. The age range of Canadian diamonds suggest numerous diamond-forming events that took place from the Paleo-Archean to the Neoproterozoic. • Petrological and geochemical differences exist among Canadian cratons. • Diamonds formed in different pulses from the Paleo-Archean to the Neoproterozoic. • Oxidizing fluids are involved in the formation of Canadian diamonds. • Lithospheric diamond stability field extends from ∼5 to ∼7 GPa. [ABSTRACT FROM AUTHOR]

Positive δ13C carb excursions are correlated through an upper Turinian to lower Chatfieldian carbonate-platform succession along the axis of the Ottawa Embayment and into outliers of the northern Ottawa-Bonnechere graben in central Canada. Successive Turinian excursions (E1 and E2) are lithostratigraphically constrained by erosional surfaces and hosted within the Watertown and overlying L'Orignal formations, respectively, the latter coeval with the Selby Formation in the adjacent northern Appalachian Basin. The excursions coincide with periods of regional transgression, but geographic patterns of 13C depletion versus enrichment coincide with structurally defined areas of stratigraphically condensed and preferentially thickened formation successions, respectively. Differential subsidence is interpreted to have created bathymetric variation resulting in intrabasinal restriction of seawater exchange between these areas, with preferential C org recycling with stratigraphic condensation. By early Chatfieldian time, segmentation of the once regional carbonate platform (L'Orignal Formation) produced a regional mosaic of low-energy muddy carbonate banks (Rockland Formation) and a deeper water platform (lower Hull Formation) settings subject to fluctuating high to low energy current flow. Excursion E3 occurs in both successions, but 13C enrichment is associated only with the bank-top muddy facies. This may identify preferential photosynthetic drawdown of 12C across the bank tops due to limited seawater exchange across the bank-deeper platform boundaries. Excursions E1 to E3, and a younger excursion (E4) in the Hull Formation, are correlated with varying confidence with excursions across southern Laurentia, excursion E3 being the local expression of the Guttenberg δ13C excursion. Our study supports local modulation of regional, if not global, δ13C excursions arising from structurally controlled changes in oceanography and productivity. • Turinian and early Chatfieldian δ13C excursions occur in the Ottawa Embayment. • Lithostratigraphic constraints reveal local excursion truncation, notably the GICE. • Lateral variation in excursion magnitude reflects local syndepositional controls. • Local controls modulate regional to global isotopic signals. [ABSTRACT FROM AUTHOR]

• Extensive new Ba isotopic survey of modern barites. • First Proterozoic Ba isotopic results. • Provides genetic model for enigmatic post-Marinoan barite formation. • Provides evidence for stratified post-Marinoan ocean. • Provides arguments for why barite horizons are confined to Marinoan and not Sturtian or Paleoproterozoic strata. Measurements of triple oxygen isotope ratios in barite horizons within post-Marinoan cap carbonates have provided some of the most compelling evidence that the Marinoan glaciation was a Snowball Earth event. However, the origin of these barite horizons remains unresolved. To constrain the Ba sources, and thus formation mechanisms of these horizons, we analyzed the Ba isotope composition of post-Marinoan barite deposits from Northwest Canada, Northern Norway, Brazil and South China. We augment these analyses with a Ba isotope survey of almost 100 modern and ancient additional barite measurements, including samples from pelagic (or 'marine'), hydrothermal, terrestrial, Proterozoic stratiform and cold seep environments. Unlike modern cold seep or terrestrial barites, we find that globally-distributed post-Marinoan barites exhibit a relatively narrow isotopic range, suggesting a well-mixed, effectively limitless Ba source. Moreover, post-Marinoan deposits exhibit a similar mean Ba isotope composition to modern marine barites, which we interpret as evidence of a marine Ba source. Considered alongside existing geochemical, geological, and new Ba isotope survey data, we conclude that Ba in barite horizons was sourced from a well-mixed, Ba-replete but SO 4 -poor reservoir that accumulated during the Marinoan Snowball Earth interval. This deep Ba reservoir was then transported upward—either by ocean circulation or dolomitization of underlying cap carbonates—and was brought into contact with continental weathering-derived sulfate in a post-glacial meltwater surface layer. Thus, in addition to providing a plausible mechanism for generating globally-synchronous deposition of post-Marinoan barite horizons that reconciles all existing geochemical and geological data, our results demonstrate the utility of Ba isotopes to interrogate the origin of enigmatic barite deposits throughout the sedimentary record. [ABSTRACT FROM AUTHOR]

The abundance of ungulate populations may fluctuate in response to several limiting factors, including climate, diseases, and predation. In the northern Richardson Mountains, Canada, Dall sheep (Ovis dalli dalli) have undergone a major decline in the past decades and predation by grizzly bears (Ursus arctos) and wolves (Canis lupus) was suspected as a leading cause. To better understand the relationship between these three species located in this rugged and remote ecosystem, we relied on a combination of indirect methods. We investigated the apparent role of predation on the Dall sheep population using spatial ecology and stable isotopes. We examined seasonal variation in predation risk, focusing on how it may affect Dall sheep habitat use and sexual segregation, and we evaluated the proportion of Dall sheep in the diet of both predators using stable isotopes. The movements of the three species were monitored by satellite telemetry. Dall sheep habitat use patterns were analyzed using topographical features, greenness index, land cover, and apparent predation risk. The diets of grizzly bears and wolves were examined using a Bayesian mixing model for carbon and nitrogen stable isotopes. We found that Dall sheep habitat use varied seasonally, with different patterns for ewes and rams. Exposure to grizzly bear risk was higher for rams during summer, while ewes were further exposed to wolf apparent predation risk during winter. The importance of safe habitats for ewes was reflected in space use patterns. Stable isotopes analyses suggested that the diet of grizzly bears was largely from animal sources, with mountain mammals comprising about one quarter. Wolves mostly fed on both aquatic browsers and mountain mammals. Diet variation between individual predators suggested that some individuals specialized on mountain mammals, likely including Dall sheep. We conclude that grizzly bear and wolf apparent predation risk are important in driving Dall sheep habitat use and play a role in sexual segregation. Overall, this study presents an innovative combination of indirect methods that could be applied elsewhere to better understand predator-prey dynamics in remote ecosystems. [ABSTRACT FROM AUTHOR]

Highlights • Thioaromatic concentrations of Peace River oils decreased with biodegradation. • Alkyl thioaromatic isomers showed different susceptibilities to biodegradation. • First detailed investigation of S isotope fractionation of OSCs in biodegraded oils. • Alkyl BTs were 34S-enriched in more biodegraded oils. • The δ34S values of alkyl DBTs showed no 34S fractionation in biodegraded oils. Abstract The heavy sulfur-rich oils of the Peace River oil sands were formed by severe anaerobic biodegradation. To investigate the impacts of biodegradation on organic sulfur compounds (OSCs) we have measured the distribution and δ34S values of alkylated thioaromatics detected in four oils from each of two Peace River wells (A and B). The fluid composition of the Peace River oil sands can be highly complex due to the variable contributions of sources, thermal maturity and secondary alteration. Nevertheless, a previous multi-molecular investigation of samples from well B oils (PR2 oil-leg of Marcano et al., 2013, Organic Geochemistry 59, 114–132) indicated that the oils had biodegradation levels (BLs) of 5–6, with biodegradation increasing down the oil column. The hydrocarbon composition of oils isolated from well A were biodegraded to a lesser degree than well B (i.e., the presence of isoprenoids and high molecular weight [MW] n -alkanes suggests BLs of ∼3–4). The concentrations of C 1 –C 3 alkylated benzothiophenes (BTs) and C 1 –C 3 alkylated dibenzothiophenes (DBTs) declined sharply through both wells consistent with increased biodegradation, although other alteration impacts (e.g., water washing) might also contribute. The rates of decrease recorded for selected isomers showed variable responses (e.g., 3&4-mBT > 2-mBT; 4-eDBT > 1,3-dmDBT) which implies different susceptibilities to biodegradation and which may contribute additional useful molecular parameters for evaluating the BL of biodegraded S-rich petroleum. The S-isotopic measurements showed a 34S enrichment in several alkyl BTs down the oil leg in well B, with their δ34S values increasing by up to 6‰, consistent with the microbial utilisation of 32S (n.b., the δ34S values of alkyl BTs were not measured in well A oils because of low aromatic sub-fraction concentrations). In contrast, there was little variation in the δ34S values of alkyl DBTs down both wells indicating negligible S-isotopic fractionation of these OSCs in the deeper more biodegraded oils, possibly because of their higher MW and resistance to biodegradation. The δ34S DBT (and bulk δ34S) values of the well B oils were generally slightly enriched than the well A oils probably due to differences in the relative contribution of the major Devonian and Jurassic source rocks. [ABSTRACT FROM AUTHOR]

• Calibration to both flow and isotope tracers produced the most robust results. • Tracer-aided modelling improves flow path identifiability. • Inclusion of isotope tracers can improve flow simulation performance. • Isotope metrics that include timing error are most helpful in calibration. Standard hydrologic model evaluation and calibration approaches focus on the accurate simulation of streamflow, disregarding internal process simulations. Stable isotope tracers can provide additional information on water sources, and process flux and storage, which can be used to inform model calibration. This study assesses the added value of isotope data in comparison to current best-practice flow-only calibration methods and evaluates the merits and limitations of isotope simulation performance metrics for the purposes of hydrological model calibration. Following several years of regular isotope sampling and measurement, an isotope-enabled process-based hydrologic model was tested on a large watershed in western Canada (Athabasca River), which allowed model calibration using global sensitivity analyses, Monte Carlo simulations, and multi-objective optimizations. Isotope tracer data were found to improve both process and streamflow component identifiability and produced some minor improvement in individual parameter value identifiability. Calibrating to optimize both flow and isotope simulation performance produced better flow simulation ensembles, with improved observation capture and validation performance, relative to calibrating to optimize flow simulations alone. Using an isotope simulation performance metric which includes timing error as a secondary optimization objective led to more robust streamflow modeling, even in mesoscale watersheds with limited isotope observation datasets. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is a by-product of phosphorus fertilizer that is typically stacked near production sites. Phosphogypsum contains trace elements and naturally occurring radioactive materials which may be hazardous to the surrounding environment. Phosphogypsum stack reclamation typically involves placing a soil cap and seeding grass to create a barrier for reducing environmental impacts; using woody species is uncommon. This study used three soil treatments with grass and woody species to determine whether mixing PG with soil affects soil chemical properties, and metal and radionuclide concentrations in tissue. None of the elements in soil was above Canadian guidelines for industrial land use. Aluminum, beryllium, chromium, copper, iron, magnesium, manganese, nickel, and vanadium were significantly higher in both study and reference sites than in pure PG; cadmium, calcium, fluoride, and strontium were significantly higher in pure PG. There was a poor correlation between soil and plant concentrations for most elements indicating trace elements were not in a bioavailable form. Trace elemental concentrations in plant tissue generally differed significantly with vegetation type but not within similar species. Trace elements and isotopes in PG were not high enough to affect plant growth. Among the isotopes, 222 Ra emissions differed significantly with vegetation covers; activity of 226 Ra in pure PG was above Canadian guidelines, but lower in vegetation tissue. This study suggests 15 cm soil mixed with PG can be used for PG stack revegetation when fast-growing Salix and Populus species are used in reclamation., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The Silurian bedrock aquifer constitutes a major aquifer system for groundwater supply across the Ontario province in Canada. The application of natural and industrial fertilizers near urban centers has led to groundwater NO 3 − -N concentrations that sometimes have exceeded the drinking water limit, posing a threat to the usage of groundwater for the human consumption. Therefore, there is a growing interest and concern about how nitrate is being leached, transported and potentially attenuated in bedrock aquifers. This study assesses the local distribution of groundwater NO 3 − in the up-gradient area of two historically impacted municipal wells, called Carter Wells, in the City of Guelph, Canada, in order to evaluate the potential nitrate attenuation mechanisms, using both groundwater geochemical and isotopic analysis ( 3 H, δ 15 N-NO 3 , δ 18 O-NO 3 , δ 18 O-SO 4 , δ 34 S-SO 4 ) and a detailed vertical hydrogeological and geochemical bedrock characterization. The results indicate that probably the main source of nitrate to the Carter Wells is the up-gradient Arkell Research Station (ARS), an agricultural research facility where manure has been historically applied. The overburden and bedrock groundwater with high NO 3 concentrations at the ARS exhibits a manure-related δ 15 N and δ 18 O signature, isotopically similar to the high nitrate in the down-gradient groundwater from domestic wells and from the Carter Wells. The nitrate spatial distribution appears to be influenced and controlled by the geology, in which more permeable rock is found in the Guelph Formation which in turn is related to most of the high NO 3 − groundwater. The presence of an underlying low permeability Eramosa Formation favors the development of oxygen-depleted conditions, a key factor for the occurrence of denitrification. Groundwater with low NO 3 − -N concentrations associated with more oxygen-limited conditions and coincident with high SO 4 2− concentrations are related to more enriched δ 15 N and δ 18 O values in NO 3 − and to more depleted δ 34 S and δ 18 O values in SO 4 2− , suggesting that denitrification coupled with pyrite oxidation is taking place. The presence of macro crystalized and disseminated pyrite especially in the Eramosa Formation, can support the occurrence of this attenuation process. Moreover, based on tritium analysis, some denitrification can occur in shallow bedrock and within relatively short residence times, associated with less permeable conditions in depth which facilitates oxygen consumption through sulfide oxidation. The role of denitrification mediated by organic carbon cannot be discarded at the study site. This study suggests that the geological configuration and particularly the presence of low permeability Eramosa Formation can play an important role on nitrate natural attenuation, which may serve as a decision factor on defining the bedrock water supply system for both domestic and municipal purposes. [ABSTRACT FROM AUTHOR]

The silicon isotopic composition of silicic acid (δ30Si(OH)4) and biogenic silica (δ30Si-bSiO2) were measured for the first time in marine Arctic waters from the Mackenzie River delta to the deep Canada Basin in the late summer of 2009. In the upper 100 m of the water column, δ30Si(OH)4 signals (+1.82‰ to +3.08‰) were negatively correlated with the relative contribution of Mackenzie River water. The biogenic Si isotope fractionation factor estimated using an open system model, 30 ε = −0.97 ± 0.17‰, agrees well with laboratory and global-ocean estimates. Nevertheless, the δ30Si dynamics of this region may be better represented by closed system isotope models that yield lower values of 30 ε, between −0.33‰ and −0.41‰, depending on how the contribution of sea-ice diatoms is incorporated. In the upper 400 m, δ30Si-bSiO2 values were among the heaviest ever measured in marine suspended bSiO2 (+2.03‰ to +3.51‰). A positive correlation between δ30Si-bSiO2 and sea-ice cover implies that heavy signals can result from isotopically heavy sea-ice diatoms introduced to pelagic assemblages. Below the surface bSiO2 production zone, the δ30Si(OH)4 distribution followed that of major water masses. Vertical δ30Si(OH)4 profiles showed a minimum (average of +1.84 ± 0.10‰) in the upper halocline (125-200 m) composed of modified Pacific water and heavier average values (+2.04 ± 0.11‰) in Atlantic water (300-500 m deep). In the Canada Basin Deep Water (below 2000 m), δ30Si(OH)4 averaged +1.88 ± 0.12‰, which represents the most positive value ever measured anywhere in the deep ocean. Since most Si(OH)4 enters the Arctic from shallow depths in the Atlantic Ocean, heavy deep Arctic δ30Si(OH)4 signals likely reflect the influx of relatively heavy intermediate Atlantic waters. A box model simulation of the global marine δ30Si(OH)4 distribution successfully reproduced the observed patterns, with the δ30Si(OH)4 of the simulated deep Arctic Ocean being the heaviest of all deep-ocean basins. [ABSTRACT FROM AUTHOR]

• The Nulliak supracrustal assemblage confirmed to be Eoarchean. • Zircon Hf isotope results indicate the presence of depleted mantle domains underneath the Saglek Block during the Eoarchean. • O-isotope signatures of Eoarchean metamorphic zircon indicate the reworking of material that experienced alteration at low temperature. The Archean Saglek Block, North Atlantic craton, is one of the oldest crustal segments preserved on Earth. This area records two granulite facies metamorphic events: one in the late-Eoarchean at ca. 3.7 Ga and one in the Neoarchean, at ca. 2.75 Ga. Here, we report the results of combined U–Pb/Hf/O in-situ isotope analyses of detrital and metamorphic zircon domains from two meta -sedimentary samples, one psammitic, and one pelitic. Both samples are components of the oldest supracrustal assemblage of the Saglek Block: the Eoarchean Nulliak supracrustal assemblage. The isotopic data presented in this study: (i) confirm deposition age of the Nulliak supracrustal assemblage before ca. 3.65 Ga, (ii) indicate local provenance of the detrital zircon, (iii) suggest deposition of the sedimentary protoliths in a convergent setting, such as an arc, (iv) crystallization of the oldest zircon during the early Eoarchean in a protolith derived from a depleted mantle component, (v) involvement of material that experienced prolonged low temperature alteration during the late Eoarchean granulite facies metamorphism and (vi) selective metamorphic overprinting during the Neoarchean granulite facies metamorphism. The new zircon U–Pb/Hf/O isotope data presented here in conjunction with previously published analyses suggest that a depleted mantle domain existed in the early Archean, as reflected in the positive εHf signature of zircon from the Saglek Block. Yet, such positive Hf isotope deviations are not the norm, but rather the exception in the preserved early Earth zircon record. In addition, mildly elevated zircon δ18O values, i.e. those ≥ 5.9 ‰, are as common in the early Archean as they are in the late-Archean zircon record, implying that crustal reworking was an active and efficient process all through the Archean. Hence, no significant variation in the nature of the reworking and broader geodynamic processes occurred during this period of time. [ABSTRACT FROM AUTHOR]

The Rock Canyon Creek REE–F–Ba deposit is a carbonate-hosted REE deposit located in the Alkaline Province of British Columbia, Canada, which hosts most REE mineralization. It shares tectonic, stratigraphic and structural similarities with nearby Mississippi Valley-type deposits. To constrain the dolomitization and mineralization processes, the δ26Mg, 87Sr/86Sr, and elemental compositions of dolomite, calcite, and fluorite were determined. The δ26Mg values of dolomite from the unmineralized zone (−1.83 ‰ and −1.67 ‰) are consistent with marine evaporative dolomite, but those from the mineralized zone (−0.97 ‰ to −0.17 ‰) are higher and more variable. The linear 87Sr/86Sr–Sr/Mg relationships, both in the dolomite and calcite from the unmineralized zone, suggest dolomitization in an evaporative marine environment. The high δ26Mg values with large variation and the non-stoichiometric Ca/Mg ratios in the dolomite from the mineralized zone suggest that this dolomite interacted with a relatively low-temperature hydrothermal fluid (<200 °C). Considering the Na, Ca, Sr, Ba, and LREE-enrichment and low 87Sr/86Sr signature in the dolomite from the mineralized zone as well as mineral paragenesis in the deposit, the most plausible scenario for the formation of the deposit is that marine-evaporitic dolomite re-equilibrated with basinal fluids along permeable zones, and at a later stage, carbohydrothermal REE-bearing fluids infiltrated into the Rock Canyon Creek brecciated zone and deposited the REE mineralization. Late-stage, post-mineralization calcite veins and iron oxides formed in the upper part of the deposit under supergene conditions, as suggested by combination of textural observations, REE patterns, and differences in isotopic compositions between dolomite and calcite from the mineralized zone. This study demonstrates that δ26Mg, 87Sr/86Sr, and element/Mg ratios in carbonate minerals are useful for characterizing mineralizing fluids in carbonate-hosted deposits, and discriminating mineralization-related dolomite from marine evaporative dolomite and unmineralized hydrothermal dolomite. • Mg and Sr isotopes of carbonates from carbonate-hosted REE–F–Ba deposit were determined. • Mg and Sr isotopes from the unmineralized zone suggested evaporative marine dolomitization. • Hydrothermal dolomite formed by a relatively low-temperature (<~200 °C) hydrothermal fluid. • REE mineralization caused by carbohydrothermal fluid after hydrothermal dolomite formation. • Mineralization-related and unmineralized dolomite can be discriminated by Mg isotopes. [ABSTRACT FROM AUTHOR]

• δ98Mo data of 0.85Ga microbial carbonate, lime mudstone and black shale fill temporal gap in Proterozoic Mo isotope record. • Carbonates and black shales are compared as suitable seawater δ98Mo archives. • Significant δ98Mo variation in carbonate samples likely related to porewater redox conditions. • 0.4‰ discrepancy between heaviest δ98Mo value of carbonate and shale indicates shale is unsuitable as seawater estimate. • Possible archive-dependent bias in δ98Mo interpretation may lead to underestimation of extent of Proterozoic oxic Mo sink. This study addresses marine palaeoredox conditions of the mid-Neoproterozoic by analysing the Mo isotope, trace element, and U-Th-Pb isotope compositions of shallow water microbial carbonate, deep water pelagic carbonate, and shale from the Stone Knife Formation (SKF) in NW Canada. The U-Th-Pb isotope SKF systematics of reef microbialite carbonates, and the moderately expressed negative Ce anomalies are consistent with the presence of dissolved O 2 in the surface waters. Thirteen of 14 analysed samples yield a depositional 206Pb/238U regression age of 0.850 ± 0.028 Ga. The Mo isotope data (δ98Mo) are distinct for the microbial and pelagic carbonates and the deeper water shales, with the isotopically heaviest black shales 0.4 ‰ lighter than the heaviest carbonate. The bulk digestion carbonate δ98Mo data scatter widely, ranging up to 1.64 ‰, and are not reproducible between repeat digestions. The spread in shallow-water carbonate δ98Mo cannot be attributed to a single origin (e.g., admixture of silicate-hosted Mo) and probably reflects a combination of factors, including the complex pathway of Mo into microbial carbonates. Regardless, we propose a minimum δ98Mo of 1.64 ‰ for the 0.85 Ga ocean, similar to other Neo- and Mesoproterozoic estimates from studies of proxies other than black shale. Our new black shale δ98Mo data agree with most previous results from 1.8 to 0.7 Ga shales. If interpreted as reflecting seawater, this would mean a minimum oceanic δ98Mo composition of only 1.29 ‰, implying a limited oxic reservoir compared to the modern Mo budget in agreement with previous studies. This study's results suggest that the discrepancy could also be explained by a systematic offset between δ98Mo compositions of black shales and the overlying water columns, regardless of depositional environment, akin to the relative depth distribution of δ98Mo in modern euxinic water columns such as the Black Sea. If valid, an implied heavier seawater δ98Mo throughout the Proterozoic would indicate that the magnitude of the Mo oxic sink remained relatively stable throughout the Proterozoic, shifting the apparent expansion of oxygen towards the younger boundary of the interpreted onset of the NOE (ca. 1.0–0.54 Ga). [ABSTRACT FROM AUTHOR]

Unique deposits that formed in the Precambrian oceans are the Banded Iron-Formations (BIFs) which are chemical sediments comprised of alternating layers of iron- and silica-dominated precipitates. The origin of this enigmatic banding is still debated, with most favoring a primary sedimentary and a few others arguing for a secondary diagenetic origin. We here use a high-resolution integrated multi-proxy approach and report on the Ge-Si-Fe and Th-U systematics and on the isotopic composition of Cr in exceptionally pure adjacent magnetite and metachert bands from the ∼2.7 billion years old Temagami BIF, Ontario, Canada. While each of the geochemical proxies alone may be controversial, our multi-proxy approach sheds new light on their applicability, as the two types of adjacent BIF bands are each characterised by a distinct geochemical signature. The magnetite bands show super-crustal (i.e. fractionated) Ge/Si ratios approaching those of modern marine high-temperature hydrothermal fluids, unfractionated Th/U ratios similar to those of crustal rocks, and unfractionated Cr isotope ratios similar to "Bulk Silicate Earth". Adjacent metachert bands, however, show lower (i.e. unfractionated) Ge/Si ratios close to those of modern seawater, sub-crustal (i.e. fractionated) Th/U ratios, and fractionated Cr isotope ratios above those of Bulk Silicate Earth. The composition of the magnetite bands suggests that the original iron-oxyhydroxide precipitated during periods when the dissolved Ge, Th, U, and Cr inventory of ambient seawater was dominated by input from mafic crust via anoxic high-temperature hydrothermal fluids. In contrast, the composition of the metachert bands indicates that these formed during times when ambient seawater was dominated by low-temperature riverine input from an evolved landmass that despite its Neoarchean age had provided environments for oxidative Cr and U mobilization during terrestrial weathering. This suggests that habitats with oxygenic photosynthesis existed on land at least 200 million years before the Great Oxidation Event. The systematic and internally consistent difference between the geochemical signatures shown by the two types of adjacent BIF bands also demonstrates that the prominent banding of BIFs is a primary depositional feature reflecting precipitation from different watermasses and is not the result of post-depositional separation of an initially homogeneous chemical sediment. • Metachert bands in Temagami BIF provide information about Neoarchean landmasses. • Temagami BIF's metacherts show unfractionated Ge/Si and fractionated δ 53 Cr and Th/U. • Fractionated δ 53 Cr and Th/U reveal oxidative weathering on land 200 my before the GOE. • Temagami magnetite bands show fractionated Ge/Si and unfractionated δ 53 Cr and Th/U. • Internally consistent signals from various proxies show primary origin of BIF banding. [ABSTRACT FROM AUTHOR]

Stable isotopes of oxygen and hydrogen were measured in water samples collected annually from a representative suite of 50 lakes in northeastern Alberta over a 9-year period and are interpreted using a steady-state isotope mass balance model to determine water yield and runoff ratios for the lake watersheds and residence time of the lakes. This isotopic perspective on hydrology of the region provides new insight into the role of land cover, watershed morphometry, climatic drivers and permafrost thaw on lakes. Bog cover, permafrost and presence of thaw features in bogs are found to be the dominant hydrologic drivers, although morphometric properties such as elevation, lake area and drainage basin area are also influential. In addition to quantifying the hydrologic fluxes, the analysis establishes contrasting conditions in more southerly lakes, located in the Stony Mountains and west of Fort McMurray, as compared with more northerly sites in the Birch Mountains, Caribou Mountains and northeast of Fort McMurray, mainly because of contributions from thawing permafrost at the northerly sites. Distinct hydrologic conditions are also noted for Shield systems north of Lake Athabasca where bogs and permafrost are absent. While permafrost thaw is not directly labelled by oxygen and hydrogen isotope composition, isotope mass balance calculations suggest that contributions of up to several hundred millimetres per year are occurring in 14 of the 50 lake watersheds under study. Several of these lakes have water yields in excess of precipitation in some years, and regional groups of lakes display significant correlations between water yield and percentage of bogs that have collapsed. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock's history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event. [ABSTRACT FROM AUTHOR]

Nature archives record atmospheric mercury (Hg) depositions from directly emitted Hg and re-emitted legacy Hg. Tracing the legacy versus newly deposited Hg is still, however, challenging. Here, we measured Hg isotope compositions in three dated sediment cores at different distances from the Flin Flon smelter, the largest Canadian Hg sources to the atmosphere during the 1930s-2000s. During the smelter's operative period, Hg isotope compositions showed limited variations in the near-field lake (<10 km) sediments but were rather variable in middle- (20-75 km) and far-field lake (∼800 km) sediments. Only the post-2000 sediments in middle/far-field lakes showed significantly negative Hg isotope shifts, while sediments from the 1970s-1990s had Hg isotope values resembling those of near-field lake post-1930 sediments. We suggest that the smelter's peak Hg emissions during the 1970s-1990s, which coincided with the deployment of a super stack in the mid-1970s, largely increased the long-range dispersion of smelter plumes. For the top post-2000 sediments, the fugitive dust from ore tailings and terrestrial legacy Hg re-emissions dominated Hg deposition in near-field lakes and middle/far-field lakes, respectively. Our study demonstrates that legacy Hg remobilization now exports substantial amounts of Hg to ecosystems, highlighting the need for aggressive remediation measures of Hg-contaminated sites.

The basement-hosted Bong uranium deposit in the Kiggavik region is associated with a broad hydrothermal alteration halo characterized by an inner illite-rich zone and an outer chlorite-rich zone. The uranium-bearing zones characterized by intense illite alteration yield high δ56Fe and δ26Mg values relative to the host rocks, with average whole-rock values of δ56Fe = 0.58 ± 0.15‰ and δ26Mg = 0.61 ± 0.29‰, and clay-size fraction values of δ56Fe = 0.51 ± 0.20‰ and δ26Mg = 0.82 ± 0.09‰. These isotopic values correlate with a decrease in average Fe2+ concentrations (0.47 versus 2.30 mol% Fe2+ in least-altered hosts). The high δ26Mg values reflect intense illite alteration, which preferentially incorporated heavier magnesium isotopes during alteration of both the ore zones and an upper hematite-altered horizon. Although the clay alteration with high δ56Fe and δ26Mg values coincides with the main uranium-bearing zone, the δ56Fe signatures reflect multiple stages of alteration and mineralization. The high δ56Fe values and lower Fe2+ contents of the uranium-bearing zones support leaching of Fe2+ (aq) enriched in lighter iron isotopes. Sequential leach δ56Fe experiments also indicate that formation of fine-grained iron oxides/hydroxides with positive δ56Fe values (+0.23 to +0.60‰) in late chemical fronts enhanced the primary positive δ56Fe signatures recorded in ore zones. Near surface samples with similar isotopic signatures provide clues to buried mineralization and support structural disruption of the systems after primary mineralization. Distal geochemical expressions of this system may include enrichment in iron contents with negative δ56Fe values and/or negative δ26Mg whole-rock or clay-size fractions values, reflecting precipitation of the isotopically light iron and magnesium leached during hydrothermal alteration. Although more costly to process, sequential leach δ26Mg or δ56Fe analyses produced greater variance in the ore zones relative to background values and removed anomalous values from carbonate minerals. Isotopic analyses of the clay-size fraction produced results comparable to the final digestion in the sequential leach process but this method in particular requires greater understanding the mineralogical controls on the isotopic signatures. [Display omitted] • Application of iron and magnesium isotope methods to hydrothermal uranium deposits • Complex hydrothermal fluid history revealed through iron and magnesium isotopes • Quantifying fluid-rock and redox reactions in the formation of unconformity-related uranium deposits [ABSTRACT FROM AUTHOR]

• Geochemistry, geochronology and zircon Hf isotopic compositions of the Eoarchean to Neoarchean crust from the Saglek-Hebron Complex (SHC). • The SHC felsic crust formed over one billion years through six distinct magmatic events. • Newly identified Paleoarchean Iluilik magmatic event. • Hadean to Eoarchean mafic crustal source for the SHC TTG. • Reworking of Eoarchean TTG producing granite over one billion years. • Distinct shift to more juvenile Hf isotopic composition at ∼3.2 Ga. • Implications for Earth's early crust evolution. The Saglek-Hebron Complex (SHC) located in Northern Labrador, Canada, includes some of the oldest crustal rocks on Earth. This granite-greenstone terrain is dominated by trondhjemite, Mg-rich tonalite, granite, with subordinate granodiorite, and recorded over one billion years of early magmatic history between ∼3900 Ma and ∼2700 Ma. New in-situ U-Pb analyses on zircons from eighteen rock samples, suggest that six distinct magmatic events formed the felsic crust of the SHC, during the Archean Eon. Age deconvolution analysis constrains these magmatic episodes at ca. 3857 Ma, 3744 Ma, 3575 Ma, 3330 Ma, 3224 Ma and 2750 Ma, respectively defined as the Iqaluk, the Uivak I, the Uivak II, the Iluilik, the Lister and the late granite events. The 3330 Ma Iluilik represents a newly defined magmatic event, distinct from the Lister event previously recognized at ∼3200 Ma. Uranium-Pb geochronology, combined with in-situ Hf isotopic data on zircons and geochemistry of the host rocks, reveal a complex and protracted crustal history of the SHC marked by the reworking of mafic and felsic crust over one billion years. Zircons from the oldest Iqaluk and Uivak I samples yield slightly suprachondritic initial εHf values (up to ∼+4), consistent with the involvement of a long-term depleted source in the Eoarchean. The 3330 Ma Iluilik granodiorite exhibits a low initial εHf value of −6, clearly diverging from the near-chondritic Hf isotopic composition of the 3224 Ma Lister tonalites. Considering a mafic crustal precursor (with a 176Lu/177Hf ratio of ∼0.02) for trondhjemite-tonalite-granodiorite (TTG) samples, the initial Hf isotopic compositions of the SHC Eoarchean to Paleoarchean zircons would be consistent with the reworking of Hadean mafic crust. The zircon εHf vs. time trend for granite samples corresponds to a 176Lu/177Hf ratio of ∼0.01, suggesting that the granitic crust was mainly produced by crustal reworking of the oldest TTG. Similarly to the felsic crust of the Itsaq Gneiss Complex of SW Greenland, the SHC granitoids appear to record a shift to more juvenile compositions at the end of the Paleoarchean. However, contrary to what is observed in SW Greenland, almost no input of juvenile material has been recorded by the SHC Neoarchean felsic crust. [ABSTRACT FROM AUTHOR]

Hinchey (2021) uses new Nd isotope data for metavolcanic and plutonic rocks from the Aillik Domain of the Makkovik Province to propose a reinterpretation of the Makkovik Province, arguing that the Aillik and Cape Harrison domains of the orogen should be combined into a single new domain. However, Hinchey reaches this conclusion by re-plotting the locations of the analysed samples to give the impression that Makkovikian rocks of the Aillik and Cape Harrison domains had similar ranges of (initial) Nd isotope composition. I will show in this comment that Hinchey's claim of largely overlapping Nd isotope signatures in the Aillik and Cape Harrison domains is incorrect, and that multiple lines of isotopic evidence do not support her tectonic model. [ABSTRACT FROM AUTHOR]

Heavy metal(loid) (Cd, Co, Cr, Ni, Cu, Zn, Pb, V, Tl, and As) and Pb isotope compositions of two black shale weathering profiles were determined to investigate the geochemical behaviors of these toxic elements during black shale weathering and the heavy metal(loid) contamination and source apportionment of Pb in black shale-associated soils. Black shale has higher heavy metal(loid) concentrations than the upper continental crust and the worldwide average shale. In contrast, the surface soils have much higher heavy metal(loid) concentrations than the profile soils. The heavy metal(loid) concentrations in black shale-associated soils are higher than the Chinese and worldwide soil background values, except for Co and Pb. Black shale-associated soils, especially the surface soils, have higher average concentrations of As, Cd, Cr, Ni, Cu, and Zn than Chinese, Dutch, and Canadian soil guidelines. The enrichment factor (EF) and geoaccumulation index (I geo ) values indicate various degrees of heavy metal(loid) contamination in these soils, particularly for the heavy metals Cd, Tl, and V and metalloid As. Co and Pb contamination in these soils is not a current concern. According to the mass transfer coefficient (τ Ta,j ) values, Cd, Co, Ni, and Zn show overall losses, and other metals (Cr, Cu, Pb, and V) exhibit different behavior in the studied black shale weathering profiles. Based on a simple binary Pb isotopic mixing model, black shale is the dominant contributor to the Pb in black shale-associated soils (70.5-91.1% to profile soils and 81.2-88.8% to surface soils), and vehicle exhaust contributes less (8.9-29.5%) to the Pb in profile soils. Vehicle exhaust can exert an impact on the Pb isotopic evolution at depth intervals of 60-80 cm below the soil surface., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The tempo and magnitude of ocean oxygenation during the rise of animals in the Ediacaran Period (635 to 539 million years ago, or Ma) is debated. Reconciling this debate is key to understanding what role, if any, oxygen played in the rise of large morphologically complex life on Earth. We reconstruct a portion of Ediacaran ocean oxygenation history using thallium isotope records (reported as ε205Tl) captured in shales from South China (Wuhe section) and northwestern Canada (Goz A and Sekwi Brook sections). At first blush, our ε205Tl data from these two locations are very different. South China shales reveal two pronounced and extremely negative Tl isotope excursions, in mid-members II and III of the Doushantuo Formation (where ε205Tl authigenic reach nadirs of −10.4 ± 0.2; 2SD and − 9.1 ± 0.2; 2SD, respectively). In contrast, northwestern Canada shales reveal fairly invariant values (average ε205Tl authigenic = −2.1 ± 1.6; 2SD, n = 75). These disparate records are in much better agreement, however, if we cull from our dataset shales that were inferred in previous work to have been deposited in restricted settings. By comparison to analogous modern settings (e.g., the Black Sea), ε205Tl data in these shales most likely fingerprint local-scale processes. On the other hand, and also by comparison to modern settings (e.g., Cariaco and Santa Barbara basins), shales deposited in an open ocean setting probably captured a globally homogenous seawater ε205Tl (ε205Tl SW). Moving forward with this assumption, we find that Ediacaran open ocean ε205Tl SW values were predominantly comparable to bulk upper continental crust (ε205Tl = ~−2). These relatively heavy open ocean ε205Tl SW imply limited Mn oxide burial in global marine sediments for large periods of time during the Ediacaran, and by inference also limited accumulation of O 2 in global marine bottom waters. Only for what appear to be very brief episodes of time (≪5–10 million years) at ~635 Ma and ~580 Ma did open ocean ε205Tl SW reach values considerably lighter than bulk upper continental crust (for example, ε205Tl SW as low as −4.4 ± 0.2; 2SD at ~635 Ma and − 5.3 ± 0.3: 2SD at ~580 Ma). These much rarer negative ε205Tl SW values require short-lived episodes of globally enhanced Mn oxide burial in marine sediments, and by implication also brief episodes of enhanced accumulation of O 2 in global marine bottom waters. When interpreting geochemical data, it is important to make global-scale inferences only after identifying and accounting for local-scale overprints. Applying this strategy ourselves, we find compelling evidence for an Ediacaran global ocean that only very briefly experienced widespread bottom water oxygenation during the rise of animals. [ABSTRACT FROM AUTHOR]

Honey from Apis mellifera is a useful and inexpensive biomonitor for mapping metal distributions in urban centers. The sampling resolution of a biomonitoring survey (e.g., city versus global scale) determines which geochemical processes are reflected in the results. This study presents Pb isotopic compositions and metal concentrations in honey from around the world, sampled at varying resolutions: honey from Canada (n = 21), the United States (n = 111), Belgium (n = 25), and New Zealand (n = 10), with additional samples from Afghanistan, Brazil, Cuba, Germany, Liberia, Taiwan, and Turkey. Honey was sampled at high resolution in two uniquely different land-use settings (New York Metro Area and the Hawaiian island of Kaua'i), at regional-scale resolution in eastern North America (including the Great Lakes region), and Pb isotopic compositions of all samples were compared on a global scale. At high sampling resolution, metal concentrations in honey reveal spatially significant concentration gradients: in New York City, metals associated with human activity and city infrastructure (e.g., Pb, Sb, Ti, V) are more concentrated in honey collected within the city compared to honey from upstate New York, and metal concentrations in honey from Kaua'i suggest polluting effects of nearby agricultural operations. At lower resolution (regional and global scales), lead isotopic compositions of honey are more useful than metal concentrations in revealing large-scale Pb processes (e.g., the enduring legacy of global leaded gasoline use throughout the twentieth century) and the continental origin of the honey. Lead isotopic compositions of honey collected from N. America (especially from the eastern USA) are more radiogenic ( 206 Pb/ 207 Pb: 1.132-1.253, 208 Pb/ 206 Pb: 2.001-2.129) compared to European honey, and honey from New Zealand, which has the least radiogenic isotopic compositions measured in this study ( 206 Pb/ 207 Pb: 1.077-1.160, 208 Pb/ 206 Pb: 2.090-2.187). Thus, biomonitoring using honey at different resolutions reflects differing processes and, to some extent, a honey terroir defined by the Pb isotopic composition. The data presented here provide important (and current) global context for future studies that utilize Pb isotopes in honey. Moreover, this study exhibits community science in action, as most of the honey was collected by collaborators around the world, working directly with local apiarists and hobby beekeepers., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The petrogenesis of the Pridoli to Early Lochkovian granites in the Miramichi Highlands of New Brunswick, Canada, is controversial. This study focuses on the Pridoli Nashwaak Granite (biotite granite and two-mica granite). In situ trace elements and O and Hf isotopes in zircon, coupled with O isotopes in quartz, are used to reveal its magmatic sources and evolution processes. In the biotite granite, inherited zircon cores have broadly homogenous δ18OZrc ranging from +6.7‰ to 7.4‰, whereas magmatic zircon rims have δ18OZrc of +6.3‰ to 7.2‰ and εHf(t) of −0.39 to −5.10. The Hf and Yb/Gd increase with decreasing Th/U. Quartz is isotopically equilibrated with magmatic zircon rims. The biotite granite is interpreted to be solely derived by partial melting of old basement rocks of Ganderia and fractionally crystallized at the fO2 of 10−21 to 10−10 bars. The two-mica granite has heterogeneous inherited zircon cores (δ18OZrc of +5.2‰ to 9.9‰) and rims (δ18OZrc of +6.2‰ to 8.7‰), and εHf(t) of −11.7 to −1.01. The two-mica granite was derived from the same basement, but with supracrustal contamination. This open-system process is also recorded by Yb/Gd and Th/U ratios in zircon and isotopic disequilibrium between magmatic zircon rims and quartz (+10.3 ± 0.2‰). [ABSTRACT FROM AUTHOR]

Little is known about how forests adjust their gas-exchange mode while atmospheric CO 2 rises globally and air quality changes regionally. The present study aims at addressing this research gap for boreal spruce trees growing in three different regions of Canada, submitted to distinct levels of atmospheric emissions, by examining the amount of carbon gained per unit of water lost in trees, i.e., the intrinsic water use efficiency (iWUE). Under pristine air quality conditions, middle-to long-term trends passed from no-reaction mode to passive strategies due to atmospheric CO 2 , and short-term iWUE variations mostly ensue from year-to-year climatic conditions. In contrast, in trees exposed to pollutants from a copper smelter and an oil-sands mining region, air quality deterioration generated swift, long-term iWUE rises immediately at the onset of operations. In this case, the very active foliar strategy sharply reduced the intra-foliar CO 2 (Ci) pressure. Statistical modeling allowed identifying emissions as the main trigger for the iWUE swift shifts; subsequent combined effects of emissions and rising CO 2 led to passive foliar modes in the recent decades, and short-term variations due to climatic conditions appeared all along the series. Overall, boreal trees under different regional conditions modified their foliar strategies mostly without changing their stem growth. These findings underline the potential of acidifying emissions for prompting major iWUE increases due to lowering the stomatal apertures in leaves, and the combined influence of rising CO 2 in modulating other foliar responses. A fallout of this research is that degrading air quality may create true divergences in the relationship between tree-ring isotopes and climatic conditions, an impact to consider prior to using isotopic series for paleo-climatic modeling. Image 1 • IWUE was determined for boreal trees submitted to distinct levels of atmospheric emissions. • Trees from remote stands rise iWUE proportionally with atmospheric pCO 2. • IWUE trends of exposed stands depart from regular pCO 2 -induced reactions. • Trees modified their foliar strategies without changing their stem growth. • Modeling underlines the individual and combined influences of pCO 2 and acidifying pollutants. Gas exchange strategies of forests exposed to acidifying emissions create major divergences from responses to pCO 2 and climatic conditions, a concern for modeling global C and water cycles. [ABSTRACT FROM AUTHOR]

• We present LASS U–Pb and Sm–Nd isotope data from the Acasta Gneiss Complex, Canada. • Sm–Nd redistribution occurred at 3.3 Ga and again during the 1.89 Ga Wopmay orogen. • Sm–Nd redistribution is a common feature of ancient poly-metamorphic terranes. • Sm–Nd mobility may compromise the initial Nd isotope composition of ancient rocks. • Analysis of Nd-rich minerals proves useful for assessing bulk-rock Nd isotope data. The whole rock 143Nd isotope record of the Acasta Gneiss Complex (AGC) has been used to argue for the development of both depleted mantle and enriched crustal reservoirs during the Hadean. The 147Sm–143Nd isotope compositions of rocks from AGC, however, fall on an array with an errorchron date of ∼3.3 Ga, despite the majority of samples yielding substantially older zircon U–Pb ages. This has led to the suggestion of a major Sm–Nd "resetting" event at this time in the AGC. To better understand the Sm–Nd bulk-rock systematics of the AGC, we investigate the U–Pb age and Sm–Nd isotope compositions of apatite and titanite from the AGC, using the laser ablation split stream (LASS) method. Apatite from all samples yield broadly similar U–Pb dates of ∼1.89 to 1.83 Ga, in agreement with resetting during the 1.9 Ga Wopmay orogen. The Sm–Nd isotope compositions of the apatite, however, lie off the WR errorchron and show a high degree of initial Nd isotope heterogeneity. Conversely, titanite Sm–Nd systematics are consistent with the ∼3.3 Ga whole rock errorchron further supporting Sm–Nd modification at ∼3.3 Ga. Taken together, these show that the oldest rocks in the AGC underwent at least two post-crystallization events (at 3.3 and 1.9 Ga) that modified the Sm–Nd isotope system. These results also demonstrate the relative mobility of the Sm–Nd isotope system during orogenic events, which may compromise the ability to determine robust bulk-rock 143Nd isotope signatures. [ABSTRACT FROM AUTHOR]

Migratory songbirds breeding in the Canadian Boreal forest are exposed to mercury (Hg), a potent neurotoxin that impairs avian health, however, the degree of exposure depends on many factors. As breeding grounds are geographically remote and vast, the measurement of Hg in individual birds is impractical particularly at large spatial scales. Here, we present a Canada-wide dataset of nearly 2000 migratory songbirds that were used to assess summer Hg exposure of 15 songbird species sampled during fall migration. We measured Hg concentrations in tail feathers and related those to dietary guild, geographic capture location, age, sex and probable breeding ground locations using feather δ 2 H. Overall mean (±SE) feather Hg concentration was 1.49 ± 0.03 μg/g (N = 1946): however, a clear geographic gradient in feather Hg concentrations emerged being highest in East and lowest in West. Dietary guild was the next strongest predictor of feather Hg with insectivorous songbirds in Eastern Canada at particular risk due to Hg exposure on summer breeding grounds. This broad-scale assessment of Hg exposure in migratory songbirds in Canada can be used to guide future studies on finer-scale determinants of Hg exposure in birds., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Mining activities at Duparquet in Western Quebec (Canada) have significantly affected the local environment and left behind significant amounts of metals. Monitoring this contamination is essential to infer its past and present impacts on environmental quality and to evaluate the resulting human exposure. In that context, we measured long time series of Pb concentrations and their corresponding stable isotope ratios in long-lived white cedars (Thuja occidentalis L.) growing at Duparquet Lake in order to evaluate potential time variations of the Pb environmental contamination as well as to identify the responsible source(s). Results show that before 1950, Pb at Duparquet is mostly terrigenous. Lead concentrations rapidly increase afterwards. A simultaneous shift to lower 206 Pb/ 207 Pb ratios identifies the smelting of Abitibi ores as the source of contamination. An isotope mass balance model evaluates at roughly 7.5-20%, 5-40%, 5-9% and <3% the Pb contributions from local smelters at distances of 3.6, 3.9, 7 and 9 km, respectively. The dispersion of the Pb contamination plume is possibly driven by the distance from the Beattie smelter. We finally estimated a delay of at least 13 years between atmospheric emissions from the Beattie smelting activities and the time they are recorded by tree rings. Ultimately, this study demonstrates that white cedar tree rings series provide reliable archives of past and present Pb atmospheric contamination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Feeding ecology of Atlantic bluefin tuna (ABFT, Thunnus thynnus), from the Gulf of Saint Lawrence, Canada, was assessed by stomach content and stable isotope analyses. Stomachs were collected from 161 individuals averaging 249 ± 20 cm in curved fork length and 248 ± 64 in round weight. The fish were caught by commercial fishing boats using rod and reel gear during fall 2015-2017. Liver and muscle samples were taken from 133 fish for stable isotope analysis. Atlantic mackerel (Scomber scombrus) was the most abundant prey item in 2015 (%Alimentary index, %AI = 88.94), whereas in 2016 and 2017 the ABFT diet was mainly composed of Atlantic herring (Clupea harengus) (%AI = 56.73 and %AI = 77.23, respectively). PERMANOVA analysis revealed significant differences in the dietary composition between years. δ 15 N values varied between 12.3 and 15.4‰ for muscle and between 11.1 and 14.6‰ for liver. δ 13 C values ranged from -19.9 to -16.5‰ for muscle and from -20.7 to -17.3‰ for liver. PERMANOVA analysis also detected inter-annual isotopic differences in both muscle and liver samples (p < 0.05). Daily rations (DR) were similar in 2015 and 2016 (DR = 1.02 ± 0.32 and DR = 1.10 ± 0.21, respectively), but higher in 2017 (DR = 1.73 ± 0.54)., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Ecosystem reconstruction after mining disturbance is a challenge considering the multitude of factors that affect soil formation and revegetation. In the boreal forest of western Canada, peat material is often used as the organic amendment for land reclamation to upland forest. Carbon and water dynamics of peat-dominated ecosystems differ from natural upland forest soils. The objective of this work was to evaluate the evolution of soils reconstructed after mining disturbance using 13 C and 2 H analyses of n-alkane tracers. Ten soils from natural ecosystems were sampled (0-10 cm) and compared with 11 soils from novel ecosystems ranging in age from 0 to 30 yr, as well as a fresh peat sample. Soils supported different vegetation, including pine (Pinus spp.), aspen (Populus spp.), and white spruce [Picea glauca (Moench) Voss]. Despite overlaps for some individual n-alkanes, we found a dominance of n-C 25 in reconstructed soils, also dominant in the peat material, and a dominance of n-C 27 in natural soils, one of the dominant n-alkanes in natural forest vegetation. In addition, there was a significant difference in odd n-alkane δ 2 H and δ 13 C values between natural and reconstructed soils (p < .05). Differences in δ 2 H values, more negative for reconstructed soils than for natural soils, were attributed to changes in soil moisture, from wetter peat-dominated soils to drier upland forests; among forest types, δ 2 H values were most negative under pine vegetation. The δ 13 C composition of odd n-alkanes, in particular n-C 27 , was significantly related to tree age (p < .05). Overall, both 2 H and 13 C isotopic signatures of odd n-alkanes exhibited differences between natural and reconstructed soils. However, within the reconstructed soils, neither isotopic signature showed a clear evolution with age since reclamation., (© 2020 The Authors. Journal of Environmental Quality © 2020 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

• Quebecia terrane (Grenville Province) consists of over 95% juvenile 1.5 Ga oceanic arcs. • Slivers of crust with 1.8 Ga Nd ages divide Quebecia into a composite arc belt of terranes. • 1.5 Ga oceanic arcs were accreted to Laurentia after the 1.5 Ga Pinwarian orogenic event. • Some Quebecia terranes were rifted from the active margin and re-accreted further east. • Oblique tectonics may explain Pinwarian arc accretion without a major collisional orogen. There continues to be confusion in the geological community concerning the ages of crustal formation and crustal accretion within the central Grenville Province of Quebec. To clarify the geological history of crustal growth in the eastern part of the Quebecia terrane, sixty new Nd isotope analyses are presented from a 60,000 km2 area northwest of Baie Comeau. Most samples yield Pinwarian Nd model ages that suggest them to be derived from juvenile oceanic arc terranes. However, two large slivers with Paleoproterozoic TDM ages attest to the existence of hidden blocks of old crust, which divide the area of juvenile Pinwarian crust into a composite arc belt of smaller accreted terranes. The old crustal blocks probably do not reach the present surface, but represent an igneous crustal protolith of younger I-type magmatism. By comparison with a Mesozoic tectonic analogue, it is proposed that accreted juvenile arc crust with attached slivers of older crust were rifted away from an active margin to the west, and translated eastwards until blocked by the previously accreted Labradoria terrane. Although the Quebecia composite arc belt consists of over 95% of Pinwarian juvenile arc crust, the age of arc accretion was post-Pinwarian. The proposed oblique nature of the accretion process may explain the lack of a major collisional orogen at that time. This paper shows the usefulness of large-scale Nd isotope mapping of Precambrian crustal terranes to clarify complex processes of crustal formation and arc accretion. [ABSTRACT FROM AUTHOR]

The article reports on the concerns about a shortage of medical isotope supply in Canada due to decision of the National Research Universal (NRU) nuclear research reactor in Chalk River, Ontario to stop production in October 2016. Particular focus is given to the statement of Andrew Ross, president of the nuclear medicine organization Canadian Association of Nuclear Medicine, on the lack of transparency on the stability of isotope supply.

The isotope ratios of strontium (Sr) and lead (Pb) in water derive from local geology and their isotopic signature can be linked to the age and type of underlying bedrocks and soils (if applicable), and are transferred up the food-chain. Both elements are transferred to human blood through diet and water, and some of it will ultimately be incorporated into the hair structure, making Sr and Pb isotopes interesting tools for tracing human mobility. In this study, we analyzed both the elemental concentration and isotope ratios of Sr and Pb from four different women of different ages to monitor their permanent relocation from central France to Eastern Canada during the summer 2012. For comparison, we also characterized bulk hair samples of sedentary individuals and local tap waters from their regions of origin and of settlement. Our results indicate that the 87Sr/86Sr and 206Pb/204Pb ratios are significantly modified by the change of environment, but also confirm that human hair compositions are impacted by other external factors (such as dust). Sr and Pb isotope systematics demonstrate their added value for detecting human mobility, but require further studies to better constrain the main sources and processes controlling their respective budgets in human hair for provenancing purposes., (Copyright © 2014 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.)