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•Characterization of ore mineral assemblages from Fåvne and Loki’s Castle SMS deposits.•Investigation into the mineralogical distribution and genetic aspects of Co.•Stratigraphic ...footwall composition influences enrichment and spatial zonation of Co.•Saline hydrothermal fluids may be important for Co endowment in SMS deposits.
The demand for responsibly sourced cobalt has increased dramatically as a result of the global transition to ‘fossil-free’ electromobility. However, the distribution, mineralogical expressions and mechanisms of concentration of Co in different types of hydrothermal ore deposits remain poorly constrained, inhibiting resource assessments and exploration. Here we report Co and other metal concentrations in ores from the active Fåvne and Loki’s Castle seafloor massive sulfide (SMS) deposits located along the Mohns Ridge and assess some genetic aspects of Co. The assemblages from the recently discovered Fåvne deposit are dominated by either pyrrhotite-isocubanite or sphalerite, in both cases with abundant anhydrite and local Fe-oxides. They show high whole-rock Co concentrations (average 0.31 wt%, up to 0.98 wt%) and Co is enriched in the Cu-rich relative to the Zn-rich assemblages. No independent Co-minerals are observed; rather, Co is variably hosted in pyrrhotite (up to 1.03 wt%), isocubanite (up to 0.71 wt%), sphalerite (up to 0.14 wt%) and magnetite (∼100 ppm). The assemblages from Loki’s Castle are dominated by pyrrhotite, isocubanite, sphalerite, amorphous silica and barite, and they exhibit distinctly lower Co concentrations in both whole-rock samples (average 62 ppm, up to 368 ppm) and in individual minerals (up to 152, 148 and 99 ppm in isocubanite, sphalerite and pyrrhotite, respectively). At both deposits, Co is interpreted to enter the Fe-, Cu-Fe- and Zn-sulfides and Fe-oxides via simple Co2+ ↔ (Fe,Zn)2+ substitutions and its mineralogical distribution reflects a combination of crystal-chemical controls (e.g., spin state compatibility between Co2+ and the divalent cation) and changing hydrothermal fluid conditions (e.g., temperature) during mineral formation. Based on a comparison with global SMS and VMS deposits, we suggest that the ‘diffuse’ high-temperature venting at Fåvne can in part explain the enrichment of Co in the surficial sulfides, whereas at Loki’s Castle more Co-rich sulfides might occur in the interior of the deposit. Furthermore, Fåvne and several Co-rich deposits elsewhere show evidence for the involvement of saline hydrothermal fluids with enhanced capacity to mobilize and transport Co during their evolution. While their future role as a source of Co and other critical commodities remains uncertain, active SMS deposits provide unique insights into the processes and conditions associated with formation of hydrothermal Co mineralization that will aid both deep-sea and onshore exploration.
The acidification of agricultural soils in high rainfall regions is usually countered by the application of finely ground calcite or dolomite. As this carbonate dissolves, soil pH is raised, but CO2 ...is released. Mining activities often produce large quantities of very fine silicate rock-derived powders that are commonly deposited in stockpiles. However, the dissolution of such powders can also result in an increase in pH, without any direct release of CO2. Of particular interest are those silicate powders that have a high reactivity and higher capacity for raising pH. In this contribution, we report experimental work addressing the dissolution of various silicate rock-derived powders that were produced during mining activities in Norway under conditions that were representative of weathering in agricultural soils. Three different powders—derived from Åheim dunite, Stjernøya nepheline syenite, or Tellnes ilmenite norite—were exposed to different acids at pH 4 in unstirred flow cells, and dissolution or leaching kinetics were determined from the changes in the fluid composition. Based on these kinetics, pH neutralization rates were determined for the individual powders and compared to expected values for carbonates. Based on this comparison, it is concluded that the application of silicate rock-derived powder dissolution to replace carbonate-based liming may not be feasible due to slower reaction rates, unless larger quantities of a finer particle size than normal are used. The application of larger volumes of slower-reacting silicates may have the additional benefit of reducing the required frequency of liming.
Laser ablation ICPMS (inductively coupled plasma mass spectrometry) analysis is a powerful tool for studies of fish ecology, based on measurement of the chemical composition of otoliths (ear stones). ...A key trade-off for this analysis is selecting the size of the ablation area to maximize the resolution for discrete temporal intervals during the life of an individual fish, vs the amount of otolith material required to produce reliable data. Three different widths of ablation lines were used to analyze the otoliths of European hake (
Merluccius merluccius
). The best temporal resolution was produced by ablation lines of 10 μm width, corresponding to less than 2 weeks in the fish’s life, but the data from this configuration were variable and often below the detection limit for many elements. Ablation lines of 20 and 30 μm width produced accurate and precise data corresponding to approximately 20 and 30 days in terms of temporal resolution. When tested on hake otoliths, the measured element concentrations differed significantly between the 20 and 30 μm lines. The 30 μm ablation line resulted in a better multivariate model for discrimination between populations, with higher classification success and higher probability of individual assignment to source location.
Connectivity between spawning and nursery grounds influences the colonization, replenishment and resilience of populations of marine organisms. Connectivity rate, measured as the exchange of ...individuals between spawning and nursery grounds, is therefore a crucial determinant of stock size. However, connectivity of early-life stages is hard to explore due to sampling limitations and insufficient knowledge on potential larval sources. Here we present new insights into pre- and post-settlement dispersal of the common sole (Solea solea L.) at a spatial scale of 5–500 km in the Southern North Sea. Patterns at a scale of <100 km were considered local, whereas patterns further than 100 km were considered regional. Multi-elemental signatures of the otolith edge of 213 juvenile sole were used to discriminate at 79% of overall accuracy three main nursery grounds in the Southern North Sea, namely UK coast, Belgian coast and Dutch Wadden Sea. Interregional differences in otolith composition (especially for Mg, Mn and Ba) suggest that sole migration following settlement is limited in the Southern North Sea. Elemental signatures of the same fish indicated mixing during larval dispersal. Each nursery ground recruited an important mix of juveniles from three of the four chemically distinct natal sources identified from the larval otolith signatures. However the percentage of correct regional re-assignment varied from 67 to 80% with a maximum in the Wadden Sea. The results contributed to the validation of biophysical models of larval drift. Our findings support decision making for both fisheries management and marine spatial planning at the national and European level.
•In the North Sea, juvenile otolith signatures differ at the regional scale (100 km).•Movement appears to be limited once the juveniles have reached a nursery ground.•Local nursery areas receive larvae from four chemically distinct natal sources.•Mixed larval contributions to nurseries point to an extensive larval dispersal.
A double focusing inductively coupled plasma mass spectrometer with an ultrasonic nebulizer and a desolvation unit was used to measure lead-206 lead-207, lead-206 lead-208 and lead-207 lead-208 ...ratios in lead standard SRM981, diluted to total lead concentrations of 1 to 1000 ng per litre. At lead concentrations down to 10 ng per litre, it was possible to determine isotope ratios with sufficient precision, accuracy and reproducibility for many environmental studies. At 1 ng per litre, the procedural blanks were a problem. The method was used to obtain lead isotope ratios for synthetic (SRM1643d) and natural (SLRS-3) standard waters. Reproducibility was excellent for the synthetic water, but lower for the natural water, probably due to matrix effects. Isotope measurements at the sub-ng per litre level will require further work to reduce procedural blanks. In particular, instrument contamination and memory effects for lead will need to be solved.
Elemental and isotopic analyses of lead present at ultra-trace levels were obtained with a double focusing inductively coupled plasma mass spectrometer on a Pyrenean springwater. The sampling was ...carried out across a time series of 598 days encompassing an earthquake of magnitude 5.2. Lead concentrations show a tenfold increase and isotopic compositions shift toward anthropogenic values four days prior to the quake. The time lag between these geochemical anomalies and the earthquake, combined with hydrogeological constraints, are then used to infer where and when strain changes during earthquake preparation processes went beyond the threshold required to temporarily mix waters from normally independent aquifers. The occurrence of pre-seismic centrifugal strain waves propagating from the epicenter area is proposed on the basis of the observed geochemical anomalies.
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