Lithium (Li) is a strategic element in the global energy transition, largely driven by its use in lithium-ion batteries for electric vehicles. This study examines the distribution of Li and associated elements (Cs, Rb, K, Be, Sn) in Minas Gerais State, southeastern Brazil, through a low-density stream sediment geochemical survey combined with robust statistical approaches. Baseline values were defined using different calculation methods, multivariate statistics, and compositional data analysis, aiming to delineate Li-rich zones and evaluate the Ara & ccedil;ua & iacute; Fold Belt, a key domain of the Eastern Brazilian Pegmatite Province. Results show that lithological diversity across the seven geotectonic units strongly controls geochemical baselines. The Ara & ccedil;ua & iacute; Fold Belt exhibits the largest concentration range and highest correlation coefficients between Li and related elements, reflecting a common source in pegmatites and parental granites. Among the tested methods, median +/- 2MAD, or mMAD (where MAD is median absolute deviation), provided more consistent baselines and thresholds than Tukey's inner fence. Staged factor analysis (centered log-ratio and isometric log-ratio transformations) characterized main geochemical associations and supported the generation of the Geochemical Mineralization Probability Index mineralization map, a predictive layer integrated into a Mineral Prospectivity Map. The study demonstrates how stream sediment geochemistry, treated with advanced statistical methods, can effectively guide mineral exploration strategies for critical elements such as Li.
The arid alpine landscape on the northern margin of the Qaidam Basin, northern Tibetan Plateau, presents a challenge for conventional geochemical background modeling. Leveraging a unique multi-scale geochemical dataset (1:200 000, 1195 samples; 1:50 000, 18 855 samples; 1:25 000, 35 675 samples) from the Qinghai Geological Exploration Fund, this study systematically evaluates scale effects on background estimation. We compared the performance of four prevalent methods - iterative exclusion, median absolute deviation, exploratory data analysis, and the concentration-area fractal method - and found that a multi-method approach effectively balances the comprehensiveness and precision of the background modeling framework. To address the spatial heterogeneity of backgrounds caused by complex geology, we propose a novel subzone robust background method (SRBM). This method calculates robust median background values within distinct geological units and generates an adaptive background field through area-weighted fusion. In the Banhongshan area, application of the SRBM precisely calibrated the gold background to 0.47 ng g-1, successfully identifying two concealed gold anomalies obscured by traditional methods; one anomaly coincides perfectly with known industrial orebodies. This research demonstrates that high-density sampling (1:25 000) significantly enhances the signal-to-noise ratio for chalcophile elements in arid alpine terrains. The SRBM, by integrating geological knowledge with robust statistics, provides a powerful and reliable tool for weak geochemical signal extraction in both mineral exploration and environmental assessment.
Tree canopy fluids, transpired through leaf stomata, can be collected and readily analyzed for their elemental concentrations. However, these transpired fluids have rarely been considered as a sample medium in the context of exploration geochemistry. The objective of this proof-of-concept study was to test sampling and analytical protocols for transpired fluids from Norway spruce, and to examine whether they contain a geochemical signal of the underlying geology. Seventeen samples were collected over two Au-Co prospects and the surrounding background calc-silicate and mafic rocks in the glaciated terrain of northern Finland. A polyethylene plastic bag was tied over a bundle of sun-lit branches for four days in mid-July. Under partially cloudy conditions, 10 ml of fluid was collected, sufficient for single quadrupole inductively coupled plasma mass spectrometry analysis after laboratory filtering. The quality of the uncensored data was adequate for 27 elements, the concentrations of which ranged from a maximum of 1.5 g l(-1) for Sn to 75.5 mg l(-1) for Ca. The framework of compositional data analysis was used to detect element log-ratios that discriminate samples according to the underlying lithology and mineralization. The results indicate that lithological units can be discriminated with log-ratios of Al, B, and Li. Cesium, La, and Ce exhibit anomalies on top of the subcropping prospects. Transpired fluids from the Norway spruce canopy are a practical non-invasive sampling medium, making them suitable for the exploration of environmentally sensitive and other restricted regions. Further research is necessary to validate the effectiveness of transpired fluids from Norway spruce as a sampling medium in mineral exploration.
In remote semi-arid regions like the San Juan River watershed, determining the distribution and sources of aluminum (Al), arsenic (As), and lead (Pb) can inform water managers and users in mitigating potentially negative effects on human and ecosystem health. Water samples were collected from 33 tributaries and sites along the San Juan River during the monsoon seasons of 2021 and 2022. Synoptic water quality samples collected during baseflow along the San Juan River in February 2021 had Al, As, and Pb concentrations below U.S. Environmental Protection Agency (EPA) drinking water thresholds (50-200 & micro;g l(-1) Al, 10 & micro;g l(-1) As, 15 & micro;g l(-1) Pb). Total water concentrations of Al, As, and Pb were generally higher in 2022 than in 2021 with average Al concentrations 9.74-98.45% higher in 2022 than in 2021. Average As and Pb concentrations were 18.27-96.29% higher and 11.54-98.66% higher in 2022 than 2021, respectively. Total water concentrations of Al, As, and Pb were greater than EPA thresholds at most sites and highest at Chinle Creek near Bluff, La Plata River, Comb Wash, and Gallegos Canyon. Most sites also had higher particulate Al, As, and Pb concentrations in total water compared to filtered concentrations. A combination of water chemistry, geology, water use, and geomorphology suggested that the source(s) of Al, As, and Pb in total water is likely geogenic non-point. This study enhances understanding of the distribution and potential sources of Al, As, and Pb in the San Juan River watershed, bringing awareness to the community, and providing tools to evaluate metals concentrations in remote semi-arid regions worldwide.
We assessed the spatial extent and source signatures of metal contamination in the Sudbury region, Ontario, Canada, using three lichen species (Stereocaulon spp., Cladonia rangiferina, Evernia mesomorpha), moss (Dicranum scoparium), humus forms, mineral soils, and snowpack. Baseline concentrations were established for 23 elements across these 7 monitors. Of the biomonitors, Stereocaulon spp. generally shows the highest baseline concentrations for most metals, C. rangiferina the lowest, and E. mesomorpha intermediate. In contrast, the moss D. scoparium has higher concentrations of nutrient elements (e.g. Ca, Mg, K) but comparatively low metal concentrations relative to the lichen species. Distances from the city to the baseline concentrations for As, Cd, Co, Cu, Ni, and Pb were compared across media types. Elemental concentrations in snow particulate matter (PM) returns to baseline within 9-15 km of the city (with one exception at 30 km for Ni), whereas soils remain elevated to 25-46 km. Lichens exhibit a steep 'principal' contamination gradient like snow PM but remain elevated until 26-38 km, roughly matching soil patterns and suggesting resuspended legacy contamination. The Bioaccumulation Scale was applied to lichens for cross-species comparison and determining environmentally relevant elements. The scale reduces cross-species variability but does not eliminate species-specific effects. Around the smelters, 13 of 32 elements exceed the environmentally relevant threshold (Bioaccumulation ratio >3.4). This work provides updated baseline values and baseline distances for a region historically impacted by mining activity, and integrates multiple media to reveal relationships between modern and legacy contamination.
