Geochemical Indicators Research Articles

Lipid Biomarkers in Urban Soils of the Alluvial Area near Sava River, Belgrade, Serbia.

This study focused on the investigation of soil samples from the alluvial zone of the Sava River, located near the heating plant in New Belgrade, Serbia. Using gas chromatography with flame ionization detection (GC-FID), a broad range of alkanes, including linear n-alkanes (C10 to C33) and isoprenoids, was analyzed in all samples. The obtained datasets were effectively made simpler by applying multivariate statistical analysis. Various geochemical indices (CPI, ACL, AI, TAR, etc.) and ratios (S/L, Paq, Pwax, etc.) were calculated and used to distinguish between biogenic and anthropogenic contributions. This approach added a higher level of precision to the source identification of hydrocarbons and provided a detailed geochemical characterization of the investigated soil. The results showed that the topsoil had a high content of TPH (average value, 90.65 mg kg-1), potentially related to an accidental oil spill that occurred repeatedly over extended periods. The uncommon n-alkane profiles reported for the investigated soil samples are probably the result of inputs related to anthropogenic sources, emphasizing that petroleum was the main source of the short-chain n-alkanes. The methodology developed in this study was proven to be efficient for the assessment of the environmental quality of the soil in an urban part of New Belgrade, but it can also be a useful tool for soil monitoring and for a pollution assessment in other (sub)urban areas.

Material source, sedimentary environment, and mineralization process of Shengzhou diatomite deposit in Eastern Zhejiang Province, China

ABSTRACT The Shengzhou diatomite deposit, located in the Shengzhou-Xinchang basin, is recognized as one of the largest diatomite deposits in China. The scanning electron microscopy (SEM-EDS), mineral compositions and elemental geochemistry of the samples were analysed to identify the nutrient sources, depositional environments, and mineralization process. Through scanning electron microscopy, the predominant diatom species observed are Aulacoseira granulata (Ehrenberg) Simonsen and Cyclotella shengxianensis Huang and Cai. The results of X-ray diffraction (XRD) analysis results indicate that the mineral composition of diatomite mainly consists of opal-A, quartz, clay minerals, feldspar, carbonate minerals, and pyrite. The results of XRF and ICP-MS analysis show that the content of SiO2 ranges from 59.11% to 69.44%, and the trace nutrient elements such as Mo, U, V, Co, Ni, Cu, and Zn are enriched. The correlation of geochemical composition between diatomite and Cretaceous volcanic rocks in the study area indicates that the weathering of volcanic rocks provides nutrients for diatom growth. Multiple geochemical indicators (Sr/Ba, V/Cr, Ni/Co, U/Th, V/(V+Ni), C-value, CIA, and Sr/Cu) and palaeontological evidence indicate that the diatomite was formed in a freshwater, oxic, and hot-humid environment. As the diatomite is susceptible to denudation, the overlying basalt may protect the deposit.

Assessment of Heavy Metal Content and Identification of Their Sources in Bottom Sediments and Various Macrophyte Species of the Narew River (Poland)

The condition of the aquatic environment, particularly in protected areas of high ecological value such as the Narew River, requires detailed monitoring to identify and minimise the impact of anthropogenic factors on the ecosystem. This study focused on the content of heavy metals in bottom sediments and macrophytes of the Narew River, emphasising the influence of human activities and natural factors on this ecologically valuable ecosystem. Pb, Cr, Zn, Cd, Fe, and Mn concentrations were analysed in sediment samples, and ten macrophyte species were collected at 11 sampling points along the river. A geochemical index (Igeo) and multivariate statistical analyses were employed to identify sources of contamination. The digested samples (sediments and plants) were analysed for Pb, Cr, Cu, Zn, Ni, Cd, Fe, and Mn using flame atomic absorption spectrometry (AAS) on an ICE 3500 Thermo Scientific spectrometer, with a measurement error below 5%, validated against certified reference materials. The study results indicated that most metals, including Ni, Cr, Co, Fe, and Mn, predominantly originate from natural geological processes. In contrast, Zn, Cd, Cu, and Pb were identified as being enriched due to anthropogenic activities. An analysis of macrophytes revealed varied patterns of metal accumulation, which correspond to the bioavailability of metals and their environmental concentrations. Comprehensive statistical analyses provided insights into the predominant sources of metal contamination, closely associated with industrial emissions, agricultural runoff, and transportation activities. The integration of sediment and macrophyte monitoring allowed for a thorough evaluation of the Narew River ecosystem, facilitating the identification of key pollution sources. These findings highlight the critical need for measures to mitigate anthropogenic contributions of heavy metals—particularly from industrial, agricultural, and transportation sectors—to safeguard the Narew River’s unique ecological and natural heritage.

Dominance of Particulate Mercury in Stream Transport and Rapid Watershed Recovery from Wildfires in Northern California, USA.

Frequency and intensity of wildfires are expected to increase due to climate change, especially in areas with a long summer drought. Forests are a major sink for the global pollutant mercury (Hg), and fluvial transport of Hg from recently burned watersheds has not been widely investigated. Here, we examined two years of fluvial transport of Hg and its speciation (total Hg, methyl-Hg, particulate, and dissolved forms) under storm events and baseflow in two recently burned watersheds with different burned proportions and one nonburned reference watershed in the Coastal Ranges of northern California. We examined postfire storm-event transport of Hg and its methylated form (methyl-Hg), addressed the importance of the "initial runoff pulse" to postfire Hg fluvial transport and its predominant association with suspended solids, and elucidated potential sources of Hg exports from the burned landscapes using geochemical indicators, which suggested that ash materials were likely the significant sources of particulates in the first high-flow season postfire but not subsequently. The maximum total suspended solid and total Hg levels in the "first pulse" at the severely burned watershed were 442 and 46 times higher, respectively, than those at the reference watershed. Stream suspended solid and Hg levels declined substantially in the burned watersheds after just a few months of rainfall likely due to the rapid regrowth of vegetation commonly observed in postfire landscapes, implying that the wildfire effects on immediate Hg inputs from the burned landscape are at most transient in nature.

Mass organic matter accumulation induced by rapid redox variations in lakes: Evidence from the Miaoxi area, Bohai Bay Basin, China

The Member 4 of the Paleogene Shahejie Formation (Es4) in the Bohai Bay Basin is interspersed with a set of high-quality source rocks typified as intercalation of red and black mudstones. A large amount of petroleum (crude oil) originates from these source rocks. The Paleocene–Eocene Thermal Maximum (PETM) event occurred during the deposition of Es4 in the Bohai Bay Basin, and the organic matter enrichment model under this event is worth further investigation due to its relationship with and influence on petroleum accumulations. Well LK25-A, as the first oil exploration well drilled into the Es4 in Miaoxi area, serves as a valuable case to study organic matter accumulation. In this study, we integrate total organic carbon (TOC), Rock-Eval pyrolysis, microscopic observation, vitrinite reflectance (VRo), elemental analysis, and gas chromatography–mass spectrometry (GC–MS) to evaluate the hydrocarbon generation potential, organic matter types, thermal maturity, and sedimentary environment of the Es4 in Miaoxi area. The analysis of maceral and rock pyrolysis data reveals that Type I and Type II organic matter make up the majority of Paleogene mudstones in this region. The TOC and rock pyrolysis data show that mudstones in this area have high organic matter abundance and oil-generation potential. The measured vitrinite reflectance distribution of mudstone samples, which ranges from 0.3% to 0.74%, demonstrates that the Paleogene strata are at the immature to mature stage, and the samples from this area contain a sizable amount of bituminite and mineral-bituminous groundmass. The analysis of biomarkers in the mudstone samples indicates that most of the mudstones in this area are in lacustrine and brackish-hypersaline lacustrine environment under a reducing condition, and some of the red mudstones in the Es4 are formed under a suboxic condition. Based on the size and morphology of the pyrite framboid, the redox conditions of the water mass during deposition or diagenesis are further analyzed. The ratio of the size of framboid pyrite (D) to the size of its micrograins (d) suggests that the Es4 black mudstone developed in an anoxic sulfuretted water environment. Both the inorganic and organic geochemical indexes show that the Paleogene paleoclimate has a great influence on the source rocks of Es4 in this area. The distribution of red–black strata in the area is the result of the combined action of the water redox state and the climatic variation during the PETM event. The development models of organic-rich source rocks from the Es3 and Es4 in this area have been created in light of potential connections between rapid redox variation and the PETM event during the Paleogene. These models may offer a theoretical guidance for petroleum exploration in Miaoxi area of Bohai Bay Basin and other contemporaneous continental basins around the world.

Assessment of landscape impact on snow chemical composition in terms of mineral geochemical exploration

In areas with cold climate seasonal snowpack is an attractive sampling material for geochemical exploration of deep mineral accumulations. However, previous studies on assessment of exploration efficiency of snow cover have paid little attention to snow composition variability conditioned by local landscape structure.The layered sampling of snow sections was performed in different landscape settings of the local area. The research area is characterized by the absence of ore mineralization zones and low anthropogenic load. The physical-chemical parameters and concentration of wide range of elements were identified in snowmelt. Multi-component data was integrated by means of factor principal component analysis. Besides, additive and differential geochemical indexes were used. The classification snow models were developed using hierarchical cluster analysis. The variance of chemical elements distribution and factor models of geochemical pattern were compared before and after reduction of background fluctuation. In terms of variation coefficient values of chemical elements the area has background parameters of chemical inhomogeneity. In total variance a lateral component prevails over a vertical one. The highest concentrations of chemical elements were found in snow section of forest landscape. It is necessary to take into account the fact of geochemical background fluctuation when interpreting the data of metal assay snow survey.After the reduction of lateral geochemical background fluctuation, the factor model has better classified the chemical elements in terms of their connection with soluble and insoluble occurrence forms. The values of differential index of liquid and solid phases have a similar satisfactory vertical variability in different landscapes. The analysis of chemical elements concentration reveals snow horizons that were or are affected by thaw and percolating water. The snow bottom layer, which is sampled at geochemical exploration, is not strong influenced by elution.

Apatite geochemical indicators for magma mixing and fractional crystallization in the origin of A-type granite

Geological and geochemical observations show that magma mixing and fractional crystallization are fundamental processes in the origin of A-type granites, with the dominant process determining their specific genesis. However, it is difficult to evidently distinguish such two processes using whole-rock geochemistry. Apatite has a long crystallization history and can precipitate from the melt during the whole magmatic evolution process, and its geochemical and Sr isotopic data would constrain the magma mixing and crystal fractionation processes. Here we present the integrated geochemical data and Sr isotopic compositions of apatite from mafic microgranular enclaves (MMEs) and their host A-type granites in the early Cretaceous Qianshan pluton to fingerprint apatite geochemical indicators for tracing magma mixing and fractional crystallization. The variable Sr isotopic compositions of apatites in the mafic microgranular enclaves (0.7097 to 0.7211) and the host biotite granite (0.7131 to 0.7171) suggest a magma mixing process, which cannot be revealed by consistent whole-rock Sr isotopic compositions. The trend between Eu/Eu* and rare earth elements + yttrium (REE + Y) contents and Sr contents in apatite among different samples mimics the magma mixing trend observed in whole-rock, suggesting that the broad range of Sr contents and abrupt increases in REE + Y contents can record the mixing process. However, the effect of fractional crystallization on the apatite composition depends on the partition behavior of elements in different minerals. Specifically, the continuous decreases in Eu/Eu* and Sr contents of apatites effectively indicate progressive feldspar crystallization, and the decreases in the (La/Sm)N and (La/Yb)N ratios of apatites suggest the crystallization of feldspar, biotite and apatite, while the increases of these ratios may trace the crystallization of minerals rich in MREE and/or HREE such as hornblende, zircon, and titanite. These observations confirm the sensitivity of apatite Sr isotopes and trace elements content, as well as REE patterns to magma mixing and fractional crystallization, thus providing valuable insights into the complicated magma evolution processes and petrogenesis of A-type granites. Furthermore, the universality of apatite in granitic rocks and the commonality of magmatic mixing and fractional crystallization in granite origin highlight the broader applicability of our study, offering a valuable perspective for understanding the origin of other granitoids.

Characterisation of Five Natural Magnetite Reference Materials for In Situ Iron Isotope Measurement with Application to Magmatic Ni‐Cu Sulfide Mineralisation

Iron isotope ratios in magnetite have been widely used to reveal critical geological and biological processes. Laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS) is ideally suited for measurement of Fe isotope ratios, however the lack of suitable reference materials poses a significant challenge for in situ Fe isotopic measurements in magnetites. In this study, five high‐quality natural magnetite crystals were characterised for Fe isotope ratios using solution nebulisation (SN)‐MC‐ICP‐MS and LA‐MC‐ICP‐MS. The effects of LA‐MC‐ICP‐MS analytical conditions were investigated to obtain precise and accurate Fe isotope ratios. The yielded intermediate measurement precisions for the δ56Fe values in the five investigated magnetites were ± 0.05–0.06‰ (2s) using SN‐MC‐ICP‐MS and ± 0.08–0.14‰ (2s) using LA‐MC‐ICP‐MS. Magnetites with homogeneous Fe isotopic compositions in hand‐specimen measurements and microanalysis can serve as potential reference materials for in situ Fe isotopic measurement. Furthermore, the Fe isotope ratios in the magnetites from the Jinchuan Ni‐Cu‐PGE sulfide deposit were measured using LA‐MC‐ICP‐MS with natural magnetite as the bracketing calibrator. The increase in the Fe isotopic composition with magmatic sulfide evolution was primarily dominated by oxygen fugacity (fO2) and hydrothermal fluids. This finding implies that the Fe isotopic composition of magnetite can serve as a potential geochemical indicator of magmatic Ni‐Cu sulfide mineralisation.

An evaluation of morphometrical trends in a population of Woodringina hornerstownensis Olsson, 1960 (Foraminifera) reveals the role of intraspecific variations for paleoceanographical studies

The foraminiferal species Woodringina hornerstownensis is stratigraphically limited between the stages Danian and Selandian and was adapted to inhabit the mixed layer water column. We present a case study based on morphometry of W. hornerstownensis recovered in upper Danian strata (biozone P2) in the Pernambuco-Paraiba Basin at the Poty quarry. The morphometric data, associated with abundance and geochemical indicators, point to (i) an increase in size towards the top of the studied interval, associated with the shallowing-upward trend of the Maria Farinha Formation, and (ii) an increase in size directly related to the increase in abundance. By integrating and incorporating a specific variation of W. hornerstownensis into abundance parameters, we conclude that the shell increase appears to be consistent. Our results suggest that the increase in size responds to environmental optimum conditions for the species W. hornerstownensis. In a broader context, our work demonstrates the usefulness of morphometric indicators and the significance of intraspecific variation when interpreting macroecological patterns. Keywords: planktic foraminifera, paleoceanography, intraspecific variation, upper Danian, South Atlantic Ocean.

Paleoenvironmental evolution and East Asian monsoon records through three stages of paleochannels since the mid-pleistocene in the Western Bohai Sea, North China

Three stages of paleochannels development, dating back to the Mid-Pleistocene, have been identified in the western Bohai Sea (BS) region. However, the factors controlling their sedimentary formation remain unclear. This study analyzed samples from DZQ01 and adjacent boreholes to establish a chronological framework through AMS 14C and OSL dating, complemented by grain size and geochemical analyses. End-member analysis using the Generalized Weibull method successfully separated three components: EM1, EM2, and EM3. EM3 (<26.28 μm) reflects the influence of the East Asian Summer Monsoon (EASM), while EM2 (26.28–105.1 μm) is indicative of the East Asian Winter Monsoon (EAWM). Geochemical indicators, such as the Rb/Sr ratio, reflect the impact of paleoclimatic changes. This study identified five major glaciation events since the Mid-Pleistocene. The DU6 unit recorded two glacial stages (300–272 cal. ka B.P.), characterized by a weakened EASM and a stronger EAWM. Similarly, the DU4 unit recorded two glacial stages (165–127 cal. ka B.P.), also marked by a subdued EASM and an enhanced EAWM. The DU2 unit reflects a prolonged glacial stages (71–14 cal. ka B.P.), dominated by the EAWM, resulting in cold and dry conditions. Overall, the uplift of the Tibetan Plateau and sea-level fluctuation significantly influenced the formation and evolution of paleochannels, with the sedimentary characteristics closely tied to the intensities of the East Asian Monsoon (EAM).

Application of a new multi-elevation method for determining the elemental composition of atmospheric precipitation in coastal marine zones.

Assessing local air quality using traditional methods, such as analyzing precipitation composition, is often difficult due to the complex data, which is influenced by a variety of chemical elements from distant atmospheric sources and cyclone formation areas. This study presents a new approach to overcome these challenges: a multi-elevation sampling method that improves the accuracy of local air quality measurements. By collecting precipitation samples at different ground elevations, the technique takes advantage of the natural process where raindrops and snowflakes collect more elements as they fall through the air. This method helps to distinguish local air quality from background levels found at higher, non-industrial elevations. The primary goal was to isolate and identify the elemental fingerprints of marine influences, while excluding contributions from cyclones. In February 2023, 51 meltwater samples were collected from 17 observation points in the city of Sochi under southeast wind conditions. These samples revealed a spectrum of chemical elements, predominantly of marine origin (Mg > Na > Sr > Ca > K > Ce > Mn). The results showed significant differences in elemental concentrations between upland and coastal areas. The Geochemical Indicator of Marine Origin (GIM) ranged from 22 to 3235, confirming the strong influence of marine aerosols in the area. These findings demonstrate the effectiveness of the multi-elevation sampling method in providing robust environmental assessments. This approach, combined with the GIM index, offers valuable insights for improving environmental policies and public health, particularly in coastal regions affected by marine aerosols.

Resilience and Resistance of Vegetation in Response to Droughts in a Subtropical Humid Region Dominated by Karst

The resilience and resistance of vegetation are important indicators of the vegetation’s response to droughts. Owing to the uniqueness of the environment in humid karst areas, results from studies on other climatic zones may not necessarily present the status of vegetation resilience and resistance in humid karst areas. Herein, We calculated vegetation resilience and resistance by autoregressive modeling using Enhanced Vegetation Index (EVI), Total Water Storage Anomaly (TWSA), temperature (TA), precipitation (PRE) data, An analysis of variance (ANOVA) was then conducted to compare the differences in resilience and resistance of different vegetation types in the study area, as well as the differences in resilience and resistance of vegetation in different sub-geomorphic zones. Finally, natural factors affecting vegetation resilience and resistance were quantified using partial least squares structural equation modeling (PLS-SEM). The results demonstrate the following points. First, vegetation resilience, total-water-storage anomaly resistance, and vegetation resistance against precipitation anomalies were lower in karst areas of the study area than in non-karst areas of the study area (except for vegetation resistance against temperature anomalies). Second, vegetation resilience was the lowest in some sub-geomorphic zones within karst areas, and it was still comparable to that in semiarid areas. Third, precipitation and temperature were important factors that affected the resilience and resistance of vegetation in karst areas, and the geochemical indicators (CaO, MgO, and SiO2) of soil parent material were major factors that affected the resistance and resilience of vegetation in non-karst areas. In summary, this study was undertaken to reveal the natural characteristics of vegetation resilience and resistance in humid karst regions. Our findings complement and expand the existing body of knowledge on vegetation resilience and resistance in other ecologically fragile zones limited by moisture.

U-Pb geochronology and trace elements in zircon from hydrothermal alteration zones of Sharlo Dere target, Chelopech deposit (Bulgaria)

Accessory zircon is an important geochemical indicator of magma fertility in magmatic-hydrothermal deposits. It is used in ore deposit exploration due to the widely accepted consideration of the resistant zircon behavior during overprinting processes. The main purpose of present study is to investigate the geochemical characteristics of zircons in the high sulfidation epithermal deposit Chelopech deposit (Bulgaria) and test their stability in hydrothermal alteration zones of different intensity – from propylithic through sericitic and the most intensive advanced argillic. The zircon grains were selected from the main igneous rock type of the Sharlo Dere target – the diorite porphyries. In the different samples, the ore hosting diorite porphyries have undergone varying degrees of alteration. According to the combined LA-ICP-MS U-Pb age and trace element data, in advanced and even moderate argillic alteration zones some trace elements in the zircons reveal signs of mobility.

Multiple generations of garnet and their genetic significance in the Niukutou cobalt-rich Pb-Zn-(Fe) skarn deposit, East Kunlun orogenic belt, western China

The Niukutou deposit, situated within the Qimantagh ore-concentrated area of the East Kunlun Orogenic Belt (EKOB), represents a typical skarn-type Pb-Zn-(Fe) deposit that is also associated with cobalt (Co) mineralization. The main ore minerals include galena, sphalerite, magnetite, hematite, Co-bearing arsenopyrite, cobaltite and glaucodot. This study conducted geochronological and chemical composition analyses of multi-generational garnets from the deposit, aiming to elucidate their genetic significance in the mineralization process. Field and mineralogical observations indicate the presence of three generations of garnets: Grt-I, Grt-II, and Grt-III. The earliest garnet generation (Grt-I) formed during the prograde stage, typically in garnet skarns, and is often replaced by epidote. The second generation (Grt-II), which coexists with pyroxene, also formed during the prograde stage, whereas the third generation (Grt-III) is associated with pyrrhotite stockworks, suggesting its formation during the sulfide stage. Using in-situ LA-ICP-MS U-Pb dating, garnets yield ages of approximately 230–234 Ma, which aligns with the age of 231.8 ± 7.5 Ma obtained from hydrothermal titanite in the deposit. These ages, combined with those of the previous studies, indicate major magmatic and metallogenic activity of 220–240 Ma in the Qimantagh area. Each generation of garnets displays oscillatory zoning characterized by alternating andradite and grossular compositions. The variations in Sn and high field-strength element (HFSE) contents across different garnet generations indicate an increasing trend in oxygen fugacity as mineralization progresses. The high Sn contents in the Niukutou garnets provide geochemical clues for the potential of Sn-W mineralization in this deposit, which should pay attention to in future exploration. Additionally, the high As concentrations in the Niukutou garnets suggest an As-rich hydrothermal fluid, which, owing to the stronger affinity of cobalt for sulfarsenides over sulfides, provides a geochemical indicator for the formation of abundant Co-bearing sulfarsenides rather than cobaltiferous sulfides in the deposit.

Tracing fluid signature and metal mobility in complex orogens: insights from Pb-Zn mineralization in the Pyrenean Axial Zone

AbstractOrogenic processes encompass a complex interplay of deformation and metamorphic events, which can impact the formation of ore deposits to various degrees. However, distinguishing fluid signatures from orogenic versus post-orogenic events presents a significant challenge due to the scarcity of robust geochemical indicators that remain unaffected during multiple post-mineral reworking events. This study carefully examines the properties and chemistry of primary and secondary fluid inclusions (FIs), identifying distinct signatures of two fluid populations linked to different styles of Pb-Zn mineralization in the Pyrenean Axial Zone (PAZ) of Southern-France/Northern-Iberia: These included late-Carboniferous stratabound epigenetic Pb-Zn deposits and Mesozoic crosscutting Pb-Zn(-Ge) vein systems. Population (I) is identified in primary and secondary FIs in a few crosscutting Pb-Zn veins and constitutes a minor component in stratabound epigenetic bodies. It exhibits Na-dominated low to intermediate salinity (&lt; 20 wt% NaCl eq.), intermediate temperatures (200–350 °C), abundant CO2-rich FIs and shows low homogeneous Cl/Br molar ratios. These characteristics are consistent with a metamorphic origin of the fluids, associated with Late-Variscan metamorphism. Population (II) is commonly observed in the crosscutting vein systems where it occurs as primary and pseudosecondary FIs, as well as in stratabound epigenetic bodies where it represents the main fluid component of secondary FIs. Population (II) is Ca-dominated with intermediate to high salinity (15–35 wt% NaCl eq.), relatively low temperature (&lt; 200 °C), and shows high Cl/Br molar ratios with significant variations. This last characteristic is typical of mixing of at least two fluids, one with a probable low Cl/Br molar ratio at shallow crustal levels and another with high Cl/Br molar ratio at deeper levels. Characteristics of population (II) are consistent with a fluid of basinal origin that interacted with the basement while circulating in the Pyrenees during the Mesozoic, although a Pyrenean-Alpine age cannot be excluded. Locally, in sphalerite-hosted secondary FIs that form trails in the crosscutting veins, we find evidence of high Ge concentrations (up to few 1000s ppm), which correlate with anomalous Pb and Tl concentrations. Very high metal concentrations (up to 1–2 wt% Pb, Zn), which are inversely proportional to Cl/Br molar ratios, are found in FIs mainly within veins hosted in deep-seated high-grade metamorphic rocks. Based on a compilation of fluid data from the literature, a first-order correlation can be deduced between the metamorphic grade of the rocks hosting the mineralization and the Pb and Zn content in the FIs. Early stratabound orebodies are considered likely sources of metal for the development of the late crosscutting vein mineralization. This study demonstrates the significance and complexity of orogen-scale fluid circulation and supports the importance of pre-existing metal enrichment in the crust, especially in high-grade metamorphic rocks as a prerequisite for the formation of Pb-Zn veins in complex multi-stage orogens.

Determination of geochemical stability of swamp ecosystems of the taiga zone of Western Siberia to anthropogenic impact

Relevance. The need for scientifically based regulation of impacts on wetland ecosystems taking into account their specificity and geochemical stability. Aim. To determine the geochemical stability of wetlands in the taiga zone of Western Siberia to pollutants for two typical cases associated with: 1) operation of sludge pits; 2) discharge of domestic and industrial wastewater. Methods. Mathematical modeling, statistical methods. Results and conclusions. The authors have carried out the analysis of the results of studies of the chemical composition of wetland waters and extracts from peat and mineral soils of wetlands in the taiga zone of Western Siberia (mainly in the Tomsk region, as well as in the adjacent territories of the Khanty-Mansiysk Autonomous Okrug, Novosibirsk and Omsk regions). They obtained the estimates of the average values of geochemical indicators of wetland waters and peat by the depth of the peat deposit in peat bogs with varying degrees of anthropogenic impact. The paper introduces the method for assessing the anthropogenic impact of wastewater discharge and geomigration on swamps in areas where oil and gas facilities are located (permissible concentrations in wastewater entering swamp ecosystems), taking into account the «geochemical background» and sorption capacity of peat. In particular, the authors substantiated and tested the method for assessing the values of permissible concentrations, which should be considered as a «relatively safe» level of impact on swamp ecosystems, at which secondary pollution of swamp waters is not expected. It is shown that anthropogenic changes are mainly limited vertically by the upper layer of the peat deposit up to 1–2 m, and horizontally (within the active horizon of the peat deposit) – by areas up to 100–200 m.

Evaluation of Granite Fertility Utilizing Porphyry Indicator Minerals (Zircon, Apatite, and Titanite) and Geochemical Data: A Case Study from an Emerging Metallogenic Province in the Taimyr Peninsula, Siberian High Arctic

The Taimyr Peninsula in the Russian High Arctic comprises a late Paleozoic-early Mesozoic collisional belt where several porphyry-type mineralization occurrences were identified during the last decade, making this area a potential exploration target for Cu-Mo deposits. In order to further evaluate the metallogenic potential of the poorly outcropped northeastern part of Taimyr, samples from seven granitoid intrusions were investigated in this study aimed to evaluate the granite fertility based on petrography, geochemistry, and composition of porphyry indicator minerals (zircon, apatite, and titanite). The studied intrusions represent small to moderate-sized bodies (40–800 km2) composed of biotite (±amphibole) quartz monzonites, granodiorites, granites, and biotite leucogranites that formed in the course of late Paleozoic-early Mesozoic tectono-magmatic events at the Siberian margins. The late Carboniferous Tessemsky massif represents suprasubduction granitoid series, while the Pekinskiy, Shirokinskiy, Dorozhinskiy, Kristifensenskiy, and Yuzhno-Lodochnikovskiy massifs are correlated with the early Triassic Siberian Traps LIP. The rocks of intrusions comprise a relatively uniform geochemically, predominantly magnesian, slightly peraluminous, calc-alkaline high-K amphibole-bearing I-type granitoid series with adakitic affinity, where Triassic plume-related granitoids inherit geochemical signatures of Carboniferous supra-subduction granitoids, and all rock types are marked by enrichment in LILE and negative Ta, Nb, and Ti anomalies. It is suggested that the adakitic geochemical characteristics of the Taimyr granites are a result of derivation from a relatively homogeneous mafic lower crustal source that formed at the stage of Carboniferous continental subduction and continued to produce granitic melts in the course of the early Mesozoic magmatic evolution. Whole rock geochemistry and composition of porphyry mineral indicators (zircon, apatite, and titanite) indicate that the Taimyr granites crystallized from oxidized water-saturated magmas at moderate temperatures, with the majority of samples showing characteristics typical for porphyry-fertile granites worldwide (fO2 = ΔFMQ +1 to +3 with zircon Eu/Eu* &gt; 0.4 and apatite SO3 &gt; 0.2 wt.%). Data from Dorozhinskiy, Kristifensenskiy, Pekinskiy, and Tessemskiy intrusions fully match geochemical criteria for porphyry-fertile granitoids, and these massifs are considered the most prospective for Cu-Mo mineralization. Granites from Shirokinskiy and Yuzhno-Lodochnikovskiy intrusions only partially match compositional constraints for fertile melts and can be considered as second-tier exploration targets. Finally, available data for the Simsovsky massif preclude its classification as a porphyry-fertile body. These conclusions are in line with previously developed exploration criteria for the northeastern Taimyr, showing that geochemical indicators of granite-fertility can be used on a regional scale in parallel with other exploration methods.

Emission Factors, Chemical Composition and Ecotoxicity of PM10 from Road Dust Resuspension in a Small Inland City

Road dust resuspension in urban environments can contribute to high human exposure to metal(loid)s, polycyclic aromatic hydrocarbons, and other potentially toxic organic compounds. However, for many regions, information on loadings, emission factors and chemical profiles is lacking to accurately apply emission inventories and source apportionment models. In the present study, PM10 samples were collected with an in situ road dust sampler from eleven representative streets of Bragança, an inland city of the Iberian Peninsula, and were analysed for organic and elemental carbon by a thermal-optical technique, elemental composition by ICP-MS and ICP-OES, and ecotoxicity by a luminescence inhibition bioassay with Allivibrio fischeri. A global emission factor of 5.36 ± 2.35 mg veh−1 km−1 was obtained but in suburban areas the values reached twice the average. Total carbon accounted for 14.9 ± 6.8% of the PM10 mass, while element oxides represented the largest share (28.6 ± 18.7%). Very high enrichments were found for typical traffic-related elements such as Cu, Zn, S, Pb and Ni. The geochemical index Igeo further confirmed that road dust of the study region is extremely contaminated by elements mainly originated from tyre and brake wear. Although the total non-carcinogenic and carcinogenic risks associated with metal exposure were found to be low for both children and adults, the bioluminescence inhibition assay showed (eco)toxic responses for all samples, indicating that road dust resuspension may pose a significant human health and ecological threat.

Depositional characteristics in the Lower Congo Basin during the Cenomanian-Turonian stage: Insights from fine-grained sedimentary rocks

The Cenomanian-Turonian (C-T) stage, marked by extensive black shales and Oceanic Anoxic Event 2 (OAE 2), is pivotal for deciphering paleoceanographic conditions and the main drivers of hydrocarbon formation. Despite its significant oil and gas potential, the Lower Congo Basin (LCB) in central West Africa, particularly during the C-T stage (Likouala Formation), has been severely understudied, primarily due to limited exploration and a historical preference for other basins. Therefore, understanding the depositional characteristics of the C-T stage in the LCB is essential for elucidating paleoceanographic conditions, evaluating hydrocarbon potential and interpreting environmental changes. Due to the limited availability of published data and samples, we employed a targeted and integrated geological analysis to gain comprehensive insights, encompassing logging, lithofacies identification, thin-section observations, grain size measurements, and geochemical analyses (major, trace, and rare earth elements), to provide a cohesive and confirmatory assessment. Utilizing relative sea-level curves and geochemical indicators, and by comparing with other relevant basins, this study preliminarily identified OAE 2 stratigraphic intervals and attempted to discuss the impact of OAE 2 on organic matter enrichment in the LCB. The results indicate that, during the C-T stage, the LCB featured a restricted sea bay environment with limited terrestrial input and anoxic waters. Multiple geochemical proxies suggest that relative sea-level changes significantly affected paleoproductivity, thereby influencing organic matter enrichment. During the depositional period of Lower Likouala Formation (LLF), a relative sea-level drop resulted in weakly reducing conditions in a marginal restricted sea bay environment, leading to low primary productivity. Conversely, during the depositional period of Upper Likouala Formation (ULF), enhanced aeolian input and sea-level rise increased nutrient supply from the open ocean. This led to elevated surface marine productivity and intensified reducing conditions in the water column, forming a marginal semi-restricted sea bay environment. Enhanced reducing conditions within the lower stratigraphic intervals of the ULF are likely consequences of OAE 2. However, the marginal restricted sea bay environment and limited water exchange may have constrained the enhancement of paleoproductivity by OAE 2. These insights not only significantly enhance our understanding of the organic-rich fine-grained sedimentary rocks in the LCB during the C-T stage, but also contribute to a broader comprehension of the South Atlantic's paleoceanographic conditions and the interplay between regional geological processes and global climate events during the C-T stage.

Regime shift of skeletal δ13C after 1997/1998 El Nino event in Porites coral from Green Island, Taiwan

The 1997/1998 El Niño event caused mass coral bleaching and mortality in many tropical and subtropical regions, including corals on Green Island, Taiwan, in the northwestern Pacific Ocean. This study analyzed coral carbon isotope ratios (δ13C), oxygen isotope ratios (δ18O), and Sr/Ca ratios for 29 years, including the 1997/1998 El Niño period, to examine how high water temperature events are recorded in coral geochemical indicators. Sr/Ca ratios in coral skeletons from Green Island show the lowest peak, means the highest temperature during the 1997/1998 El Niño period. However, we couldn’t observe high-temperature events on δ18O. Furthermore, a negative δ13C shift was observed after El Niño events. The regime shift of δ13C might have been caused by temporal bleaching and/or a decrease in symbiotic algae due to high water temperature stress under the continuous decrease in δ13C in DIC due to the Suess effect.