Chemie Der Erde-Geochemistry最新文献

The Sadisdorf Sn-Li-(W-Cu) prospect in the eastern Erzgebirge (Germany) comprises two distinct styles of magmatic-hydrothermal mineralization, namely greisen-type mineralization at the Kupfergrube site, and stockwork-type mineralization at both the Kupfergrube and the Zinnklüfte sites. Previously, these two sites were regarded as expressions of two temporally distinct mineralization events. In this study, this temporal relation was tested by LA-ICP-MS U-Pb data obtained for 16 cassiterite samples, including samples from both sites and styles of mineralization. All 16 samples define a narrow range of ages between 315.1 ± 1.7 / 3.3 Ma and 311.0 ± 3.1 / 4.0 Ma. All ages overlap within uncertainty, suggesting that mineralization across the Sadisdorf prospect is likely related to the same magmatic-hydrothermal event.

On the regional scale, the cassiterite ages suggest that Sn-Li mineralization is associated with late-stage felsic magmatism directly following the collapse (∼314–313 Ma) of the Altenberg-Teplice Caldera. The cassiterite ages also overlap with garnet U-Pb LA-ICP-MS ages of Sn-rich skarn occurrences in the western Erzgebirge (e.g., Breitenbrunn, Antonsthal and Hämmerlein). This observation provides direct evidence that greisen and skarn-hosted Sn mineralization are related to the same period of magmatism. The data indicate that the majority of Sn-mineralization in the Erzgebirge formed after 318 Ma (likely between 318 and 310 Ma), challenging previous models which invoked an older suite of granites (326–318 Ma) as causative source intrusions.

The Inlice high sulfidation epithermal gold deposit with 262,300 oz of gold ore is located in the Erenlerdağ-Alacadağ Volcanic Complex (EAVC) at the northern part of central Taurides. The volcanic succession of the study area is stratigraphically represented by andesite, block and ash flow, basaltic andesite lava flow and andesite lava flow. The deposit consists of seven neighboring mineralized veins termed Ana East, Ana West, West, Discovery, Güllü, Merkez and North Zone and is associated with an andesite (ca 8–9 Ma). Hydrothermal alteration from the innermost to the outermost parts of the deposit includes silicification, advanced argillic, intermediate argillic and propylitic. At the surface, quartz veins related to silicification are exposed as linear topographic relief trending mainly northwest-southeast and secondarily northeast-southwest and east-west. Deep drill core samples, including magnetite, quartz, biotite and anhydrite, imply the presence of potassic alteration in depth (50 to 970 m) possibly related to a porphyry Cu system. Ore assemblages are described as hypogene and supergene. The hypogene ore mainly includes pyrite (Py-I and Py-II) and enargite, and to a lesser extent chalcopyrite, sphalerite and marcasite. The supergene ore incorporates hematite and goethite, and minor covellite, chalcocite, malachite and native copper. Hypogene gold precipitation is associated with the mineral association of Py-II, chalcopyrite and enargite, while enargite mineral is a major host for gold (up to 600 ppm). Supergene oxidation resulted in the development of a secondary enrichment zone for gold (up to 14 g/t) extending to a depth of about 45 m.

Microthermometric measurements show that the silicification associated with the mineralization was formed at homogenization temperatures ranging between 147 and 360 °C and salinities up to 6.5 wt% NaCl. This suggests that the fluid mixing and/or fluid dilution processes were important factors controlling the precipitation of gold. δ³⁴S isotope compositions are between −0.9 and − 9 ‰, and further indicate a significant involvement of magmatic components into the hydrothermal fluids. Thus, it is concluded that at Inlice the hydrothermal fluids responsible for the alteration and mineralization processes were derived by relatively dilute fluids formed by the mixing of magmatic fluids with meteoric waters.

In this paper, we address two key features of the behaviour of Fe-rich amphibole at high temperatures: (1) the Fe²⁺ → Fe³⁺ + e⁻ exchange within the crystal bulk, and (2) the consequent rise in electrical conductivity. Cycling heating-cooling experiments were done in situ up to 542 °C (815 K) at beamline B11 of the Diamond Synchrotron Laboratory (UK). X-ray absorption spectra at the Fe K-edge and electrical resistivity were measured simultaneously on a single crystal of riebeckite with a composition very close to the ideal formula ^A□^BNa₂^C(Fe²⁺₃Fe³⁺₂)^TSi₈O₂₂^W(OH)₂. The Fe³⁺/Fe_tot ratio was monitored via analysis of the pre-edge feature in the XANES spectra. Our data show slight oscillations of the oxidation state of Fe with temperature cycling up to around 400 °C (673 K), followed by a substantial gradual increase in Fe²⁺ → Fe³⁺ oxidation that starts at ~450 °C (~723 K) and is completed at ~525 °C (~798 K). The conductivity (σ) measured along the crystallographic c-axis oscillates strongly with cycling temperature allowing us to conclude that it is intrinsically related to the electron hopping induced by thermal treatment. The activation-energy derived from the σ(T) trend is E_a = 74.4 ± 0.6 kJ/mol (0.77 ± 0.01 eV), in agreement with small-polaron conduction. This study provides direct and robust support of the conduction mechanisms in Fe-amphibole previously inferred from indirect methods. Given that riebeckite is a significant component in the glaucophanitic amphiboles common in blueschists associated with subducted oceanic crust, our data provide a link between atomic-scale processes and Earth-scale anomalous conductivity observed via geophysical measurements.

Identifying the geochemical signatures of valuable mineral deposits using regional geochemical data from stream sediments is a challenging task due to the intricate characteristics of geological formations. Our team is currently investigating the potential of unsupervised clustering analysis (CA) and hybridization with the grey wolf optimizer (GWO) in developing multi-element geochemical models using stream sediment data. To cluster the geochemical data and uncover any unusual patterns, we opted to use the K-means (KM) algorithm due to its straightforward implementation, fast computation speed, and capacity to handle the large datasets. Despite its benefits, the KM method also has notable limitations, such as the random selection of cluster centroids. This can result in higher systematic uncertainty in unsupervised geochemical modeling and longer computation times. To mitigate this concern, we have introduced a new hybrid approach, grey wolf optimizer with K-means so-called the GWOKM algorithm to enhance the delineation of multi-elemental patterns in stream sediment geochemical data. This method incorporates the grey wolf optimization algorithm with KM to optimize the identification of both anomalies and backgrounds using factor analysis and sample catchment basin modeling techniques. This approach was utilized to detect anomalous multi-elemental geochemical patterns indicative of porphyry and skarn copper deposits in the Baft area, Kerman belt, Iran. Upon comparison of the geochemical models derived from KM and GWOKM clustering methods, the latter outperformed the former, as evidenced by its higher prediction rate. The outcomes affirm the efficacy of unsupervised KM clustering analysis (CA) as a means of breaking down geochemical anomaly-background populations. Moreover, the integration of clustering methods with optimization algorithms has proven to be successful for enhancing the credibility of mineralized areas, which could be advantageous in future exploration phases. Based on the results, the GWOKM approach generates more reliable and efficient geochemical anomaly targets.

Climate-driven shifts in soil temperature and soil moisture are crucial factors that control the ecosystem-atmosphere greenhouse gas (GHG) balance. In the present study, the relationship between CO₂, CH₄ fluxes and soil moisture content and temperature sensitivity was examined in three dominating types of urban ecosystems: grassland, city park and arable land. The analysis was based on the field measurements at biweekly intervals over a year using a static closed chamber method in Wroclaw urban area, Poland. The observed patterns of land-atmosphere CO₂ and CH₄ exchange varied across land cover types and were strongly influenced by seasonal variations in temperature and soil water content. Emission of CO₂ from grassland and the city park was two times higher than from the arable land. The calculated CH₄ oxidation rate was one and half times higher (p < 0.05) under grassland and the city park as compared to arable land.

The estimated Q₁₀ values ranged between 1.68 and 1.79 for CO₂ and from 1.26 to 1.49 for CH₄, depending on the ecosystem type. The temperature sensitivity of soil respiration decreased when the temperature was above 24.5 °C across the moisture gradient from 20 to 25 % m/v. Results suggest that despite the urban areas with agricultural land use revealed the lowest CO₂ fluxes compared to grassland and city park, the former showed the lowest seasonal mean CH₄ oxidation. This indicates that with ongoing warming, the higher Q₁₀ of CO₂ production vs. CH₄ oxidation will further shift the carbon balance towards the source and this shift will be especially critical for arable lands in urban areas.

The flow path of a river draining a lowland into the southern Baltic Sea, the Warnow River, was investigated to evaluate its freshwater composition and potential to be a source of dissolved substances for regional coastal waters. A spatial study was conducted in April 2019 to follow the variations from the source to the estuary. A temporal study of the composition, for five years (2017–2021), was carried out at a site just before the river reaches the estuary. Surface water was sampled to analyse major and trace elements, stable (H, C, O, S), and short-lived (Ra) isotopes. The results show that the composition of the Warnow River along the flow path is controlled by a complex interplay between in-situ processes, exchange with the atmosphere, diffuse groundwater, and surface water inlets. On a temporal scale, pH, nutrient, and redox-sensitive trace element concentrations are strongly impacted by pelagic primary production in spring. During summer and autumn, influences occurred due to benthic microbial activity, associated diffusive release from soils/sediments, and surface water inlets. Throughout the investigation period, the Warnow River was a source of isotopically light CO₂ to the atmosphere and DIC to the estuarine waters. The delivered DIC concentrations seemed to vary with season due to changes in biological pelagic and benthic activities. DOC was derived from a mixture of dominated C₃ organic sources and potentially from fertilizers. From concentration-discharge relationships, examples of dilution, mobilization, and chemostasis trends were found. Discharge-controlled seasonal trends were superimposed by system internal processes and the hydrological consequences of the river management. Our analysis thus provides new insights into the controls on the variations of water and solutes in a managed river at the land-sea interface as part of the regional hydrological cycle of a lowland catchment-coastal water system.

This article presents results of chemical and isotopic studies of shallow groundwater and surface waters in order to determine the degree of their contamination near to artificial irrigation fields. The study applied the methodology of detailed sampling around the river in order to capture the direction of pollutant flow and to determine the state of the environment. Samples were taken on both sides of the river, from its bottom and directly from the river. Thanks to bottom pressure measurements, it was possible to determine in what section the river drains or infiltrates groundwater, which, combined with chemical and isotope analyses, made it possible to determine the aims of this study. As it turns out, the nature of the river in the study area is mainly neutral and in lesser extent draining, which does not translate into the degree of groundwater pollution at every point. Due to the sampling methodology used, it was also possible to determine the depth of redox processes and the origin of sulfur in water, which comes mainly from precipitation and other anthropogenic sources. Chemical tests indicate an average quality of shallow groundwater, anthropogenically transformed to varying degrees depending on the location of measurement point. These preliminary results support the applicability of this sampling methodology to other studies and indicate the need to perform more detailed chemical analysis.

Alkaline volcanics (felsites) and A-type granites are spatially and temporally associated in the Wadi Atalla area, Central Eastern Desert, Egypt. These rocks represent final Neoproterozoic magmatic activity in the Northern Nubian Shield. Wadi Atalla felsites form NW-trending elongate mass consisting of silicic volcanics, which is intruded by A-type granites of Um Had and Um Effein plutons. Field relations indicate that both felsites and A-type granites were emplaced in a series of magmatic pulses. Felsites include tuffaceous, porphyritic and hypabyssal varieties, while A-type granites comprise syenogranite and alkali feldspar granite. Geochemically, they are highly silicic rocks and display a narrow range of SiO₂. They have high-K alkaline nature with metaluminous to peraluminous character and were erupted in a post-collisional tectonic setting. Mineral chemistry of biotite supports the alkaline and A-type characters of the studied rocks. Atalla felsites and associated A-type granites show light REE enrichment relative to heavy REE [(La/Lu)_n = 2.67–5.72] with pronounced negative Eu anomalies (Eu/Eu* = 0.15–0.52). Compositional similarities between Atalla felsites and A-type granites in the studied area suggest that the intrusive and extrusive events are broadly related. The systematic variation of major- and trace-element contents of the felsites and A-type granites indicates derivation from similar sources through partial melting of juvenile crustal rocks, followed by extensive fractional crystallization. The main fractionated phases are feldspars, with minor role of fractionation of amphibole, biotite, apatite and FeTi oxides. Multiple saturation calculations indicate water-saturated storage and final equilibration conditions for the felsites ranging from 788 °C at 90 MPa to 740 °C at 255 MPa. The parental magmas of the felsites and A-type granites were linked to lithospheric delamination and upwelling of asthenospheric mantle material. This process led to generation of mantle melts that supplied heat to melt the juvenile crust of the Arabian-Nubian Shield (ANS), along with crustal uplift recorded by intersecting strike-slip faults and shear zones. Atalla felsites represent a distinctive post-collisional alkaline volcanic phase in the Nubian Shield that has been emplaced in an extensional tectonic regime, during a phase of fracturing and crustal uplift, which followed the end of the Pan-African orogeny. This volcanic phase is younger than the Dokhan volcanics in the Eastern Desert and older than the typical Katherina volcanics in southern Sinai.

Age constraints on early solar system processes and events can be derived from meteorites and their components using different radioisotope systems. Due to the short time interval from the first formation of solids in the solar nebula to the accretion and differentiation of planetesimals and some planets, a high temporal resolution of the chronometers is essential and can be obtained in most cases only with short-lived isotope systems, particularly the decay schemes ²⁶Al-²⁶Mg, ¹⁸²Hf-¹⁸²W and ⁵³Mn-⁵³Cr. These chronometers provide highly resolved time constrains for the formation of the first solids (Ca-Al-rich inclusions or CAIs), chondrules, planetary cores, for the accretion and differentiation of planetesimals and hydrous/thermal alteration. Formation of Ca-Al-rich inclusions was restricted to the inner solar system and to a short time interval of ≪1 Ma, and marks the “beginning of the solar system”. It was immediately followed by planetesimal formation. The oldest planetesimals accreted within a few 10⁵ a after the formation of CAIs. The accretion of early formed planetesimals and their subsequent differentiation into a metallic core and a silicate mantle was a continuous process that occurred at different times in different locations of the solar nebula and extended over a time interval of at least ~4 Ma. During this time interval the accretion process may have changed from planetesimal formation via streaming instability to pebble accretion. The earliest formed bodies that still needed to settle into stable orbits could have created bow shocks in the adjacent regions still composed of dust and gas which resulted in the formation of silicate chondrules in a narrow time interval from 1.8 to 3 Ma. The chondrule forming interval was immediately followed by the accretion of the chondrite parent bodies, which did not differentiate due to their late accretion when most of the heat producing ²⁶Al had already decayed. Thus, the chondrite parent bodies are a second generation of planetesimals, but chemically they are the most primitive material preserved from the early solar system. Aqueous alteration of volatile rich planetesimals peaked at ca. 3.5 Ma and coincided with metamorphism recorded in ordinary chondrite parent bodies. The compilation of ages from different meteorites and their components demonstrates that similar accretion and differentiation processes do not follow an identical time line from dust to planetesimal formation and they do not correlate with the location in the disk. The accretion of matter into planetesimals was a local phenomenon with stochastic spatial distribution. The spatial distribution of accretion processes operating in the early solar system appears to be similar to those in some directly observable nascent exo-planetary systems.

Discharge of acid mine drainage (AMD) along with heavy metals mobilization is a critical environmental concern. An urgent need is to manage or treat AMD in the minefield effectively. To this end, based on a hydrogeological investigation, the d-T (deuterium excess parameter-Tritium content) technique was adopted to trace the recharge, runoff, and discharge of AMD in the abandoned Dashu pyrite mine in China. The results reveal that AMD in the minefield originates from local precipitation and shallow groundwater and exhibits apparent seasonal runoff variations. The AMD is associated with shallow groundwater from the top of the Quaternary platform on the axis of the Dashu anticline, and protons could originate from the pyrite oxidation. Therefore, an engineering practice to purify the AMD is combined with (1) water diversion to stop AMD formation and blockage of the AMD outlets. (2) Acceleration of Fe(II) oxidation through aeration promotes the precipitation of Fe-oxide and hydroxide. (3) Neutralization of AMD using Karst water from the Maokou Formation (P₂m). This study provides a new research idea and tracing method for improving hydrogeological surveys and effectively handling environmental problems related to AMD of abandoned mines.