Acta Geochimica最新文献

The migration mechanisms of ore-forming fluids have long been a focus in the field of ore deposit studies. Calcite is ubiquitously present in various types of rocks in the lithosphere, and the underlying mechanisms of its influence on fluid migration are of crucial importance. While previous studies have revealed that salinity changes can modulate fluid migration, the underlying mechanisms remain poorly understood. We employ molecular dynamics simulations to elucidate how salinity variations in ore-forming fluids modulate the adsorption onto calcite nanopore walls, thereby revealing the microscopic mechanisms governing ore fluid transport through calcite nano-fractures. The results show that the adsorption energy E_int of the solution on the calcite surface increased from −14,948.84 ± 182.48 kcal/mol to −12,144.08 ± 118.2 kcal/mol as salinity increased, which is conducive to the long-range transport of the fluid in the calcite nanopore.

Recent studies have confirmed the critical and essential role of elemental hydrolysis in metallogenic processes, such as metal migration and precipitation. However, the kinetic processes, characteristics, and formation mechanisms of hydrolyzed precipitates require further comprehensive investigation. This paper is based on a systematic investigation of the hydrolysis mechanisms of Pb and Zn in various systems under ambient temperature and pressure, the storage conditions of the hydrolyzed precipitates, and the characterization of these precipitates. The results indicate that the hydrolysis behaviors of Pb and Zn exhibit significant differences across various systems. Within the monometallic regime, there is a pronounced disparity in the hydrolysis rates between Pb ions and Zn ions. Pb ions demonstrate a substantially higher degree of hydrolysis, a trend that persists over time and remains largely unaffected by the "fluid retention or isolation" phenomenon in the surrounding environment. Both hydrolytic precipitation rates were observed to decrease in the mixed system, with Zn ions exhibiting less reduction than Pb ions. After hydrolysis, hydrolyzed precipitates can remain in the fluid environment for extended periods of time, which can lead to re-dissolution. Over time, this re-dissolution can increase, eventually leading to significant loss of hydrolyzed precipitates. The hydrolyzed precipitates obtained from the experiments primarily consisted of alkaline carbonates of Pb and Zn. Notably, the crystalline characteristics of the hydrolysis products of Pb and Zn ions exhibited significant differences across various experimental systems; however, the crystallographic characteristics of the primary hydrolysis products are essentially identical to those of their corresponding natural counterparts. Based on the findings from physical phase analysis and previous research, it is concluded that the hydrolysis process consists of three main stages: oxides/hydroxides, carbonates, and alkali carbonates. In the Pb-Zn-NaCl-H₂O system, the proportion of the basic carbonate products of Pb and Zn is 6:2. This research offers an in-depth analysis of the hydrolysis dynamics of lead and zinc under ambient temperature and pressure conditions. Furthermore, it characterizes the crystallization features of the hydrolyzed precipitates and reconstructs the three stages of the formation process. This study holds significant scientific value for understanding the metallogenic mechanisms of Pb and Zn.

Mining activities are often associated with significant environmental degradation, particularly due to the accumulation of mine tailings (MTs). These waste materials are frequently stored in dams or open ponds without adequate treatment, posing serious risk of heavy metals (HMs) contamination to surrounding ecosystems. Given these challenges, restoration of MTs to mitigate their negative impacts has become highly important. This study attempts to compile different types of MTs, their characteristics, and associated issues such as acid mine drainage (AMD) and HMs contamination, along with other environmental impacts. It also explores the fundamentals of phytoremediation, highlighting key processes, recent advancements, benefits, limitations, and strategies for post-harvest management. The findings indicate that MTs are a major source of HM pollution and contribute significantly to environmental deterioration. Phytoremediation has emerged as a promising, cost-effective, and eco-friendly solution for MT restoration. In addition to mitigating contamination, phytoremediation enhances soil quality, prevents erosion, reduces HM leaching into groundwater, and improves the visual appeal of degraded sites. Research suggests that revegetating MT-contaminated soils with specific plant species can effectively remediate these areas, reducing HM leaching risks while improving soil properties. This review serves as a valuable resource for researchers working on MT restoration, offering insights into the latest advancements in phytoremediation technology and its potential to address the environmental challenges posed by MTs.

Lithium is a critical strategic metal with significant reserves in pegmatites, serving as the primary source for global Li production. Apatite has attracted increasing attention as an indicator in petrogenesis studies and for the exploration of ore deposits. In this study, we investigated the volatile compositions and major and trace elements of apatite from the Qiongjiagang pegmatite-type lithium deposit in Himalaya. Apatite derived from spodumene pegmatite exhibits relatively constant and high total rare earth element (ΣREE+Y) concentrations, ranging from 5899 to 8540 ppm. In contrast, apatite in barren pegmatite displays evidently lower (ΣREE+Y) concentrations, varying between 1345 and 3095 ppm. The REE patterns of apatite in spodumene pegmatite generally exhibit a flat shape [(La/Yb)_N = 1.55–2.15)], with distinctively negative Eu anomalies (Eu_N/Eu_N* = 0.14–0.22), slightly positive Ce anomalies (Ce_N/Ce_N* = 1.03–1.13), and low Y/Ho ratios (28–30). By contrast, apatite in barren pegmatite shows middle rare earth element (MREE)-depleted downward-convex patterns [(La/Yb)_N = 1.99–20.4)], strongly negative Eu anomalies (Eu_N/Eu_N* = 0.01–0.14), slightly positive Ce anomalies (Ce_N/Ce_N* = 1.10–1.24), and high Y/Ho ratios (30–55, with an average of 50). Overall, the high concentrations of ΣREE (and Y) and low Th/U and Y/Ho ratios can serve as diagnostic indicators to distinguish apatite in spodumene pegmatite from that in barren pegmatite. Furthermore, the flat REE pattern may represent a common feature of apatite from lithium deposits. Differences in the Ce and Eu anomalies between apatite from these two kinds of pegmatites likely reflect formation under different redox conditions. Consequently, based on calculations derived from apatite volatile compositions, the melt associated with spodumene pegmatite may contain higher water content compared to that of the barren one. Therefore, the mineralized pegmatite system may incorporate substantial amounts of H₂O-rich fluids, which play a crucial role in lithium mineralization.

Over 90% of Earth’s carbon is stored in the mantle and core. The deep carbon cycle plays a critical role in regulating surface carbon fluxes, global climate, and the habitability of Earth. Carbon mainly residing within the sediments, altered oceanic crust, and mantle peridotite as carbonate minerals and organic carbon is transported to the deep Earth via plate subduction. A series of reactions (e.g., metamorphism, dissolution, and melting) occurring in the subducting slab drive the carbon removal. Some of the carbon is recycled to the surface via arc volcanism, while the rest is carried into the deeper Earth. More than two-thirds of the global subduction carbon input comes from sedimentary carbon, whose fate during subduction directly affects the flux in the global carbon cycle. Over the past two decades, the sedimentary carbon cycle in subduction zones has been extensively studied by experiments and computational approaches. Here, we provide a comprehensive review of the sources, species, decarbonation reactions, carbon cycle tracing, and fluxes of sedimentary carbon in subduction zones, and the role of sedimentary carbon subduction in climate evolution and mantle chemistry. Further research is required for our understanding of deep carbon cycle processes and their role in Earth's climate.

The Triassic granitoids and associated diorites in the Qinling orogenic belt reveal critical evidence of crust–mantle interaction during the terminal collision between the North China and Yangtze Blocks. This study presents new constraints from zircon U–Pb age, Lu–Hf isotopes, and amphibole-plagioclase-apatite geochemistry for the Maoerliang diorite in the Foping area. Zircon U–Pb dating yields a crystallization age of 212 ± 2.8 Ma, with εHf(t) values ranging from −8.6 to +3.0 and corresponding two-stage Hf model ages (T_DM2) of 886–1479 Ma, indicative of derivation from an evolved lithospheric mantle source. Petrogenetic indicators reveal a mantle affinity: amphiboles exhibit high MgO (9.8–11.2 wt%) and elevated Nb/Ta ratios (14.3–18.1), while apatites display F-rich (2.1–2.8 wt%) and Cl-poor (0.08–0.15 wt%) characteristics. Thermobarometric calculations based on amphibole chemistry constrain crystallization conditions of 805–866 °C and 211–383 MPa, corresponding to mid-crustal emplacement depths (8–14 km). Both amphibole and zircon indicate elevated oxygen fugacity (ΔNNO = −4.08 to −3.71; ∆FMQ = −1.14 to +3.96) and hydrous magma conditions (H₂O = 4.22–4.94 wt%). Late-stage plagioclase crystallization (An21–26.5) reflects prolonged fractional crystallization in a hydrous dioritic magma. These diagnostic features—mantle-derived signatures, high fO₂, and hydrous nature—exhibit remarkable convergence with gold-mineralized granites in the East Qinling. Our findings suggest that Triassic dioritic magmatism may have played an underappreciated role in facilitating gold enrichment processes within the South Qinling metallogenic belt.

The size of basalt fragments in Chang’E-5 (CE-5) regolith are small (< 6 mm²), resulting in large variation on the estimated bulk composition of CE-5 basalt. For example, the estimated TiO₂ content of CE-5 basalt ranges from 3.7 wt% to 12.7 wt% and the Mg# (molar percentage of Mg/[Mg + Fe]) also shows a wide range (26.2 − 42.4). Preliminary experimental studies have shown that these geochemical characteristics of CE-5 basalt are critical for investigating the crystallization sequence and formation mechanism of its parent magma. This study presents new experimental data on the distribution coefficient of titanium between pyroxene and lunar basaltic magma (left( {{text{D}}_{{{text{Ti}}}}^{{text{Px/melt}}} } right)). Combining with available literature data, we confirm that ({text{D}}_{{{text{Ti}}}}^{{text{Px/melt}}}) is affected by crystallization conditions such as pressure and temperature, but it is mainly controlled by the CaO content of pyroxene. Comparing with previous experimental results under similar conditions, we parameterized the effect as ({text{D}}_{{{text{Ti}}}}^{{text{Px/Melt}}} {text{ = D}}_{{{text{Ti}}}}^{{text{Px/Melt}}} { ;= - 0}{text{.0005X}}_{{{text{Cao}}}}^{{2}} { ;+; 0}{text{.0218X}}_{{{text{CaO}}}} { ;+; 0}{text{.0425} ({text{R}}^{2} = 0}{.82)})(text{,})where X_CaO is the CaO content in pyroxene in weight percentage. The new experimental results suggest that pyroxene with high TiO₂ content (> 2.5 wt%) in CE-5 basalt is not a product of equilibrium crystallization, and the CaO content in pyroxene is also affected by cooling rate of its parent magma. The TiO₂ content in the CE-5 parent magma is estimated to be about 5 wt% based on the Mg# of pyroxene and its calculated CaO content, which is consistent with those estimated from olivine grains.

This review critically examines strategies for sustainable groundwater and surface water management, emphasizing their integration to achieve environmental sustainability. The study synthesizes findings from a wide range of research articles, identifying key trends, gaps, and controversies within the field. It highlights the importance of cohesive management approaches that take into account climate change, policy impacts, and methodological advancements. The review aims to provide a structured, analytical discussion that aligns with the thematic focus of integrated water management. By offering original insights and practical recommendations, this review seeks to contribute to the development of more effective and sustainable water management practices. The analysis underscores the necessity of interdisciplinary approaches that integrate hydrological, ecological, and socio-economic factors. Furthermore, the review discusses the role of adaptive management and technological innovations in enhancing the resilience and efficiency of water management systems. The findings suggest that a comprehensive understanding of the interactions between groundwater and surface water is crucial for developing strategies that ensure long-term environmental sustainability. This review concludes with recommendations for future research and policy development, emphasizing the need for adaptive, resilient, and integrated water management strategies that can address the challenges posed by climate change and other environmental pressures.

The deep geologic processes between the Xing’an-Mongolian Orogenic Belt and the North China Craton in the Mesozoic are crucial to reveal the magmatic and tectonic evolution and their constraints on mineralization in the Jiapigou-Haigou collage zone. In this paper, We have presented the geochronology, geochemistry and Sr–Nd–Hf isotopic compositions of the Middle Jurassic granitic complexes in the Songjianghe area, Jilin Province. The granitic complexes can be categorized into four groups based on their geologic characteristics, with corresponding zircon U–Pb isotope ages of 177 Ma, 172 Ma, 169 Ma and 168–167 Ma, respectively. These granitoids exhibit calc-alkaline to high-K calc-alkaline, metaluminous to weakly peraluminous I-type characteristics, which show relative enrichment in LILEs (Rb, Sr, Ba) and depletion in HFSEs (Nb, Zr). Geochemical analyses reveal high initial ⁸⁷Sr/⁸⁶Sr ratios of 0.70633–0.70740, coupled with low εNd(t) values ranging from −10.65 to −13.23. The zircon analyses show similarly negative εHf(t) values ranging from −16.9 to −3.2. The integrated elemental and Hf–Sr–Nd isotopic signatures demonstrate that the primitive magmas of the four group rocks were primarily derived from partial melting of thickened Archean lower crust, with the exception of the Group IV rocks, which exhibit significant evidence of crustal contamination. The residual mineral assemblages during the magma-forming process varied from amphibole to eclogite facies. These findings indicate that magmatism in the Songjianghe region likely resulted from the accretion and delamination of the Archean crust in the collage zone during the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.

The Cretaceous Koum Basin is a rift-related half-graben in northern Cameroon, which constitutes a portion of the Yola Arm of the Upper Benue Trough. This study presents the first comprehensive dataset combining mineralogical, bulk-rock geochemical, and stable C–H–O isotopic data for dark-gray, fine-grained mudstones from the basin, providing new insights into its sediment source, paleoenvironment, and geodynamic setting. The mudstones primarily consist of phyllosilicates (~ 8.6%), feldspars (~ 30.5%), carbonates (~ 13.7%), and minor iron oxides (~ 2.7%), with vermiculite, illite, and kaolinite as the main clay minerals. The presence of analcime, ankerite, and dolomite suggests low-grade metamorphism and/or hydrothermal alteration. Fe₂O₃/K₂O (1.52–6.40) and SiO₂/Al₂O₃ (2.97–4.68) ratios classify the mudstones as compositionally immature shales (ICV ~ 1.64) with low-moderate chemical weathering (CIA ~ 56.35; PIA ~ 59.74; R³⁺/R³⁺ + R²⁺ + M⁺  ~ 0.51). Trace element ratios (Th/Sc ~ 1.70, Zr/Sc ~ 1.33, La/Sc ~ 6.30, La/Th ~ 4.14) indicate an intermediate igneous provenance from a continental crustal source. Paleoenvironmental proxies suggest deposition in a dynamic basin environment marked by fluctuating redox (C_org/P: 0.21–178.34) and salinity (Sr/Ba: 0.34–3.25; N-values: 48–35.92) conditions, ranging from oxic to anoxic and brackish to saline. Major element data (SiO₂ vs. Al₂O₃ + K₂O + Na₂O) indicate a semi-arid regime, while Paleoclimatic indicators such as Sr/Cu (1.88–37.47) and C-values (0.12–0.93) suggests alternating humid and arid conditions. Notably, stable isotope data, reported here for the first time in the Koum Basin, reveal a predominantly terrestrial, fluvial-deltaic C₃ plant source for organic carbon (δ¹³C − 25.2‰ to − 35.2‰) and complex fluid-rock interactions involving meteoric and magmatic-metamorphic fluids under a warm, equatorial climate (δ¹⁸O + 3.6‰ to + 24.9‰, δ²H − 104‰ to − 50‰). The combined mineralogical, geochemical, and isotopic data point to deposition in a tectonically active continental arc setting, with contributions from ocean island arc and passive margin sources.