Acta Geochimica最新文献

The world-class Jiaodong gold province in the North China Craton hosts over 5000 t of Au resource and is characterized by abundant visible gold mineralization. However, the critical processes controlling the formation of visible gold in this province remain poorly understood. To solve this problem, integrated microtextural, trace elemental, and sulfur isotopic analyses of pyrite from the high-grade Linglong gold deposit in the Jiaodong gold province were conducted in this study. Two distinct pyrite types were identified within auriferous quartz-sulfide veins: (1) Py1 aggregates in quartz-pyrite veins (hydrothermal stage II), and (2) euhedral to subhedral, coarse-grained Py2 crystals in quartz-polymetallic sulfide veins (hydrothermal stage III). Microtextural and elemental analyses revealed that visible gold predominantly occurs as intergranular particles between primary pyrite crystals within Py1 aggregates. The Py1 exhibits complex microtextures with abundant mineral inclusions of polymetallic sulfides and has low concentrations of Au (median: 0.032 ppm) with a narrow δ³⁴S range (4.86‰–6.75‰), indicative of rapid crystallization under unstable, disequilibrium conditions. By contrast, the Py2 is texturally homogeneous and contains higher Au concentrations (median: 0.304 ppm) with progressively increasing δ³⁴S values (5.25‰–10.14‰) over time, suggesting slow crystal growth under more stable, near-equilibrium conditions. Based on the microtextural and geochemical information, it is proposed that fluid boiling occurred only during the hydrothermal stage II, which resulted in the unstable physicochemical environment and rapid deposition of gold. During the boiling processes, gold colloids likely occurred and promoted the formation of visible gold.

This paper describes a method for estimating the continuation of ore bodies at depth based on concentration-volume (C-V) fractal modeling of the pyrite thermoelectric coefficient in the Pujon gold deposit, Democratic People’s Republic of Korea. The method is first established using data in the Kumjomdong area, a well-explored brownfield, and it is then applied to estimate the continuation of ore bodies at depth in the Pyongsandok area, a less-explored greenfield. The methodology consists of four steps: (1) 3D modeling of ore bodies using surface geological mapping, mining tunnels in different levels, and a borehole dataset; (2) 3D modeling of thermoelectricity coefficients from Au-bearing pyrites based on discrete smooth interpolation and C-V fractal techniques; (3) determination of levels used for calculation of the thermoelectric parameter of pyrite by C-V fractal modeling instead of traditional levels; and (4) determination of the thermoelectric parameter vertical gradient of pyrite reflecting the variation characteristics of pyrite thermoelectricity in the Pujon deposit. The results indicate that (1) pyrites in the Pujon deposit are dominantly P-type, and it is not reasonable to use traditional levels to calculate the thermoelectric parameter of pyrite; (2) thresholds determined by C-V fractal modeling can be used as levels to calculate the thermoelectric parameter of pyrite; (3) the thermoelectric parameter vertical gradient of pyrite ranges from 1 to 2 in the Pujon deposit; and (4) ore body Pyongsan No. 9 extends 85 m to 235 m downward from the current borehole location.

The middle-scale Heima zinnwaldite deposit is situated in the southeastern Tibetan Plateau, SW China. The NNW- to NS-trending orebodies are hosted in the Gaoligongshan metamorphic zone. To clarify the zinnwaldite genesis at Heima, this study presents an integrated investigation of the Heima pegmatites, combining precise geochronology, isotopic tracing, and detailed mineral chemistry to constrain its formation age, petrogenetic origin, and mineralization processes. Our robust geochronological framework, employing magmatic zircon (56.93 ± 0.53 Ma) and cassiterite (57.0 ± 4.2 Ma), establishes the pegmatite emplacement during the Late Paleocene to Early Eocene, representing the maximum age of lithium mineralization. Hf isotopic compositions (εHf_(t) =  −14.3 to −12.4) demonstrate that the Heima pegmatite originated from remelting of ancient sediments, distinguishing it from contemporaneous Eocene Gangdese–Tengchong granites (εHf_(t) =  −12.7 to +11.0) that show mantle contributions. This crustal signature aligns with the evolutionary trend of Hf isotopes in regional gneissic granites (600−420 Ma), supporting an anatectic origin from ancient continental crust rather than being derivatives of nearby Eocene granitic plutons. Detailed geochemical analysis of Li-micas reveals two distinct generations with contrasting formation mechanisms. The primary mica-Ia (53.45 ± 0.86 Ma, Rb–Sr age) exhibits extreme incompatible element enrichment (Li, Be, Rb, Cs) and remarkably low K/Rb ratios (3.98–4.37), characteristic of crystallization from highly fractionated granitic melts. In contrast, secondary mica-Ib and mica-II (17.9–16.0 Ma, Rb–Sr age) show significant Nb–Ta–W enrichment, reflecting precipitation from F–P-rich hydrothermal fluids during Miocene metamorphic–hydrothermal events. Principal component analysis (PCA) confirms the compositional disparity between these mica generations, with the later phases attributed to fluid-induced alteration and reworking. Regional correlation identifies two distinct lithium mineralization episodes in the Gongshan area, southeast Tibetan Plateau. The Eocene phase (~ 55 Ma) is zinnwaldite-dominant (e.g., Heima, Puladi), associated with crustal melting following Neo-Tethyan closure. The Miocene phase (~ 17 Ma) is spodumene-dominant (e.g., Danzhu, Peili), linked to Himalayan leucogranites formed as the rapid exhumation, denudation, and decompression partial melting of Himalayan Crystalline Complex.

The Jalilabad Cu (± Au) deposit lies in the central section of the Tarom-Hashjin Metallogenic Belt, in northern Zanjan Province, NW Iran. Mineralization predominantly occurs within quartz-sulfide veins, veinlets, and breccia zones, primarily hosted by the Eocene volcanic and volcaniclastic units of the Karaj Formation. The mineralization trends NW–SE and is influenced by several strike-slip faults. Chalcopyrite and bornite are the principal hypogene sulfides, with chalcocite and covellite representing the supergene stage. The post-ore stage is characterized by brecciated calcite and quartz. Geochemical analyses show that the monzonite intrusion contains SiO₂ levels ranging from 69.80 to 70.24 wt.%, K₂O+Na₂O values between 8.10 and 8.15 wt.%, and K₂O/Na₂O ratios of 1.36 to 1.61. The intrusion is enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) while being depleted in high-field-strength elements (HFSEs). A low Hf/Sm ratio indicates an orogenic-related magma, and a low Nb/La ratio points to a depleted mantle source. Microthermometric studies of three quartz types reveal moderate to high formation temperatures (195.4–322.7 °C) and salinities ranging from 8.10 to 11.82 wt.% NaCl_equiv. Oxygen isotope data (δ¹⁸O_H2OO) range from +4.8‰ to +8.1‰, suggesting a magmatic origin for the ore-forming fluids, later diluted by meteoric water. Sulfur isotope values (δ³⁴S_H2S) between −6.0‰ and −9.1‰ confirm a magmatic source. Fluid mixing and dilution are identified as the primary mechanisms for ore precipitation. Raman spectroscopy enables nondestructive identification of minerals through their unique vibrational peaks. Chalcopyrite (213, 280, 1304 cm⁻¹), hematite (214, 282, 469, 689, 1309 cm⁻¹), goethite (967 cm⁻¹), and quartz (125, 198, 458 cm⁻¹) show distinct spectral fingerprints indicating mineral differentiation, alteration tracking, and structural analysis in geological studies. Based on its geological context, the Jalilabad Cu (± Au) deposit is interpreted as resembling a high-sulfidation epithermal deposit.

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.