Acta Geochimica最新文献

With the development of aviation, superconducting, and other steel industries, the demand for niobium (Nb) has significantly increased worldwide, positioning it as a critical strategic metal. The Bayan Obo rare-earth elements (REE)-Nb-iron (Fe) deposit contains over 70% of China’s Nb resources and hosts the world’s largest reserves of REE. However, due to technical and environmental challenges, a substantial portion of the Nb resources remains underutilized and stored in tailings. Research and development of efficient, environmentally friendly, low-energy consumption, and less complex methods for extracting Nb from the Bayan Obo tailings possess significant scientific value and strategic importance. This paper reviews the current research status and distinctive geological and mineralogical characteristics of Nb resources in the Bayan Obo deposit, as well as existing pyrometallurgical and hydrometallurgical technologies for extracting Nb from ores and tailings, subsequently comparing their advantages to guide the development of new processes. Based on a comprehensive consideration of the technical, economic, environmental, quality, and safety aspects, it is suggested that future research should prioritize establishing a systematic recommendation procedure for targeted Nb-bearing mineral characterization and analysis for the Bayan Obo tailings, developing fluoride-free or low-fluoride hydrometallurgical techniques, and exploring innovative methods for Nb mineral coarsening. This review thus provides new insights into the efficient utilization of the Bayan Obo Nb resources and supports the development of innovative and effective strategies for optimizing Nb extraction from ores and tailings.

Tectono-geochemical analysis is one of the key technical methods for deep prospecting and prediction, but the extraction of information on weak and low degrees of mineralization remains a significant challenge. This study takes the Maoping super-large germanium-rich lead–zinc deposit in northeastern Yunnan as an example, systematically analyzes the mineralization element assemblages and their anomaly distribution characteristics, extracts information on low and weak anomalies at depth, clarifies the spatial distribution of ore-forming element anomalies and fluid migration patterns, and establishes tectono-geochemical deep anomaly evaluation criteria and prospecting models, thereby proposing directions for deep prospecting in the deposit. This research shows that the mineralization element assemblage of the F1 factor (Cd-Cu-Ge-Zn-Sb-In-Pb-Sr(-)-As-Hg) anomalies represents near-ore halos; the element assemblage of the F2 factor (Ni-Co-Cr-Rb-Ga) anomalies represents tail halos; the element assemblage of the F3 factor (Rb-Mo-Tl-As) anomalies represents front halos; and the element assemblage of the F4 factor (Ba-Ga) anomalies represents barite alteration anomalies. Elements such as Zn and Pb exhibit significant anomalies near the lead–zinc ore bodies. In the study area, vertical anomalies in the eastern region of the Luoze River indicate that ore-forming fluids migrated from the SE at depth to the NW at shallower levels, whereas in the western region, ore-forming fluids migrated from the SW at depth to the NE at shallower levels. Thus, the lateral extensions of different ore bodies in the eastern and western regions of the river have been determined. On this basis, tectono-geochemical deep anomaly evaluation criteria for the deposit are established, and directions for deep prospecting are proposed. This study provides scientific value and practical significance for deep prospecting and exploration engineering planning for similar lead–zinc deposits.

The Saxi tungsten deposit, located in the Laojunshan ore district of southeastern Yunnan Province, is a significant W-polymetallic deposit. The origins of tungsten-bearing pegmatite dikes and quartz vein mineralization in the Saxi deposit remain poorly understood. This study employs in situ U–Pb dating of apatite from the altered granite, along with trace element and S–Pb isotopic analysis of arsenopyrite, to investigate the timing, source of ore-forming fluids and the mechanisms of tungsten enrichment. The apatite in the altered granite yields a U–Pb age of 147.0±4.0 Ma, indicating magmatic activity during the Early Cretaceous. Three generations of arsenopyrite (Apy) are identified: Apy-1 in the altered granite, Apy-2 in the pegmatite dikes and Apy-3 in the quartz veins. The S/Fe ratios for Apy-1, Apy-2 and Apy-3 range from 0.98 to 1.09, 0.89 to 0.92 and 0.86 to 1.02, respectively (average 0.97), suggesting a magmatic-hydrothermal origin. Sulfur isotope values (δ³⁴S = 4.29‰–8.11‰) indicate that it was likely sourced from deep magmatic-hydrothermal fluids. Lead isotopic compositions of arsenopyrite suggest that the granitic parental magma is derived from the upper crust. These findings point to a magmatic-hydrothermal origin for the vein-type tungsten mineralization, linked to a concealed magmatic-hydrothermal system in the Early Cretaceous.

The Suizhou meteorite is a heavily shock-metamorphosed L6 chondrite which contains thin shock melt veins. So far, 26 high-pressure phases have been identified from the meteorite. Among the high-pressure phases, ten of them were approved as new minerals which include tuite, xieite, wangdaodeite, chenmingite, hemleyite, poirierite, asimowite, hiroseite, elgoresyite, and ohtaniite, by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association. Other high-pressure phases identified from the meteorite are ahrensite, akimotoite, bridgmanite, lingunite, magnesiowüstite, majorite, majorite–pyrope_ss, maskelynite, riesite, ringwoodite, wadsleyite, and 5 other phases including phase A, vitrified phase B and phase C, phase D (Ca-rich majorite), and partly inverted ringwoodite. The occurrence and abundance of high-pressure phases makes this meteorite the one with the richest variety of high-pressure minerals to date.

The extra-peninsular Gondwana Group rocks are exposed in narrow patches within the Lesser Himalayan sequence of the NE-Arunachal Himalayas, India. The bulk of sediments for the sandstones of the Gondwana Group were derived from felsic/acidic to intermediate igneous rocks, with minor mafic input from the upper continental crust (UCC), as supported by various discrimination diagrams based on quantification of detrital minerals coupled with sandstone geochemistry. The inputs from metamorphic sources in subordinate amounts cannot be ruled out, as indicated by quantification of the quartz varieties. These sediments were found to be sourced from the interior part of a craton or shield and recycled platformal sediments which were derived from both passive and active margin settings. The sediments experienced a wide variance in climatic conditions, from arid to humid, suffering low–moderate-intensity weathering (CIA: 63.43; CIW: 86.18; WIP: 44.84; PIA: 75.37; ICV: 2.39; C-value: 0.42; PF: 0.49; Sr/Cu: 9.23 and Rb/Sr: 1.68) within the vicinity of the low plains to moderate hills. Additionally, redox-sensitive elements indicate the deposition of sediments under oxygenated or oxygen-rich conditions (U_au: −2.91; Th/U: 7.37; U/Th: 0.18; V/Cr: 1.71; δU: 0.67 and Ce/Ce*: 0.93).

As one of the typical deposits in the Sichuan-Yunnan-Guizhou Pb–Zn metallogenic province, the Daliangzi Pb–Zn deposit has a close genetic relationship with the structural system of the black/fracture zone formed under the action of the NWW-approximately EW strike-slip structures in the metallogenic province. The R1 black/fracture zone has a close relationship with ore forming; however, the mechanism of the rock- and ore-controlling action of the structural system remains unclear. Based on a detailed analysis of the tectonite-mineralized alteration lithofacies of the R1 black/fracture zone, the tectonite-mineralized alteration lithofacies zones can be divided into four types in succession outward from the Pb–Zn mineralization center (F₅, F₁₀₀, and other faults), i.e., (1) the brecciated and stockwork-like Pb–Zn mineralization-complex breccia facies zone; (2) the stockwork-like Pb–Zn mineralization-simple breccia and cataclasite facies zone; (3) the veined pyrite–sulfide–dolomitic cataclasite facies zone; (4) the fine-veined calcite-black carbonized dolomite facies zone. With the evolution of the ore-forming fluid, the homogenization temperature decreases from Zone 1 to Zone 4; the salinity increases from Zone 1 to Zone 2 and then it decreases from Zones 3 and 4. The fluid density shows little change overall. The contents of Zn, Pb, Cu, Ga, Ge, Cd, Ag, and other metallogenic elements, Zn/Pb ratio, and CaO/MgO mole ratio decrease gradually from Zone 1 to Zone 4, and the REE fractionation, calcilization, silicification, and pyritization enhance gradually from Zone 1 to Zone 4. This series of changes is the product of diapirism (cryptoexplosion) of strike-slip structures and the black/fracture zone, among which the second-order structures derived from NWW-approximately EW-striking dextral shear-tension faults F₁ and F₁₅ control the brecciated and stockwork-like Pb–Zn mineralized complex breccia facies zones and the stockwork-like Pb–Zn mineralized simple breccia and cataclasite facies zones. Therefore, this paper establishes the zoning mode of tectonite-mineralized alteration lithofacies of the black/fracture zone and proposes that Zones 1 and 2 provide important prospecting criteria.

The Tong’an-Baishuidong mining district (TBMD), located in the eastern section of the Jiangnan Orogen, is a newly discovered granite-type lithium mining district. Thisstudy presents new monazite U–Pb chronological, whole-rock geochemical, and Nd–Pb isotopic data to reveal the petrogenesis and geodynamic setting of the Wutang granites in the TBMD. The monazite U–Pb age of 145.8 ± 1.0 Ma indicates that the granites were emplaced at the end of the Late Jurassic. Whole-rock geochemical results demonstrate that the Wutang granites are enriched in SiO₂ (72.80–73.40 wt%) but depleted in CaO (0.44–0.90 wt%) and MgO+TiO₂+TFeO (1.79–2.05 wt%). These granites exhibit negative Eu anomalies (δEu = 0.3−0.4) and high aluminum saturation indexes (A/CNK = 1.2−1.6), differentiation indexes (DI = 90–92), and Rb/Sr ratios (4.7–8.1). They also have moderate Ba contents (239–278 ppm) and low Sr contents (52.7–82.0 ppm) as well as low Nb/Ta (2.2–5.3) and Zr/Hf (21.3–31.5) ratios. All these indicate that they are highly fractionated granites. Additionally, these granites contain 5–10 wt% muscovite but no hornblende, with calculated corundum contents of 2.3–5.5 wt%. They have low high-field strength element (HFSE) contents (Zr + Nb + Ce + Y = 182–202 ppm) and zircon saturation temperatures (700–770 °C), with Th and Y negatively linked with Rb. These petrographic and geochemical features further reveal that the Wutang granites belong to highly fractionated S-type granites. The ε_Nd(t) values of these granites range from −9.03 to −8.23, corresponding to two-stage model ages (T_DM2) of 1488–1553 Ma. The initial Pb isotope ratios are: (²⁰⁶Pb/²⁰⁴Pb)_i = 18.38–18.55, (²⁰⁷Pb/²⁰⁴Pb)_i = 15.67–15.68, and (²⁰⁸Pb/²⁰⁴Pb)_i = 38.62–38.67. These Nd–Pb isotopic results demonstrate that the parental magma originated from the partial melting of ancient crustal materials. In the meantime, the TBMD in the eastern section of the Jiangnan Orogen was in a compression-extension transitional setting associated with the episodic subduction of the Paleo-Pacific Plate.

Brachinite is a group of primitive achondrites that enables investigating the evolution of asteroids not fully differentiated in the early stage of the solar system. Kumtag 061 is a new meteorite sample collected on October 27, 2019, in Kumtag Desert, Xinjiang Province, China. The oxygen isotope composition (δ¹⁸O = 5.086‰, δ¹⁷O = 2.396‰, Δ’¹⁷O =  − 0.298‰) and petrologic and mineralogic analysis suggest Kumtag 061 is a heavy-impacted brachinite (S4–S5). The geochemical composition suggests Kumtag 061 represents a partial melting residue of the brachinite parent body. Based on the noble gas composition, the cosmic ray exposure age of Kumtag 061 is 60.9 ± 9.0 Ma. Combined with the gas retention ages, they indicate a (series of) thermal events on the parent body of brachinites before Kumtag 061 was ejected into space.

The Damiao Fe-Ti-P deposit, located within the Damiao anorthosite complex in northeastern China, features Fe-Ti oxide ores and nelsonites that occur as irregularly inclined stratiform-like bodies, lenses, or veins with sharp contacts against anorthosite and gabbronorite. This deposit is characterized by abundant titanomagnetite that hosts diverse ilmenite exsolution textures, including blocky, lamellar, and cloth-like forms. In this study, we investigate the geochemistry and mineralogy of ilmenite exsolutions in titanomagnetite to understand their formation mechanisms and implications for the ore-forming process. Detailed petrographic observations and electron microprobe analyses reveal that the exsolution textures result from multiple mechanisms: oxy-exsolution due to titanomagnetite oxidation; subsolidus re-equilibration between magnetite and ilmenite involving elemental diffusion of Fe, Ti, Cr, Co, and Ni; and exsolution related to lattice defects caused by rapid cooling. Thermodynamic modeling using Gibbs free energy calculations, and the QUILF program indicates that blocky, lamellar, and cloth-textured ilmenite exsolutions formed at temperatures above and below the solid-solution solvus under decreasing oxygen fugacity. Additionally, our results indicate that the exsolution of zircon and pleonaste at ilmenite grain boundaries is attributed to the saturation and precipitation of elements like Zr and Al, due to the oxidation of titanomagnetite, rather than interactions between ilmenite and adjacent clinopyroxene. Reconstruction of the cooling history suggests that the oxygen fugacity of oxide–apatite gabbronorites was significantly higher than that of Fe-Ti-P ores. This confirms that increasing oxygen fugacity during magma evolution promoted immiscibility, leading to the formation of nelsonitic melts and ultimately the development of Fe-Ti-P ores.

The Dharwar Craton in India, as one of the oldest cratons in the world, preserves key information of early continental crust evolution. However, a ~ 3.0 Ga tectono-thermal event was previously recognized only in the Western Dharwar Craton, and the coeval tectono-thermal event has been rarely reported in the Central Dharwar Block. In this study, zircon U–Pb dating of the gabbroic diorite xenolith from Neoarchean Closepet batholith yields an age of 2995 ± 13 Ma, confirming the ~ 3.0 Ga magmatism in the Central Dharwar Block. The gabbroic diorite is characterized by low SiO₂ (52.62%–53.42%) and high MgO (5.38%–5.42%), Cr (48–70) × 10^–6, and Ni (115–124) × 10^–6, with relative enrichment in LILEs and LREE and depletion in HFSEs as well as negative Nd (ε_Nd(t) =  − 4.8 to − 4.5) and Hf (ε_Hf(t) =  − 6.64 to − 2.36) isotopes, indicating an enriched mantle source. Furthermore, geochemical signatures of zircon, clinopyroxene, and hornblende indicate that this magmatism occurred in an environment with water enrichment and high oxygen fugacity, similar to the island-arc setting, suggesting that the gabbroic diorite was produced by partial melting of enriched mantle source under a subduction zone. Additionally, the mafic magmatism in the Dharwar Craton evidently decreased from 3.2 to 3.0 Ga, accompanied by a transition of crustal components from Na-rich to K-rich, implying that a significant tectonic regime shift had already happened in the Dharwar Craton around ~ 3.0 Ga. Considering the enriched isotopic composition of the gabbroic diorite and previous studies on the Dharwar Craton from 3.2 to 3.0 Ga, it suggests that the Dharwar Craton might have undergone a vertical-to-lateral tectonic transition beginning at ~ 3.2 Ga and lasting until ~ 3.0 Ga, and the subduction related to the plate tectonic probably started in a specific scale.