Kimberlitic zircons represent a common type of mantle-derived zircon megacryst entrained in kimberlites, and they have been shown to reliably record ages of kimberlite emplacement. Here, we present results of U–Pb geochronology, as well as oxygen-isotope, trace-element, and mineral-inclusion analyses of zircon megacrysts from the Obnazhennaya and Olivinovaya kimberlite pipes of the Kuoika field, northern Siberian craton. These zircons exhibit mantle-like oxygen-isotope compositions (δ18O = 5.11–5.86‰), low U concentrations (5–90 ppm), low total rare-earth-element (REE) concentrations (8–186 ppm), relatively flat heavy-REE patterns, and weak or absent Eu anomalies. Together, these characteristics indicate that the analyzed megacrysts are mantle-derived kimberlitic zircons, an interpretation further strengthened by the identification of olivine inclusions in one of the zircons. As such, these are the first kimberlitic zircons reported from the Obnazhennaya and Olivinovaya kimberlites. U–Pb dating of these zircons yielded Late Jurassic concordia ages of 152.5 ± 2.7 Ma (2σ) for the Obnazhennaya pipe and 148.5 ± 3.4 Ma (2σ) for the Olivinovaya pipe, which are consistent with the Middle Jurassic-to-Early Cretaceous age range previously reported for kimberlite magmatism within the Kuoika field. Our U–Pb age for the Obnazhennaya pipe is consistent with previous age estimates obtained using other geochronological methods and therefore provides a new, independent constraint on its emplacement age. The U–Pb age obtained for kimberlitic zircons from the Olivinovaya pipe provides the first reliable age constraint for this kimberlite.
This study examined the efficacy of BKG721 (BK), an auxiliary collector, in the flotation of an oxidized copper–cobalt ore from the Democratic Republic of the Congo (DRC). The run-of-mine ore assays 2.22% Cu and 0.25% Co, with an oxidation degree exceeding 30%. A sulfide-then-oxide locked-cycle flotation process using NaHS as a sulfidizer and sodium butyl xanthate (SBX) as a primary collector was employed. With the addition of BK, copper oxide recovery in closed-circuit tests rose from 22.49% to 26.26% and cobalt recovery from 20.00% to 28.09%, representing absolute increases of 3.77 and 8.09 percentage points, respectively. To elucidate the underlying mechanisms, contact angle, zeta potential, FTIR, and XPS measurements were performed. Contact angle results showed that BK significantly increased surface hydrophobicity. Zeta potential determinations revealed a pronounced negative shift in the surface potential of the treated malachite, indicating strong adsorption of collector anions. FTIR spectra exhibited more intense Cu–S vibration at 617 cm−1 for the NaHS + BK + SBX system compared to NaHS + SBX alone, implying strengthened chemical bonding. XPS analysis further detected the characteristic phosphorus element of the dithiophosphate constituent on treated malachite surfaces, confirming chemical adsorption. Collectively, these findings demonstrate that BK chemisorbs onto copper–cobalt oxide minerals, synergizes with the primary collector, and enhances bubble-particle attachment, thereby achieving superior flotation performance. The NaHS + BK + SBX reagent scheme provides a viable route for processing similar refractory oxidized ores.
The Ergadiji Pb–Zn deposit is located in the northern part of the Sichuan–Yunnan–Guizhou (SYG) metallogenic district in southwestern China. This study presents mineralogical observations, electron probe microanalysis (EPMA) of sulfides and Pb–As–Sb sulfosalts, laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) summaries and elemental maps of sphalerite, and in situ S–Pb isotope results obtained by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA–MC–ICP–MS). These datasets describe ore-mineral associations, mineral compositions, and isotopic variability. Germanium (Ge) distribution and possible incorporation pathways are considered within this broader mineralogical and geochemical context. Ge is hosted predominantly by sphalerite, and its enrichment shows a pronounced stage dependence: mean Ge concentrations increase from 41.87 ppm in Stage I to 155.35 ppm in Stage II. This increase is accompanied by a change in sphalerite trace-element systematics. Stage II sphalerite shows moderate positive Ge–Cu and Ge–(Cu + Ag) correlations (R2 = 0.5915 and 0.5661, respectively), while elemental maps show preferential enrichment of Ge–In–Cd toward outer growth zones. Taken together, these observations define a coherent Stage I-to-Stage II evolution in which changes in the hydrothermal system and sphalerite composition increasingly favored Ge incorporation during later growth. The available data are consistent with several possible substitution pathways, including vacancy-assisted substitution (Ge4+ + □ ↔ 2Zn2+), Cu-coupled substitution (2Cu+ + Ge4+ ↔ 3Zn2+), and Cu–Ag-coupled substitution [2(Cu+, Ag+) + Ge4+ ↔ 3Zn2+], but they do not uniquely establish their relative contributions because Ge valence and local coordination were not directly determined at Ergadiji. The stage-related increase in Ge is therefore interpreted as the integrated response of sphalerite to evolving temperature, sulfur and oxygen fugacity, fluid composition, and crystal chemistry, rather than to any single parameter alone. These results constrain the mineral-scale behavior of Ge at Ergadiji and highlight the importance of hydrothermal physicochemical conditions in controlling its incorporation into sphalerite. They also provide a basis for evaluating Ge enrichment and the potential comprehensive utilization of Ge-bearing Pb–Zn resources in the SYG metallogenic district.
Coal can enrich hazardous trace elements in specific depositional environments, and their distribution and modes of occurrence are controlled by multiple geological factors. This study investigated the geochemistry of hazardous trace elements in the Middle Jurassic Xishanyao Formation coals of the Piliqing Open-Pit Mine, Yili Coalfield, using proximate, mineralogical (XRD, SEM-EDS), and geochemical (ICP-MS, carbonate C-O isotope) analyses. The coals were ultra-low-ash and low-sulfur subbituminous, with a whole-coal weighted-average CaO content of 1.95%. Most hazardous trace elements were not enriched relative to world coal averages: F, Cr, Ni, Co, As, Sr, and Th were near global values; whereas Se, Cd, Mo, Tl, Pb, U, and Hg were depleted. Vertically, F, V, Cr, Hg, Pb, Tl, Th, and U were higher in the roof and floor strata than in the coal seams, indicating terrigenous detrital input as the primary control, whereas Sr was governed by carbonate and aluminosilicate minerals. The only pronounced enrichment was the anomalously high V (212 μg/g) in sample C407, which possibly recorded locally reducing conditions at the base of the No. 4 seam; however, this single-sample observation precludes a firm syngenetic interpretation. Carbonate C-O isotopes showed that the calcite veins precipitated from coal-altering epigenetic hydrothermal fluids that carried an admixed organic-matter-derived carbon component. These fluids delivered mainly Ca, Mn, and Sr, without adding harmful elements to the coal. This signature reflects a dominantly syngenetic geochemical pattern that was locally overprinted by non-oxidizing hydrothermal fluids, in which weakly oxidizing, shallow-water conditions were unfavorable for the reducing enrichment of U, Mo, Re, and Se. In contrast to the coal-hosted uranium deposits of the Southern Yili Basin margin, Piliqing coals showed no evidence of post-depositional oxidized-fluid infiltration, indicating limited environmental risk.
Cadmium (Cd) is recognized as a toxic element with environmental hazards and is frequently concentrated in agricultural and metallurgical solid wastes (AgSW and MetSW). Incorporating these wastes into cement is a primary route for resource recovery. Although Cd immobilization in cement systems containing AgSW-MetSW has been examined, its mechanisms, assessment methods, and long-term stability have not been systematically synthesized from an organic–inorganic interaction perspective. This review details physicochemical characteristics and Cd occurrence forms of AgSW and MetSW, and critically evaluates Cd leaching, microstructural methods, and long-term stability. Furthermore, multidimensional immobilization pathways in AgSW-MetSW cement systems are elucidated, including physical sequestration, chemical bonding, and synergistic fixation, which exhibit significantly enhanced Cd leaching reduction in hybrid systems. The long-term stability of Cd immobilization is governed by the balance between organic matter properties and inorganic alkalinity, which determines the reaction pathways and final Cd speciation. Organic matter can immobilize Cd via complexation and pore refinement or mobilize it through soluble complexes and degradation, depending on its properties and chemical environment. Based on these findings, future priorities should include standardized leaching evaluation, in situ speciation monitoring, durability prediction under combined actions, and life-cycle cost assessment for harmless utilization of Cd.
