The Lalingzaohuo cobalt-bearing Cu polymetallic skarn deposit, located in the central part of the East Kunlun Orogenic Belt, is mainly hosted in the Paleoproterozoic Jinshuikou Group. The occurrence and genesis of cobalt at Lalingzaohuo were investigated by field geology, mineralogy, geochronology, and electron probe microanalyses (EPMA), that these data provide some insights into the ore-forming process and also show the key characteristics of a cobalt-bearing skarn. Garnet U-Pb dating yielded a lower intercept 206Pb/238U date of 207.5 ± 4.9 Ma, younger than spatially related quartz diorite (SHRIMP zircon U–Pb dating, 246.8 ± 1.7 Ma), which suggested that the Lalingzaohuo was formed during the Late Triassic. Photomicrographs and EPMA data confirm that Co mineralization is associated with metal sulfides, which develop at the sulfide stage. Cobalt occurrence in Lalingzaohuo is restricted to Co mineral (cobaltite) and other metal sulfides (pyrite, pyrrhotite, chalcopyrite, and sphalerite) where isomorphic substitution occurred. Cobaltite is mainly distributed at the periphery of the skarn alteration zone with more pyroxene. The isomorphic substitution content of Co in pyrite (2.43–3.05 wt%), pyrrhotite (1.87–2.47 wt%), chalcopyrite (0.63–1.38 wt%), and sphalerite (0.73–0.90 wt%) is high. The negative correlation between Co + Ni (wt.%) and Fe (wt.%) suggests that Co + Ni replaces Fe in pyrite and pyrrhotite. The weak correlation between Co (wt.%) and Cu or Fe (wt.%) indicates that only part of the isomorphic Co in chalcopyrite is carried out by substituting Fe and Cu. The high Fe and Co content in sphalerite indicate that Co + Fe replaces Zn by isomorphic substitution. The isomorphic substitution of Co in the Lalingzaohuo deposit is an important potential available resource. Based on the magmatic activity records, the Triassic Lalingzaohuo deposit was formed under an extensional environment, which is related to the subduction of the branch of the Paleo-Tethyan Ocean. This study together with the regional developed cobalt-bearing skarn deposits indicates that the East Kunlun Orogenic Belt is an important cobalt-bearing skarn mineralization potential region.
Laterite Fe–Mn deposits are widespread in South China, with the majority of Fe–Mn ore being present in residual quaternary clay beds. However, detailed geological data on the lateritization of low-iron-content carbonate rocks are rare. In this study, we present new results on the mineralogy and geochemistry, as well as a genetic model, of the Maojun laterite Fe–Mn deposit in the Lanshan area, Hunan Province, South China. The profile sequence of laterite consists of an eroded bedrock horizon at its base, an intermediate black–brown clay layer containing earthy Fe–Mn ore, and a reddish-brown clay layer with nodular ferromanganese ore in contact with reddish-brown or yellowish-brown clay on top. Field evidence and chemical analysis indicated that during lateritization, the Mn-Fe-containing carbonate rocks of the Huanggongtang (D2h) and Shetianqiao formations (D3s) saw a more significant removal of mobile elements (Mg, Ca, and Na) whilst insoluble elements (Fe, Mn, Si, Al, Pb, and Zn) exhibited persistent enrichment in situ. Discriminative diagrams of Fe–Mn mineralization, as well as the assemblage-related enrichment of Y, U, Mo, Pb, and Zn and depletion of high-field-strength elements Zr, Nb, and Th, imply that subsequent hydrothermal circulation overprinted on the previously formed hydrogenous deposit. Mineralogical studies conducted using XRD, EPMA, HR-TEM, and TIMA indicated the predominance of iron and manganese oxides; hematite, goethite, limonite, and hollandite were identified as major oxide phases and cryptomelane, pyrolusite, and coronadite were present in minute quantities. Similar minerals constitute the upper ferromanganese nodule horizons, although they possess distinct textures and concentrations. The mineralogy, geochemical associations, and Ti mass balance show a continuous vertical evolution from top to bottom in the lateritic profile. Ferromanganese concretions from the drenching zone with poorly crystallized Al–goethite, Al–hematite, limonite, Fe–kaolinite, Fe–Mn oxides and hollandite predominate in shallow parts, and microcrystalline hematite, goethite and hollandite were found in deeper layers. Mn2+ can be rapidly oxidized and precipitated on the surface of hematite and limonite as high-valence-state (Mn4+) manganese oxides and binds strongly with mobile elements (Ba, K, Pb, Zn, Ca, and Ni). Petrographical, mineralogical, and geochemical studies show that three stages comprised the formation of the Maojun laterite Fe–Mn deposit.
Abstract The Harizha Ag–Pb–Zn deposit is located in the eastern part of the eastern Kunlun Orogen, NW China. Two episodes including five paragenetic stages of vein mineralization has been recognized for the Harizha Ag–Pb–Zn deposit through petrographic observation: quartz + pyrite + arsenopyrite (Stage I), quartz + pyrite + chalcopyrite + pyrrhotite (Stage II), quartz + pyrite + chalcocite + pyrrhotite + sphalerite + galena + pyrargyrite (Stage III), quartz + calcite + pyrite + tetrahedrite + pyrolusite (Stage IV), and calcite + covellite + malachite + goethite + graphite (Stage V). In the quartz or calcite three types of fluid inclusions (FIs) were identified: L‐type, C‐type, and S‐type. The S‐type inclusions are only found in quartz in the wall rocks. The C‐type inclusions occur in quartz from early episodes (Stage I and II). The FIs from the early episodes homogenized at 240–320°C, with salinities of 9–12 wt.% NaCl equivalent. The ore‐forming fluids at the early episodes belong to an H 2 O–CO 2 –CH 4 –NaCl system. The FIs from late episodes (Stage III and IV) homogenized at 140–240°C, with salinities of 2–8 wt% NaCl equivalent. The ore‐forming fluids from the late episodes are dominated by an H 2 O–NaCl fluid system. The HO and CO isotopic compositions of quartz and calcite indicate that the ore‐forming fluids were derived from a primary magmatic‐hydrothermal system, with subsequent meteoric water involvement at a later stage. Sulfides have δ 34 S values of −3.7 to –1.0‰, and 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb ratios ranging from 18.381 to 18.425, 15.661 to 15.683, and 38.498 to 38.677, respectively. These likely suggest a magmatic sulfur affinity combined with the ore features, mineral associations, alteration characteristics, ore‐forming environment, and fluid evolutionary process. We conclude that the Harizha Ag–Pb–Zn deposit is a typical medium‐low temperature hydrothermal deposit.
Metal-organic frameworks (MOFs) have been extensively applied in supercapacitors. Unfortunately, metal active sites in MOFs are commonly blocked and saturated by organic ligands, leading to insufficient positions available for the electrochemical reaction. To address this issue, we develop a novel strategy to design and prepare a series of hollow metal sulfide/MOF heterostructures, which simultaneously alleviate the large volume expansion, avoid slow kinetics of metal sulfides and expose more electrochemically active sites of the MOF. Consequently, the optimized Co9S8/Co-BDC MOF heterostructure presents outstanding electrochemical performance with a high areal specific capacitance of 15.84 F cm-2 at 2 mA cm-2 and a capacitance retention rate of 87.5% after 5000 charge-discharge cycles. The asymmetric supercapacitors based on the heterostructure deliver a high energy density of 0.87 mW h cm-2 and a power density of 19.84 mW cm-2, as well as long cycling stability. This study provides a new strategy for the rational design and in situ synthesis of metal sulfide/MOF heterostructures for electrochemical applications.
The most severe challenge for troops in a high-altitude environment is hypoxia. Pressure swing adsorption coupled with membrane separation is an ideal solution for oxygen production in high-altitude areas, but the molecular sieve membranes and organic membranes used in this technique are greatly affected by the ambient temperature, humidity, and pressure. Compared with traditional porous materials, metal-organic frameworks (MOFs) have outstanding features such as low densities, large specific surface areas, high crystallinities, and flexible structures. Cr-MIL-101 (MIL: Matérial Institut Lavoisier) and its derivatives are MOFs with high nitrogen adsorption capacities and can be used for oxygen production by air separation. However, since the plateau climate is complex, the applicability of Cr-MIL-101 for oxygen production in high-altitude environments awaits clarification. Therefore, this study constructed a molecular model of Cr-MIL-101, simulated the adsorption equilibrium of N2 and O2 molecules on this material using the grand canonical Monte Carlo (GCMC) method, and obtained their adsorption isotherms and densities. At 298 K and 100 kPa, the maximum adsorption capacities of Cr-MIL-101 for N2 and O2 were 0.94 per cell and 0.23 per cell, respectively. While at 238 K and 100 kPa, the maximum adsorption amounts of Cr-MIL-101 for N2 and O2 were 5.10 and 1.07 per cell, respectively. The thermodynamic parameters and adsorption equilibrium parameters during the adsorption process were analyzed. The conclusion of this study provides theoretical support for optimizing the N2/O2 separation performance of Cr-MIL-101 in high-altitude environments.
Developing energy-efficient alternatives for pressure swing adsorption for methane separation from unconventional natural gas is crucial and challenging in the petrochemical industry. Herein, a heptazine-based porous MOF featuring a triple-layered supramolecular framework built on 2D stacked honeycomb layers was reported, which revealed 1D elliptic channels decorated with high concentrations of binding sites arising from unsaturated metal sites and exposed N atoms. The MOF displays high C2 and CO2 loadings and IAST selectivities with respect to CH4. The molecular simulation reveals that a high concentration of binding sites in 1D elliptic channels accounts for the highly selective separation of methane.
Ultrathin two-dimensional metal-organic frameworks (MOFs) have convincing performances in energy storage, which can be put down to their accessible active sites with rapid charge transfer. Herein, NiCo-layered double hydroxide (LDH) nanosheet arrays are used as self-sacrificial templates to in situ fabricate ultrathin NiCo-MOF nanosheet arrays on Ni foam (NS/NF) by using organic ligands without adding metal sources. Two ultrathin MOF nanosheets with different ligands, terephthalate (BDC) and 2-aminoterephthalate (NH2-BDC), are synthesized, characterized, and discussed in detail. Specifically, NiCo-NH2-BDC-MOF NS/NF exhibits the best electrochemical performance as a battery-type electrode for supercapacitors, achieves an areal capacitance of 12.13 F cm-2 at a current density of 2 mA cm-2, and retains the original capacitance of 73.08 % after 5000 cycles at a current density of 50 mA cm-2. Furthermore, when NiCo-NH2-BDC-MOF NS/NF is assembled with activated carbon (AC) to form an asymmetric supercapacitor (ASC), an energy density of 0.81 mWh cm-2 can be provided at a power density of 1.60 mW cm-2. These results offer an effective and controllable synthetic strategy to in situ prepare ultrathin MOF nanosheet arrays with different ligands and metal ions from LDH precursors.
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