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ABSTRACT Bacillus sp. Abq, belonging to Bacillus cereus sensu lato, was isolated from an aquifer in New Mexico, USA and phylogenetically classified. The isolate possesses the unusual property of precipitating Pb(II) by using cysteine, which is degraded intracellularly to hydrogen sulfide (H2S). H2S is then exported to the extracellular environment to react with Pb(II), yielding PbS (galena). Biochemical and growth tests showed that other sulfur sources tested (sulfate, thiosulfate, and methionine) were not reduced to hydrogen sulfide. Using equimolar concentration of cysteine, 1 mM of soluble Pb(II) was removed from Lysogeny Broth (LB) medium within 120 h of aerobic incubation forming black, solid PbS, with a removal rate of 2.03 µg L−1 h−1 (∼8.7 µM L−1 h−1). The mineralogy of biogenic PbS was characterized and confirmed by XRD, HRTEM and EDX. Electron microscopy and electron diffraction identified crystalline PbS nanoparticles with a diameter <10 nm,  localized in the extracellular matrix and on the surface of the cells. This is the first study demonstrating the use of cysteine in Pb(II) precipitation as insoluble PbS and it may pave the way to PbS recovery from secondary resources, such as Pb-laden industrial effluents. This article describes a novel strategy employed by bacteria to reduce the toxicity of lead by forming a mineral with limited solubility.

Galena is a sulfide mineral with the chemical formula PbS (lead sulfide) and is recognized as the primary lead source. Geologically, galena mineralization is generally formed through hydrothermal processes, particularly under low to moderate temperature conditions. This study aims to determine the distribution of galena mineralization zones. The identification was carried out using the magnetic method by analyzing the magnetic field anomaly responses at the measurement area. The magnetic data processing results indicate that galena mineralization zones are characterized by high magnetic anomalies (0.4-3.9 nT) and the presence of fractures that serve as pathways for hydrothermal fluids toward the mineralized areas. The distribution of galena mineralization within the measurement area was identified in the northwest, southwest, and southeast regions. These findings are expected to be a reference for geophysical exploration in mining activities, particularly in exploring galena mineral deposits.

A well reasoned lead (Pb) isotope-driven provenance study lies in concert with a comprehensively evaluated database of geological ore sources and accompanying archaeological and contextual information. In this paper we have compiled and evaluated all currently available Pb isotope data for galena and K-feldspars in China, and provided geological interpretations for how their ore-forming substances evolved across relevant tectonic terrains. We pay particular attention to the geological settings of host ore deposits that were likely exploited in ancient and historic China, detailing the heterogeneity and homogeneity of their ore formation across different metallogenic provinces and belts. Using the isotope database, and supportive geological and archaeological background information, three case studies are presented that detail the provenancing of Chinese cultural materials. The isotope data themselves are presented in ternary diagrams that allow for their concise and accurate comparison.

Concentration data are reported for 18 trace elements in chalcopyrite from a suite of 53 samples from 15 different ore deposits obtained by laser-ablation inductively-coupled plasma-mass spectrometry. Chalcopyrite is demonstrated to host a wide range of trace elements including Mn, Co, Zn, Ga, Se, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb and Bi. The concentration of some of these elements can be high (hundreds to thousands of ppm) but most are typically tens to hundreds of ppm. The ability of chalcopyrite to host trace elements generally increases in the absence of other co-crystallizing sulfides. In deposits in which the sulfide assemblage recrystallized during syn-metamorphic deformation, the concentrations of Sn and Ga in chalcopyrite will generally increase in the presence of co-recrystallizing sphalerite and/or galena, suggesting that chalcopyrite is the preferred host at higher temperatures and/or pressures. Trace-element concentrations in chalcopyrite typically show little variation at the sample scale, yet there is potential for significant variation between samples from any individual deposit. The Zn:Cd ratio in chalcopyrite shows some evidence of a systematic variation across the dataset, which depends, at least in part, on temperature of crystallization. Under constant physiochemical conditions the Cd:Zn ratios in co-crystallizing chalcopyrite and sphalerite are typically approximately equal. Any distinct difference in the Cd:Zn ratios in the two minerals, and/or a non-constant Cd:Zn ratio in chalcopyrite, may be an indication of varying physiochemical conditions during crystallization. Chalcopyrite is generally a poor host for most elements considered harmful or unwanted in the smelting of Cu, suggesting it is rarely a significant contributor to the overall content of such elements in copper concentrates. The exceptions are Se and Hg which may be sufficiently enriched in chalcopyrite to exceed statutory limits and thus incur monetary penalties from a smelter.

In order to recover low-grade complex zinc ore in a reasonable way, this study adopts bioleaching method to study it. The ore samples contain 1.52%, 2.03% and 14.4% zinc, respectively, which occurs in the form of sphalerite. Other major minerals include pyrite, galena, quartz and mica. The inoculation of the domesticated strain was basically free of adaptation period, and the cell concentration could be rapidly increased after a short decrease. The leaching extent of zinc increased continuously, while the leaching rate decreased gradually. After the bioleaching process, sliver, lead and iron were mainly present in the residue phase. X-ray diffraction spectroscopy analysis showed that sphalerite, galena and pyrite were dissolved, and the latter two further precipitated to produce PbSO4 and jarosite. In addition, the dissolution of calcium compounds can lead to the formation of gypsum precipitation. These precipitates covered the fresh ore surface may hinder the further bioleaching process. The Exponential model was used to simulate the bioleaching process, and it was found that the fit coefficients were all greater than 0.98, and a reasonable leaching cycle was further discussed. The results provide a good basis for the economic and environmentally friendly recovery of low-grade complex zinc ores.

The Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province (SYGMP) is an important region for Pb-Zn resources in China. However, considerable controversy remains as to whether the Pb-Zn deposits are Mississippi Valley Type (MVT). The Maozu deposit, a typical example of the carbonate-hosted Pb-Zn deposits in the SYGMP, occurs in the late Ediacaran Dengying Formation and its ore bodies are divided into three types: lower layer (LL), vein layer (VL), and upper layer (UL) ore bodies based on their spatial relationship. In this study, laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) was used to systematically analyze the trace-element compositions of sphalerite and galena in these three ore bodies. The results show that sphalerite is characterized by Cd and Ge enrichment; Fe, Mn, and Co depletion; and local In and Sn enrichment. Most of these elements likely appear as solid solutions in sphalerite and show a wide compositional variation, which is probably related to the medium- and low-temperature mixing of the ore-forming fluids. The local enrichment of In and Sn is likely attributed to the long-distance migration of ore-forming fluids through In-Sn-bearing volcaniclastic rocks. In vs. Sn and (Cu + Sb) vs. (Ag + Ge) show strong correlations and similar element distribution in the mapped images, indicating that these elements may be incorporated into sphalerite via a coupled substitution for Zn as 2In + Sn + 2◻ ↔ 5Zn (◻ = vacancies) and 4(Cu + Sb ) + (Ge + 2Ag ) + 2◻ ↔ 13Zn . Galena is enriched in Ag and Sb with minor Cd and Se and depleted in Bi, and most of the elements may occur as solid solutions. Ag vs. Sb in galena displays a strong positive correlation, implying the coupled substitution of Ag + Sb ↔ 2Pb . Notably, the majority of the trace-element concentrations gradually decrease in the order LL → UL except Fe, Co, Cu, and Ge, while Fe, In, and Sn in sphalerite and Ag and Sb in galena have the highest concentration in the VL, indicating that the VL is a secondary migration channel for the ore-forming fluids. Furthermore, the trace-element compositions of the sulfides in the Maozu Pb-Zn deposit are consistent with the typical MVT deposit (hosted in the carbonate sequence) but are markedly different from sedimentary exhalative (SEDEX), volcanogenic massive sulfide (VMS) and skarn-type deposits. Based on these results, as well as the geological and geochemical characteristics of the deposit, the Maozu Pb-Zn deposit is an MVT deposit.

Sphalerite which is highly continuous with galena cannot be effectively separated by flotation, the extraction of zinc from sphalerite in bioleaching process has become an alternative method. By testing the initial iron concentration, pulp density, grinding fineness and other parameters as well as monitoring pH, potential and dissolved oxygen, the zinc content of the lead concentrate decreased from 8.41% to less than 1% after bioleaching in 8L agitator tank. The initial concentration of ferric is the most significant factor affecting the zinc extraction efficiency of sphalerite, and when the concentration of ferric ions reaches 9g/L, acceptable leaching yield can be achieved.

Abstract The Dongping gold deposit, located near the northern margin of the North China Craton, contains ore bodies spatially associated with the Devonian Shuiquangou syenite, Cretaceous Shangshuiquan granite, and Archean metamorphic rocks. Major and trace elements and S–Pb isotopes of pyrite from two stages of gold-quartz veins and wall rocks were used to constrain the composition of hydrothermal fluids and metal sources. Stage-1 (early) pyrites are euhedral to subhedral, medium- to coarse-grained, and have low gold contents. Py1a is homogeneous with few fractures, whereas Py1b, which occurs on the edges of Py1a, is porous and has higher metal contents. Stage-2 (late) pyrites are mostly anhedral to subhedral and have smaller grain sizes and higher gold contents than Stage 1. Py2a occurs with sulfide minerals such as galena and chalcopyrite, and Py2b is porous and has the highest gold content (up to 1839 ppm) and smallest grain size. All pyrite samples yield negative δ34S values (− 7.5 to − 3.5‰), reflecting oxidized conditions during mineralization. The ~ 2‰ decrease in δ34S values from Stage 1 (− 4.3‰, − 4.9‰) to Stage 2 (− 7.0‰, − 6.4‰) may reflect a change in the fluid source and/or an increase in fO2. The Pb isotope composition of Stage-1 pyrite is suggestive of a mantle source similar to that of the Shuiquangou syenite, whereas Stage-2 pyrite has more radiogenic Pb isotopic compositions suggestive of an Archean metamorphic source. Combined with previous studies, our trace element and isotopic results indicate that the two stages of pyrite had different sources, with Stage-2 pyrite being more strongly influenced by metasedimentary rocks. We propose that the early stage of low-grade gold mineralization was related to emplacement of the Devonian Shuiquangou syenite, whereas the late stage of high-grade gold mineralization was related to emplacement of the Cretaceous Shangshuiquan granite and leaching of gold from Archean metamorphic rocks.

Heterocoagulation between fine particles can interfere with the flotation separation of different minerals. Therefore, the study of particle heterocoagulation is significant. This study found that fine calcite affected galena flotation and examined the interactions between galena and fine calcite particles in suspension pulp. The best flotation behaviour was observed for pure galena minerals at pH 9; however, the flotation separation of galena and fine calcite yielded unsatisfactory results under these conditions. The results of zeta potential measurement, scanning electron microscopy, and X-ray photoelectron spectroscopy indicate that heterocoagulation occurred between the calcite and galena particles at pH 9. The interaction mechanism shows that dissolved hydroxy calcium could be absorbed on the surface of galena and render a positive charge, causing coagulation between the calcite and galena particles due to electrostatic attraction. This new discovery provides a reference for the pre-inhibition of gangue minerals and adjustment of the chemical ratio during the flotation process.

To understand the controls of basin paleogeographic evolution on sediment-hosted gold metallogenesis, a study was undertaken of pyrite texture and geochemistry of the Jinya, Nakuang, and Gaolong gold deposits in the Youjiang Basin, SW China. Syn-sedimentary/diagenetic pyrite and three generations of hydrothermal pyrite (As-Au-poor core, anomalously As-rich but Au-poor mantle, and As-Au-rich rim) are defined in the three gold deposits. The syn-sedimentary/diagenetic pyrites deposited in the basin facies at Jinya and slope facies around platforms at Gaolong have δ34S values of –3.4 ‰ to + 7.3 ‰ and + 14.8 ‰ to + 16.1 ‰, respectively. Compared to As-Au-poor pyrite with abundant fine-grained galena inclusions and high-radiogenic Pb isotopic ratios, the As-Au-rich pyrite shows a ~ 2–3 ‰ increase in average δ34S values (Jinya: –5.9 ‰; Nakuang: –7.6 ‰; Gaolong: + 12.2 ‰) towards those of syn-sedimentary/diagenetic pyrite and a decrease in average Pb isotopic ratios. These phenomena can be explained by the interaction of ore fluids with the pyritic sedimentary host rocks. A regional feature of the Youjiang Basin is that most of the gold deposits share similar pyrite textures and trace element compositions. However, the δ34S values of auriferous pyrite range from –9 ‰ to –5 ‰, –5 ‰ to + 5 ‰, and + 5 ‰ to + 19 ‰ in these gold deposits with host rocks deposited in the basin facies, open platforms, and slope facies around platforms, respectively. Thus, it is demonstrated that the sulfur isotope compositions of auriferous pyrite were mostly determined by the syn-sedimentary/diagenetic pyrite formed under different sedimentary facies.