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The world-class Huize deposit hosts significant germanium (Ge) resources in the Sichuan–Yunan–Guizhou (SYG) Mississippi Valley-type (MVT) Pb–Zn province of China. The distribution and enrichment mechanism of Ge is still poorly understood. In the main ore-forming stage of Huize, we identified six sphalerite colors from C1 (black) to C6 (white) in transmitted light. Two color sequences are confirmed, including C1 → C2 → C3 → C6 and C1 → C2 → C4 → C5 → C6. We used multiple analytical methods to reveal the Ge distribution and incorporation mechanism into sphalerite and the possible enrichment factors. Our results show that Ge occurs as argutite (GeO2), and in the sphalerite crystal lattice, C1 and C3 sphalerite has up to 593 ppm Ge. Two substitution mechanisms, i.e., Ge4+ + □(vacancy) → 2Zn2+ (e.g., C1 and C2) and Ge4+  + 2Cu+ → 3Zn2+ (e.g., C2, C3, C4, and C5), are inferred from the Huize sphalerite. They show different spatial structures of sphalerite and a weak shift of the white line observed by high-resolution X-ray absorption near-edge structure (XANES) spectroscopy. The trace-element composition of sphalerite suggests that reduced sulfur content of the ore-forming fluid contributes to Ge enrichment, followed by high temperature (> 300 °C).

Various genetic models have been proposed for the supergiant Proterozoic Broken Hill Pb–Zn–Ag deposit largely based on geological and geochronological evidence. Here we present Zn, Cd and S isotope compositions as well as Zn/Cd ratios of sphalerite from Broken Hill and minor Broken Hill-type deposits (Australia) to help constrain these models but focus on syngenetic and magmatic–hydrothermal processes, since epigenetic models can be rejected because the orebodies were deformed and metamorphosed by the Olarian Orogeny. Values of δ34SVCDT, δ66ZnAA-ETH and δ114CdNIST SRM 3108 for sphalerite from Broken Hill range from +0.27 to +4.73 ‰, −1.15 to +0.46 ‰ and −0.48 to +0.01 ‰, respectively, while those for the smaller Broken Hill-type deposits range from −5.11 to +1.28 ‰, −0.97 to +0.10 ‰ and −1.02 to +2.59 ‰, respectively. By combining published S isotope data of sulfides from the Broken Hill district with those obtained here, the sources of sulfur via thermochemical sulfate reduction, bacterial sulfate reduction and a magmatic origin cannot be distinguished. However, when the S isotope compositions are considered along with the broad range of Cd and Zn isotope data for sphalerite, which are among the lightest and heaviest yet reported for a sulfide deposit, the isotopic datasets are consistent with low-temperature biogenic processes associated with syngenetic deposition of sulfides. Cadmium isotope compositions when coupled with Zn/Cd ratios of sphalerite have previously been used to classify Pb–Zn deposits, including low-temperature, high-temperature and exhalative ores. However, the Zn/Cd ratios of sphalerite from Broken Hill cannot be used for such classification purposes.

Economic interest in indium (In) and other critical metals has accelerated efforts to understand how such elements occur in nature and the controls on their mineralogy. In this contribution, the distribution of In and other trace elements in the Dulong Zn–Sn–In deposit, China, is described, using a holistic approach which targets not only sulfides but also the potential for In and Sn within co-existing oxides and skarn silicates. Sphalerite is the most significant In carrier. Four distinct types of sphalerite are identified, which differ with respect to ore texture and the concentration of In (0.74–4572 ppm). Subordinate amounts of In also occur within chalcopyrite and within andradite garnet, an abundant mineral in the skarn at Dulong and possibly accounting for a significant proportion of total In. Tin is not especially concentrated in either sphalerite or chalcopyrite, occurring instead as cassiterite but with measurable concentrations also in magnetite and skarn silicates. The study confirms that the dominant substitution for In in sphalerite is 2Zn2+ ↔ Cu+ + In3+ but that Ag and Sn may also play a subordinate role in some sphalerite sub-types via the substitution: 3Zn2+ ↔ Ag+ + Sn2+ + In3+. The study highlights that concentrations of In in sphalerite are likely to be heterogeneous at scales from single mineral grains to that of the deposit. The observed partitioning of both In and Sn into skarn silicates, and to a lesser extent, oxides, is a critical factor that may significantly compromise estimations of by-product elements that would be economically recoverable during exploitation of sulfide ores.

Laser ablation-inductively coupled plasma-mass spectrometry and electron-probe microanalysis were used to investigate the trace-element contents of sphalerite, chalcopyrite and pyrite from the Plaka Pb–Zn–Ag deposit. Using petrographic observations, the analytical results could be linked to the temporal evolution of the Plaka ore-forming system. Sphalerite chemistry reliably records the temperature and fS2 evolution of the system, with estimated formation temperatures reproducing the microthermometric results from previous fluid-inclusion studies. Chalcopyrite chemistry also shows systematic variations over time, particularly for Cd, Co, Ge, In, Sn and Zn concentrations. Measurable pyrite was only found in association with early high-temperature mineralisation, and no clear trends could therefore be identified. We note, however, that As and Se contents in pyrite are consistent with formation temperatures estimated from co-existing sphalerite. Statistical analysis of the sphalerite data allowed us to identify the dominant geological controls on its trace-element content. The three investigated factors temperature, fS2, and sample location account for > 80% of the observed variance in Mn, Fe, Co, Ga, Ge, In, Sb and Hg concentrations, and > 60% of the observed variance in Cd and Sn concentrations. Only for Cu and Ag concentrations is the explained variance < 50%. A similarly detailed analysis was not possible for chalcopyrite and pyrite. Nevertheless, comparison of the results for all three investigated minerals indicates that there are some systematic variations across the deposit which may be explained by local differences in fluid composition.

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.

The Freiberg mining district in the Erzgebirge hosts three principal types of polymetallic veins. These are (1) the quartz-bearing polymetallic sulfide type, (2) the carbonate-bearing polymetallic sulfide type, and (3) the barite-fluorite-sulfide type. We investigated the genesis of each vein-type using Rb-Sr sphalerite geochronology, Sm-Nd fluorite geochronology, and Pb, Sr, and Nd isotope systematics of ore and gangue minerals. Field relationships and the Rb-Sr and Pb isotope systematics of sulfides from quartz-bearing polymetallic sulfide veins and carbonate-bearing polymetallic sulfide veins confirm their close genetic affiliation and yield a combined Rb-Sr errorchron age of 276 ± 16 Ma. The high mean squared weighted deviation (MSWD) value of 42 on the regression is considered to reflect initial isotopic heterogeneity, which is probably related to fluid-rock interaction during the hydrothermal mineralization process. Although some sphalerites from barite-fluorite-sulfide veins have strongly disturbed Rb-Sr isotope systematics, six sphalerites and one co-genetic fahlore yield a robust isochron age of 121.3 ± 4.2 Ma with an MSWD of 2.9. This age is supported by a fluorite Sm-Nd isochron age of 101 ± 18 Ma (MSWD = 1.3). The new ages and radiogenic isotope data place robust constraints on the long-held hypothesis that veins in the Freiberg district formed during two hydrothermal events. The Lower Permian age of first stage quartz-bearing polymetallic sulfide veins and carbonate-bearing polymetallic sulfide veins coincides with post-Variscan crustal reorganization and Rotliegend volcanism. The Mid-Cretaceous age of second stage barite-fluorite-sulfide veins coincides with opening of the North Atlantic Ocean during the break-up of Pangea.

Heavy metals mainly exist on the surface of sediment particles and are transported using particulate matter as carriers. Therefore, the particle size of sediment particles can affect the adsorption, release, and migration of heavy metals. This study aim to investigate the distribution characteristics and chemical fraction of Cd, Pb, and As contents in sediments of different particle sizes using the BCR method, and to determine the key factors affecting the distribution of heavy metals through mineralogical methods such as XRD and EDS. The results revealed that the overall content of various forms of heavy metals increases with the decrease of particle size, mainly presents in fine particles. The mineralogical analysis results indicated that fine particles predominantly contained clay minerals such as chlorite and illite and coarse particles mainly include primary minerals. Due to the mining areas in the middle-upstream, Cd, Pb and As were primarily associated with galena, sphalerite and pyrite, respectively. The distribution of heavy metals is jointly influenced by sediment particle size and sediment material composition.

Carbonate-hosted Pb–Zn deposits frequently contain significant amounts of critical metals such as germanium in sphalerite. However, the textural and chemical controls leading to Ge enrichment remain poorly constrained. Based on textural observations and laser-ablation (multi-collector) inductively coupled plasma mass spectrometry analysis, we investigate the origin, textural control, and incorporation of Ge in the Zhulingou carbonate-hosted Zn(-Ge) deposit, South China, which contains > 400t Ge at 97.9 ppm. Two hydrothermal stages (I and II) and three textural types of sphalerite (Sp1, Sp2, and Sp3) are recognized in stratabound and stockwork Zn(-Ge) orebodies. Acicular colloform Sp1 formed in stage I, whereas euhedral sector-zoned Sp3 is related to stage II. In acicular-euhedral Sp2, both Sp1 and Sp3 are observed. A large variation of Ge concentrations is observed with an average Ge of 1013 ppm in Sp1, decreasing to 621 ppm in Sp2 and to 492 ppm in Sp3. In the three types of sphalerite, Ge concentrations are not correlated to monovalent cations (Cu and Ag), indicative of unusual substitution mechanisms coupled to divalent cations such as Mn, Pb, or Cd. Trace element distribution, sulfur, and lead isotopes suggest that the deeply circulating brines interacted with Ge-rich basement rocks and mixed with shallow biogenic sulfur: This mixing process was certainly the main factor controlling the Ge endowment. The precipitation of acicular sphalerite was likely controlled by a combination of specific fluid conditions (i.e., low T and pH, and rapid mineral growth rate) and fluid mixing. These conditions leading to the formation of acicular sphalerite were favorable for Ge enrichment, compared to co-existing euhedral grains generally less rich in Ge.

The historic silver mining district of Freiberg (Germany) comprises hydrothermal vein-style mineralization of Permian and Cretaceous age. We compare sphalerite compositions with associated ore-forming fluids and constrain the behavior of critical metals such as In, Ge, and Ga in contrasting hydrothermal environments. Fluid inclusion studies reveal that the Permian veins formed due to boiling and cooling of a low-salinity (0 to 6% eq. w[NaCl]) magmatic-hydrothermal fluid at 350 to 230 °C. In contrast, Cretaceous veins formed by mixing of highly saline (17 to 24% eq. w[NaCl + CaCl2] and variable Na/(Na + Ca) ratios) brines at low temperatures (~ 120 °C). Sulfides of the Permian ore stage have a narrow range of δ34SVCDT from − 2.3 to + 0.9‰, while the sulfides of the Cretaceous stage have a large scatter and significantly more negative δ34SVCDT values (− 30.9 to − 5.5‰), supporting the different nature of the hydrothermal systems. Contrasting fluid systems and ore-forming mechanisms correspond to markedly different trace element systematics in sphalerite. Permian sphalerite is significantly enriched in In (up to 2500 μg/g In) relative to two sphalerite generations of Cretaceous veins. The latter have higher Ge (up to 2700 μg/g Ge) and Ga (up to 1000 μg/g Ga) concentrations. The observed trace element systematics of different sphalerite generations imply that In is enriched in high-temperature, low- to intermediate-salinity fluids with a significant magmatic-hydrothermal fluid component, while Ge and Ga are more concentrated in low-temperature, high-salinity crustal fluids with no obvious magmatic-hydrothermal affiliation.

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.