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Textural, chemical, isotopic and microthermometric features of sphalerite from the Wunuer deposit, Inner Mongolia: Implications for two stages of mineralization from hydrothermal to epithermal
Abstract
The Wunuer Pb–Zn–Ag–Mo deposit is a newly explored polymetallic ore deposit located in the middle segment of the Great Xing'an Range, Inner Mongolia, NE China. Three stages of mineralization, composed of an early porphyry stage, an intermediate hydrothermal (cryptoexplosive breccia) stage, and a later epithermal stage, have been identified in the Wunuer deposit. Sphalerite is one of the principal metal sulphides in both hydrothermal and epithermal stages, and thus two generations of sphalerite, with the first‐generation sphalerite (Sp1) precipitated in hydrothermal stage and the second‐generation sphalerite (Sp2) precipitated in epithermal stage, were discriminated. The Sp1 is generally euhedral, transparent and colour‐zoned, and is usually replaced by Sp2, galena and chalcopyrite. The Sp2 is generally anhedral, opaque and black in colour. Chalcopyrite inclusions in Sp1 and Sp2 have different genetic mechanisms: chalcopyrite inclusions in Sp1 were produced by replacement as the result of interaction of sphalerite with Cu‐rich fluids, while chalcopyrite inclusions in Sp2 were produced by coprecipitation of sphalerite and chalcopyrite during crystal growth. Electron probe microscope analyser and laser ablation inductively coupled plasma mass spectrometry in‐situ analysis techniques have been used to obtain chemical compositions of sphalerite. The Sp1 is enriched in Cd and In, and depleted in Mn, Fe, Cu, Ag, Sb and Pb. In contrast, the Sp2 is enriched in Mn, Fe, Cu, Ag, Sb and Pb, and depleted in Cd and In. Elements of Pb, Ag, Bi and some of Fe, Cu concentrated in Sp2 are greatly attributed to micro‐mineral inclusions like chalcopyrite and galena, while most elements concentrated into Sp1 are generally incorporated into crystal structure in mechanisms of direct substitution (e.g. Fe2+ → Zn2+) or coupled substitution ((Cu+ + In3+) → 2Zn2+). In‐situ sulphur isotope results reveal similar slightly positive sulphur isotope compositions (+1.55‰ to +3.33‰ δ34SV‐CDT for Sp1, and +1.71‰ to +2.34‰ δ34SV‐CDT for Sp2) of the two generations of sphalerite, implying a magmatic material for both Sp1 and Sp2. Fluid inclusions in molybdenite‐bearing quartz vein, Sp1 and Sp2‐coexisting quartz have been studied to reveal fluid temperature and salinity evolution from porphyry to hydrothermal and to epithermal stage mineralization. Primary fluid inclusions in porphyry stage quartz homogenized to a liquid phase by high homogenization temperatures (range from 385 to 416°C, with an average of 399°C), with salinities ranging from 12.4 to 25.3 wt% (average of 19.4 wt%). The Sp1 was precipitated from fluids with medium temperature (302–317°C) and medium salinity (5.1–7.3 wt% NaCl) in the hydrothermal stage, and later been altered by metasomatic fluids with low temperature (142–186°C) and low salinity (0.7–5.3 wt% NaCl). The Sp2 was precipitated from fluids with low temperature (150–234°C) and low salinity (0.4–6 wt% NaCl) in the epithermal stage.
... These fluid inclusions homogenized to the liquid phase at temperatures of 216 • C-366 • C (generally 250 • C-309 • C) and have a relatively wide range of salinities (0.4-21.5 wt% NaCl equivalent). One type III inclusion homogenized by the disappearance of halite at 272 • C, yielding a salinity of Zhu et al., 2007;Jiang et al., 2010;Shu et al., 2013;Zhai et al., 2013Zhai et al., , 2019Zhai et al., , 2020Chen et al., 2014;Ouyang et al., 2014;Wang et al., 2014;Li et al., 2015Li et al., , 2016Wang et al., 2018;Fan et al., 2020;Xu et al., 2020) with the sulfur isotope composition range of magmatic sulfur (Hoefs, 2009). 36.1 wt% NaCl equivalent (Fig. 7c-d). ...
... The sulfur in the Erdaohe deposit is isotopically similar to most Ag-Pb-Zn deposits that had a magmatic sulfur source in the Great Xing'an Range (Figs. 1a, 8b), including the vein-type Chaganbulagen (average δ 34 S = 2.6‰; Li et al., 2016), Erdaohezi (δ 34 S = 1.8‰; Xu et al., 2020), and Wunuer (average δ 34 S = 2.3‰; Fan et al., 2020) Zhu et al., 2007), and skarn type Haobugao (average δ 34 S = -1.9‰; Wang et al., 2018) and Baiyinnuoer (average δ 34 S = -5.4‰; ...
The large-scale Erdaohe Ag–Pb–Zn deposit in the central Great Xing’an Range, China, contains >9.04 Mt of ore reserves. The deposit consists of skarn-type Ag–Pb–Zn orebodies located within a contact zone that is mainly between an Early Cretaceous porphyritic granite and Jurassic calcareous tuff. The deposit records four stages of formation, which are skarn, early quartz–sulfide (disseminated ores), late quartz–sulfide (veined ores), and carbonate stages. Fluid inclusion microthermometry indicates that skarn stage fluids were higher temperature (330°C to >500°C) and more saline (up to 59.8 wt.% NaCl equivalent) than the early quartz–sulfide (250°C–300°C, <36.1 wt.% NaCl equivalent) and late quartz–sulfide stage (160°C–220°C, <32.1 wt.% NaCl equivalent) fluids. Fluid inclusions of the carbonate stage record even lower temperatures (150°C–170°C) and have generally low salinity (2.1–5.1 wt.% NaCl equivalent). Raman microprobe data indicate that these fluids are dominated by H2O–NaCl ± CO2 system phases. Sulfides formed during the early and late quartz–sulfide stages of mineralization have a relatively narrow range of δ³⁴S values (4.4‰–8.4‰) that are indicative of sulfur derived from a magmatic source. Quartz samples from the early and late quartz–sulfide stages have δ¹⁸Ofluid values of 0.1‰–2.1‰ and from −5.0‰ to −3.2‰, respectively, suggesting that the mineralizing fluids were originally magmatic with later stage mineralization involving the addition of meteoric water. LA–ICP–MS U–Pb dating of zircons from the mineralization-related porphyritic granite yielded a weighted mean age of 131.4 ± 0.3 Ma (MSWD = 1.5), indicating that the deposit formed during the Early Cretaceous. Deposit formation involved an aqueous fluid that was exsolved during the final crystallization of the porphyritic granite and ascended along fracture zones until it reacted with Ca-rich wall rocks, cooled to <300°C, and boiled under hydrostatic conditions. This caused a decrease in temperature and sulfur fugacity in the ore-forming fluid system, which triggered Ag–Pb–Zn mineralization.
... The first group, comprising transition elements Ag, Cu, B, Mo, Ni, and Zn, reflects diverse hydrothermal overlays, with Ag, Cu, and Mo exhibiting closer spatial associations. The second group includes transition elements Cd and Mn, which represent a combination of oxidophile elements [35]. The third group, containing metal elements Fe, Th, U, As, and Sn, indicates the influence of medium-and high-temperature hydrothermal fluids, with Sn demonstrating greater spatial independence. ...
To explore the potential of plant trace elements as indicators in the search for concealed deposits within the W–Sn polymetallic mining area of Shizhuyuan, Hunan Province, this study focused on the geochemical characterization of 21 trace elements, including Ag, As, B, Bi, Cd, Mo, Ni, Pb, and U, in the stem and leaf tissues of three predominant plants in the area. A total of 126 plant samples were collected, covering an area of about 10 km2, and analyzed using ICP-MS. The best indicator plants and sampling sites were selected using multiple indicators, including the biological absorption coefficient (XBAC), the enrichment coefficient (KNJ), and the contrast coefficient (KCD). The results showed that plant leaf tissues represent the most effective sampling components for phyto-geochemical surveys in this region. Dicranopteris dichotoma exhibited markedly pronounced geochemical anomalies of Ag (0.137 µg/g), As (86.12 µg/g), Mo (0.963 µg/g), Pb (15.4 µg/g), Sb (2.03 µg/g), and Se (0.547 µg/g) and demonstrated superior absorption capabilities for Ni, Sn, Sb, Pb, and Bi in the soil, with XBAC values of 12.0, 54.2, 23.3, 2.9, and 83.9, respectively. R-type cluster analysis and factor analysis identified four distinct mineralization element combinations: (1) Sn–As, (2) Ag–Cu–Mo, (3) Pb, and (4) Bi–Sb–Se. Consequently, D. dichotoma is a viable indicator plant for the phyto-geochemical detection of concealed Ag, Bi, Mo, Pb, Sb, Se, and Sn mineralization in mining areas. The results demonstrate that using phyto-geochemical methods for mineral prospecting is feasible and has significant application value in the Shizhuyuan mining area, which is characterized by dense vegetation and complex geological conditions.
... Box plots of trace elements in sphalerite from the Nanmushu deposit and five Pb-Zn deposit types. Epithermal data are collected from references [5,13,14,[65][66][67][68][69][70][71]; MVT data are collected from references [3,5,18,30,[41][42][43]50,66,[72][73][74]; SEDEX data are collected from references [75][76][77][78][79]; Skarn data are collected from references [3,5,13,14,67,[80][81][82]; and VMS data are collected from references [3,5,66,83,84]. ...
The Nanmushu Zn–Pb deposit is a large-scale and representative deposit in the Mayuan ore field on the northern margin of the Yangtze Block. This study investigates the trace element geochemistry of sphalerite from this deposit using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results show that the main trace elements in sphalerite include various trace elements, such as Mn, Fe, Cu, Ga, Ge, Ag, Cd, Pb, Co, Hg, Tl, In, Sn, and Sb. Among them, Ag, Ge, Cd, and Cu are valuable components that may be recovered during mineral processing or smelting techniques. The histograms, LA-ICP-MS time-resolved depth profiles, and linear scan profiles indicated that most trace elements occur in sphalerite as isomorphs, while partial Pb, Fe, and Ag occur as tiny mineral inclusions. The correlation diagrams of trace elements revealed that Fe2+, Mn2+, Pb2+, and Tl3+ can substitute Zn2+ in sphalerite through isomorphism. In sphalerite, Cd2+ and Hg2+ together or Mn2+, Pb2+, and Tl3+ together can replace Zn2+, i.e., ((3Mn, 3Pb, 2Tl)6+, 3(Cd, Hg)2+) ↔ 3Zn2+. Moreover, there is a mechanism of Ge4+ with Cu+ or Ga3+ with Cu+ replacing Zn2+ in the Nanmushu deposit, i.e., Ge4+ + 2Cu+ ↔ 3Zn2+ or 2Ga3+ + 2Cu+ ↔ 4Zn2+. Furthermore, the trace element compositions indicate that the Nanmushu Zn mineralization occurred under low-temperature conditions (<200 °C) and should be classified as a Mississippi Valley-type (MVT) deposit. This study provides new insights into the occurrence and substitution mechanisms of trace elements in sphalerite and the metallogenic constraints of the Nanmushu deposit.
A shear-enhanced method based on strong homogenization was proposed and applied in the goethite process for iron removal from the zinc process solution to overcome the low reaction efficiency and the difficulty in residue filtration. A 3D shear-enhanced rector model was designed, and the process was simulated to reveal the characteristics of fluid flow, gas mass transfer, and goethite particle movement under the coupling multi-physical field at different shearing speeds. The results showed that the homogenization of the solution in the reactor is improved by increasing the flow rate of fluids. The gas dispersion is strengthened to increase the mass transfer rate, further accelerating the iron removal reaction. In addition, after iron precipitation, the formed goethite particles and grains can be broken and refined at a high shearing speed. Zinc in the iron precipitation residue is present in adsorption instead of incorporation, indicating fewer zinc losses. Finally, the reliability of the model was verified by experiments. The shear-enhanced goethite process was suggested to improve iron removal efficiency, and it obtains the iron precipitation residue with the crystal structure of α-FeOOH, suggesting further good filtration performance in the following solid/liquid separation stages.
The determination of ore genesis is a main challenge in ore deposit research. Advanced and rapid analytical techniques have given rise to the accumulation of massive amounts of geoscientific data. Therefore, it is imperative to conduct data mining on ore geochemical data to efficiently extract useful metallogenic information. In this contribution, 4095 sets of sphalerite trace element data from 86 deposits of different origins (VMS, MVT, porphyry, epithermal, SEDEX, and skarn) were compiled and analyzed. Factor analysis revealed the effects of physicochemical conditions on sphalerite trace element compositions. Specifically, the high Mn-Fe-Cu-Co-In but low As-Ga-Ge-Sb-Pb concentration of sphalerite is commonly related to decreasing pH or increasing temperature; high sulfur fugacity favors the entry of Fe and Co (but not Ga or Sn) into the sphalerite lattice; and high salinity causes enrichment in Cd-Ga-Ge-Mn, but depletion in Ag-Cu-In-Sb. Multivariate statistical analysis reveals that the Mn-Ge-Sn contents in sphalerite have good potential to differentiate among ore genetic types, the Mn-Ge-In are used to determine between magmatic-hydrothermal and non-magmatic-hydrothermal deposits. Furthermore, machine learning models demonstrate high accuracy of sphalerite trace element data in distinguishing ore types, i.e., 93.02 % (random forest) and 92.82 % (gradient boosting), and its reliability was validated by receiver operating characteristics. Additionally, the blind tests by machine learning on sphalerite trace elements indicate that the Qingshuitang deposit (in the Qin-Hang metallogenic belt, South China), have been an MVT deposit, which is also supported by its low-temperature and high-salinity fluids, wallrock alterations (esp. bariteization), and the obvious age distinction between mineralization and local magmatism. This study highlights that machine learning and multivariate statistical analysis on sphalerite trace-element data can differentiate metallogenic origin and conditions.
Due to the combined influences such as ore-forming temperature, fluid and metal sources, sphalerite tends to incorporate diverse contents of trace elements during the formation of different types of Lead-zinc (Pb-Zn) deposits. Therefore, trace elements in sphalerite have long been utilized to distinguish Pb-Zn deposit types. However, previous discriminant diagrams usually contain two or three dimensions, which are limited to revealing the complicated interrelations between trace elements of sphalerite and the types of Pb-Zn deposits. In this study, we aim to prove that the sphalerite trace elements can be used to classify the Pb-Zn deposit types and extract key factors from sphalerite trace elements that can discriminate Pb-Zn deposit types using machine learning algorithms. A dataset of nearly 3600 sphalerite spot analyses from 95 Pb-Zn deposits worldwide determined by LA-ICP-MS was compiled from peer-reviewed publications, containing 12 elements (Mn, Fe, Co, Cu, Ga, Ge, Ag, Cd, In, Sn, Sb, and Pb) from 5 types, including Sedimentary Exhalative (SEDEX), Mississippi Valley Type (MVT), Volcanic Massive Sulfide (VMS), skarn, and epithermal deposits. Random Forests (RF) is applied to the data processing and the results show that trace elements of sphalerite can successfully discriminate different types of Pb-Zn deposits except for VMS deposits, most of which are falsely distinguished as skarn and epithermal types. To further discriminate VMS deposits, future studies could focus on enlarging the capacity of VMS deposits in datasets and applying other geological factors along with sphalerite trace elements when constructing the classification model. RF’s feature importance and permutation feature importance were adopted to evaluate the element significance for classification. Besides, a visualized tool, t-distributed stochastic neighbor embedding (t-SNE), was used to verify the results of both classification and evaluation. The results presented here show that Mn, Co, and Ge display significant impacts on classification of Pb-Zn deposits and In, Ga, Sn, Cd, and Fe also have relatively important effects compared to the rest elements, confirming that Pb-Zn deposits discrimination is mainly controlled by multi-elements in sphalerite. Our study hence shows that machine learning algorithm can provide new insights into conventional geochemical analyses, inspiring future research on constructing classification models of mineral deposits using mineral geochemistry data.
Pb–Zn deposits supply a significant proportion of critical metals, such as In, Ga, Ge, and Co. Due to the growing demand for critical metals, it is urgent to clarify the different types of Pb–Zn deposits to improve exploration. The trace element concentrations of sphalerite can be used to classify the types of Pb–Zn deposits. However, it is difficult to assess the multivariable system through simple data analysis directly. Here, we collected more than 2200 analyses with 14 elements (Mn, Fe, Co, Ni, Cu, Ga, Ge, Ag, Cd, In, Sn, Sb, Pb, and Bi) from 65 deposits, including 48 analyses from carbonate replacement (CR), 684 analyses from distal magmatic-hydrothermal (DMH), 197 analyses from epithermal, 456 analyses from Mississippi Valley-type (MVT), 199 analyses from sedimentary exhalative (SEDEX), 377 analyses from skarn, and 322 analyses from volcanogenic massive sulfide (VMS) types of Pb–Zn deposits. The critical metals in different types of deposits are summarized. Machine learning algorithms, namely, decision tree (DT), K-nearest neighbors (KNN), naive Bayes (NB), random forest (RF), and support vector machine (SVM), are applied to process and explore the classification. Learning curves show that the DT and RF classifiers are the most suitable for classification. Testing of the DT and RF classifier yielded accuracies of 91.2% and 95.4%, respectively. In the DT classifier, the feature importances of trace elements suggest that Ni (0.22), Mn (0.17), Cd (0.13), Co (0.11), and Fe (0.09) are significant for classification. Furthermore, the visual DT graph shows that the Mn contents of sphalerite allow the division of the seven classes into three groups: (1) depleted in Mn, including MVT and CR types; (2) enriched in Mn, including epithermal, skarn, SEDEX, and VMS deposits; and (3) DMH deposits, which have variable Mn contents. Data mining also reveals that VMS and skarn deposits have distinct Co and Ni contents and that SEDEX and DMH deposits have different Ni and Ge contents. The optimal DT and RF classifiers are deployed at Streamlit cloud workspace. Researchers can select DT or RF classifier and input trace element data of sphalerite to classify the Pb–Zn deposit type.
Aschamalmite, ideally Pb6-3xBi2+xS9, ordered monoclinic homeotype of heyrovskyite from the Rudnik Pb-Zn/Cu,Ag,Bi,W polymetallic deposit in the central part of Serbia has been investigated. This polymetallic deposit includes over 90 hydrothermal and skarn-replacement orebody types, primarily hosted by Cretaceous sediments and occassionally by Oligocene dykes and sills of dacitic composition, and contact-metamorphic-metasomatic rocks. These rocks are host to an assemblage of pyrrhotite, colloform pyrite, chalcopyrite, galena, arsenopyrite, native bismuth and scheelite as well as minor pyrite, sphalerite, bismuthinite, argentopentlandite, and native silver. The chemical composition of the ore is very complex, where weight contents of valuable metals range as follows (%): Zn 0.49-4.49; Pb 0.90-5.66; Cu 0.08-2.18; WO3 0.05-1.18; Ag 0.005-0.030; Bi 0.005-0.081; and Cd 0.002-0.016. Well-developed aschamalmite crystals have not been observed, only stocky and spindle-like aggregates up to 10 mm in length intergrown with sulfides. Electron-microprobe analysis gave the average crystallochemical formula (Pb5.82Ag0.20)(Sigma 6.02)Bi-2.03(S8.93Te0.02Se0.01)(Sigma 8.96). The strongest diffraction reflections of the X-ray powder diffraction pattern [d(in angstrom)(I)] are: 3.419(100), 3.382(92), and 3.334(66). Monoclinic unit-cell parameters are a=13.727(7); b=4.122(3); c=31.32(2)angstrom; beta=90.72(5)degrees; and V=1771.8(1)angstrom(3). Mineral assemblages and genesis of the Rudnik polymetallic deposit are discussed in detail and the thiobismuthite mineralization has been compared with similar well-known deposits.
As one of the most important Pb-Zn polymetallic deposit, Laochang, Lancang, Yunnan Province is located on the southern end of Sanjiang metallogenic belt. Researching on trace elements for sphalerite by LA-ICPMS and ICP-MS in the deposit, it show that the sphalerite belongs to marmatite, formed on medium temperature and be characterized by riching in Fe, Mn, Cd, In etc., which are present isomorphously in sphalerite. There are wide variation ranges for Pb, Cu, Sn, Bi and other trace elements, which present as micro-inclusion (e. g. galena, chalcopyrite etc.) in sphalerite. The character of rich in Fe and Mn is similar to that of VMS deposit in sphalerite, but the anomalous enrichment of In and Cd may imply that there is a particular metallogenic mechanism in the deposit. Our research show that the trace elements composition of sphalerite is same as that of some Chinese volcanogenic massive sulfide Pb-Zn deposits which were overprinted by Himalayan-Yanshanian granite (e. g. Bainiuchang, Yunnan Province and Dabaoshan, Guangdong Province) and quite different with that of skarn Pb-Zn deposits (e. g. Hetaoping and Luziyuan, Baoshan, Yunnan Province), MVT Pb-Zn deposit (e. g. Niujiaotang, Huize and Mengxing) and Jinding Pb-Zn deposit. Based on the geological feature of the deposit, it is suggested that, with the multi-stages opening and closing of Paleo Tethys Ocean, it formed a obvious multi-stages overprint metallization at same place in the deposit. The trace elements composition is characterized by that of volcanogenic massive sulfide Pb-Zn deposits, and there are no any genetic relationship between Pb-Zn mineralization and concealed Himalayan granite-porphyry, but the sulfide assemblage and their trace elements composition were changed to some extent with the intrusion of the rock mass (e. g. enrichment of Sn and Sb partly). Furthermore, the contrast of two different analysis method for trace elements in sphalerite show that LA-ICPMS could provide more accurate results, it not only show the exist of different trace elements real-timely, but also avoid the error resulted in by impure sample in ICP-MS analysis.
There is an abundance of published trace element data for sphalerite, galena and chalcopyrite in natural systems, yet for a co-crystallized assemblage comprising these base metal sulphides, there is no detailed understanding of the preferred host of many trace elements. Laser-ablation inductively-coupled plasma mass spectrometry trace element maps and spot analyses were generated on 17 assemblages containing co-crystallized sphalerite and/or galena and/or chalcopyrite from 9 different ore deposits. These deposits are representative of different ore types, geologic environments and physiochemical conditions of ore formation, as well as superimposed syn-metamorphic remobilisation and recrystallization. The primary factors that control the preferred base metal sulphide host of Mn, Fe, Co, Cu, Zn, Ga, As, Se, Ag, Cd, In, Sb, Te, Tl and Bi are element oxidation state, ionic radius of the substituting element, element availability and the maximum trace element budget that a given sulphide mineral can accommodate. Temperature, pressure, redox conditions at time of crystallization and metal source, do not generally appear to influence the preferred base metal sulphide host of all the trace elements. Exceptions are Ga, In and Sn recrystallized at high metamorphic grades, when the preferred host of Ga and Sn usually becomes chalcopyrite. In more typical lower temperature ores, the preferred host of Ga is sphalerite. Indium concentrations also increase in chalcopyrite during recrystallization. At lower temperatures the partitioning behaviour of Sn remains poorly constrained and shows little predictable pattern among the data here. The results obtained may be used as a tool to assess co-crystallization. If trace element distributions in a given base metal sulphide assemblage match those reported here, and assuming those distributions have not been significantly altered post (re-) crystallization, then it may be suggestive of a co-crystallized assemblage. Such information provides a foundation for novel attempts to develop trace element-in-sulphide geothermometers.
While a significant amount of analytical data on trace and minor element concentrations in sphalerite has been collected over the last six decades, no meta-analysis of this data has ever been conducted. In this study, the results of such an analysis are presented. While the study focusses on Ga, Ge and In, data for six other elements (Ag, Cd, Co, Cu, Fe and Mn) was also included.
The results show that there are systematic, statistically significant differences in the mean concentrations of Fe, Ga, Ge, In and Mn in sphalerite from different deposit types, while Cd and Cu concentrations show no such differences, and Ag and Co concentrations are only significantly different for vein-type deposits. A principal component analysis demonstrates that the differences between deposit types are approximately one-dimensional, being expressible in terms of a single number. This number correlates strongly with the homogenisation temperature of fluid inclusions (R^2 = 0.82, p < 2×10^(− 16)). It may be expressed as follows:
PC1' = LN[{c(Ga)^0.22*c(Ge)^0.22}/{c(Fe)^0.37*c(Mn)^0.20*c(In)^0.11}]
with Ga, Ge, In and Mn concentrations in ppm, and Fe concentration in wt.%. The relationship is sufficiently strong to be used as a geothermometer (GGIMFis). The empirical relationship between PC 1' and the homogenisation temperature, T, is:
T(°C) = - (54.4 ± 7.3)*PC1' + (208 ± 10).
Our results indicate a strong control of sphalerite chemistry by fluid temperature, particularly for the concentrations of Ga (R^2 ~ 0.40), Ge (R^2 ~ 0.65), Fe (R^2 ~ 0.30) and Mn (R^2 ~ 0.60), and to a lesser degree In (R^2 ~ 0.10). The concentrations of Ag, Cd, Co and Cu appear to be independent of temperature.
As a consequence of the strong temperature control on PC 1', metamorphic overprinting of Pb–Zn deposits, even by lower greenschist facies events, may lead to significant changes in sphalerite composition, namely a relative decrease in Ga and Ge concentrations, and increase in Fe, Mn and, to a lesser degree, In concentrations. The closure temperature of sphalerite in regional metamorphic events appears to be around 310 ± 50 °C, such that higher-grade events will not be reflected in its composition.
Factors other than temperature, such as differences in fluid salinity or source-rock composition, do not appear to be responsible for differences between deposit types, but rather appear to cause differences between individual deposits. Particularly, the Cu activity in ore-forming systems appears to have a strong influence on In concentrations in sphalerite.
The observed trends in sphalerite compositions provide a useful tool for future studies of different types of Pb–Zn deposits, as well as for mineral exploration. They should be particularly relevant for the identification of new resources of Ga, Ge and In.
The Baoshan Pb-Zn deposit is one of the representative deposits in southern Hunan Province. The metallogeny of the Baoshan Pb-Zn deposit is closely related to the 156~158 Ma granodiorite porphyry. The granodiorite porphyry was mainly derived from partial melting of old crustal rocks. Sulfur, lead, carbon and oxygen isotope geochemical results are analyzed and discussed in this paper in order to constrain the sources of metallogenic materials. The δ34S values of pyrite, sphalerite and galena in the Baoshan deposit show a narrow tower-like distribution, ranging from -2.17‰ to +6.46‰ with an average of 3.10‰. The δ34S values of all sulfides display a decreasing trend from pyrite through sphalerite to galena (δ34Spyrite>δ34Ssphalerite>δ34Sgalena), which suggests a sulfur isotopic equilibrium. Based on the characteristics of sulfur isotope of sulfides, the authors infer that sulfur in magma was mainly derived from old crust and that sulfur in ores was dominantly derived from the magma. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios for sulfides vary in ranges of 18.188 ~ 18.844, 15.661 ~ 15.843 and 38.562 ~ 39.912, respectively. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios for wall rocks are 18.268 ~ 19.166, 15.620 ~ 15.721 and 38.364 ~ 39.952, respectively. Lead isotopic compositions of some ore sulfides are significantly more radiogenic than those of the ore-hosting wall rocks. A part of lead of the ores in the Baoshan deposit might have come from the granodioritic magma. The lead in the magma mostly originated from old crust. A part of lead in ores was derived from the ore-bearing strata during the migration process of the ore-forming fluid. The carbon and oxygen isotopic compositions of the hydrothermal calcites vary between those of magma and carbonates and it is deduced that the hydrothermal calcites might have been formed by the interaction between magmatic water and carbonates in variable proportions. The relative low δ13CPDB values of hydrothermal calcites were probably related to involvement of sedimentary organic matter in the Ceshui Formation.
Sphalerite is a common sulphide and is the dominant ore mineral in Zn-Pb sulphide deposits. Precise determination of minor and trace element concentrations in sulphides,
including sphalerite, by Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry (LA-ICP-MS) is a potentially valuable petrogenetic tool. In this study, LA-ICP-MS is used to analyse 19 sphalerite samples from metamorphosed, sphalerite-bearing volcanic-associated and sedimentary exhalative massive sulphide deposits in Norway and Australia. The distributions of Mn, Fe, Co, Cu, Ga, Se, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb and Bi are addressed with emphasis on how concentrations of these elements vary with metamorphic grade of the deposit and the extent of sulphide recrystallization.
Results show that the concentrations of a group of trace elements which are believed to be present in sphalerite as micro- to nano-scale inclusions (Pb, Bi, and to some degree Cu and Ag) diminish with increasing metamorphic grade. This is interpreted as due to release of these elements during sphalerite recrystallization and subsequent remobilization to form discrete minerals elsewhere. The concentrations of lattice-bound elements (Mn, Fe, Cd, In and Hg) show no correlation with metamorphic grade. Primary metal sources, physico-chemical conditions during initial deposition, and element partitioning between sphalerite and co-existing sulphides are dominant in defining the concentrations of these elements and they appear to be readily re-incorporated into recrystallized sphalerite, offering potential insights into ore genesis. Given that sphalerite accommodates a variety of trace elements that can be precisely determined by contemporary microanalytical techniques, the mineral has considerable potential as a geothermometer, providing that element partitioning between sphalerite and coexisting minerals (galena, chalcopyrite etc.) can be quantified in samples for which the crystallization temperature can be independently constrained.
Experimental studies have shown that temperature, pressure, sulfur fugacity (fS2), and oxygen fugacity ( fO2) influence the Fe content of sphalerite. We present compositional in situ data on sphalerite from submarine volcanic-hosted massive sulfide (VHMS) ores of hydrothermal vents from different plate tectonic settings and with variable host-rock compositions. Sphalerite from sediment-hosted vents has systematically higher S contents and Fe/Zn ratios than those of the sediment-starved vents, reflecting an influence of fS2 and fO2 on Fe partitioning between fluid and sphalerite. The Fe/Zn ratios of sphalerite from sediment-starved vent systems apparently increase systematically with the fluid temperatures of the corresponding vents. We conclude that the composition of sphalerite can be used to (1) distinguish between sediment-hosted and sediment-starved hydrothermal processes, and (2) estimate minimum fluid temperatures of sphalerite precipitation from inactive sediment-starved hydrothermal vent sites and fossil VHMS deposits.
Laser-ablation ICP mass-spectroscopy has been used to investigate the geochemistry of sphalerite in a range of nine Zn–Pb deposits in South China. The deposits, which are of different ages and belong to different metallogenic provinces, have been assigned to the following genetic types: skarn (Hetaoping, Luziyuan), syngenetic massive sulphide (Dabaoshan, Laochang and Bainiuchang) and Mississippi-Valley-type (Huize, Mengxing, Niujiaotang) based on the features of the ore, even though their origin is heavily debated based on other criteria. The giant Jinding deposit is considered separately. Sphalerite from each genetic class of deposit shows a distinct chemical signature. Sphalerite from the skarn deposits is characterised by elevated, lattice-bound concentrations of Co and Mn. The distal character of these skarn systems is reflected by the low In content of sphalerite. The three syngenetic massive sulphide deposits feature sphalerite strongly enriched in In, Sn and Ga, whereas the deposits of MVT-type are typically enriched in Ge, Cd, Tl and As. These divergent characters are reflected in absolute element abundances as well as in element ratios.Time-resolved depth profiles for sphalerite from the Chinese deposits confirm the presence of elements such as Co, In, Ge, Ga, and Cd in solid solution, but the dataset expands the understanding of sphalerite mineral chemistry by also indicating that other elements, whose ability to enter the crystal structure of sphalerite has been previously debated (Ag, Sn, Tl, Sb), may also be in solid solution.Sphalerite is a refractory mineral and trace element analysis of sphalerite shows promise as a tracer of ore genesis even in overprinted ores. Systematic work on larger sample suites may help define the geochemical signature of different metallogenic epochs in regions as geologically complex as South China and help resolve the mechanism by which many of the debated ore deposits were formed.
Chalcopyrite inclusions in sphalerite, once considered to be only exsolution poducts, have been suggested to be replacements
of Fe-rich sphalerite. This study reveals that (1) chalcopyrite inclusions were found in sphalerite with different iron contents:
both Fe-poor varieties from 0.5 to 2 wt percent and Fe-rich, from 8 to 14 wt percent; (2) chalcopyrite inclusions were produced
by replacement as the result of interaction of sphalerite with solutions, which transported both copper and iron; and (3)
coprecipitation of sphalerite and chalcopyrite is an alternative mechanism of formation of the chalcopyrite inclusions in
the ore deposits studied.
Primary and secondary barites from hydrothermal mineralizations in SW Germany were investigated, for the first time, by a combination of strontium (Sr) isotope systematics (87Sr/86Sr), Sr contents and δ34S values to distinguish fluid sources and precipitation mechanisms responsible for their formation. Barite of Permian age derived its Sr solely from crystalline basement rocks, whereas all younger barite also incorporate Sr from formation waters of the overlying sediments. In fact, most of the Sr in younger barite is leached from Lower and Middle Triassic sediments.In contrast, most of the sulfur (S) of Permian, Jurassic and northern Schwarzwald Miocene barite originated from basement rocks. The S source of Upper Rhinegraben (URG)-related Paleogene barite differs depending on geographic position: for veins of the southern URG, it is the Oligocene evaporitic sequence, while central URG mineralizations derived its S from Middle Triassic evaporites.Using Sr isotopes of barite of known age combined with estimates on the Sr contents and Sr isotopic ratios of the fluids' source rocks, we were able to quantify mixing ratios of basement-derived fluids and sedimentary formation waters for the first time. These calculations show that Jurassic barite formed by mixing of 75–95% ascending basement-derived fluids with 5–25% sedimentary formation water, but that only 20–55% of the Sr was brought by the basement-derived fluid to the depositional site. Miocene barite formed by mixing of an ascending basement-derived brine (60–70%) with 30–40% sedimentary formation waters. In this case, only 8–15% of the Sr was derived from the deep brine. This fluid-mixing calculation is an example for deposits in which the fluid source is known. This method applied to a greater number of deposits formed at different times and in various geological settings may shed light on more general causes of fluid movement in the Earth's crust and on the formation of hydrothermal ore deposits.
Sphalerite in the Au-Cu volcanic-hosted, Palai-Islica deposit appears in three locations with differences in chemistry, mainly in the Fe content: a) included in pyrite (Fe: 0.49-5.47 at.%) within the quartz veins; b) disseminated or in crustiform bands, also within the quartz veins; and c) disseminated in hydrothermally altered volcanic rocks from the deepest part of the deposit (Fe: 0.28-1.12 at.% - the only one which is cathodoluminescent). Disseminated- or crustifom band-sphalerite is the most abundant type, with two varieties: "dark" (Fe: 3.16-8.66 at.%) and "light" (Fe: 0.08-2.52 at.%). The former is associated with zones rich in gold and other metals. The Fe content of sphalerite reflects an evolution in fs2 of the hydrothermal fluids. Fe-rich, "dark" sphalerite could be related to a mixing process triggering noble- and base metal sulphide precipitation. Different types of sphalerite have significant amounts of minor elements, such as Cu (up to 1.34 at.%), Sb (up to 0.67 at.%), Sn (up to 0.31 at.%), Ge (up to 0.29 at.%), Cd (up to 0.24 at.%), In (up to 0.18 at.%), Mn (up to 0.15 at.%) and Ga (up to 0.12 at.%), some of which are elements not traditionally recognized in sphalerite. Among them, Sb, Sn, Ga-Ge and In are proportional to Cu content, and the following charge balanced coupling substitutions have been demonstrated: Sb3+ + Cu+ + Cu2+ → 3Zn2+; Sn4+ + 2Cu+ → 3Zn2+; 2Ge2+ + Ga3+ + 2Cu2+ + Cu+ → 6Zn2+. The first two substitutions have been shown to correlate with red coloration in Fe-poor sphalerite. The latter substitution, could be related to incorporation into the hydrothermal system of Ga-Ge bearing fluids from the basin. The presence of cathodoluminescent sphalerite seems interesting since it could reflect distinctive trace element content, and could help to distinguish a different type of mineralization and fluid/metal source manifested in an unexplored part of the deposit.
The analytical performance of laser ablation (LA) for the determination of Co, Fe, Cd, Ag, Mn, Cu and S in sphalerite was evaluated using double focusing sector field inductively coupled plasma mass spectrometry (ICP-SFMS). Samples were collected from Zinkgruvan, situated in the south central Sweden. The use of Zn for internal standardisation, together with correction for FeS impurities in sphalerite, allows straightforward quantification without using external methods for the determination of the actual Zn content. LA–ICP-SFMS results were compared with data obtained by conventional pneumatic nebulisation introduction of sample solutions following acid digestion. Good agreement between the two methods was obtained for homogeneously distributed elements. For the majority of the elements under consideration, LA–ICP-SFMS precision was better than 10% RSD.
Sphalerite is an important host mineral for a wide range of minor and trace elements. We have used laser-ablation inductively coupled mass spectroscopy (LA-ICPMS) techniques to investigate the distribution of Ag, As, Bi, Cd, Co, Cu, Fe, Ga, Ge, In, Mn, Mo, Ni, Pb, Sb, Se, Sn and Tl in samples from 26 ore deposits, including specimens with wt.% levels of Mn, Cd, In, Sn and Hg. This technique provides accurate trace element data, confirming that Cd, Co, Ga, Ge, In, Mn, Sn, As and Tl are present in solid solution. The concentrations of most elements vary over several orders of magnitude between deposits and in some cases between single samples from a given deposit. Sphalerite is characterized by a specific range of Cd (typically 0.2–1.0 wt.%) in each deposit. Higher Cd concentrations are rare; spot analyses on samples from skarn at Baisoara (Romania) show up to 13.2 wt.% (Cd2+ ↔ Zn2+ substitution). The LA-ICPMS technique also allows for identification of other elements, notably Pb, Sb and Bi, mostly as micro-inclusions of minerals carrying those elements, and not as solid solution. Silver may occur both as solid solution and as micro-inclusions. Sphalerite can also incorporate minor amounts of As and Se, and possibly Au (e.g., Magura epithermal Au, Romania). Manganese enrichment (up to ∼4 wt.%) does not appear to enhance incorporation of other elements. Sphalerite from Toyoha (Japan) features superimposed zoning. Indium-sphalerite (up to 6.7 wt.% In) coexists with Sn-sphalerite (up to 2.3 wt.%). Indium concentration correlates with Cu, corroborating coupled (Cu+In3+) ↔ 2Zn2+ substitution. Tin, however, correlates with Ag, suggesting (2Ag+Sn4+) ↔ 3Zn2+ coupled substitution. Germanium-bearing sphalerite from Tres Marias (Mexico) contains several hundred ppm Ge, correlating with Fe. We see no evidence of coupled substitution for incorporation of Ge. Accordingly, we postulate that Ge may be present as Ge2+ rather than Ge4+. Trace element concentrations in different deposit types vary because fractionation of a given element into sphalerite is influenced by crystallization temperature, metal source and the amount of sphalerite in the ore. Epithermal and some skarn deposits have higher concentrations of most elements in solid solution. The presence of discrete minerals containing In, Ga, Ge, etc. also contribute to the observed variance in measured concentrations within sphalerite.
The sedimentary- and granite porphyry-hosted Pangjiahe gold deposit is located in the north belt of the South Qinling Orogen, with a proven reserve of 38 t Au at 6.3 g/t. A total of 26 samples, from various rock types and locations from the Panjiahe deposit, were taken in order to determine the paragenesis, sulfur source and absolute age of mineralization. Magmatic activities of ca. 240 Ma occurred around the whole study area, which is common in the northwest part of the West Qinling orogen. Field observations confirm that the emplacement of granite porphyry dykes is earlier than the gold mineralization, because they were both altered and mineralized. Moreover, post ore stage diabase dykes, which cut cross the ore bodies, display an age of ca. 220 Ma. Zircons from strongly mineralized granite porphyry samples show typical hydrothermal trace element characteristics. Theses zircons return a concordia age at ca. 230 Ma. Therefore, we infer that the ore-forming age of the Pangjiahe deposit is at ca. 230 Ma. Optical microscopy, EMPA and LA-(MC)-ICPMS have been used to determine the physical and chemical features of pyrite. Five stages of pyrite have been identified in mineralized phyllite and granite porphyry rocks. Diagenetic pyrite in phyllite, Py1-P, displays a wide range of δ³⁴S (−1.5% to +9.4%). The magmatic pyrite in the granite porphyry, Py1-G, display relatively narrow range of δ³⁴S (+2% to +5%) consistent with magmatic sulfur. The main ore stage pyrite in both rocks, Py2 (Py2-P and Py2-G), is the most common sulfide in the deposit. Py2 grains predominantly show oscillatory zoning and either replace or overgrown the Py1-P and Py1-G, or occur as individual fine grains. Arsenopyrite is typically associated with Py2. Pyrite grains in late stage quartz (Qz) veins that cross cut phyllite and granite, Py-Qz, display weak oscillatory zoning. Native gold is commonly observed as inclusions in the Py-Qz grains or within/proximal to quartz veins. Py3 pyrite (Py3-P and Py3-G), which also belong to the later ore stage and can be distinguished by the native gold inclusions in them, all occur as the outer rims that overgrown or replace on Py2. The ore stage Py2, Apy, Py-Qz and Py3 have a similar narrow range in sulfur isotopic composition, from +8% to +10%. This range is slightly lower than the age equivalent SEDEX Pb-Zn deposits situated in graben basins to the East, but totally different from the earlier Py1-P and Py1-G. EMPA element mapping and spot analyses, and in-situ sulfur isotope analyses indicate that the ore stage pyrites in both phyllite and granite rocks have similar major element chemistry and sulfur isotopic composition, indicating that they are likely sourced from the same ore fluids. Therefore, we propose that prograde metamorphism of the underlying Devonian sedimentary sequences during the seafloor exhalation, which are thought to be enriched in Au, As, Sb, B, F and S, may have released H2S that forming these auriferous sulfides. Gold mineralization in the south belt of the South Qinling orogen shows the same mineralization style as observed in the North belt. However, mineralization is younger and the δ³⁴S values of the hydrothermal ore stage sulfide are consistent with magmatic sulfur, which is consistent with intense magmatic activities within the South Qinling orogen. The δ³⁴S values in the South Belt are distinctly different from those of gold deposits in the north belt. We propose that the source of the sulfur and gold in north belt came from the Devonian graben basins, and in the south belt came from a deep magmatic source. More focused studies of the gold and Devonian graben basin hosted SEDEX Pb-Zn deposits are required to further prove or develop this hypothesis.
The Great Xing'an Range in north-eastern China hosts numerous super-large Ag–Pb–Zn deposits and some Fe–Sn deposits. The Mesozoic Haobugao Fe–Zn polymetallic skarn deposit in the southern Great Xing'an Range is contemporaneous with the regional Ag–Pb–Zn mineralization. Numerous ore bodies are hosted in the Lower Permian carbonate strata or along the contact with the Early Cretaceous granite. According to the field and systematic petrography and mineralography research, the Haobugao mineralization phases are divided into 3 paragenetic stages: prograde stage, retrograde stage, and sulphide stage. Magnetite mainly occurred in the retrograde stage and replaced the anhydrous skarn minerals (e.g., garnet and diopside). Two types of magnetite (Mag1 and Mag2), including 6 subtypes, can be distinguished based on the scanning electron microscopy and back scattered electron images. Electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometer analysis were used to determine major and trace elements in different types of magnetite. Mag1 has higher Ti and V concentrations than Mag2, indicating a relatively higher depositional temperature. Mag1 also contains relatively higher Mg and Mn concentrations, coupled with much lower Si and Al concentrations, which reflects a low fluid/rock ratio at the site of Mag1 deposition. Element variation features of Mag1 and Mag2 reveal that the Haobugao mineralization fluids gradually evolved from high-temperature and low fluid/rock ratio fluids to relatively low-temperature and high fluid/rock ratio fluids. However, electron probe microanalysis data of Mag2 display significantly higher Sn concentrations (up to 2.82 wt.%) than that in Mag1, which indicates that Sn can be incorporated into magnetite crystal lattice. We propose a possible substitution mechanism of Sn4+ + Mn2+ = 2Fe3+, supported by the strongly positive correlation between Sn4+ and Mn2+, whereby a substitution of Sn4+ for Fe3+ in octahedral sites of magnetite requires a compensatory substitution of Mn2+ for Fe3+ to maintain the charge balance.
This study reports a detailed evaluation of how key parameters of operation influence the measurement of sulfur isotopes using laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Sulfur isotopes are observed to display a fractionation up to 2‰ δ³⁴S during analysis of pyrite with different laser parameters using a 193 nm ArF excimer laser. In order to understand why the laser parameters affect S isotope fractionation when measuring S isotopes in pyrite, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques were used to characterize debris formed during the ablation of pyrite, i.e., morphology and speciation of phases. The results show that pyrite decomposes to two phases: ball-like troilite (FeS) and a sulfur-rich floc-like agglomeration surrounding the troilite. The measured δ³⁴S values vary due to the different proportions of troilite balls and the floc-like material generated under different laser parameters. The proportion of troilite and S was evaluated with a LA-(Quadrupole)-ICP-MS through direct comparison of the counts per second (CPS) ratio of ⁵⁶Fe to ³²S. In contrast to pyrite, natural pyrrhotite shows no decomposition process and the particle size of the debris from pyrrhotite is nearly 10 times larger than that of pyrite (~ 5 μm for pyrrhotite compared to < 1 μm for pyrite). Therefore, a biased analysis of pyrite may happen using laser ablation although this problem can be minimized using high raster velocity. Last but not least, we provide a case study of S isotope mapping using high raster velocity, which extends the application of the in-situ S isotope analysis technique. The results here carry implications for the choice of settings needed to obtain accurate LA-MC-ICP-MS S-isotope maps of pyrite.
The Erentaolegai silver deposit is a large epithennal silver deposit in Inner Mongolia. In this paper, chronologic and geochemical research were carried out on such intrusions as quartz porphyry, quartz monzonite, biotite syenogranite and finegrained granite in the ore district. The zircon LA-ICP-MS U-Pb dating results show that the zircon U-Pb ages of the four intrusion samples are (285.4±1.9) Ma, (294.3±0.6) Ma, (287.0±1.2) Ma and (243.9±1.6) Ma respectively, which shows that the intrusions in the ore district were formed in the two periods of Late Hercynian and Indosinian. The age of the first three samples show that they were formed by magmatic evolution in the Late Hercynian period, and their geochemical features show the depletion of large ion incompatible elements such as Ba, Nb, Sr, Zr and Ti, the remarkable enrichment of K and the depletion of Ta, with weak negative Eu anomalies, and exhibit arc granite characteristics in (Y + Nb)-Rb and Yb-Ta tectonic environment discrimination diagrams for granitic rock and peraluminous S type granite, which suggests that they were formed in a tectonic environment of syn-collison in combination with the regional tectonic evolution. The zircon U-Pb age of the fine-grained granite is (243.9±1.6) Ma, suggesting that it was formed by magmatic evolution in the Indosinian period; in addition, its geochemical features show the depletion of large ion incompatible elements such as Ba, Nb, Sr, Ti, Zr and Ti, the remarkable enrichment of K and the loss of Ta, with weak negative Eu anomalies, and has arc granite characteristics in (Y + Nb)-Rb and Yb-Ta tectonic environment discrimination diagrams for granitic rock and peraluminous S type granite, which implies that it was formed in a tectonic environment of volcanic arc in conjunction with the regional tectonic evolution. According to previous studies, the wall rock of the ore district is Tamulangou volcanic rock formed in the Middle Jurassic, and its 40Ar-39Ar isochron age is (162.6±0.7) Ma, which shows that there is no genetic relationship between the intrusion and the deposit.
Introduction The mechanism of ductile mode cutting of brittle materials The chip formation in cutting of brittle materials Machined surfaces in relation to chip formation mode References
The Jiawula Pb-Zn-Ag deposit, situated 150km southwest of Manzhouli City, Inner Mongolia, is located in the northwest of the Derbugan fault, which is located on the southeast edge of the Central Mongolia-Argun Khanka orogenic belt. Seven sphalerite samples and six pyrite samples was selected for the Rb-Sr isochron dating method to determine the mineralization age of the Jiawula Pb-Zn-Ag deposit. A Rb-Sr isochron defined by seven sphalerite samples yields an age of 143.0 ± 2. OMa (MSWD =3.2), with initial Sr isotopic composition ISr =0.71265: six pyrite samples yield a Rb-Sr isochron age of 142.0 ± 3. OMa (MSWD = 5.7), with initial Sr isotope composition ISr = 0.71267: the Rb-Sr isochron age from sphalerite and pyrite is 142.7 ± 1.3Ma (MSWD = 3.8), with initial Sr isotope composition ISr =0.71266. These dating results indicate that the Jiawula deposit formed approximately 143 Ma ago during the Early Cretaceous. The Rb contents range from 0.1034 × 10-6 to 7.367 × 10-6, the Sr contents range from 1.301 × 10-6 to 7.148 × 10-6, and the initial Sr isotope ratios (87Sr/86Sr)i range from 0.71238 to 0.71277, with an average of 0.71264. Both Rb and Sr geochemical characters imply that ore-forming minerals of the Jiawula deposit mainly originated from the earth's crust, but also mixed with small amount of mantle material. The origin of the Jiawula deposit may be related to Mesozoic post-collisional orogeny of the Mongolia-Okhotsk orogen.
Digestion with aqua regia in a Carius tube and separation of Re with anion exchange resin is commonly employed for Re–Os dating of molybdenite and pyrite. However, the recovery of Re is extremely low when this routine anion exchange method is applied to galena, causing difficulty in Re–Os dating of galena. In this study, we investigated the mechanism of Re loss during sample preparation and tested a revised procedure for Re–Os dating of galena and sphalerite. © 2015, Science Press, Institute of Geochemistry, CAS and Springer-Verlag Berlin Heidelberg.
This study presents new whole-rock major and trace element geochemistry, zircon U–Pb ages, and Hf-isotope compositions for volcanic rocks from the Manketouebo Formation of the central Great Xing’an Range, NE China. These data provide precise ages and information on the petrogenesis and source of the magmas that formed this formation, furthering our understanding of the geodynamic setting of the large-scale late Mesozoic magmatism in the Great Xing’an Range and other areas in NE China. The Manketouebo Formation in the study area is dominated by rhyolites and rhyolitic tuffs with minor trachydacites. The LA-ICP-MS zircon U–Pb dating indicates that these volcanic rocks formed between 143 and 139 Ma. The volcanic rocks contain high silica (66.70–79.91 wt.%) and total alkali (5.93–9.72 wt.%) concentrations, and low concentrations of MgO (0.08–1.15 wt.%), total FeO (0.68–4.50 wt.%), and CaO (0.10–2.56 wt.%). They are enriched in large-ion lithophile elements (LILEs; e.g. Rb, Th, and U) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs; e.g. Nb, Ta, Ti, and P) and heavy rare earth elements (HREEs), indicating that they are similar to highly fractionated I-type igneous rocks. All of the magmatic zircons from the analysed samples have high initial 176Hf/177Hf ratios (0.282900–0.283093), positive εHf(t) values (7.48–14.19), and young Hf two-stage model ages (954–344 Ma) that suggest the primary magma that formed the volcanic rocks of the Manketouebo Formation was derived from the partial melting of Neoproterozoic to Phanerozoic juvenile crustal material, indicating in turn that significant crustal growth occurred at this time within the Xing’an Terrane. These data, combined with previous research into the spatial–temporal distribution of Mesozoic volcanic rocks in NE China, suggest that the Early Cretaceous magmatism in the Great Xing’an Range was influenced by both the subduction of the Palaeo-Pacific Plate and the closure of the Mongol–Okhotsk Ocean. This was a crucial period in the transformation from the Mongol–Okhotsk Ocean to the Palaeo-Pacific tectonic regimes. In summary, the early stages of Early Cretaceous magmatism in this area were related to the closure of the Mongol–Okhotsk Ocean, whereas the later stages of magmatism in this area and elsewhere in NE China were related to the subduction of the Palaeo-Pacific Plate.
As a major component of continental crust, granites have been served as the most important subject in geology. Based on advancements obtained during past decades, this paper provides a comprehensive overview about the issues related to granitic formation. As for genetic types, the classifications between I-, S-and A-type granites are sometimes difficult, especially for those of highly fractionated rocks. It is stated that the concentrations of zirconium in whole-rock and titanium in zircon can be used to provided information on the temperature of partial melting and magma crystallization, but the pressure under which the source partially melted is hard to estimate. The granites are mostly occurred in the subduction zones and post-orogenic extensional settings, where the inputs of volatile and heat resulted in crustal partial melting of orogenic roots, and then the formation of granites. The traditionally used geochemical diagrams for the tectonic discrimination could not get right answer in most cases. This paper also presents a concise summary about the recent achievements of granitic study in China. Finally, potential breakthroughs for the Mesozoic granites in eastern China are explored.
Agua Rica is a world-class Cu (Mo-Au) deposit located in Catamarca, Argentina, in which the porphyry and high sulfidation epithermal stages are juxtaposed due to the telescoping of the mineralizing system. Pyrite is the most abundant sulfide in the analyzed section of the deposit and shows variations in textures and trace metal content (determined by LA-ICPMS), between the porphyry and epithermal stages. Pyrite from the porphyry stage is fine grained and depleted in most trace elements analyzed, except for traces of Co (up to 276 ppm) and Ni (up to 131 ppm). Pyrite from the epithermal stage is texturally complex, compositionally heterogeneous, and the trace metal content varies with depth and within sub-stages of mineralization. At an intermediate depth, epithermal pyrite from the cement of the jig-saw and clast-supported hydrothermal breccias are enriched in Cu (up to 2961 ppm) that correlates with the highest Cu grades in the section. This pyrite contains micro-inclusions of sulfosalt minerals as inferred by LA-ICPMS elemental mapping and individual spot ablation profiles. They are zoned and show a Co-rich core, an intermediate zone enriched in Cu, and an outer rim rich in Zn. At shallower levels, epithermal pyrite cements in the heterolithic hydrothermal breccia are unusually rich in trace metals that correlate with the highest Pb, Zn, and Au-Ag grades. The ore-stage pyrite occurs as either successive colloform bands on earlier Co-bearing cores or as veinlets infill. The colloform pyrite bands and veinlets are As-poor (< 30 ppm) and enriched in Pb (up to 4528 ppm), Cu (up to 3900 ppm), Zn (up to 1078 ppm), Ag (up to 136 ppm), Au (up to6.7 ppm), Bi (up to1077 ppm), and Te (up to 3.1 ppm). In LA-ICPMS elemental maps, arsenic concentrates in a thin inner band within the thicker, trace element-rich rims. The colloform banding in pyrite is interpreted to reflect rapid crystallization during fluid boiling at a hydrothermal fluid-meteoric water interface, creating intense fluctuations in temperature and producing undercooling in the mixed fluid. This late and shallow fluid was depleted in As and Cu and also precipitated alunite, Fe-poor sphalerite, and marcasite enriched in trace metals. Maximum Au and Ag inputs into the system occurred towards the end of the epithermal cycle and is expressed by the Au-Ag-rich rims in hydrothermal pyrite. Based on Au-As data in pyrite, ore fluids forming early pyrite were undersaturated with respect to native Au (solid solution incorporation), while later fluids precipitating colloform pyrite where supersaturated with respect to native Au forming Au nanoparticles.
Introduction to Ore-Forming Processes is the first senior undergraduate – postgraduate textbook to focus specifically on the multiplicity of geological processes that result in the formation of mineral deposits.
The southern Great Xing'an Range is one of the most important metallogenic belts in northern China, and contains numerous Pb–Zn–Ag–Cu–Sn–Fe–Mo deposits. The Huanggang iron–tin polymetallic skarn deposit is located in the Sn-polymetallic metallogenic sub-belt. Skarns and iron orebodies occur as lenses along the contact between granite plutons and the Lower Permian Huanggangliang Formation marble or Dashizhai Formation andesite. Field evidence and petrographic observations indicate that the three stages of hydrothermal activity, i.e., skarn, oxide and sulfide stages, all contributed to the formation of the Huanggang deposit.
The skarn stage is characterized by the formation of garnet and pyroxene, and high-temperature, hypersaline hydrothermal fluids with isotopic compositions that are similar to those of typical magmatic fluids. These fluids most likely were generated by the separation of brine from a silicate melt instead of being a product of aqueous fluid immiscibility. The iron oxide stage coincides with the replacement of garnet and pyroxene by amphibole, chlorite, quartz and magnetite. The hydrothermal fluids of this stage are represented by L-type fluid inclusions that coexist with V-type inclusions with anomalously low δD values (approximately − 100 to − 116‰). The decrease in ore fluid δ¹⁸OH2O values with time coincides with marked decreases in the fluid salinity and temperature. Based on the fluid inclusion and stable isotopic data, the ore fluid evolved by boiling of the magmatic brine. The sulfide stage is characterized by the development of sphalerite, chalcopyrite, fluorite, and calcite veins, and these veins cut across the skarns and orebodies. The fluids during this stage are represented by inclusions with a variable but continuous sequence of salinities, mainly low-salinity inclusions. These fluids yield the lowest δ¹⁸OH2O values and moderate δD values ( − 1.6 to − 2.8‰ and − 101 to − 104‰, respectively). The data indicate that the sulfide stage fluids originated from the mixing of residual oxide-stage fluids with various amounts of meteoric water. Boiling occurred during this stage at low temperatures.
The sulfur isotope (δ³⁴S) values of the sulfides are in a narrow range of − 6.70 to 4.50‰ (mean = − 1.01‰), and the oxygen isotope (δ¹⁸O) values of the magnetite are in a narrow range of 0.1 to 3.4‰. Both of these sets of values suggest that the ore-forming fluid is of magmatic origin. The lead isotope compositions of the ore (²⁰⁶Pb/²⁰⁴Pb = 18.252–18.345, ²⁰⁷Pb/²⁰⁴Pb = 15.511–15.607, and ²⁰⁸Pb/²⁰⁴Pb = 38.071–38.388) are consistent with those of K-feldspar granites (²⁰⁶Pb/²⁰⁴Pb = 18.183–18.495, ²⁰⁷Pb/²⁰⁴Pb = 15.448–15.602, ²⁰⁸Pb/²⁰⁴Pb = 37.877–38.325), but significantly differ from those of Permian marble (²⁰⁶Pb/²⁰⁴Pb = 18.367–18.449, ²⁰⁷Pb/²⁰⁴Pb = 15.676–15.695, ²⁰⁸Pb/²⁰⁴Pb = 38.469–38.465), which also suggests that the ore-forming fluid is of magmatic origin.
The increasing worldwide demand in germanium (Ge) is driving renewed research for understanding its geological cycle and the factors controlling its concentration in minerals. The advent of accurate, high-resolution trace element analysis by LA-ICP-MS, as well as the advances in MC-ICP-MS technique for Ge isotopes in sulphides, has enhanced studies in this field. Ge isobaric interferences, standard calibration and data interpretation remain outstanding issues needing to be addressed for more precise and comprehensive LA-ICP-MS analyses.
The data on the composition of metacinnabar and Hg-sphalerite with an isomorphous Cd admixture from some mercury and complex ore objects are summarized. There are two varieties of metacinnabar: (1) cadmium-rich (9.25–15.80 wt.%), with the minimum quantity of Zn admixture (0.67–3.94 wt.%), which has the idealized formula (Hg,Cd,Zn)S (Ulandu) and (2) with increased amounts of Zn (2.21–10.83 wt.%) and Cd (6.00–14.10 wt.%), having the formula (Hg,Zn,Cd)S (Arzak, Kadyrel’, Murzinskoe, Ravnou-1, Ravnou-2). The maximum content of isomorphous Cd (15.80 wt.%) was determined in the metacinnabar from the Ulandu ore occurrence. The Hg-sphalerites are compositionally divided into two groups: (1) with an increased Cd concentration (up to 7.96 wt.%) and (2) mainly with a low content of Cd admixture (0.0n–1.63 wt.%). The sphalerites of the first group are typical of mineral assemblages including Cd-Zn-enriched metacinnabar (Arzak, Kadyrel’, Murzinskoe, Sarasa). The sphalerite of the Sarasa deposit is included into this group arbitrarily, because it contains more cadmium than the sphalerites of the second group, which are constituents of parageneses only with Zn-metacinnabar or lacking it (Nikitovka, Khaidarkan, Dzhizhikrut, Bayan-Khan, Aktash). There are some Hg-bearing varieties of sphalerite with the idealized formulas (Zn,Hg,Fe)S, (Zn,Hg,Cd)S, (Zn,Cd,Hg,Fe)S, (Zn,Fe,Cd,Hg)S, (Zn,Hg,Cd,Fe)S, (Zn,Fe,Hg,Cd)S, and (Zn,Hg,Cu)S, which transforms into (Zn,Cu,Hg)S. The maximum Cd admixture (7.96 wt.%) was established in Hg-sphalerite from the Kadyrel’ ore occurrence. It is the highest content observed in natural Hg-bearing β-ZnS. The studied metacinnabar and sphalerite varieties are the only cubic phases of the natural system Zn–Hg–Cd–S, which is sometimes expanded because of minor admixtures of other metals. These varieties have a structure identical to the cubic phases of the synthetic systems Me–S and Me–Me–S, where Me = Zn, Cd, and Hg. None of Hg-bearing hexagonal solid solutions were found in the natural system Zn–Hg–Cd–S. The continuity of the natural isomorphous series ZnScub–HgScub has not been confirmed by finding of natural intermediate solid solutions at the series fragment between (Zn0.752Hg0.248)S and (Hg0.539Zn0.461)S. The metacinnabar varieties enriched in both Zn and Cd show no correlation between these elements. It is assumed that the host rocks with an increased content of cadmium compounds were the source of Cd for the formation of specific varieties β-HgS and β-ZnS.
Indium-bearing tin-polymetallic base metal deposits in Japan (Toyoha, Ashio and Akenobe), China (Dulong and Dachang), and Bolivia (Potosi, Huari Huari, Bolivar and Porco), were studied using femto-second Laser Ablation ICPMS (fsLA-ICPMS) and EPMA analyses for major and minor elements in sphalerite, paying special attention to In concentrations.Sphalerite is a principal mineral in these tin-polymetallic deposits and a broad range of In concentration is measured in the ores. There are distinct differences in mode of occurrence of the sphalerite and the distribution of In. The highest In concentration (up to 18 wt.%) occur as a Zn–In mineral within black sphalerite zones in an oscillatory-zoned sphalerite from the Huari Huari deposits. Additionally, jamesonite from the Huari Huari deposit also contains anomalous In values, ranging from several hundreds to thousands μg/g. Sphalerite from the Toyoha and the other Bolivian deposits are characterized by oscillatory and chemical zoning, whereas those from Akenobe and the Chinese deposits are represented by homogeneous distribution of In. The 1000In/Zn values of sphalerite are in good agreement with those of the ore grade for each of the selected tin polymetallic deposits indicating that sphalerite is the principal host of In.The In-bearing sphalerite principally involves the combined coupled substitutions (2Zn2 +) ↔ (Cu+, In3 +), (3Zn2 +) ↔ (Cu+, Ag+, Sn4 +) and (3Zn2 +) ↔ (2Cu+, Sn4 +). The first of these is apparent in sphalerite from Huari Huari and Bolivar, whereas the second is prominent in sphalerite from Toyoha, Ashio, Potosi, Porco and Dachang. Akenobe and Dulong sphalerite features the dominant coupled substitution of (2Zn2 +) ↔ (Cu+ or Ag+, In3 +), owing to their poor Sn content. Occasionally, sub-micron inclusions of minerals such as stannite and Pb–Sb-bearing sulfides can occur in sphalerite, contributing to high Cu–Sn and high-Ag contents, respectively. The observed correlations of each element in the In–Cu–Ag–Sn-bearing sphalerite can be proposed as a fundamental reason for the indium enrichment related to sulfur-rich oxidized magmatism. In addition, the Ag content in sphalerite is considered a possible indicator of formation depth, which ranges from plutonic to subvolcanic environments.
An asymmetric, Margules-type, solid solution model was used to model the mixing behavior of Fe-Zn sphalerites. The model is based on an analysis of experimental results from fifteen independent data sources. After a careful, stepwise, analysis of the available runs, the solid solution model was constrained using a refined experimental database of 279 experiments which were simultaneously regressed to obtain the excess parameters and a general geobarometric equation. The model indicates that, when pressures are low, the value of γFeSSph, which is always greater than one, is higher at low FeS contents and an increase in temperature causes it to decline. However, for certain compositions γFeSSph values might be slightly less at low T than at high T. This behavior is corrected when pressure increases, regardless of the composition. The excess Gibbs free energy has positive values at any P&T while it is asymmetric. Pressure increases the value of the excess free energy. On the other hand, the Gibbs free energy of mixing is always negative, with a single minimum that tends to move towards Fe-poorer compositions as the pressure goes up. An increase in temperature leads to a more negative Gibbs free energy mixing function suggesting that increasingly Fe-poorer sphalerite would be expected at high temperatures and pressures. The application of the solid solution model to a selection of case-studies provided results which are consistent with independent pressure estimates. However, the pressure determinations for sphalerite + pyrite + pyrrhotite and sphalerite + pyrrhotite assemblages are very sensitive to uncertainties in the composition of the phases involved and, to a lesser extent, to temperature. The results of the application of the model to a field case (scheelite-mineralized Hercynian veins from the Central Pyrenees) were also consistent when compared with independent pressure-constraining silicate assemblages. Thus, the solid solution model described in this paper provides a workable framework with which to compute the pressures of the formation of rocks over a wide range of geological conditions.
Discussions of methods of isotope dating using Rb-Sr, K-Ar, /sup 40/Ar//sup 39/Ar, Re-Os, Lu-Hf, K-Ca, U, Tb-Pb, /sup 14/C, common lead, S,O,H, fission track, and U-series disequilibrium are included in respective chapters. Introductory chapters discussing the basics of isotope geology, atomic structure, decay mechanisms and mass spectrometry are included along with two appendices; the geological time scale for the Phanerzoic and a fitting of isochrons for Rb-Sr dating methods. (DLS)
A series of natural sphalerite samples, characterized by an inhomogeneous (zonal) distribution of Fe, Mn, and Cd atoms substituting for Zn, has been investigated by electron probe microanalysis and X-ray element distribution mapping. The cation distributions are markedly inhomogeneous due to the reciprocal effects of the minor elements on their respective solubilities. In particular, zonal partitioning between Fe and Mn and between both cations and Hg was observed in sphalerite, as well as coupled Cu-In and Cu-Fe substitutions. Distinctly different distribution patterns were identified in Mn-free samples with a low Fe-content, as compared to Mn-bearing samples. In the former case, Fe and Cd distribution patterns are very similar, whereas in the latter case, Cd is distributed homogeneously and Mn and Fe patterns are antithetic. The different oscillatory zoning observed in Mn-free samples is attributed to a fast, self-organized solute (Fe, Cd) deposition, although an alternative external origin cannot be ruled out. On the other hand, in the presence of Mn, zoning may be related to an absorption process at the mineral-fluid interface controlled by a competition between Mn and Fe that may explain the observed limited coupled concentration of these elements in sphalerite. The homogeneous distribution of Cd suggests relatively slow crystal growth.
Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to study the Cu activation of the (110) surface of sphalerites with Fe content varying from 0 to 14.79wt%. Time resolved AFM images show the development of surface oxidation products at high-energy step edges. These small protrusions evolve into larger conglomerates and finally full surface coverage with time. Surface morphology changes show an increase in the number of cleavage steps and the size of precipitates as a function of Fe concentration. Both of these factors contribute to the increased rate of Cu activation of high Fe sphalerite as compared to low Fe sphalerite. XPS analysis of the sphalerites Cu activated for 1h at pH 5, indicates an increased Cu concentration and the formation of disulphide and polysulphide that correlates with an increase in bulk Fe content.
Experimental results obtained with the thermal gradient transport and the isothermal in situ recrystallization methods are presented and described. -G.J.N.
The emplacement of basaltic magma into sulfide-bearing country rocks provides a favorable geologic environment for magmatic sulfide ore formation related either directly to assimilation of country rock sulfur or indirectly to a depression of sulfide solubility caused by assimilation-induced changes in magma composition. Pelitic country rocks of the Proterozoic Tasiuyak Gneiss in the area of the Voisey's Bay Ni–Cu–Co deposit contain sulfidic layers that may have provided sulfur to basaltic magmas during emplacement of the Voisey's Bay intrusion. Sulfur isotopic compositions of the Tasiuyak Gneiss range from −0.9 to −17.0‰, values typical for sulfides produced via bacterial sulfate reduction in an open marine environment. Archean gneisses in the area contain low amounts of sulfide and are less likely to have served as a source of externally-derived sulfur. Sulfur isotopic compositions of the sulfide minerals from the Voisey's Bay deposit show consistent variations, both spatially and with rock types. Disseminated and massive sulfides show a decrease in δ34S to the west, with values typically between 0 and −2‰ in the Eastern Deeps, Ovoid, and Discovery Hill zone, and between −2 and −4‰ in the Reid Brook zone. δ34S values of the Mushua intrusion to the north and the Normal Troctolite in the Eastern Deeps are more positive, ranging between −0.5 and 1.8‰. This range is taken to represent the isotopic composition of primary mantle-derived sulfur in the area because the Mushua intrusion and Normal Troctolite show the least geochemical evidence for contamination by country rocks. Sulfur isotopic data from the Reid Brook zone are consistent with up to a 50% sulfur contribution from the Tasiuyak Gneiss. Correspondingly lower proportions are indicated for the eastern portion of the deposit where country rocks are predominantly low-sulfide enderbitic and quartzofeldspathic gneisses. Oxygen isotopic values of gneiss fragments in the Basal Breccia Sequence and Feeder Breccia suggest that the assimilation process involved a greater proportion of high−18O contaminant to the west. δ18O values of the Tasiuyak Gneiss (5.9 to 14.0‰), enderbitic gneiss (6.4 to 8.7‰), and Archean quartzofeldspathic gneiss (9.5 to 9.7‰) are consistent with an increased proportion of Tasiuyak Gneiss contaminant to the west. Isotopic data strongly indicate that sulfur from the Tasiuyak Gneiss has been involved in ore deposition at the Voisey's Bay deposit. However, sulfur and oxygen isotopic data also strongly suggest that the addition of externally derived sulfur was not the sole process responsible for mineralization, and that assimilation of both Proterozoic and Archean country rocks played a key role in depressing sulfide solubility prior to sulfide localization via dynamic, physical mechanisms.
Hydrothermal coprecipitation experiments were performed at 350 and 300°C, in order to reproduce the “chalcopyrite disease” texture involving Fe-bearing sphalerite. Sector-zoned chalcopyrite disease textures were obtained in some runs using a hydrothermal transporting method, and this shows that coprecipitation is responsible for formation of the texture in Fe-bearing sphalerite. These chalcopyrite disease textures with compositions similar to the run products occur in Fe-bearing sphalerite ores from the modern seafloor deposits at the Okinawa Trough and North Fiji Basin, suggesting a possibility that the chalcopyrite disease textures in the deposits were caused by the process of coprecipitation in short spans of time.
Secondary ion mass spectrometry (SIMS) measurement of sulfur isotope ratios is a potentially powerful technique for in situ studies in many areas of Earth and planetary science. Tests were performed to evaluate the accuracy and precision of sulfur isotope analysis by SIMS in a set of seven well-characterized, isotopically homogeneous natural sulfide standards. The spot-to-spot and grain-to-grain precision for δ34S is ±0.3‰ for chalcopyrite and pyrrhotite, and ±0.2‰ for pyrite (2SD) using a 1.6nA primary beam that was focused to 10µm diameter with a Gaussian-beam density distribution. Likewise, multiple δ34S measurements within single grains of sphalerite are within ±0.3‰. However, between individual sphalerite grains, δ34S varies by up to 3.4‰ and the grain-to-grain precision is poor (±1.7‰, n=20). Measured values of δ34S correspond with analysis pit microstructures, ranging from smooth surfaces for grains with high δ34S values, to pronounced ripples and terraces in analysis pits from grains featuring low δ34S values. Electron backscatter diffraction (EBSD) shows that individual sphalerite grains are single crystals, whereas crystal orientation varies from grain-to-grain. The 3.4‰ variation in measured δ34S between individual grains of sphalerite is attributed to changes in instrumental bias caused by different crystal orientations with respect to the incident primary Cs+ beam. High δ34S values in sphalerite correlate to when the Cs+ beam is parallel to the set of directions , from [111] to [110], which are preferred directions for channeling and focusing in diamond-centered cubic crystals. Crystal orientation effects on instrumental bias were further detected in galena. However, as a result of the perfect cleavage along {100} crushed chips of galena are typically cube-shaped and likely to be preferentially oriented, thus crystal orientation effects on instrumental bias may be obscured. Test were made to improve the analytical precision of δ34S in sphalerite, and the best results were achieved by either reducing the depth of the analysis pits using a Köhler illuminated primary beam, or by lowering the total impact energy from 20keV to 13keV. The resulting grain-to-grain precision in δ34S improves from ±1.7‰ to better than 0.6‰ (2SD) in both procedures. With careful use of appropriate analytical conditions, the accuracy of SIMS analysis for δ34S approaches ±0.3‰ (2SD) for chalcopyrite, pyrite and pyrrhotite and ±0.6‰ for sphalerite. Measurements of δ34S in sub-20µm grains of pyrite and sphalerite in ∼3.5Ga cherts from the Pilbara craton, Western Australia show that this analytical technique is suitable for in situ sulfur isotope thermometry with ±50°C accuracy in appropriate samples, however, sulfides are not isotopically equilibrated in analyzed samples.
The Da Hinggan Mountains mineral province (DHMP), northeastern China, is divided into three tectonic units and corresponding metallogenic belts. The tectonic units of the Da Hinggan Mountains are the Erguna fold zone on the northwest, the Hercynian fold zone on the north, and the Hercynian fold zone on the south. The corresponding metallogenic belts are the Erguna Cu-Pb-Zn-Ag-Mo-Au belt of the NW DHMP, the Cu-Pb-Zn-Mo-Fe-Au belt of the northern DHMP, and the Pb-Zn-Ag-Cu-Sn-Fe-Mo belt of the southern DHMP. Distinct ore bodies, mostly associated with Mesozoic granites and volcanics, comprise (1) hydrothermal vein deposits including Pb-Zn-Ag-(Cu) and W‐Sn-Cu, (2) exhalative (Pb-Zn-Ag, Cu) deposits, (3) porphyry (Cu, Au, Mo), (4) skarn (Fe, Zn, Cu), and (5) epithermal Au-Ag deposits. The hydrothermal veins are hosted by a range of different rock types, whereas the exhalative ores are confined to Permian strata. The porphyry deposits occur within granite porphyries. The epithermal deposits are related to Mesozoic volcanic-subvolcanic rocks and occur within superjacent igneous structures. The first type, represented by the Bairendaba deposit, shows many characteristics of hydrothermal deposits. The second type occurs in a Permian clastic-chemical sedimentary sequence. Most Fe-Zn-Cu deposits related to granites and granodiorites are skarns. Granodiorite and granite-related deposits are typical porphyry ores, formed during Hercynian and Mesozoic time. Promising metallogenic conditions and the recent discovery of many large metal deposits indicate that this mineral province has a great exploration potential.
Various models have been proposed to explain the formation mechanism of colloform sphalerite, but the origin is still under debate. In order to decipher influences on trace element incorporation and sulfur isotope composition, crystalline and colloform sphalerite from the carbonate-hosted Mississippi-Valley Type (MVT) deposit near Wiesloch, SW Germany, were investigated and compared to sphalerite samples from 52 hydrothermal vein-type deposits in the Schwarzwald ore district, SW Germany to study the influence of different host rocks, formation mechanisms and fluid origin on trace element incorporation. Trace and minor element incorporation in sphalerite shows some correlation to their host rock and/or origin of fluid, gangue, paragenetic minerals and precipitation mechanisms (e.g., diagenetic processes, fluid cooling or fluid mixing). Furthermore, crystalline sphalerite is generally enriched in elements like Cd, Cu, Sb and Ag compared to colloform sphalerite that mainly incorporates elements like As, Pb and Tl. In addition, sulfur isotopes are characterized by positive values for crystalline and strongly negative values for colloform sphalerite. The combination of trace element contents, typical minerals associated with colloform sphalerite from Wiesloch, sulfur isotopes and thermodynamic considerations helped to evaluate the involvement of sulfate-reducing bacteria in water-filled karst cavities. Sulfate-reducing bacteria cause a sulfide-rich environment that leads in case of a metal-rich fluid supply to a sudden oversaturation of the fluid with respect to galena, sphalerite and pyrite. This, however, exactly coincides with the observed crystallization sequence of samples involving colloform sphalerite from the Wiesloch MVT deposit.
A thermodynamic analysis of the intermediate solid solution (Iss) of near-cubanite composition has been attempted by considering an Fe–Zn exchange equilibrium between Iss and sphalerite. The interchange free-energy parameter of Fe–Zn mixing in Iss (WIss) and the free energy of the exchange equilibrium (G1,T
) have been deduced at 500, 600, 700 and 723 C using the compositional data of sphalerite and Iss from phase equilibrium experiments and by the standard method of linear regression analysis. For sphalerite, two independent activity-composition models have been chosen. The extracted values of G1,T
and WIss, using both models, are compared. Although the values match, the errors in the extracted parameters are relatively larger when Hutcheon's model is used. Both G1,T
and WIss show linear variations with temperature, as given by the following relations: G1,T
= –35.41 + 0.033 T in kcal (SE=0.229)WISS= 48.451 – 0.041 T in kcal (SE=0.565) Activity-composition relations and different mixing parameters have been calculated for the Iss phase. A large positive deviation from ideality is observed in Iss on the join CuFe2S3–CuZn2S3. No geothermometric application has been attempted in this study, even though Iss of cubanite composition (isocubanite) in association with sphalerite, pyrite and pyrrhotite is reported from seafloor hydrothermal deposits. This is due to the fact that: (a) the temperatures of formation of these deposits are significantly lower than 500 C, the lower limit of appropriate experimental data base; (b) microprobe data of the coexisting isocubanite and sphalerite in the relevant natural assemblages are not available.
Microprobe and fluid inclusion analyses of hydrothermal ore deposits containing the subassemblage sphalerite+ tetrahedrite-tennantite ∼[(Cu, Ag)10(Fe, Zn)2(As,Sb)4S13] reveal that the Gibbs energies of the reciprocal reaction Cu10Zn2Sb4S13 + Cu10Fe2As4S13 = Cu10Fe2Sb4S13 + Cu10Zn2As4S13 and the Fe-Zn exchange reaction 1/2Cu10Fe2Sb4S13 + ZnS = 1/2Cu10Zn2Sb4S13 + FeS are within the uncertainties of the values established by Sack and Loucks (1985) and Raabe and Sack (1984), 2.59±0.14 and 2.07±0.07 kcal/gfw. However, this study suggests that the Fe-Zn exchange reaction between sphalerite and Sb and Ag-rich tetrahedrites does not obey the simple systematics suggested by Sack and Loucks (1985) wherein tetrahedrite is assumed to behave as an “ideal” reciprocal solution. Instead these studies show that the configurational Gibbs energy of this exchange reaction,RTln[(X
Fe/X
Zn)TET(X
ZnS/X
FeS)SPH], corrected for sphalerite nonideality exhibits both a local maximum and minimum as a function of Ag/(Cu+Ag) ratio at a givenX
FeSSPHand temperature. The local maximum forX
FeSSPH∼0.10 corresponds to the position of the cell edge maximum established for natural tetrahedrites by Riley (1974), Ag/(Ag+Cu)∼0.4. These studies and the results of structural refinements of Ag-bearing tetrahedrites suggest that in low silver tetrahedrites Ag is preferentially incorporated in trigonal-planar sites but that in tetrahedrites with intermediate and greater Ag/(Ag+Cu) ratio, Ag is preferentially incorporated in tetrahedral sites. A nonconvergent site ordering model for tetrahedrite is developed to quantify and extrapolate these predictions.
Here we describe an internal standard-independent calibration strategy for LA-ICP-MS analysis of anhydrous minerals and glasses. Based on the normalization of the sum of all metal oxides to 100 wt.%, the ablation yield correction factor (AYCF) was used to correct the matrix-dependent absolute amount of materials ablated during each run., where cpssamj and cpsrmj are net count rates of analyte element j of the sample and reference material for calibration, Crmj is concentration of element j in the reference material, N is the number of elements that can be determined by LA-ICP-MS. When multiple reference materials were used for calibration, l value can be calculated with regression statistics according to the used reference materials.Applying an AYCF and using the USGS reference glasses BCR-2G, BHVO-2G and BIR-1G as reference materials for external calibration, analyses of MPI-DING reference glasses generally agree with recommended values within 5% for major elements (relative standard deviation (RSD) = 0.3–3.9% except for P2O5, n = 11), and 5–10% for trace elements. Analyses of anhydrous silicate minerals (clinopyroxene, orthopyroxene, olivine, plagioclase and garnet) and spinel generally agree with the results of electron microprobe analysis within 0.2–7% for SiO2, Fe2O3, MgO and CaO. RSD are generally < 5% for elements with concentrations > 0.1 wt.%. The results indicate that, by applying an AYCF and using USGS reference glasses as multiple reference materials for calibration, elements of these anhydrous minerals can be precisely analyzed in situ by LA-ICP-MS without applying internal standardization. The different element fractionations between the NIST glasses and those glasses with natural compositions indicate that NIST SRM 610 is a less than ideal reference material for external calibration of analyses of natural silicates.
Quantum mechanical techniques, based on density functional theory, have been used to study the distribution of iron impurities in sphalerite (ZnS) at compositions ranging from 3.125 to 12.5 mol% FeS. Our results show that iron is most easily incorporated by direct substitution onto the zinc site and that energies for solution reactions involving FeS are exothermic when the system is zinc deficient. Furthermore, there appears to be a small driving force for the formation of bound Fe? Fe pairs at low iron concentrations, though there is no particular preference found for larger clusters of iron. The influence of iron on the sphalerite cell parameter is shown to be sensitive to the presence of Fe-Fe pairs and to the degree of sample non-stoichiometry.
Sulfide microanalysis and S isotope of the Miaoshan Cu polymetallic deposit in western Guangdong Province, and its constraints on the ore genesis
- B. Xing
- W. Zheng
- Z. Ouyang
- W. Lin
- Y. Tian
Trace and minor elements in sphalerite from the Mayuan lead–zinc deposit, northern margin of the Yangtze Plate: Implications from LA‐ICP‐MS analysis
- P. Hu
- Y. Wu
- C. Zhang
- M. Hu
LA‐ICP‐MS analysis of trace elements in sphalerite from the Huanggangliang Fe–Sn deposit, Inner Mongolia, and its implications
- Z. Xu
- Y. Shao
- Z. Yang
- Z. Liu
- W. Wang
- X. Ren
Cd primarily isomorphously replaces Fe but not Zn in sphalerite
- T. Liu
- L. Ye
- J. Zhou
- X. Wang
LA‐ICP‐MS analysis of trace elements in sphalerite from the Huanggangliang Fe–Sn deposit, Inner Mongolia, and its implications
- Xu Z.