Phosphorite-hosted zinc and lead mineralization in the Sekarna deposit (Central Tunisia)

The Sekarna Zn–Pb deposit is located in Central Tunisia at the northeastern edge of the Cenozoic Rohia graben. Mineralization comprises two major ore types: (1) disseminated Zn–Pb sulfides that occur as lenses in sedimentary phosphorite layers and (2) cavity-filling zinc oxides (calamine-type ores) that crosscut Late Cretaceous and Early Eocene limestone. We studied Zn sulfide mineralization in the Saint Pierre ore body, which is hosted in a 5-m-thick sedimentary phosphorite unit of Early Eocene age. The sulfide mineralization occurs as replacements of carbonate cement in phosphorite. The ores comprise stratiform lenses rich in sphalerite with minor galena, Fe sulfides, and earlier diagenetic barite. Laser ablation–inductively coupled plasma mass spectrometry analyses of sphalerite and galena show a wide range of minor element contents with significant enrichment of cadmium in both sphalerite (6,000–20,000 ppm) and galena (12–189 ppm). The minor element enrichments likely reflect the influence of the immediate organic-rich host rocks. Fluid inclusions in sphalerite give homogenization temperatures of 80–130°C. The final ice melting temperatures range from −22°C to −11°C, which correspond to salinities of 15–24 wt.% NaCl eq. and suggest a basinal brine origin for the fluids. Sulfur isotope analyses show uniformly negative values for sphalerite (−11.2‰ to −9.3‰) and galena (−16‰ to −12.3‰). The δ³⁴S of barite, which averages 25.1‰, is 4‰ higher than the value for Eocene seawater sulfate. The sulfur isotopic compositions are inferred to reflect sulfur derivation through bacterial reduction of contemporaneous seawater sulfate, possibly in restricted basins where organic matter was abundant. The Pb isotopes suggest an upper crustal lead source.     

Primary minerals of Zn-Pb mining and metallurgical dumps and their environmental behavior at Plombières,Belgium

The primary phases and minerals of the Plombières dumps include typical smelting furnace products such as metallic Fe, Pb, Cu, Zn, Fe-Zn alloys, carbides, phosphides, sulfides of Fe, Zn, Pb, Cu, Mn (alabandite), and FeAs. Spinels, mainly of Fe and Al, are common constituents of the primary assemblage; substitution by Zn, V, Cr, Ti, Mg, and Ca occurs. Primary phases also include the most common Zn-rich fayalite, Zn-rich Ca-Fe silicates, melilite, corundum, and apatite. Most of the Zn is incorporated in iron silicates, ZnO and ZnS. Lead occurs mainly as PbS, metallic lead, and is also present in coal residues. Cadmium is found mainly in metallic zinc and its alloys and in ZnO. The dumps also contain mining wastes composed of pyrite, melnikovite, and iron oxides produced by natural weathering of Zn-Pb ores. Melnikovite and iron oxides are rich in As, Pb, and Zn and possess an increased content of Tl. Leaching tests carried out on the surfaces of polished sections indicate that acid rain (solutions I and II) will mobilize mainly Zn and Cd and, to a much smaller extent, Pb and Sb. Leaching of metals by sulfate-chloride fluids present in the pore network of dumps (solutions III, IV, and V) depends on the pH, which in the dumps is controlled by the proportion of carbonates to sulfides. The more acid fluids leach both sulfides and silicates.     

柿竹园和香炉山W多金属矿床中硫化物微量元素特征:来自原位LA-ICP-MS分析

华南包括两个世界级的W矿带,分别是南岭和江南造山带W成矿带。柿竹园W多金属矿床位于南岭地区,香炉山W矿床位于江南造山带东北部。两个矽卡岩W矿床都发育硫化物成矿阶段。但硫化物和成矿元素组成存在显著的差异。前者由含Pb、Zn、Ag硫化物和黝铜矿、银黝铜矿、含Ag斜方辉铅铋矿和铁硫锡铜矿硫盐组成;后者主要为磁黄铁矿。柿竹园远接触带Pb-Zn-Ag矿脉中硫化物(闪锌矿、黄铜矿、方铅矿和磁黄铁矿)较富集B、Mn、Cr、Sb、Sn和Hg,香炉山似层状矽卡岩和硫化物-白钨矿矿体中硫化物(磁黄铁矿、黄铜矿和闪锌矿)较富集W、Se和Bi。两个矿床中黄铜矿、闪锌矿和方铅矿较富集Ag,黄铜矿、闪锌矿富集In和Sn,闪锌矿还富集Cd。两个矿床中的硫化物微量元素分析表明与矽卡岩W矿成矿相关的硫化物可载有多种微量元素。这些元素参与到硫化物中程度由多种因素控制。具体如下,硫化物中B含量高低与成矿相关岩体中B含量相关;在相对高温和还原条件下,硫化物中W含量较高;闪锌矿中Mn和Cd与Zn发生取代作用; Cr可以一定程度进入到硫化物中,并受成矿流体中Cr含量影响; Se与S发生了一定程度的取代进入硫化物,并受流体中它的含量控制; Bi在闪锌矿与黄铜矿易形成固溶体;硫化物中Sb含量受初始流体中它的含量影响,方铅矿中易包裹一定的辉锑矿(Sb_2S_3)或含Sb的硫盐矿物; Ag是否形成独立的矿物相和进入哪些硫化物中,取决于流体中Ag的初始含量和硫化物的沉淀次序;硫化物中Hg的含量受温度影响。     

Phosphate amendment of metalliferous waste rocks, Century Pb-Zn mine, Australia: Laboratory and field trials

The aim of the study was to determine whether the application of phosphate compounds (phosphorite rock, phosphate fertilizer) to polyminerallic waste rocks can inhibit sulfide oxidation and metal mobility (Cu, Pb, Zn, Cd, Ni, Mn, Mg). Waste rocks comprised sulfidic carbonaceous shales and were sourced from the Century Pb-Zn mine, NW Queensland, Australia. The acid producing, Pb-Zn rich rocks consisted of major quartz, muscovite/illite, dolomite, siderite and kaolinite as well as smaller amounts of sulfide minerals (e.g. galena, sphalerite, pyrite). Laboratory leach experiments were conducted on finely granulated phosphate-treated waste rocks (>2 to <30 mm) over 13 weeks, whereas phosphate amendment of coarsely granulated waste rocks (sand to boulder size) was investigated using heap leach piles at the mine site over an 11 months period. Results of the laboratory experiments demonstrate that the treatment of finely granulated waste rocks with phosphorite rock produced leachates with near-neutral pH values due to calcite dissolution. This in turn did not allow the leaching of apatite, formation of secondary phosphate phases and phosphate stabilization to occur. Metal mobility in these amended wastes was restricted by the dissolution of calcite and the resultant near-neutral pH conditions. By contrast, the application of the water-soluble phosphate fertilizer MKP (KH₂PO₄) to polyminerallic sulfidic waste rocks during the short-term laboratory experiments led to the formation of phosphate coatings and precipitates and inhibited acid and metal release (Cd, Mn, Ni, Pb, Zn). At least in the short term, the application of phosphate fertilizers proved to be an effective method. However, results of the long-term field trials demonstrate that coarsely granulated waste rocks were not coated by secondary phosphate phases and that amendment by phosphorite rock or superphosphate fertilizer did not improve leachate quality compared to the unamended waste. Thus, phosphate stabilization appears ineffective in suppressing oxidation of sulfides in coarsely granulated mine wastes.     

Minerals in the Triassic carbonaceous silicites of Sikhote Alin

Over 60 minerals, including native elements, intermetallic compounds, haloids, sulfides, sulfates, arsenides, oxides and hydroxides, silicates, borosilicates, wolframates, phosphates and REE phosphates, were established in Triassic siliceous rocks of Sikhote Alin. Allothigenic and authigenic minerals in the carbonaceous silicites were formed over a long period through several stages. Judging from morphology, chemical composition, and structural position, K-feldspar (K-Fsp), illite, kaolinite, metahalloysite, monazite, xenotime, zircon, rutile, or its polymorphs are the disintegration products of sialic rocks of continental crust. Authigenic sulfides are dominated by diagenetic pyrite (fine-crystalline, microglobular, framboidal, as well as those developed after biogenic siliceous and carbonate fragments), which has been formed prior to precipitation of siliceous cement and lithification of siliceous rocks. Most of other sulfides (sphalerite, galena, chalcopyrite, pyrrhotite, argentite, pentlandite, antimonite, ulmanite, and bravoite), arsenides and sulfoarsenides (arsenopyrite, nickeline, skutterudite, cobaltite, glaucodot, and gersdorffite), wolframates (scheelite and wolframite), intermetallides (Cu₂Zn, Cu₃Zn₂, Cu₃Zn, Cu₄Zn, CuSn, Cu₄Sn, Cu₈Sn, Cu₄Zn₂Ni, Ni₂Cu₂Zn, Ni₄Cd), and native elements (Au, Pd, Ag, Cu, Fe, W, Ni, Se) were crystallized later (during catagenesis after the lithification and brecciation of siliceous beds) from metals involved in the easily mobile fractions of bitumens. Supergene mineral formation was mainly expressed in the sulfide oxidation and replacement of diagenetic pyrite by jarosite and iron hydroxides.     

贵州筲箕湾铅锌矿床硫化物中Tl-Cd-Ga富集机制及地质意义

筲箕湾铅锌矿床位于黔西北铅锌成矿区中部,为该区铅锌矿床中的又一典型代表,其金属资源量（Pb＋Zn）超过20万t。本文利用电感耦合等离子体质谱（ICP-MS）分析了不同类型矿石中原生矿石硫化物（黄铁矿、闪锌矿和方铅矿）中分散元素含量,结果显示除Cd含量较高外,Ga、In、Se、Tl和Re的富集程度均较低。不同分散元素在硫化物中表现出不同的富集规律,表现为Ga含量在闪锌矿中最高,黄铁矿次之,方铅矿最低;方铅矿中Tl含量高于闪锌矿,黄铁矿最低;Cd在闪锌矿中含量最高,方铅矿次之,黄铁矿最低;从黄铁矿→方铅矿→闪锌矿In含量依次升高;Re含量表现出在闪锌矿中最高,黄铁矿次之,方铅矿最低;Se富集程度从黄铁矿→方铅矿→闪锌矿依次升高。Ga、In和Re在不同颜色闪锌矿中富集程度相似,而Se、Cd和Tl则相对富集在棕色闪锌矿中。统计发现闪锌矿中Zn含量与Cd、Ga含量不呈类质同象的负相关特征,而其中的Fe含量与Cd、Ga含量间表现出曲线相关或负相关特征,暗示Cd、Ga可能是通过替代先进入闪锌矿中的Fe而占据其晶格,这可能是一种新的机制。闪锌矿Ga、Cd、In含量及Ga/In、Zn/Cd比值等参数,指示筲箕湾铅锌矿床形成于中-高温条件,其矿床成因类型与沉积-改造型相似。     

Evaluation of phosphate fertilizers for ameliorating acid mine waste

The aim of the study was to determine whether the application of bulk industrial chemicals (potassium permanganate and water-soluble phosphate fertilizer) to partly oxidized, polyminerallic mine wastes can inhibit sulfide oxidation, and metal and metalloid mobility. The acid producing waste rocks were metal (Pb, Zn, Cu) and metalloid (As, Sb) rich and consisted of major quartz, dickite, illite, and sulfide minerals (e.g., galena, chalcopyrite, tetrahedrite, sphalerite, pyrite, arsenopyrite), as well as minor to trace amounts of pre- and post-mining oxidation products (e.g., hydrated Fe, Cu, Pb, and alkali mineral salts). SEM-EDS observations of treated waste material showed that metal, metal–alkali, and alkali phosphate coatings developed on all sulfides. The abundance of phosphate phases was dependant on the fertilizer type and the availability of metal and alkali cations in solution. In turn, the release of cations was dependent on the amount of sulfide oxidation induced by KMnO₄ during the experiment and the dissolution of soluble sulfates. Mn, Ca, Fe, and Pb phosphates remained stable during H₂O₂ leaching, preventing acid generation and metal release. In contrast, the lack of complete phosphate coating on arsenopyrite allowed oxidation and leaching of As to proceed. The mobilized As did not form phosphate phases and consequently, As displayed the greatest release from the coated waste. Thus, the application of KMnO₄ and the water-soluble phosphate fertilizer Trifos (Ca(H₂PO₄)₂) to partly oxidized, polyminerallic mine wastes suppresses sulfide oxidation and is most effective in inhibiting Cu, Pb, and Zn (Sb) release. However, the technique appears ineffective in suppressing oxidation of arsenopyrite and preventing As leaching.     

Compounds with mixed and intermediate sulfur valences as precursors of banded sulfides in carbonate-hosted Zn-Pb deposits in Belgium and Poland

Compounds of Fe, Pb and Zn with mixed and intermediate sulfur valences form ubiquitous inclusions and relics in banded sphalerite, pyrite-melnikovite and galena. Banded sulfides continuously grade into banded compounds with mixed and intermediate sulfur valences, the latter with a fibrous microtexture. A fibrous microtexture is also shown by banded sphalerite and pyrite from Zn-Pb deposits of Belgium and Poland. It is therefore suggested that the fibrous sphalerite inherited such a microtexture, unusual for cubic ZnS, by direct replacement of a fibrous precursor with mixed and/or intermediate sulfur valences. The last band of banded sphalerite is often overgrown by idiomorphic, isometric sphalerite precipitated directly from the solution as ZnS. The following Fe, Pb and Zn compounds with mixed and intermediate sulfur valences were found in carbonate-hosted Zn-Pb deposits of Belgium and Poland: sulfoxylanes (M²⁺SO₂; S²⁺), subsulfites (M²⁺S₂O₄; S³⁺), sulfites (M²⁺SO₃; S⁴⁺), pyrosulfites (M²⁺S₂O₅; S⁴⁺) and thiosulphates(M²⁺S₂O₃; S^2– and S⁶⁺).     

常见硫化物表面的XPS研究

采用XPS分析方法,研究了黄铁矿、磁黄铁矿、方铅矿、黄铜矿、闪锌矿和毒砂等常见硫化物矿物表面的化学成分及其化学态,从而探讨硫化物表面的氧化和次生变化。研究发现：（1）硫化物矿物表面在氧逸度较高的情况下很容易发生变化,其氧化产物很复杂,主要是其金属元素的高价态氧化物、氢氧化物和硫酸盐等;（2）就一般常见硫化物而言,相对比较稳定的是黄铁矿;（3）常见硫化物经氧化后,其表面的原子比率常常显示硫富余;（4）在含铁的各种常见硫化物中,除黄铁矿表面的铁相对稳定外,毒砂表面的铁也相对较稳定,而闪锌矿表面的类质同像铁却容易被氧化而发生变化。     

The aqueous oxidation of complex sulfide concentrates in hydrochloric acid

Complex sulfides containing sphalerite, galena, chalcopyrite, and small amounts of silver in a matrix of pyrite can be decomposed at 120°C and oxygen pressure of 1000 kPa in 1–2 N HCl for 90 min to yield > 97% of the zinc and > 95% of the copper in solution while about 83% of the lead remains in the residue as PbCl₂ and PbSO₄ and 85% of the silver, together with most of the pyrite. The recovery of elemental sulfur is nearly 100% with respect to ZnS, PbS, and CuFeS₂. Leaching in HCl is faster than in H₂SO₄ at the same acid normality, and the process is diffusion-controlled (strongly dependant on agitation speed and having an activation energy of 3.6 kcal/mole). Lead jarosite, Pb_0.5Fe₃ (SO₄)₂?(OH)₆, is mainly formed when H₂SO₄ is used as a leaching agent.     

Mine drainage from the weathering of sulfide minerals and magnetite

Pyrite and pyrrhotite are the principal minerals that generate acid drainage in mine wastes. Low-pH conditions derived from Fe-sulfide oxidation result in the mobilization of contaminant metals (such as Zn, Cd, Ni and Cr) and metalloids (such as As) which are of environmental concern. This paper uses data from detailed mineralogical and geochemical studies conducted at two Canadian tailings impoundments to examine the mineralogical changes that pyrite, pyrrhotite, sphalerite and magnetite undergo during and after sulfide oxidation, and the subsequent release and attenuation of associated trace elements. The stability of sphalerite in tailings impoundments generally is greater than that of pyrrhotite, but less than pyrite. Dissolved Ni and Co derived from Fe sulfides, and to a lesser extent, dissolved Zn and Cd from sphalerite, are commonly attenuated by early-formed Fe oxyhydroxides. As oxidation progresses, a recycling occurs due to continued leaching from low-pH pore waters and because the crystallinity of Fe oxyhydroxides gradually increases which decreases their sorptive capacity. Unlike many other elements, such as Cu, Pb and Cr, which form secondary minerals or remain incorporated into mature Fe oxyhydroxides, Zn and Ni become mobile. Magnetite, which is a potential source of Cr, is relatively stable except under extremely low-pH conditions. A conceptual model for the sequence of events that typically occurs in an oxidizing tailings impoundment is developed outlining the progressive oxidation of a unit of mine waste containing a mixed assemblage of pyrrhotite and pyrite.     

Structure and reactivity of zinc sulfide precipitates formed in the presence of sulfate-reducing bacteria

The biologically mediated formation of metal sulfide precipitates in anoxic sediments represents a potentially important mechanism for the sequestration of toxic metals. Current knowledge of the structure and reactivity of these biogenic metal sulfides is scarce, limiting the ability to effectively assess contaminant sequestration in, and remobilization from, these solids. In this study, SO₄-reducing bacteria (Desulfovibrio sp.) were grown for 5 days in a high-SO₄, minimal metal media amended with Zn at either 30 or 300 micromolar. Zinc speciation in the reactor solids was determined using X-ray absorption spectroscopy, and the results compared to spectra of known metal sulfide mineral phases and freshly formed metal sulfides synthesized through purely chemical processes. Biogenically mediated Zn sulfides showed significantly more short range crystallographic order than the abiotically prepared amorphous precipitates. The presence of dissolved Fe²⁺ at similar concentrations did not affect the nature of the Zn precipitates formed. The biogenic ZnS solids were also more resistant to re-oxidation than the chemical precipitates but more soluble than sphalerite mineral samples. These results suggest that Zn sulfides formed in anaerobic sediments are likely to be more resistant to re-oxidation than would be expected based on dissolution of Fe sulfides and/or sediment acid volatile sulfides.     

豫西骆驼山多金属硫铁矿床硫化物Rb-Sr等时线年龄及其地质意义

豫西骆驼山多金属硫铁矿床位于华北陆块南缘南泥湖矿田西北侧。为确定该矿床的形成时代,文章选取了8件硫化物矿物样品,采用Rb_Sr等时线定年方法测定成矿年龄。结果获得,闪锌矿+磁黄铁矿+方铅矿等时线年龄为(137.3±2.6)Ma,闪锌矿+方铅矿等时线年龄为(138.2±5.8)Ma,闪锌矿+磁黄铁矿等时线年龄为(137±3)Ma,磁黄铁矿+方铅矿等时线年龄为(137.1±2.7)Ma,方铅矿等时线年龄为(138.4±7.6)Ma,磁黄铁矿等时线年龄为(137.2±3.7)Ma。上述定年结果表明,骆驼山多金属硫铁矿床的成矿时代为137 Ma左右,属早白垩世。硫化物Sr同位素初始比值(~(87)Sr/~(86)Sr)i介于0.713 23~0.713 32,平均值为0.713 25,小于陆源硅酸盐Sr的初始值0.7190,而高于地幔Sr的初始值0.7040,表明成矿物质来源于壳幔混合。骆驼山多金属硫铁矿床与矿田内的南泥湖_三道庄斑岩_矽卡岩钼(钨)矿床、冷水北沟铅锌矿成矿时代基本一致,是同一构造_岩浆_流体成矿活动的产物。结合前人对华北陆块南缘中生代期间地球动力学背景研究成果,笔者认为骆驼山矿床是中国东部中生代构造体制大转折过程晚期的产物。     

矿物流体包裹体中的羧酸

矿物流体包裹体中的羧酸曾贻善刘家齐（北京大学地质系，北京１００８７１）（地矿部宜昌地质矿产研究所，宜昌４４３００３）关键词矿物包裹体浸取液羧酸离子色谱分析分子中含有羧基官能团（—ＣＯＯＨ）的物质称为羧酸。Ｆｅｉｎ［１］和Ｓｈｏｃｋ［２］曾概述羧酸在自...     

Mineralogical and Geochemical Constraints on the Genesis of the Carbonate‐Hosted Jebel Ghozlane Pb–Zn Deposit (Nappe Zone,Northern Tunisia)

The Pb–Zn deposit at Jebel Ghozlane, in the Nappe zone (northern Tunisia), is hosted by Triassic dolostones and Eocene limestones and is located along faults and a thrust‐sheet boundary. The sulfide mineralization of the deposit consists mainly of galena and sphalerite and occurs as vein, stockwork, breccia, dissemination and replacement ores. Three hydrothermal stages are involved in the formation of the ores: stage I is dominated by celestite‐barite, hydrothermal dolomite DII, colloform sphalerite, and galena I; stage II consist of galena II; and stage III contains calcite. Galena in the deposit yielded average ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of 18.705, 15.667 and 38.734, respectively, suggesting a single upper crustal source reservoir for metals. Trace element data indicate the presence of Zn‐ and As‐free galena and As‐rich galena (with 0.2–0.5% As). Sphalerite contains 0.4% As, 0.7–0.9% Cd and 0.1–1.5% Fe. Microthermometric analysis of fluid inclusions in celestite shows that the deposit formed from fluids composed of heterogeneous mixtures of saline (19.5 ± 1 wt% NaCl eq.) aqueous solutions sourced from basinal brines, and gaseous CO₂‐rich phases bearing low amounts of CH₄, N₂ and/or H₂S, at temperatures of 172 ± 5°C.     

Distribution and partitioning of major and trace elements in pyrite-bearing sediments of a Mediterranean coastal lagoon

The formation of iron sulphide minerals exerts significant control on the behaviour of trace elements in sediments. In this study, three short sediment cores, retrieved from the remote Antinioti lagoon (N. Kerkyra Island, NW Greece), are investigated concerning the solid phase composition, distribution, and partitioning of major (Al, Fe) and trace elements (Cd, Cu, Mn, Pb, and Zn). According to ²¹⁰Pb, the sediments sampled correspond to depositions of the last 120 years. The high amounts of organic carbon (4.1–27.5%) result in the formation of Fe sulphides, predominantly pyrite, already at the surface sediment layers. Pyrite morphologies include monocrystals, polyframboids, and complex FeS–FeS₂ aggregates. According to synchrotron-generated micro X-ray fluorescence and X-ray absorption near-edge structure spectra, authigenically formed, Mn-containing, Fe(III) oxyhydroxides (goethite type) co-exist with pyrite in the sediments studied. Microscopic techniques evidence the formation of galena, sphalerite and CuS, whereas sequential extractions show that carbonates are important hosts for Mn, Cd, and Zn. However, significant percentages of non-lattice held elements are bound to Fe/Mn oxyhydroxides that resist reductive dissolution (on average 60% of Pb, 46% of Cd, 43% of Zn and 9% of Cu). The partitioning pattern changes drastically in the deeper part of the core that is influenced by freshwater inputs. In these sediments, the post-depositional pyritization mechanism, illustrated by overgrowths of Fe monosulphides on pre-existing pyrite grains, results in relatively high degree of pyritization that reaches 49% for Cd, 66% for Cu, 32% for Zn and 7% for Pb.     

Geochemical Characteristics of Jinwozi Gold Deposit,Xinjiang

The Jinwozi gold deposit consists of gold-bearing quartz veins in a biotite granodiorite of Hercynian age (zircon U-Pb age ≈ 335.7 Ma). Ore mineralogy is simple. In addition to native gold, there are only small amounts of sulfides, mainly pyrite and minor sphalerite, chalcopyrite and galena. δ³⁴S values average 6.69‰, and δ¹⁸O 13.99‰ Abundant CO₂ is contained in fluid inclusions from quartz. Homogenization temperatures of fluid inclusions are between 186 and 262 °C. REE distribution patterns indicate that the igneous mass may have been derived from a common initial material of calcareous-argillaceous sediments and alkali basalts as the country rocks. In other words, the Jinwozi granodiorite is of remelting origin from crustal material. Isotopic evidence of S, O and Pb shows that the ore-forming material is genetically related to magmatic hydrothermal activity.     

Onboard experiment investigating metal leaching of fresh hydrothermal sulfide cores into seawater

We observed the initial release rate of metals from four fresh (i.e., without long time exposure to the atmosphere) hydrothermal sulfide cores into artificial seawater. The sulfide samples were collected by seafloor drilling from the Okinawa Trough by D/V Chikyu, powdered under inert gas, and immediately subjected to onboard metal-leaching experiments at different temperatures (5 °C and 20 °C), and under different redox conditions (oxic and anoxic), for 1–30 h. Zinc and Pb were preferentially released from sulfide samples containing various metals (i.e., Mn, Fe, Cu, Zn, Cd, and Pb) into seawater. Under oxic experimental conditions, Zn and Pb dissolution rates from two sulfide samples composed mainly of iron disulfide minerals (pyrite and marcasite) were higher than those from two other sulfide samples with abundant sphalerite, galena, and/or silicate minerals. Scanning electron microscopy confirmed that the high metal-releasing sample contained several galvanic couples of iron disulfide with other sulfide minerals, whereas the low metal-releasing sample contained fewer galvanic couples or were coated by a silicate mineral. The experiments overall confirmed that the galvanic effects with iron disulfide minerals greatly induce the initial release of Zn and Pb from hydrothermal sulfides into seawater, especially under warm oxic conditions.     

Distribution and existing forms of trace elements from Maliping Pb-Zn deposit in northeastern Yunnan,China : A LA-ICPMS studyEI北大核心CSCD

The Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province, located in southwestern margin of the Yangtze Block, is an important part of the large-scale low-temperature metallogenic domain in southwestern China. The Maliping Pb-Zn deposit, situated in the central part of Zhaotong-Qujing metallogenic belt, was found in northeastern Yunnan Province recently. The orebody is hosted in Late Cambrian Yuhucun Formation, occurring as stratabound, tense and venis. The mineral assemblage of the Maliping deposit is relatively simple. The main sulfide minerals are sphalerite and galena with minor pyrite. Gangue minerals include mainly dolomite, calcite, quartz and barite. LA-ICPMS spots and mapping analysis for the different sulfides from Maliping Pb-Zn deposit, and the distribution and existing forms of germanium, cadmium, indium and other trace elements were investigated. The results show that different sulfides are characterized by different contents of trace elements. Mn, Cu, Sn, Cd, In and Ge are mainly enriched in sphalerite, while galena from this deposit is enrichment of Ag, Sb and Se, and pyrite is characterized by enrichment of As, Co and Ni. Comparing with the content of dispersed elements in different sulfides, the results indicate that sphalerite is the primary carrier mineral of Ge, In and Cd. Cd, Ge, In, Mn, As, Sb and Ag occur as isomorphous substitution in the sphalerite, and Cu mostly exists in sphalerite as isomorphism but part of Cu occurs as micro-inclusions (chalcopyrite) in sphalerite. Considered the distinct positive relationship between Cu and Ge, the results imply that the substitution mechanism of Ge and Cu is possibly 3Zn(2+) <-> Ge4+ + 2Cu(+). Additionally, sphalerite from Maliping Pb-Zn deposit is characterized by enrichment of Cd, Ge and depleted in Mn, Fe, Co and Sn which coincides with the feature of MVT Pb-Zn deposit and differs from the sedimentary-exhalative deposit and magmatic-hydrothermal deposit. On account of the geological features, other geochemical researches and its ore-forming temperature belonging to low temperature, it is suggested that the Maliping deposit belongs to an MVT Pb-Zn deposit. Notably, we imply that ore-forming fluid extracted indium of magmatic and volcaniclastic rocks from the metamorphic basement, resulting in the enrichment of indium in sphalerite from the deposit.     

Present-day precipitation of lead and zinc from groundwaters

Small quantities of galena and sphalerite are currently precipitating 26m below the surface, at the Vinemount quarry, Ontario, Canada from sulfurous spring waters, issuing from carbonates of the Lockport Formation. At the spring orifices, these sulfides are present in both fracture coatings and an associated black sludge. These precipitates are overlain by a crust rich in native sulfur. The mineralogy of the precipitates, and the chemistry of waters taken from three consistent spring horizons, indicates that downward-moving meteoric groundwaters leach metals from the host rocks and precipitate galena and sphalerite on encountering H₂S-rich waters at the water table. While our observation of the transport and deposition of lead and zinc by shallow groundwaters lends support to intra-karstic models for the direct precipitation of galena and sphalerite, it also enables us to propose that many carbonate-hosted Pb-Zn deposits, of differing theories of origin, may have been enriched during periods of uplift.