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.     

Graphite in Kupferschiefer (Poland) and its genetic meaning

Graphite forms crystals up to 0.08 mm in size in carbonates or argillaceous carbonates directly under- and overlying black shale. Increased contents of Si, Al, Ca, and K in graphite are related to intercalations of graphite-montmorillonite and less to intercalations of graphite-illite. Quartz and gibbsite are also detected. The formation of graphite was probably a two-stage process:

1. Catalytic oxidation of organic matter. As a result of oxidation original organic matter has been enriched as aromatic hydrocarbons (benzene ring compounds) being most resistant to oxidation.
2. Ordering of conjugated benzene rings on the 001 montmorillonite plane as a matrix. As a result, the c₀ of dry montmorillonite increased to 1.678±0.020 or 2.450±0.050 nm. Primary layers of graphite became themselves matrices for the next layers of conjugated rings producing microscopically visible graphite.

To a less extent the process of dehydrogenesis and conjugation of aromatic rings took place in a reaction with Al, Si, and OH of phyllosilicates producing Al(OH)₃ (gibbsite), former H₄SiO₄ (now quartz), and H₂O.     

Peloids in stratabound Zn-Pb deposits and their genetic importance

Peloids from sediment-hosted Zn-Pb deposits in Belgium, Ireland and Poland are composed of Zn-calcite, siderite, smithsonite, silica, pyrite, melnikovite, sphalerite, galena, thiosulphates and Zn-As-bearing limonite. The size of peloids is between 7 and 60 m. The core and the shell of peloids are composed of different minerals and the shell is usually coarsely crystalline. Peloids are present in collapse breccias of karst cavities, stromatactis cavities, debris-flow breccias, and fractures cross-cutting carbonates hosting the mineralization. In places peloids form a major microtexture of the sulfide mineralization. Peloids are cemented and replaced by sulfides. Organic acids extracted from sulfide peloids are composed of amido-acids considered to be characteristic of bacterial origin. The size and specific texture of peloids are independent of mineralogy, location and age of the mineralization. Therefore the peloids disussed are considered as forms induced by bacterial activity rather than forms precipitated inorganically.     

Precious metal alloys and organic matter in the Zechstein copper deposits,Poland

Summary Au-and PGE-bearing samples¹ from organogenic limestone located in the western part of the Lubin mine have been investigated. They contain: Au–Ag–Pt–Hg alloys, native Pd, sobolevskite (PdBi), native lead and plumbian gold which is related to an admixture of AuPb₂, electrum (Ag₂Au). Clausthalite also occurs in this association and contains up to 1% Ir. Kerogen is an important member of the association and contains, among others, 700 ppm Pt, 400 ppm Pd, 600 ppm Ir and 1100 ppm Au.These alloys are closely associated with nests of secondary calcite with dark brown internal reflections due to admixture of organic compounds. Organic matter colouring calcite II contains: ketones (chiefly diketones), nitrogen derivatives, phenols, probably tertiary alcohols and aromatic hydrocarbons. Metal carbonyls were also recorded. The organic substances investigated contain oxidation retarding derivatives.

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Edelmetall-Legierungen und organische Substanz in den Kupferlagerstätten des Zechstein (Kupferschiefer), Polen

Zusammenfassung Gold und PGE-führende Proben von organogenem Kalkstein aus dem Westteil der Grube Lubin enthalten Au–Ag–Pt–Hg-Legierungen, gediegen Pd, Sobolevskit (PdBi), gediegen Blei und bleireiches Gold. Letzteres ist mit einer AuPb₂–Ag₂Au-Verwachsung assoziiert. Außerdem konnte Clausthalit (PbSe) mit 1% Ir nachgewiesen werden.Kerogen ist ein wichtiges Glied der Edelmetall-Paragenese und enthält selbst u.a. 700 ppm Pt, 400 ppm Pd, 600 ppm Ir und 1100 ppm Au. Die Edelmetall-Legierungen sind eng mit «Nestern» von sekundärem Calcit vergesellschaftet, dessen dunkelbraune Innenreflexe auf Beimischung organischer Verbindungen zurückgehen.Letztere umfassen: Ketone (vorwiegend -Diketone), Stickstoff-Derivate, Phenole, und wohl auch tertiäre Alkohole und aromatische Kohlenwasserstoffe. Metall-Karbonyl-Verbindungen konnten ebenso nachgewiesen werden. Die untersuchten organischen Verbindungen enthalten Oxydations-verzögernde Derivate.

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With 6 Figures     

Mineralogical and geochemical (stable C and O isotopes) variability of marbles from the Moldanubian Zone (Bohemian Massif,Czech Republic): implications for provenance studies

Metacarbonates of the Moldanubian Zone (Bohemian Massif, Czech Republic) were studied to obtain qualitative and quantitative mineralogical-petrographic as well as stable isotopic data for the purpose of stone provenance studies, potentially applicable in material research studies of cultural heritage artefacts. Twenty-six samples from twelve different historical quarries, as well as two samples from historical artefacts, were analysed by both mineralogical-petrographic and geochemical methods including: polarizing microscopy, cathodoluminescence, scanning electron microscopy with microanalysis, petrographic image analysis, powder X-ray diffraction, and isotope ratio mass spectrometry. The petrographic characteristics allowed for the discrimination of groups of (1) calcitic marbles, (2) dolomitic marbles, and (3) carbonate–silicate rocks. These groups exhibit characteristic features such as (1) the presence/abundance of major rock-forming minerals, (2) grain geometric characteristics (specifically, mean carbonate grain size and index of grain size homogeneity), and (3) the presence of specific accessory phases. The content of non-carbonate minerals, some rock fabric parameters, as well as the carbon and oxygen isotope data exhibited significant variability, even within a single quarry in the case of some impure marbles and carbonate–silicate rocks. Although the carbon and oxygen isotopic ranges displayed overlaps among the quarries studied, the isotopic signatures throughout the Moldanubian Zone allowed for discrimination of a group of white calcitic marbles with high carbon and oxygen depletion, as well as white dolomite–calcitic marble with higher carbon isotope values when compared with other marble resources of the Bohemian Massif. A combination of the isotopic signature with detailed mineralogical-petrographic characteristics seems to provide sufficient information for discrimination of the Moldanubian marbles from one another. The provenance of the Vrchotovy Janovice artefact is very probably from the Rabí quarry, among the Moldanubian marbles. The provenance of the artefact from the Prague Klementinum was not definitively assigned; however, the Nehodiv quarry was considered its probable source locality.     

Tertiary metallogenesis in the Eastern Alps: the Waldenstein hematite deposit (Austria)

The specularite deposit at Waldenstein is an epigenetic replacement/vein-type hematite mineralization with distinct alteration zones. It is situated in highly metamorphosed schists and, gneisses of the Koralm Crystalline Complex. Sericitization and chloritization are strictly bound to this alteration and occur within a few meters of the hematite veins. Radiometric dating of the sericitization and the implicity of the mineralization yield a Middle Eocene age. Petrographic evidence proves an early, relatively reduced paragenesis (magnetite, ilmenite) being partly replaced by hematite and chlorite during the main phase of ore formation. Fluid inclusion and stable isotope investigations indicate that formation temperatures were approximately 300°C during the main stage and decreased to 200°C in the latest stage of the hydrothermal event. The H-isotope compositions of chlorites and of fluid inclusions in quartz indicate the influence of seawater. This also explains the high salinities determined by fluid inclusion studies (20–30% NaCl equiv.). According to the genetic model presented in this paper the hydrothermal activity started when the deformation accompanying the uplift of the Koralm Crystalline Complex passed from a ductile to brittle regime (Middle Eocene). The brittle faults acted as channelways for rising, deep fluids, probably of metamorphic origin. Temperature differences between the different uplifting crustal segments supported fluid circulation. Precipitation of the ore occurred at shallow crustal levels where the hydraulic regime was dominated by seawater, and oxidation of the original reducing fluids took place.     

Evidence for superstructuring in ankerite

Summary Ankerite from the Radmer-Buchegg and Erzberg mines, Austria, were studied by high resolution electron microscope imaging and selected area diffraction. Electron diffraction data suggest the presence of a periodic antiphase structure. The unit cell of the periodic antiphase structure of ankerite consists probably of three units: CaMg(CO₃)₂ as a basal unit, CaFe(CO₃)₂ and CaCO₃. The last CaCO₃ unit is connected with excess of Ca in ankerite. The upper size limit of CaFe(CO₃)₂ domains is 20–40 nm according to dark-field image study.Other rhombohedral dicarbonates (Zn-dolomites, Fe-poor ankerites) have probably also domain structure. The size of domains seems to be controlled by the value of misfit of domain lattice to the host lattice and by the value of octahedral distortion of units of the periodic antiphase structure.

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Überstrukturen in Ankerit

Zusammenfassung Ankerite der Lagerstätten Radmer-Buchegg und Erzberg, Österreich wurden mittels hochauflösender Elektronenmikroskopie und Elektronenbeugung untersucht. Die Beugungsbilder lassen auf eine periodische Antiphasen-Struktur schließen, die sich aus drei Einheiten aufbaut: CaMg(CO₃)₂ als Basiseinheit, CaFe(CO₃)₂ und CaCO₃. CaCO₃ ist an einen Ca-Überschuß in Ankeriten gebunden. Dunkelfeldaufnahmen entsprechend beträgt die Obergrenze der CaFe(CO₃)₂ Domänengröße 20–40 nm.Andere rhomboedrische Doppelkarbonate (Zn-Dolomite, Fe-arme Ankerite) haben wahrscheinlich ebenfalls Domänenstruktur. Die Größe der Domänen scheint durch das Zusammenpassen des Domänengitters mit dem Gitter des Wirtskristalls sowie durch den Grad der oktaedrischen Verzerrung von Baueinheiten der Antiphasen-Struktur bestimmt zu werden.

     

Sulfide — carbonate relationships in the Navan (Tara) Zn-Pb deposit,Ireland

Samples from the mineralized micrite, the bottom part of the 1–5 lens were investigated. They contain Zn and Fe bearing low Mg-calcite, dolomite, Fedolomite, minrecordite-CaZn (CO₃)₂, sphalerite, pyrite, melnikovite and overgrown quartz. — Zn-dolomite consists probably of CaMg (CO₃)₂ and CaZn (CO₃)₂ domains about 10×35 nm in size. Zn-dolomite is sulfidized (replaced by ZnS) which is demonstrated by both reflected light and electron microscope methods. — CaZn (CO₃)₂ from the Navan ore has cell parameters: a₀=0.484±0.004 and c₀=1.608±0.012 nm and is rhombohedral. It forms close, tiny intergrowths with calcite. — Base metals at Navan were exhaled to form at least partly carbonate minerals which subsequently reverted to sulfides in the diagenetic environment. The reversion of base metals carbonates to sulfides is connected with reduction in volume. The reduction in volume allowed the ore zone to retain its permeability after lithification of the host rock. It allowed lateral flow of hydrothermal solutions, which deposited further generations of sulfides and increased the base metal content producing a high grade ore.