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Gregor Markl - One of the best experts on this subject based on the ideXlab platform.
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Polyphase enrichment and redistribution processes in silver-rich mineral associations of the hydrothermal fluorite-barite-(Ag-Cu) Clara deposit, SW Germany
Mineralium Deposita, 2019Co-Authors: Maximilian F Keim, Benjamin F. Walter, Udo Neumann, Stefan Kreissl, Richard Bayerl, Gregor MarklAbstract:The silver-copper sulfide mineralization associated with the fluorite-barite vein system at the Clara deposit in SW Germany shows large scale vertical zoning. Low to moderate silver contents prevail in the upper 350 m, whereas high silver contents occur in the subsequent 450 m of the currently known vein system. This change in Ag tenor is related to conspicuous mineralogical changes with depth. A detailed petrographic and fluid inclusion study identifies evidence for five subsequent hydrothermal and one alteration stage—all contributing to mineralogical diversity. The vertical Ag zoning, however, is attributed only to the first of these stages. During this first stage, increasing oxidation of ascending hydrothermal fluids (90–160 °C, 24.2–26.7 wt% NaCl+CaCl_2) led to the formation of high-Ag tetrahedrite-Tennantite in the lower parts and basically Ag-free enargite in the upper parts of the vein system. The subsequent hydrothermal stage led to significant mineralogical changes, but inherited the pre-existing Ag zonation. In this second hydrothermal stage, which was related to fluids similar in composition to those of the first stage (70–125 °C, 23.1–26.5 wt% NaCl+CaCl_2), dissolution of high Ag-tetrahedrite-Tennantite resulted in the formation of complex Ag-sulfosalts together with moderately Ag-bearing tetrahedrite-Tennantite and chalcopyrite. The first two stages were formed by fluid mixing of a sedimentary and a hot basement fluid. The influx of fluids with high Ag, Bi and Pb activity during stage 3 and 5 resulted in the local replacement of earlier Ag-sulfosalts by galena and Ag-(Bi)-sulfosalts. The fourth stage is marked by partial dissolution of sulfides and sulfosalts by a late, hot, undiluted basement fluid (250 °C, 18.7–20.9 wt% NaCl+CaCl_2) precipitating fluorite, barite and quartz. Finally, supergene alteration lead to the dissolution of silver-bearing phases and the precipitation of acanthite and native silver. The study illustrates, how metal tenor and mineralogy are decoupled in vertically extensive, polyphase hydrothermal vein systems. This may be pertinent to similarly zoned polymetallic vein systems.
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weathering of bi bearing Tennantite
Chemical Geology, 2018Co-Authors: Maximilian F Keim, Sebastian Staude, Katharina Marquardt, Kai Bachmann, Joachim Opitz, Gregor MarklAbstract:Abstract The Tennantite-tetrahedrite solid-solution series [called fahlore; (Cu,Ag)6Cu4(Fe,Zn,Cu,Hg,Cd)2(Sb,As,Bi,Te)4(S,Se)13] is widespread in many geological environments. Since it incorporates heavy metals and toxic elements, a better understanding of its weathering behaviour and details of its weathering process is important to evaluate environmental risks (emerging mainly from the mobilization of As-Sb-Bi) and local and global metal fluxes in stream waters and oceans. In this study, weathering of Bi-rich members of this mineral group was investigated using microscopy, EMPA, SEM, TEM, LA-ICP-MS, Raman, μXRD, and MLA. Observations reveal a succession of four distinct stages of weathering: During stage 1, irregular tubes within fahlore show an assemblage of nm- to μm-sized romeite group minerals, tripuhyite, crystalline Cu-oxides and Cu-sulfides. Stage 1 textures and secondary sulfides indicate a low redox-potential and a low fluid/rock ratio, typical of cementation zones. Mass balance calculations show that during this stage all Zn and the majority of As and S are released to the weathering fluids. Bismuth is immobile in this stage and Sb and Fe are immobile, if Bi is sufficiently available from fahlore, but both are partly released, if the fahlore did not contain sufficient Bi. During stage 2, amorphous and nano-crystalline arsenates replace fahlore as weathering fronts. Such assemblages indicate a higher redox-potential than in stage 1, typical for oxidation zones. Mass balance calculations reveal that Zn, Sb, S and partially Cu are lost. Arsenic and Bi are immobile. Stage 3 occurs only locally, dissolving former weathering stages and/or precipitating amorphous Cu-arsenates/silicates reflecting processes in micro-compartments, not characteristic for the general weathering process. Stage 4 is characterized by the formation of crystalline Bi-, Cu-, Ba-, Ca- or Al-bearing arsenates and Cu-carbonates, spatially independent of the precursor fahlore. Copper and As originate from older weathering assemblages, whereas many other elements are derived externally (Ca, Ba, Al). This stage reflects the increasing importance of the local host rock and gangue mineralogy, as it is typical in near-surface environments of oxidation zones or on mine dumps, where elements are highly mobile and a high fluid/rock ratio prevails (gossan mineralization). The temporal evolution of fahlore weathering textures reflects the transition from fresh ore to cementation zone, oxidation zone and gossan assemblages in one hand specimen. Thus, one fahlore grain can record the uplift and erosion and the increasing fluid/rock interaction of a weathered ore deposit with time. Tube-like textures similar to the ones observed in stage 1 have been reported from other weathering environments and from a variety of element, oxide, arsenide, and sulfide phases. They also were produced during experimental work in ilmenite. This is clear evidence, that the diffusive process during the first contact with alteration fluids is a basic physical process and that it is not only valid for fahlore. The importance of Bi to stabilize Sb-bearing supergene phases (and thereby for the immobilization of toxic Sb) shown in the present work, may stimulate further investigations on the environmental immobilization of toxic elements by “companion metals” during weathering processes.
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Multi-stage Ag–Bi–Co–Ni–U and Cu–Bi vein mineralization at Wittichen, Schwarzwald, SW Germany: geological setting, ore mineralogy, and fluid evolution
Mineralium Deposita, 2012Co-Authors: Sebastian Staude, Teresa Mordhorst, Wolfgang Werner, Klaus Wemmer, Dorrit E. Jacob, Gregor MarklAbstract:The Wittichen Co–Ag–Bi–U mining area (Schwarzwald ore district, SW Germany) hosts several unconformity-related vein-type mineralizations within Variscan leucogranite and Permian to Triassic redbeds. The multistage mineralization formed at the intersection of two fault systems in the last 250 Ma. A Permo-Triassic ore stage I with minor U–Bi–quartz–fluorite mineralization is followed by a Jurassic to Cretaceous ore stage II with the main Ag and Co mineralization consisting of several generations of gangue minerals that host the sub-stages of U–Bi, Bi–Ag, Ni–As–Bi and Co–As–Bi. Important ore minerals are native elements, Co and Ni arsenides, and pitchblende; sulphides are absent. The Miocene ore stage III comprises barite with the Cu–Bi sulfosalts emplectite, wittichenite and aikinite, and the sulphides anilite and djurleite besides native Bi, chalcopyrite, sphalerite, galena and Tennantite. The mineral-forming fluid system changed from low salinity (
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compositional variation of the Tennantite tetrahedrite solid solution series in the schwarzwald ore district sw germany the role of mineralization processes and fluid source
Mineralogical Magazine, 2010Co-Authors: Sebastian Staude, Teresa Mordhorst, R Neumann, W Prebeck, Gregor MarklAbstract:The study presents analysis from members of the Tennantite–tetrahedrite solid-solution series (`fahlore9) from 78 locations in the Schwarzwald ore district of SW Germany. Electron microprobe analysis is used to correlate the compositional variations of the fahlores with mineral association, host rock, tectonic history and precipitation mechanisms. Results indicate that most fahlores from gneiss-hosted veins do not have distinctive geochemical characteristics and range from tetrahedrite to Tennantite end-member composition with variable trace-element content. However, diagenetically formed fahlore has a near-end-member Tennantite composition with very small trace-element content. Red-bed-hosted fahlore formed by fluid mixing is Tennantite enriched in Hg that probably has its source in the red-bed sediments. Fahlore formed from granite-related late-magmatic fluids, or from mixing of fluids of which one has equilibrated with granitic basement rocks, is typically As- and Bi-rich (up to 22.2 wt.% Bi). Gneiss-hosted fahlore formed by fluid cooling is Ag-rich near-end-member tetrahedrite. Some fahlores reflect their paragenetic association, e.g. a large Ag content in association with Ag-bearing minerals or a large Co and Ni in association with Co- and Ni-arsenides. Although they have similar compositions, gneiss-hosted fahlores show systematic variations in Ag contents and Fe/Zn ratios between the Central and the Southern Schwarzwald with Fe-rich fahlore in higher stratigraphic levels (North) and Zn- and Ag-rich fahlore in lower stratigraphic levels (South). We show that fahlore composition varies with precipitation mechanism (cooling vs. mixing vs. diagenesis), depth of formation, paragenetic association and host rock. Comparison with fahlores from other European occurrences indicates that these conclusions are consistent with fahlore systematics found elsewhere, and could be used to infer details of ore-forming processes.
John Ralston - One of the best experts on this subject based on the ideXlab platform.
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separation of enargite and Tennantite from non arsenic copper sulfide minerals by selective oxidation or dissolution
International Journal of Mineral Processing, 2001Co-Authors: Daniel Fornasiero, Damian Fullston, C Li, John RalstonAbstract:Selective oxidation of minerals was investigated as a means to separate by flotation the copper sulfide minerals of chalcocite, covellite and chalcopyrite from the arsenic copper sulfide minerals of enargite and Tennantite in mixed mineral systems. It was found that a separation of these minerals could be feasible after selective oxidation of their surfaces in slightly acidic pH conditions, or after oxidation and selective dissolution of the surface oxidation products with a complexant in basic pH conditions.
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oxidation of synthetic and natural samples of enargite and Tennantite 2 x ray photoelectron spectroscopic study
Langmuir, 1999Co-Authors: Damian Fullston, Daniel Fornasiero, John RalstonAbstract:The surface oxidation of synthetic and natural samples of enargite and Tennantite has been monitored by X-ray photoelectron spectroscopy, XPS. The minerals were conditioned at pH 11.0 in an aqueous solution purged with nitrogen gas for 20 min or with oxygen gas for 60 min. The XPS results show that the oxidation layer on the mineral surface is thin. The surface oxidation products comprise copper and arsenic oxide/hydroxide, sulfite, and a sulfur-rich layer made of metal-deficient sulfide and/or polysulfide. The proportion of all of these oxidation products at the mineral surface is more important when the minerals are treated in more oxidizing conditions (i.e., with oxygen gas and for a longer time) for Tennantite than for enargite and for the natural samples than for the synthetic samples. Different arsenic sulfide species have been found at the surfaces of enargite and Tennantite: As4S4 or As2S3 constitutes the major arsenic sulfide species at the surface of enargite, but these are the minor arsenic su...
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zeta potential study of the oxidation of copper sulfide minerals
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999Co-Authors: Damian Fullston, Daniel Fornasiero, John RalstonAbstract:Abstract The zeta potential of the copper sulfide minerals, chalcocite, covellite, chalcopyrite, bornite, enargite and Tennantite was measured as a function of pH and oxidising conditions. The changes in zeta potential observed in this study are consistent with the presence of a copper hydroxide layer covering a metal-deficient sulfur-rich surface and with the extent of this copper hydroxide coverage increasing with oxidation conditions. The existence of these surface species and their percentage were also confirmed by X-ray photoelectron spectroscopy. Analysis of the zeta potential data revealed that during the acid titration of the minerals, dissolution of the surface copper hydroxide layer occurs at pH values less than 8 while during the base titration, precipitation of copper hydroxide on the mineral surface is observed at pH values higher than 6. Hysteresis between the zeta potential acid and base titration curves was only observed in oxidising conditions and is attributed to the dissolution of the minerals at acidic pH values. The following ranking for the oxidation of these minerals is obtained: chalcocite>Tennantite>enargite>bornite>covellite>chalcopyrite.
J Mielczarski - One of the best experts on this subject based on the ideXlab platform.
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xps characterization of chalcopyrite tetrahedrite and Tennantite surface products after different conditioning 2 amyl xanthate solution at ph 10
Langmuir, 1996Co-Authors: J Mielczarski, J M Cases, M Alnot, J J EhrhardtAbstract:Characterization of the surface products formed by the interaction of amyl xanthate solution at pH 10 with mineral samples of chalcopyrite (CuFeS2), tetrahedrite (Cu12Sb4S13), and Tennantite (Cu12As4S13) was carried out by X-ray photoelectron spectroscopy (XPS). The experimental data collected directly after solution treatment and after successive sputterings have led us to determine the in-depth distribution of the different types of surface products formed by the diffusion of atoms from the bulk to the interface region and their interaction with aerated aqueous xanthate solution. The xanthate adsorption takes place by an electrochemical mechanism which involves the formation of cuprous xanthate (hydrophobic species) and metal hydroxides (hydrophilic species). In general, the following in-depth surface composition was found for the investigated mineral samples in contact with the xanthate solution: (i) the outermost layer contains the cuprous xanthate complex, which causes hydrophobic properties, and a ...
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in situinfrared characterization of surface products of interaction of an aqueous xanthate solution with chalcopyrite tetrahedrite and Tennantite
Journal of Colloid and Interface Science, 1996Co-Authors: J Mielczarski, Jean M Cases, Odile BarresAbstract:Abstract The flotation behavior of minerals depends on the balance between the hydrophobic and hydrophilic species present at the surface of the minerals. The direct characterization of the interface products formed by the interaction of an aqueous solution of ethyl xanthate (C2H5OCS−2, X−) with chalcopyrite (CuFeS2) and with mineral samples containing mainly tetrahedrite (Cu12Sb4S13) and Tennantite (Cu12As4S13) was carried out by infrared Fourier transform (FT) reflection spectroscopy. The experimental data collected fromin situattenuated total reflection (ATR) andex situdiffuse reflectance (DRIFT) measurements have allowed us to determine different types of adsorption products and to propose mechanisms of the interaction between an aqueous solution of surfactant and the surfaces of the investigated minerals. It is shown thatin situstudies provide more complete information about the composition of the adsorbed layers. It is revealed that two major processes take place at the mineral interfaces: (i) the interaction with water and oxygen, resulting in the formation of the oxidation products, mainly hydrophilic; and (ii) the adsorption of xanthate, producing three types of products, on the surfaces of these three mineral samples, that form the hydrophobic coverage. On chalcopyrite, the adsorbed xanthate ions form initially a cuprous xanthate complex and a product with an absorbance band at about 1220 cm−1. At higher than monolayer coverage, dixanthogen (X2) was found as an additional surface product. Dixanthogen is relatively unstable on the surface of the mineral after drying, and it was found only inin situmeasurements. The assignment of the band at about 1220 cm−1is temporary, and it is proposed to be due to the surface iron complex, probably Fe(OH)X2. In the cases of tetrahedrite and Tennantite, the cuprous xanthate complex is observed in submonolayer and multilayer quantities. Dixanthogen was not found on these two minerals. Only on tetrahedrite was an additional band at 1227 cm−1observed at submonolayer coverage; this was assigned to a surface metal xanthate complex other than cuprous xanthate.
J M Cases - One of the best experts on this subject based on the ideXlab platform.
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interaction of amyl xanthate with chalcopyrite tetrahedrite and Tennantite at controlled potentials simulation and spectroelectrochemical results for two component adsorption layers
Langmuir, 1996Co-Authors: J A Mielczarski, And E Mielczarski, J M CasesAbstract:Spectroelectrochemical studies of the interaction of amyl xanthate solution (C5H11OCS2-) at pH 10 with mineral samples of chalcopyrite (CuFeS2), tetrahedrite (Cu12Sb4S13), and Tennantite (Cu12As4S13) at different potentials were carried out by infrared reflection spectroscopy. The experimental data were compared with simulated results in order to evaluate in detail the composition and structure of the adsorbed layers. Two-component adsorption layers were determined on these three minerals. The first adsorption product observed spectroscopically was a cuprous amyl xanthate complex followed by an amyl dixanthogen (dimer, (C5H11OCS2)2). The dixanthogen was always observed together with cuprous xanthate complex. It was produced simultaneously with cuprous xanthate, on chalcopyrite and tetrahedrite, or at potential 100 mV higher than cuprous xanthate formation on tetrahedrite. The produced cuprous xanthate was placed close to the mineral interface, and its amount was limited from a submonolayer to a few monola...
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xps characterization of chalcopyrite tetrahedrite and Tennantite surface products after different conditioning 2 amyl xanthate solution at ph 10
Langmuir, 1996Co-Authors: J Mielczarski, J M Cases, M Alnot, J J EhrhardtAbstract:Characterization of the surface products formed by the interaction of amyl xanthate solution at pH 10 with mineral samples of chalcopyrite (CuFeS2), tetrahedrite (Cu12Sb4S13), and Tennantite (Cu12As4S13) was carried out by X-ray photoelectron spectroscopy (XPS). The experimental data collected directly after solution treatment and after successive sputterings have led us to determine the in-depth distribution of the different types of surface products formed by the diffusion of atoms from the bulk to the interface region and their interaction with aerated aqueous xanthate solution. The xanthate adsorption takes place by an electrochemical mechanism which involves the formation of cuprous xanthate (hydrophobic species) and metal hydroxides (hydrophilic species). In general, the following in-depth surface composition was found for the investigated mineral samples in contact with the xanthate solution: (i) the outermost layer contains the cuprous xanthate complex, which causes hydrophobic properties, and a ...
Damian Fullston - One of the best experts on this subject based on the ideXlab platform.
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separation of enargite and Tennantite from non arsenic copper sulfide minerals by selective oxidation or dissolution
International Journal of Mineral Processing, 2001Co-Authors: Daniel Fornasiero, Damian Fullston, C Li, John RalstonAbstract:Selective oxidation of minerals was investigated as a means to separate by flotation the copper sulfide minerals of chalcocite, covellite and chalcopyrite from the arsenic copper sulfide minerals of enargite and Tennantite in mixed mineral systems. It was found that a separation of these minerals could be feasible after selective oxidation of their surfaces in slightly acidic pH conditions, or after oxidation and selective dissolution of the surface oxidation products with a complexant in basic pH conditions.
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oxidation of synthetic and natural samples of enargite and Tennantite 2 x ray photoelectron spectroscopic study
Langmuir, 1999Co-Authors: Damian Fullston, Daniel Fornasiero, John RalstonAbstract:The surface oxidation of synthetic and natural samples of enargite and Tennantite has been monitored by X-ray photoelectron spectroscopy, XPS. The minerals were conditioned at pH 11.0 in an aqueous solution purged with nitrogen gas for 20 min or with oxygen gas for 60 min. The XPS results show that the oxidation layer on the mineral surface is thin. The surface oxidation products comprise copper and arsenic oxide/hydroxide, sulfite, and a sulfur-rich layer made of metal-deficient sulfide and/or polysulfide. The proportion of all of these oxidation products at the mineral surface is more important when the minerals are treated in more oxidizing conditions (i.e., with oxygen gas and for a longer time) for Tennantite than for enargite and for the natural samples than for the synthetic samples. Different arsenic sulfide species have been found at the surfaces of enargite and Tennantite: As4S4 or As2S3 constitutes the major arsenic sulfide species at the surface of enargite, but these are the minor arsenic su...
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zeta potential study of the oxidation of copper sulfide minerals
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999Co-Authors: Damian Fullston, Daniel Fornasiero, John RalstonAbstract:Abstract The zeta potential of the copper sulfide minerals, chalcocite, covellite, chalcopyrite, bornite, enargite and Tennantite was measured as a function of pH and oxidising conditions. The changes in zeta potential observed in this study are consistent with the presence of a copper hydroxide layer covering a metal-deficient sulfur-rich surface and with the extent of this copper hydroxide coverage increasing with oxidation conditions. The existence of these surface species and their percentage were also confirmed by X-ray photoelectron spectroscopy. Analysis of the zeta potential data revealed that during the acid titration of the minerals, dissolution of the surface copper hydroxide layer occurs at pH values less than 8 while during the base titration, precipitation of copper hydroxide on the mineral surface is observed at pH values higher than 6. Hysteresis between the zeta potential acid and base titration curves was only observed in oxidising conditions and is attributed to the dissolution of the minerals at acidic pH values. The following ranking for the oxidation of these minerals is obtained: chalcocite>Tennantite>enargite>bornite>covellite>chalcopyrite.
