Research

14 pages, 2596 KiB

Open AccessFeature PaperArticle

Nb–Ta–Ti Oxides in Topaz Granites of the Geyersberg Granite Stock (Erzgebirge Mts., Germany)

by Miloš René

Minerals 2019, 9(3), 155; https://doi.org/10.3390/min9030155 - 04 Mar 2019

Cited by 5 | Viewed by 3129

Oxide minerals (Nb–Ta-rich rutile, columbite-group minerals and W-bearing ixiolite) represent the most common host for Nb, Ta and Ti in high-F, high-P₂O₅ Li-mica granites and related rocks from the Geyersberg granite stock in the Krušné Hory/Erzgebirge Mts. batholith. This body [...] Read more.

Oxide minerals (Nb–Ta-rich rutile, columbite-group minerals and W-bearing ixiolite) represent the most common host for Nb, Ta and Ti in high-F, high-P₂O₅ Li-mica granites and related rocks from the Geyersberg granite stock in the Krušné Hory/Erzgebirge Mts. batholith. This body forms a pipe like granite stock composed of fine- to middle-grained, porphyritic to equigranular high-F, high-P₂O₅ Li-mica granites, which contain up to 6 vol. % of topaz. Intrusive breccia’s on the NW margin of the granite stock are composed of mica schists and muscovite gneiss fragments enclosed in fine-grained aplitic and also topaz- and Li-mica-bearing granite. Columbite group minerals occur usually as euhedral to subhedral grains that display irregular or patched zoning. These minerals are represented by columbite-(Fe) with Mn/(Mn + Fe) ratio ranging from 0.07 to 0.15. The rare Fe-rich W-bearing ixiolite occurs as small needle-like crystals. The ixiolite is Fe-rich with relatively low Mn/(Mn + Fe) and Ta/(Ta + Nb) values (0.10–0.15 and 0.06–0.20, respectively). Owing to the high W content (19.8–34.9 wt. % WO₃, 0.11–0.20 apfu), the sum of Nb + Ta in the ixiolite does not exceed 0.43 apfu. The Ti content is 1.7–5.7 wt. % TiO₂ and Sn content is relatively low (0.3–4.1 wt. % SnO₂). Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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16 pages, 4080 KiB

Open AccessArticle

The Gersdorffite-Bismuthinite-Native Gold Association and the Skarn-Porphyry Mineralization in the Kamariza Mining District, Lavrion, Greece

by Panagiotis Voudouris, Constantinos Mavrogonatos, Branko Rieck, Uwe Kolitsch, Paul G. Spry, Christophe Scheffer, Alexandre Tarantola, Olivier Vanderhaeghe, Emmanouil Galanos, Vasilios Melfos, Stefanos Zaimis, Konstantinos Soukis and Adonis Photiades

Minerals 2018, 8(11), 531; https://doi.org/10.3390/min8110531 - 16 Nov 2018

Cited by 12 | Viewed by 5579

Abstract

Vein-type Pb-Ni-Bi-Au-Ag mineralization at the Clemence deposit in the Kamariza and “km3” in the Lavrion area, was synchronous with the intrusion of a Miocene granodiorite body and related felsic and mafic dikes and sills within marbles and schists in the footwall of (and [...] Read more.

Vein-type Pb-Ni-Bi-Au-Ag mineralization at the Clemence deposit in the Kamariza and “km3” in the Lavrion area, was synchronous with the intrusion of a Miocene granodiorite body and related felsic and mafic dikes and sills within marbles and schists in the footwall of (and within) the Western Cycladic detachment system. In the Serpieri deposit (Kamariza area), a porphyry-style pyrrhotite-arsenopyrite mineralized microgranitic dike is genetically related to a garnet-wollastonite bearing skarn characterized by a similar base metal and Ni (up to 219 ppm) enrichment. The Ni–Bi–Au association in the Clemence deposit consists of initial deposition of pyrite and arsenopyrite followed by an intergrowth of native gold-bismuthinite and oscillatory zoned gersdorffite. The zoning is related to variable As, Ni, and Fe contents, indicating fluctuations of arsenic and sulfur fugacity in the hydrothermal fluid. A late evolution towards higher sulfur fugacity in the mineralization is evident by the deposition of chalcopyrite, tennantite, enargite, and galena rimming gersdorffite. At the “km3” locality, Ni sulfides and sulfarsenides, vaesite, millerite, ullmannite, and polydymite, are enclosed in gersdorffite and/or galena. The gersdorffite is homogenous and contains less Fe (up to 2 wt.%) than that from the Clemence deposit (up to 9 wt.%). Bulk ore analyses of the Clemence ore reveal Au and Ag grades both exceeding 100 g/t, Pb and Zn > 1 wt.%, Ni up to 9700 ppm, Co up to 118 ppm, Sn > 100 ppm, and Bi > 2000 ppm. The “km3” mineralization is enriched in Mo (up to 36 ppm), Ni (>1 wt.%), and Co (up to 1290 ppm). Our data further support a magmatic contribution to the ore-forming fluids, although remobilization and leaching of metals from previous mineralization and/or host rocks, through the late involvement of non-magmatic fluid in the ore system, cannot be excluded. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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14 pages, 8765 KiB

Open AccessArticle

Plant Tissues and Embryos Biominerals in Sarcocornia pruinosa, a Halophyte from the Río Tinto Salt Marshes

by Vicenta De la Fuente, Lourdes Rufo, Irene Sánchez-Gavilán, Esteban Ramírez, Nuria Rodríguez and Ricardo Amils

Minerals 2018, 8(11), 505; https://doi.org/10.3390/min8110505 - 05 Nov 2018

Cited by 13 | Viewed by 3003

Abstract

Although biomineralization in plants is an important area of research, there is very limited information. In this work, we report the location of Na, K, Ca, Mg and Fe biominerals in Sarcocornia pruinosa (Chenopodiacaeae), a halophyte species growing in the estuarine area of [...] Read more.

Although biomineralization in plants is an important area of research, there is very limited information. In this work, we report the location of Na, K, Ca, Mg and Fe biominerals in Sarcocornia pruinosa (Chenopodiacaeae), a halophyte species growing in the estuarine area of Río Tinto, an extreme acidic environment. The estuarine soils of the Tinto basin are characterized by slightly acidic pH and high concentrations of ions. They are exposed to Atlantic Ocean tides that contribute to the increase in pH, Na and Mg concentrations. The aim of this work was to characterize the elemental composition and to identify the biominerals detected in cell tissues of S. pruinosa. Analytical techniques, such as ICP-MS (Inductively coupled plasma mass spectrometry), XRD and microscopy such as OM (optical microscopy) with histochemical staining, SEM and TEM (scanning and transmission electronic microscopy) coupled with EDX (energy dispersive X-ray) were carried out to analyze the plant tissues of S. pruinosa and characterize the detected biominerals. The elemental composition in succulent stems and seeds of S. pruinosa showed high values of Na and K followed by Ca, Mg and Fe. The presence of halite, sylvite, weddellite, glushinskite and Fe oxides biominerals in this halophyte species is reported. Our data suggest the importance of vegetation in the biogeochemical cycles in estuarine areas. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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13 pages, 4057 KiB

Open AccessArticle

Authigenic and Detrital Minerals in Peat Environment of Vasyugan Swamp, Western Siberia

by Maxim Rudmin, Aleksey Ruban, Oleg Savichev, Aleksey Mazurov, Aigerim Dauletova and Olesya Savinova

Minerals 2018, 8(11), 500; https://doi.org/10.3390/min8110500 - 01 Nov 2018

Cited by 30 | Viewed by 5088

Abstract

Studies of mineral-forming processes in modern peat bogs can shed light on metal concentrations and their cycling in similar environments, especially in geological paleoanalogs. In terms of the mineralogical and geochemical evolution of peat bog environments, the Vasyugan Swamp in Western Siberia is [...] Read more.

Studies of mineral-forming processes in modern peat bogs can shed light on metal concentrations and their cycling in similar environments, especially in geological paleoanalogs. In terms of the mineralogical and geochemical evolution of peat bog environments, the Vasyugan Swamp in Western Siberia is a unique scientific object. Twelve peat samples were collected from the Vasyugan Swamp up to the depth of 275 cm at 25 cm intervals. The studied peat deposit section is represented by oligotrophic (0–100 cm), mesotrophic (100–175 cm), and eutrophic (175–275 cm) peat, and this is underlain by basal sediments (from 275 cm). About 30 minerals were detected using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The observed minerals are divided into detrital, clay, and authigenic phases. The detrital minerals found included quartz, feldspar, ilmenite, rutile, magnetite, zircon, and monazite. When passing from basal to oligotrophic bog sediments, the clay minerals changed from illite-smectite to kaolinite. Authigenic minerals are represented by carbonates (calcite and dolomite), iron (hydro-)oxides, galena, sphalerite, pyrite, chalcopyrite, Zn-Pb-S mineral, barite, baritocelestine, celestine, tetrahedrite, cassiterite, REE phosphate, etc. The regular distribution of mineral inclusions in peat is associated with the (bio)geochemical evolution of the environment. The formation of authigenic Zn, Pb and Sb sulfides is mainly confined to anaerobic conditions that exist in the eutrophic peat and basal sediments. The maximum amount of pyrite is associated with the interval of 225–250 cm, which is the zone of transition from basal sediments to eutrophic peat. The formation of carbonate minerals and the decreasing concentration of clay in the association with local sulfide formation (galena, sphalerite, chalcopyrite, stibnite) begins above this interval. The peak of specific carbonation appears in the 125–150 cm interval of the mesotrophic peat, which is characterized by pH 4.9–4.5 of pore water. Kaolinite is the dominant clay mineral in the oligotrophic peat. Gypsum, galena, chalcopyrite, sphalerite, and relicts of carbonate are noted in association with kaolinite. Changes in oxygen concentrations are reflected in newly formed mineral associations in corresponding intervals of the peat. This can be explained by the activity of microbiological processes such as the anaerobic oxidation of methane (AOM) and bacterial sulfate reduction (BSR), expressed in specific carbonatization (100–225 cm) and sulfidization (175–250 cm), respectively. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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10 pages, 4334 KiB

Open AccessArticle

Nano Precipitates Formed during the Dissolution of Calcite Incorporated with Cu and Mn

by Xiaohang Zhang, Shijun Wu and Fanrong Chen

Minerals 2018, 8(11), 484; https://doi.org/10.3390/min8110484 - 25 Oct 2018

Cited by 12 | Viewed by 3123

Abstract

Calcite is often doped with impurity ions that affect its dissolution behavior. In the present investigation, solid solutions of (Ca, Mn)CO₃ and (Ca, Cu)CO₃ were synthesized by coprecipitation to study their dissolution in an acidic solution (pH = 5) at 25 [...] Read more.

Calcite is often doped with impurity ions that affect its dissolution behavior. In the present investigation, solid solutions of (Ca, Mn)CO₃ and (Ca, Cu)CO₃ were synthesized by coprecipitation to study their dissolution in an acidic solution (pH = 5) at 25 °C. The solution chemical analysis results showed that the concentrations of aqueous Cu²⁺ and Mn²⁺ first increased and then decreased with the extension of dissolution time. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations revealed that rhodochrosite (MnCO₃) and malachite (Cu₂(OH)₂CO₃) formed during the dissolution. This suggested that the impurities in calcite might impact the dissolution and precipitation of carbonates in the environment. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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18 pages, 8638 KiB

Open AccessArticle

Mineralogical Study of the Advanced Argillic Alteration Zone at the Konos Hill Mo–Cu–Re–Au Porphyry Prospect, NE Greece

by Constantinos Mavrogonatos, Panagiotis Voudouris, Paul G. Spry, Vasilios Melfos, Stephan Klemme, Jasper Berndt, Tim Baker, Robert Moritz, Thomas Bissig, Thomas Monecke and Federica Zaccarini

Minerals 2018, 8(11), 479; https://doi.org/10.3390/min8110479 - 24 Oct 2018

Cited by 13 | Viewed by 7394

Abstract

The Konos Hill prospect in NE Greece represents a telescoped Mo–Cu–Re–Au porphyry occurrence overprinted by deep-level high-sulfidation mineralization. Porphyry-style mineralization is exposed in the deeper parts of the system and comprises quartz stockwork veins hosted in subvolcanic intrusions of granodioritic composition. Ore minerals [...] Read more.

The Konos Hill prospect in NE Greece represents a telescoped Mo–Cu–Re–Au porphyry occurrence overprinted by deep-level high-sulfidation mineralization. Porphyry-style mineralization is exposed in the deeper parts of the system and comprises quartz stockwork veins hosted in subvolcanic intrusions of granodioritic composition. Ore minerals include pyrite, molybdenite, chalcopyrite, and rheniite. In the upper part of the system, intense hydrothermal alteration resulted in the formation of a silicified zone and the development of various advanced argillic alteration assemblages, which are spatially related to N–S, NNW–SSE, and E–W trending faults. More distal and downwards, advanced argillic alteration gradually evolves into phyllic assemblages dominated by quartz and sericite. Zunyite, along with various amounts of quartz, alunite, aluminum phosphate–sulfate minerals (APS), diaspore, kaolinite, and minor pyrophyllite, are the main minerals in the advanced argillic alteration. Mineral-chemical analyses reveal significant variance in the SiO₂, F, and Cl content of zunyite. Alunite supergroup minerals display a wide compositional range corresponding to members of the alunite, beudantite, and plumbogummite subgroups. Diaspore displays an almost stoichiometric composition. Mineralization in the lithocap consists of pyrite, enargite, tetrahedrite/tennantite, and colusite. Bulk ore analyses of mineralized samples show a relative enrichment in elements such as Se, Mo, and Bi, which supports a genetic link between the studied lithocap and the underlying Konos Hill porphyry-style mineralization. The occurrence of advanced argillic alteration assemblages along the N–S, NNW–SSE, and E–W trending faults suggests that highly acidic hydrothermal fluids were ascending into the lithocap environment. Zunyite, along with diaspore, pyrophyllite, and Sr- and Rare Earth Elements-bearing APS minerals, mark the proximity of the hypogene advanced argillic alteration zone to the porphyry environment. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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12 pages, 1861 KiB

Open AccessArticle

Two-Stage SART Process: A Feasible Alternative for Gold Cyanidation Plants with High Zinc and Copper Contents

by Humberto Estay, Minghai Gim-Krumm and Michelle Quilaqueo

Minerals 2018, 8(9), 392; https://doi.org/10.3390/min8090392 - 07 Sep 2018

Cited by 9 | Viewed by 6279

Abstract

The SART (sulfidization, acidification, recycling, and thickening) process (SP) has been successfully implemented in gold cyanidation plants to address issues associated with high cyanide-soluble copper content ores. However, this process could produce a relatively low grade precipitate, decreasing the sale price when gold [...] Read more.

The SART (sulfidization, acidification, recycling, and thickening) process (SP) has been successfully implemented in gold cyanidation plants to address issues associated with high cyanide-soluble copper content ores. However, this process could produce a relatively low grade precipitate, decreasing the sale price when gold plants have high zinc and copper content in their solutions. A potential option in this case would be the use of a two-stage SART process (TSSP) to produce separate zinc and copper precipitates. The additional equipment involved with this process would increase the capital cost, thereby generating concerns about the optimal range of metal contents that could justify this option. This study presents a methodology to quantify the feasible range of Cu/Zn concentrations that would justify a two-stage SART process. The study is based on a thermodynamic model and a simple economic evaluation. Results show the TSSP is preferred when the Cu/Zn ratio ranges between 0.2 and 1.5 with copper concentration higher than 500 mg/L. The TSSP appears to be a viable option to consider for gold plants having concentrations of copper and zinc higher than 200 mg/L for both metals. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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16 pages, 4168 KiB

Open AccessFeature PaperArticle

Cr Release from Cr-Substituted Goethite during Aqueous Fe(II)-Induced Recrystallization

by Jian Hua, Manjia Chen, Chengshuai Liu, Fangbai Li, Jian Long, Ting Gao, Fei Wu, Jing Lei and Minghua Gu

Minerals 2018, 8(9), 367; https://doi.org/10.3390/min8090367 - 24 Aug 2018

Cited by 15 | Viewed by 4873

Abstract

The interaction between aqueous Fe(II) (Fe(II)_aq) and iron minerals is an important reaction of the iron cycle, and it plays a critical role in impacting the environmental behavior of heavy metals in soils. Metal substitution into iron (hydr)oxides has been reported [...] Read more.

The interaction between aqueous Fe(II) (Fe(II)_aq) and iron minerals is an important reaction of the iron cycle, and it plays a critical role in impacting the environmental behavior of heavy metals in soils. Metal substitution into iron (hydr)oxides has been reported to reduce Fe atom exchange rates between Fe(II)_aq and metal-substituted iron (hydr)oxides and inhibit the recrystallization of iron (hydr)oxides. However, the environmental behaviors of the substituted metal during these processes remain unclear. In this study, Fe(II)_aq-induced recrystallization of Cr-substituted goethite (Cr-goethite) was investigated, along with the sequential release behavior of substituted Cr(III). Results from a stable Fe isotopic tracer and Mössbauer characterization studies show that Fe atom exchange occurred between Fe(II)_aq and structural Fe(III) (Fe(III)_oxide) in Cr-goethites, during which the Cr-goethites were recrystallized. The Cr substitution inhibited the rates of Fe atom exchange and Cr-goethite recrystallization. During the recrystallization of Cr-goethites induced by Fe(II)_aq, Cr(III) was released from Cr-goethite. In addition, Cr-goethites with a higher level of Cr-substituted content released more Cr(III). The highest Fe atom exchange rate and the highest amount of released Cr(III) were observed at a pH of 7.5. Under reaction conditions involving a lower pH of 5.5 or a higher pH of 8.5, there were substantially lower rates of Fe atom exchange and Cr(III) release. This trend of Cr(III) release was similar with changes in Fe atom exchange, suggesting that Cr(III) release is driven by Fe atom exchange. The release and reincorporation of Cr(III) occurred simultaneously during the Fe(II)_aq-induced recrystallization of Cr-goethites, especially during the late stage of the observed reactions. Our findings emphasize an important role for Fe(II)_aq-induced recrystallization of iron minerals in changing soil metal characteristics, which is critical for the evaluation of soil metal activities, especially those in Fe-rich soils. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Mineral Science)

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