Mineralogical Studies Research Articles

MINERALOGICAL, PETROGRAPHIC, AND LITHOCHEMICAL FEATURES OF THE UPPER JURASSIC–LOWER CRETACEOUS SECTION OF THE NORDVIK PENINSULA (NORTH OF EASTERN SIBERIA)

Some intervals of the Jurassic–Cretaceous strata of the Anabar-Lena sedimentary basin have a certain oil and gas production potential, which can be realized in the synchronous offshore horizons of the adjacent territories of the Arctic shelf. Among the most representative objects in this regard are the outcrops of Upper Jurassic and Lower Cretaceous formations of the Nordvik Peninsula. The main data on the composition and structure of this section were obtained mainly at the beginning of the second half of last century. The results of complex mineralogical, petrographic, and lithochemical studies of the Urdyuk-Khaya and Paksa formations of Cape Urdyuk-Khaya of the Nordvik Peninsula presented in here enabled us to identify 10 boundaries for changing of sedimentation regimes of the paleobasin. It was found that the Urdyuk-Khaya Formation was formed mainly in the conditions of the shelf transition zone (moderate deep water) with low rates of terrigenous material intake, some depletion of oxygen in bottom waters, and a trend towards an increase in the depths of the basin. The basal stratum of the Paksa Formation was formed in offshore conditions with periodically occurring dioxic conditions in bottom waters and extremely low rates of terrigenous material intake. The overlying part of the formation was formed in various parts of offshore transition conditions with a gradual decrease in the depths of the basin, an increase in the oxygen content in the bottom layer of water, and the rate of terrigenous material intake. The main provenance area was igneous rocks of mafic, possibly intermediate composition. There was some influence of felsic igneous rocks, or ancient sedimentary rocks rich in quartz. The parent strata were subjected to moderate and severe chemical weathering, in a warm humid climate. The revealed features of the studied strata are similar to the characteristics of the same-age sediments of the lower reaches of the Anabar River, which determines their high correlation potential and allows us to judge the evolution of the western part of the Anabar-Lena basin.

Cretaceous-Paleogene Boundary in the Shapsug Section (Southern Slope of the Northwest Caucasus)

A silicite horizon corresponding to the global catastrophic event of the Cretaceous-Paleogene boundary was found in the flysch sequence of the Shapsug section on the southern slope of the Northwest Caucasus for the first time. Complexes of radiolarians and planktonic foraminifers, which substantiate the age of the sediments, were identified. Mineralogical and analytical studies testify to the presence of tectites, impact minerals, increased iridium content in the boundary layer of the studied section.

Trace element and isotope composition of calcite, apatite, and zircon associated with magmatic sulfide globules

AbstractThe formation of volatile-rich phases in magmatic sulfide systems has been interpreted at least in six different ways. The most popular model attributes their origin to secondary processes, mostly due to the presence of serpentine, chlorite, phlogopite, amphibole, and calcite. While chlorite and serpentine are likely to form as alteration products, the other volatile-rich minerals have the potential to originate in a range of ways, including by primary magmatic processes. Based on mineralogical and petrological studies, it was recently suggested that volatile- and incompatible element-rich halos around sulfide globules may form due to the interaction between three immiscible liquids: silicate, carbonate, and sulfide. This hypothesis was confirmed by experimental data revealing the systematic envelopment of sulfide globules by carbonate melt, indicating their mutual affinity. In this study, we present data on isotopic signatures and trace element distributions of three minerals commonly found in spatial association with sulfides—calcite, apatite, and zircon—to address the question of the source and nature of volatiles and other incompatible elements involved in the formation of the halos. Here we compare our new hypothesis with all the previously proposed explanations to show if they can be consistent with obtained results. Our findings indicate that both mantle and crustal sources play a role in the formation of volatile- and incompatible element-rich halos, strongly correlating with sulfur isotope data previously reported for the sulfide globules in the same intrusions. This correlation confirms the shared origin of sulfides, carbonate and fluids during ore-forming processes, ruling out the secondary origin of volatile-rich phases. The isotope and trace element signatures support the newly proposed hypothesis that volatile- and incompatible element-rich halos could have been formed due to the interaction of immiscible sulfide, carbonate, and silicate melts. The volatile-rich carbonate melt could be sourced from the mantle or it could be added from the crust. Regardless of the origin, carbonate melt and sulfide liquid both immiscible with mafic magma tend to stick to each other resulting in the formation of volatile- and incompatible element-rich halos commonly documented in magmatic sulfide deposits.

A New Feasible Opportunity for Recycling Lead and Silver from Zinc Plant Residues by Flotation

Millions of tons of zinc plant leach residues (ZPLR) have been stockpiled in Iranian hydrometallurgical zinc plants during the last few decades. Due to the low grades of zinc, lead, and silver in these residues, these residues have been abandoned without treatment. The authors of this paper studied zinc plant leach residues (ZPLR) to propose a flotation process for separating and producing lead and silver concentrate. A response surface methodology (RSM) was employed to obtain six models for optimizing the best conditions for lead recovery, lead grade, zinc recovery, zinc grade, silver recovery, and silver grade. In these models, the effect of the different main variables, including density, flotation time, pH, sodium sulfide dosage, and potassium amyl xanthate dosage, was investigated to optimize grades and recoveries. The studied ZPLRs were categorized into two types based on the disposal time, including new and old residues. The chemical analysis showed that the grades of lead, zinc, and silver in the new residues are higher than in the old residues. In a previous mineralogical study, it was found that silver forms in lead and zinc minerals as a solid solution within their structures. The resulting 3D graphs showed that the interacting variables have significant effects on responses. The ANOVA analysis exhibited the order of model significance to be lead grade (F-value of 36.46) > silver grade (19.76) > lead recovery (7.88) > zinc grade (5.63) > silver recovery (5.58) > zinc recovery (4.83). Based on these models, under the conditions of 1126.26 g/cm3 density, 20.83 min retention time, 9.9 pH, 6 kg/t sodium sulfide, and 749.66 g/t potassium amyl xanthate dosage for a new residue type, the recoveries of lead, zinc, and silver were determined to be 51.10%, 11.13%, and 72.85%, with grades of 38.87% Pb, 8.46% Zn, and 1209.11 g/t Ag, respectively. According to the feasibility study results, the presented work is reasonable in terms of technical, economic, and investment potential.

Hypogene Alteration of Base–Metal Mineralization at the Václav Vein (Březové Hory Deposit, Příbram, Czech Republic): The Result of Recurrent Infiltration of Oxidized Fluids

The Václav vein (Březové Hory deposit, Příbram ore area, Czech Republic) is a base–metal vein containing minor Cu-Zn-Pb-Ag-Sb sulfidic mineralization in a usually hematitized gangue. A detailed mineralogical study using an electron microprobe revealed a complicated multistage evolution of the vein. Early siderite and Fe-rich dolomite were strongly replaced by assemblages of hematite+rhodochrosite and hematite+kutnohorite/Mn-rich dolomite, respectively. In addition, siderite also experienced strong silicification. These changes were associated with the dissolution of associated sulfides (sphalerite, galena). The following portion of the vein contains low-Mn dolomite and calcite gangue with Zn-rich chlorite, wittichenite, tetrahedrite-group minerals, chalcopyrite, bornite, and djurleite, again showing common replacement textures in case of sulfides. The latest stage was characterized by the input of Ag and Hg, giving rise to Ag-Cu sulfides, native silver (partly Hg-rich), balkanite, and (meta)cinnabar. We explain the formation of hematite-bearing oxidized assemblages at the expense of pre-existing “normal” Příbram mineralization due to repeated episodic infiltration of oxygenated surface waters during the vein evolution. Episodic mixing of ore fluids with surface waters was suggested from previous stable isotope and fluid inclusion studies in the Příbram ore area. Our mineralogical study thus strengthens this genetic scenario, illustrates the dynamics of fluid movement during the evolution of a distinct ore vein structure, and shows that the low content of ore minerals cannot be necessarily a primary feature of a vein.

Ore Characterization and Quality Control Aspects of Gold Cyanidation: The CIL Plant as a Case Study in Sudan

Mineralogical and chemical studies are key to mineral processing because they present the problem of low-grade ores to the metallurgist or mineral processing engineer. Quality control operations are also significant in obtaining good products by flowing the sequences of processes. In this study, the ore was characterized, and quality control issues were discussed. Results showed that the gold grade is 9.7 g/ton, the minerals are mainly silicates, and the pH of the ore is high, which means that without pre-treatment, i.e., roasting, oxidation, etc., it can be cyanided directly. Therefore, the CIL plant could recover more than 90% gold. In quality control of the plant, from each unit at a different time, a representative sample and an accumulative sample were collected and then subjected to analysis like fineness and solid percentage, moisture, and conditions of cyanidation. The results showed steady operation conditions for each unit.

Investigation of geochemically induced permeability alteration in geothermal reservoirs and its implications for sustainable geothermal energy production

Geothermal resources constitute a significant portion of the world's low-carbon, renewable energy potential, with about 75% classified as low-temperature. One such potential resource exists in Precambrian basement rocks underlying the Williston Basin in southern Saskatchewan, Canada, with a reservoir temperature of 120 °C. However, geochemically induced permeability alteration in these highly reactive low-temperature granitoid resources poses a significant risk to long-term heat production. To assess and potentially mitigate this risk, we conducted a geochemical and mineralogical study of both altered and unaltered samples. Our findings facilitated the parameterization of geochemical simulations of water-rock interactions to predict mineral volume changes and, by extension, draw inferences on porosity and permeability changes resulting from these interactions. The simulations indicate an increased mineral volume in both samples, yet geothermal alteration of the unaltered, and thus more reactive, rocks induced relative mineral volume changes about 30% greater than those in the altered rocks. The resulting absolute change in porosity is 0.5 vol% for the unaltered rocks and 0.35 vol% for the altered rocks. Utilizing an empirical porosity-permeability relationship, the computed change in permeability indicates that the unaltered basement rock experienced a greater change in total permeability than the altered basement rocks. Additional calculations demonstrate the sensitivity of the porosity-permeability equation to critical porosity and power exponent, forecasting various scenarios with permeability changes ranging from 1.0 × 10−13 to 1 × 10−20 m2. Consequently, we infer that altered, permeable zones of the examined Precambrian basement rocks are likely to offer favourable conditions for sustained, multi-decade heat production, and thus should be targeted over less altered zones to justify initial capital expenditures. Globally, geothermal heat extraction from these rocks remains an underexplored yet promising resource for generating reliable, low-carbon renewable energy, crucial in our efforts to decarbonize the global economy.

Mineralogical and geochemical studies of shales from Kopili Formation, Dima Hasao district Assam, North East India: Insights into diagenesis, deposition and provenance

The Eocene Kopili Formation in the Assam foreland basin records sediment sources, tectonic activity and depositional environments following the India-Eurasia collision. Mineralogical and geochemical analysis of these shales exposed near Garampani, Assam, NE India was conducted to study the diagenesis, palaeoweathering, palaeosalinity, redox conditions, tectonic settings and provenance. The Kopili Formation is composed of mainly shale with thin beds of limestone, black shale and sandstone and these units overlie the Upper Sylhet Limestone. The presence of goethite-rich phosphatic nodules, secondary precipitation within the fissile planes of shale and the occurrence of anatase, talc, smectite and chlorite suggest diagenesis. The prevalence of kaolinite and mean Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), Al2O3/MgO and Rb/Sr values of 86.73, 97.26, 16.36 and 1.32, respectively indicates extensive source rock weathering in humid tropical climate. The Index of Compositional Variation (ICV) values ranging between 0.47 and 2.38 also signify high weathering and tectonically active basin. The Sr/Ba ratio 0.34 ± 0.27 (mean±2σ) suggest overall freshwater basin. The Ni/Co (2.84 ± 2.29), V/Cr (1.65 ± 0.45) and Ce/Ce∗ (0.97 ± 0.63) suggest fluctuating redox environment. The samples predominantly cluster in continental island arc domain on the Th-Sc-Zr/10, La-Th-Sc and Th-Co-Zr/10 discriminant diagrams. Elemental ratios of Th/Sc, La/Sc, Cr/Th with average 0.91, 3.18, 10.13 respectively and La/Th-Hf plot suggest a felsic source rock. The Kopili shale was deposited in freshwater, continental island arc basin with fluctuating redox conditions, receiving sediments from weathered Himalayan granites and gneisses under a warm and humid climate. Subsequently, they underwent diagenetic alteration by low-pH fluid(s).

Mineralogical and radiological studies on some Paleozoic yellow ochre deposits in Southwestern Sinai, Egypt

Yellow ochre is the basic material used in the manufacture of yellow oxide (a commercial product). Yellow ochre samples were taken from three different formations in southwestern Sinai: Abu Hamata, Um Bogma, and Abu Zarab. Yellow ochre occasionally exists in Abu Hamata Formation particularly in El Ferah area, associated with Fe–Mn ore in Wadi El Sahu (Um Bogma Formation) and in Himayer area (Abu Zarab Formation). The XRD analysis of the raw material reveals that they are mainly composed of goethite, which is associated with quartz and kaolinite in El Ferah area, hematite, kaolinite and quartz in Himayer area, and kaolinite, gypsum and quartz in Wadi El Sahu. The commercial product is mainly composed of goethite, quartz, and calcite. The heavy mineral investigation shows that some yellow ochre samples contain zircon and rare earth sulfate which may be responsible for the radioactivity of ochre due to their thorium and uranium content. The average values of specific radio-activities of most radionuclides in the samples of Himayer area I and II, and El Sahu I are higher than the respective world averages, while their activities are lower in El Ferah and El Sahu II. Th/U and Ra/U ratios exhibit vigorous changes in physico-chemical conditions during uranium leaching and deposition. Most of the radiological parameters in the ferruginous sediment and commercial product samples from El Ferah, El Sahu II, and Himayer II are lower than the recommended international values but higher than those from Himayer I and El Sahu I samples. The plotted hierarchical cluster analysis (HCA) exhibits that the main contributors for the hazards of these sediments and their commercial product are 238U, 232Th and 226Ra in Himayer I &II, commercial products, and El Ferah area, 232Th and 226Ra in El Sahu II , 232Th, 40K and 226Ra in El Sahu I.

Source Minerals for the Release of Salinity in the Groundwater: A Case Study of Pratapgarh District, Uttar Pradesh, India

ABSTRACT The aim of this study is to determine the salinity of groundwater, identify the nature of its sources, and to understand the physicochemical conditions that cause high level of salinity to be discharged into groundwater. There are several factors that influence groundwater salinity, including water quality, soil type, irrigation techniques, and groundwater depth. A total of 40 ground water samples were collected from dug wells, tube wells, and hand pumps in salinity-affected areas and analysed using physicochemical variables. A total of 11 sediment samples were collected and analysed for lithology and mineralogy. Due to high level of cations and anions in the groundwater, the study area is highly contaminated. It was observed that the leaching of salt is highly dependent on sediment types and salt-bearing minerals. Attempts were also made to determine the various depth zones responsible for release of salt in shallow aquifers. For sedimentological and mineralogical studies, a piezometer was installed at a maximum depth of 33 m below the ground surface. Based on the results of the study, it was observed that groundwater chemistry is primarily influenced by water-rock interactions, ion exchange processes, weathering (carbonate and silicate), and evaporation. These research findings will contribute to more effective sustainable groundwater management in areas with water scarcity and it will also boost the Indian economy.

Anomalous tellurium enrichment associated with gold mineralization: A mineralogical and isotopic study of the Yongxin Te-Au deposit, northeast China

The Yongxin tellurium-gold (Te-Au) deposit, a large epithermal deposit in the Duobaoshan polymetallic metallogenic belt (DPMB) within eastern section of the Central Asian Orogenic Belt (CAOB), is mainly hosted by syenogranite and mylonite. However, the Te-Au occurrence, precipitation mechanism and genesis in this deposit remain elusive. In this study, pyrite, the primary host of Te-Au mineralization, was studied utilizing multiparametric techniques such as scanning electron microscope (SEM), electron probe microanalysis (EPMA), in-situ laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) and femtosecond laser ablation coupled multi-collector inductively coupled plasma mass spectrometry (fs LA-MC-ICP-MS). The results show that there are three generations of pyrite termed here as Py1, Py2 and Py3. The coarse euhedral Py1 and fine vein Py2 contain negligible to low contents of Te and Au, whereas the anhedral aggregated Py3 with porosity and grain boundary (GB) shows the highest concentrations of Te and Au. Representative LA-ICP-MS profiles show that Te-Au occurs either as solid solution in the Py1 and Py2 or submicroscopic Au-Ag-Te-Bi inclusions, electrum and native gold in Py3. Thermodynamic data of telluride and sulfide show that the Te-Au was deposited under relatively oxidizing conditions with values of log f Te2 ranging from −15.2 to −11.2 and log f S2 from −16.7 to −12.1. at 200 °C. We infer that fluid mixing and fluid-rock interaction were the dominant mechanisms that triggered the precipitation of Te-Au in the Yongxin Te-Au deposit. Geochemical and geochronological data indicate that the likely source of Te is Te-rich oceanic sediments originating from the Western Pacific Plate. Pyrite and telluride from the gold deposits can be potential targets for Te exploration in the DPMB.

Mineralogical, alteration and fluid inclusion studies of the mineralization occurrence at Tazehkand, northeast of Zanjan, NW Iran

Mineralogical, alteration and fluid inclusion studies of the mineralization occurrence at Tazehkand, northeast of Zanjan, NW Iran

Influence of age of fermented Terminalia chebula fruit extract in shell lime: An ancient lime putty production technique adopted in Indian heritage structures

The study examines the influence of fermentation age of 5% w/v extract (K5%) of Terminalia chebula fruit in shell lime, using a 0.75 K5%-to-binder ratio. The carbon dioxide evolution, UV-Spectrometric analysis of K5% followed by Gas chromatography and mass spectroscopy (GC-MS) of the slaked putty variants, identified the predominance of organic acids, fatty acids, and esters. The 90th day physical, mechanical, and durability testing confirmed the lowest water-accessible porosity at 31.07 ±0.11% v/v in K5%-4-90, with capillary porosity trending as K5%-4-90<K5%-7-90<K5%-14-90<R-90<K5%-1-90, affecting compressive strength. Mineralogical and morphological studies confirmed the formation of calcite (CaCO3) polymorphs and calcium oxalates via the oxalate-carbonate pathway. Further, thermogravimetric analysis (TGA) revealed the highest %CaCO3 in K5-4-90 and K5-7-90 samples, linked to carbonation extent. The study specifies that K5% at the 4th and 7th days of fermentation age significantly alters putty characteristics, supporting its widespread application and internal and external finishes in heritage structures.

Stepwise oxidation of refractory pyrite using persulfate for efficient leaching of gold and silver by an eco-friendly copper(II)-glycine-thiosulfate system

Chemical oxidation is a promising pretreatment method for refractory pyrite enclosure to enhance Au/Ag extraction. Here, persulfate was employed for stepwise oxidation of a refractory pyrite concentrate with encapsulated Au/Ag: (i) pyrite oxidation began with heating-activation persulfate, where hydroxyl radical (•OH) acted as the primary oxidative species for fast-dissolving pyrite into Fe ions; (ii) pyrite self-dissolved Fe ions were in-suit used as a moderate activator of persulfate to generate •OH for sustainable oxidizing pyrite at room temperature. Mineralogical studies have confirmed that oxidation of the sulfide enclosure (FeS2) significantly reduced the particle size of pyrite, accompanied by pores creation and an increase in specific surface area. The variation of microstructure liberated Au and Ag particles to lixiviants for extraction, significantly improving leaching efficiency in an eco-friendly copper(II)-glycine-thiosulfate system to 92.2 % for Au and 88.6 % for Ag, respectively. This work provides a promising process for separating precious metals from refractory pyrite.

Studies to determine the influence of the basicity modulus on the qualitative and quantitative indicators of production technology and the material composition of the sintere

In recent years, the increase in the efficiency of the blast furnace process is largely associated with the use of sinter with improved metallurgical properties. In the blast furnace charge of PJSC NLMK, the share of sinter is 60–75% with a change in basicity from 1.3 to 1.8. Studying the material composition of agglomerates of different basicity and their characteristics allows us to adjust the technological process and determine the optimal modulus of basicity depending on specific conditions. Agglomerates with a basicity index of: 1.3; 1.4; 1.5; 1.6; 1.7 and 1.8. As a result of the research, it was established that the maximum vertical sintering speed and specific productivity of the sintering process correspond to the basicity of the sinter of 1.7. The influence of the basicity of the agglomerate on its strength is extreme, with a basicity of 1.4 the minimum strength of the agglomerate was obtained. Increasing the basicity of the agglomerate by more than 1.4 monotonically increases its strength. The nature of the change in the strength of the ag-glomerate with a change in basicity is determined by the mineral composition of the binder and is associated with a decrease in the proportion of glass in the structure of the agglomerate and an increase in the proportion of the crystalline silicate-ferrite binder. When studying the material composition, it was established that the samples of agglomerates have an identical phase composition, but differ in the phase ratio. Crystallization of calcium ferrites in contact with iron oxides contributes to the strengthening of the agglomerate, and the presence of impurities (Al, Si, Mg) in them increases the melting point. As a result of mineralogical and analytical studies, it was established that the highest metallurgical properties are found in agglomerates with a basicity modulus of 1.6–1.8.

Facies variability and depositional cyclicity in central Northern Switzerland: insights from new Opalinus Clay drill cores

The Opalinus Clay, a silty to sandy claystone formation, Early to Middle Jurassic (Toarcian and Aalenian) in age, has been selected as the host rock for deep subsurface disposal of radioactive waste in Switzerland. Over the past thirty years, numerous geotechnical, mineralogical, and sedimentological studies have been conducted on the Opalinus Clay within the framework of the Nagra (National Cooperative for the Disposal of Radioactive Waste) deep drilling campaigns and the Mont Terri Project, an international research program dedicated to the study of claystone. The present study aims to unravel the variability of the lateral and vertical facies of the Opalinus Clay in central Northern Switzerland and to place this variability in a regional and basinal context. Analyses of new cores drilled in central Northern Switzerland, including petrographic, mineralogical (X-ray diffraction, multi-mineral interpretation), geochemical (X-ray fluorescence), statistical (non-metric multidimensional scaling analysis), and bedding dip and azimuth data, shed new light on the depositional facies and the spatial and temporal variability of the Opalinus Clay. Petrographic descriptions encompass nine new drill cores using a revised subfacies/facies classification scheme based on texture (colour, grain size, bedding) and composition (mineralogy). Particularly, one new subfacies (SF6) is described and interpreted as mass-wasting deposits. The drill cores are correlated laterally using specific marker horizons. This correlation is achieved by combining thorough facies investigations with lithostratigraphy, biostratigraphy, and chemostratigraphy. Six to seven small coarsening-upward cycles and two long-term coarsening-upward sequences can be interpreted as regressive trends. The observed trends are influenced by the interplay between sediment supply, eustatic sea level change, synsedimentary subsidence, but also the palaeogeographic configuration in an epicontinental sea, provenance and delivery of sediments, current dynamics and climate change. Finally, combined results show that the current dynamics in the Opalinus Clay has been underestimated until now and new depositional models, including the occurrence of drift deposits, are discussed.

The Yadovitaya fumarole, Tolbachik volcano: A comprehensive mineralogical and geochemical study and driving factors for mineral diversity

Active volcanic fumaroles are one of the most spectacular natural objects in terms of mineral diversity. The Great Tolbachik Fissure Eruption (GTFE) (Kamchatka) fumaroles are renowned for its exceptional number of mineral species. The total number of minerals that have been reliably identified from this particular locality exceeds 400, which is approximately 6.5 % of all known minerals to date. In this study, we employ a comprehensive approach (bulk chemistry, microprobe analysis, powder X-ray diffraction, HR X-ray computed tomography, and 34S, 18O, and 65Cu isotope measurements) to study the distribution of primary exhalation and secondary mineral assemblages and to reveal the driving factors responsible for the unique mineral diversity in the Yadovitaya fumarole. High oxygen fugacity, the interaction of minerals with atmospheric oxygen and water from seasonal precipitation (leading to abundant hydrated mineral associations), temperature conditions controlling the spatial distribution of mineral-forming components, gas-rock interactions, and basaltic scoria morphology perfect for the crystallization of various minerals are some of the factors revealed. The combination of these factors caused a stepwise mineralization resulting in 12 zones of the Yadovitaya fumarole with characteristic mineral assemblages. The described mineralogy of the Yadovitaya fumarole demonstrates a consistent spatial evolution of fumarolic mineral assemblages that vary in complexity, chemistry, and interaction patterns with the surrounding environment. The examination of mineralogical and geochemical data yields novel insights into the active volcanic systems that are associated with the formation of distinct oxidation-type fumaroles.

The mineralogical composition of the zeolitic rocks of Santorini Island and their potential use as feed additives and nutrition supplements

AbstractThe zeolitic rocks of Akrotiri, on Santorini Island (Aegean Sea, Greece), can be grouped according to the zeolite minerals present. The first group includes zeolitic rocks that contain only clinoptilolite, the second group contains clinoptilolite and mordenite and the third group contains only mordenite. Clinoptilolite accounts for up to 56 wt.% and mordenite for up to 69 wt.% of the rocks. All samples contain feldspars (8–36 wt.%), clay minerals (6–8 wt.%), quartz (3–6 wt.%), opal-CT (2 wt.%), amphibole (2–4 wt.%) and amorphous materials (4–7 wt.%). The studied samples were classified chemically as andesites or dacites. The ammonium-exchange capacity of the studied samples was 104–158 meq 100 g–1. According to Commission Implementing Regulation (EU) No. 651/2013, zeolitic rocks that contain ≥80 wt.% clinoptilolite, ≤20 wt.% clay minerals and are free of fibrous minerals and quartz can be used as feed additives in animal husbandry. Zeolites with fibrous habit (mordenite, erionite, secondarily roggianite and mazzite) and SiO2 minerals such as quartz, cristobalite and tridymite can be dangerous to both humans and animals. The mineralogical study showed that, due to their low clinoptilolite content and the presence of both quartz and fibrous mordenite, the studied zeolitic rocks do not conform with European Regulation No. 651/2013. As a result, their use as feed additives and nutrition supplements is prohibited.

Marine Fe cycling linked to dynamic redox variability, biological activity and post-depositional mineralization in the 1.1 Ga Mesoproterozoic Taoudeni Basin, Mauritania

The concentration of redox sensitive trace metals (RSTEs) and their isotopic composition preserved in Precambrian marine sediments, are critical for the reconstruction of ocean–atmosphere oxygenation history. Particularly, the concentration of Fe, its redox speciation, and isotopic distribution, have gained widespread use for inferring the biogeochemical processes that controlled Fe cycling in Precambrian oceans linked to the reconstruction of Earth surface redox budget. However, questions remain about the biotic and abiotic processes involved in Fe cycling in these ancient oceans, including the impact of post-depositional alterative processes on the reliability of the Fe redox proxy. Here we present a multi-proxy mineralogical and geochemical study of the ∼1.1 Ga Atar and El Mreiti strata of the Taoudeni Basin in Mauritania, to better constrain pathways involved in Fe cycling, linked to Fe mineralogy, redox speciation, isotopic ratios during this time and metamorphism. We compare unmetamorphosed sedimentary deposits with facies metamorphosed by dolerite sill intrusion. The results reveal the occurrence of diagenetic Fe minerals in the basal unmetamorphosed samples associated with light δ56Fe signatures, reflecting dominant anoxic conditions that promoted microbial dissimilatory Fe reduction. Notably, δ56Fe composition of these rocks reveal several fluctuations in evolving seawater redox state from oxic to anoxic/sulfidic conditions associated with changes in sea level stand and periods of full bottom water oxygenation and redox stratification. Overall, Ce anomalies suggest a general up sequence increase in seawater oxygen content. Metamorphosed rocks display heterogeneous δ56Fe distribution, consisting of light and heavy signatures associated with secondary Fe-bearing minerals produced by metamorphic and metasomatic overprinting of carbonated rocks by hot circulating fluids. The results thus indicate metamorphic overprinting of primary seawater δ56Fe promoted by increased mobility of reactive Fe during post-depositional metamorphic transformation. They show that post-depositional metamorphic/metasomatic overprinting complicates direct reconstruction of seawater biogeochemical Fe cycling and redox state using δ56Fe systematics.

Improve flotation efficiency of refractory tungsten ore and reduce carbon emission in flotation process: A case study of Sandaozhuang deposit in Henan, China

With the rapid consumption of tungsten ore resources which were easy to beneficiation, the low-grade refractory scheelite has become the main source of tungsten production. In this study, a new reagent recipe was proposed to improve scheelite flotation efficiency and reduce carbon emission in flotation process by taking Sandaozhuang strongly altered ore as an example. The mineralogical study indicated that the content of WO3 in this ore was 0.0952 %, and 83.16 % of WO3 occurred in scheelite. The high content of calcium-containing gangue, easy-argillation gangue and fine scheelite jointly made it difficult to recover scheelite efficiently. The batch flotation tests shown that under the conditions of Na2CO3 1800 g/t, SS 600 g/t, SG 60 g/t, engine oil 20 g/t and FX-8 180 g/t, a rough concentrate with WO3 grade of 1.503 % and WO3 recovery of 79.40 % can be obtained. The industrial tests and application shown that this new reagent recipe had good industrial applicability and stability, and was conductive to improve the efficiency of the whole flotation process. The economic and environmental benefits analysis found that the application of this new reagent recipe in a 10,000 t/d scheelite flotation plant can create annual additional economic value of more than CNY 20 million, and reduce annual carbon emissions by more than 5000 t. Therefore, this new reagent recipe was worth popularizing and applying in similar refractory scheelite flotation plants.