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•Calcium hydroxide addition enhanced the unconfined compressive strength of GMFs.•Acid neutralisation and As retention capacity of GMFs highly improved with 3 wt.% CH.•The mechanism ...of As leaching from GMFs was predicted to be diffusion.•The hydration products of GMF-3C accounted for approximately 22.5 wt.%.
In this study, metallurgical-slag-based binder (MSB) with different dosages of calcium hydroxide (CH) was mixed with high-arsenic-containing mine tailings (HAMT) to form green mining fill samples (GMFs) for As solidification/stabilisation (S/S). The As leaching characteristics of the GMFs were evaluated using pH-dependent leaching tests, semi-dynamic leaching tests and toxicity leaching tests. The effective diffusion coefficient (De) decreased from 6.98 × 10−14 to 5.90 × 10−15 cm2/s and the leachability index (LI) increased from 13.53 to 14.73 after 3 wt.% CH was added to the GMFs. The GMFs containing 0 wt.% CH (GMF-0C) and those containing 3 wt.% CH (GMF-3C) reached pH = 2 with acid addition amounts of 9.0 meq/g-dry and 9.3 meq/g-dry at 90 d curing time, and the maximum As leaching concentrations of GMF-0C and GMF-3C reached 10.47 mg/L and 7.47 mg/L, respectively, indicating that GMF-3C exhibited better acid neutralisation and As retention capacities than GMF-0C. Further, a Tescan Integrated Mineral Analyser (TIMA) was used to analyse the dominant hydration products of GMF-3C, which revealed that calcium silicate hydrate, CASH, ettringite and zeolite phases represented approximately 22.5 wt.% of the products. These results provide an understanding regarding the safe large-scale utilisation of GMFs.
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(a) μ-XRF mapping and Nb content distribution maps of dolomite-type Nb-REE-(Fe) ore, displaying the representative magmatic Nb mineralization; (b) μ-XRF mapping and Nb content ...distribution maps of fluorite-type (banded) Fe-REE-Nb ore, showing the typical hydrothermal Nb mineralization; (c) back-scattered-electron images of different kinds of niobium-bearing minerals in Bayan Obo Fe-REE-Nb deposits; (d) niobium-bearing mineral compositions (Wt %) of various Fe-REE-Nb ores in Bayan Obo deposit.
•The Bayan Obo Fe-REE-Nb deposit contains huge amount of niobium resources.•Niobium occurrence and typical mineral compositions of different types of Fe-REE-Nb ores are determined.•Hydrothermal process plays an important role in controlling the migration and mineralization of niobium.
The Bayan Obo Fe-REE-Nb deposit is the largest rare earth deposit in the world, which also contains huge amounts of niobium resources, hosting 83% of industrial reserves in China. The previous researches focused on the REE mineralogy, mineralization age and REE source, whereas only a few studies paid attention to the genesis of Nb mineralization. The REE and Nb might present systematic mineralization difference as the degree of REE and Nb mineralization is distinct in different types of ores in host dolomite. Many complicated factors such as low grade, fine-grained dissemination and complex mineral composition are the main obstacles to hinder the effective utilization of Nb. In this study, a variety of niobium-bearing minerals have been identified, including aeschynite, fergusonite, columbite, pyrochlore, fersmite, baotite, and ilmenorutile. The distribution regularity of niobium in various types of ores in the giant Bayan Obo Fe-REE-Nb deposit is asserted. In massive Nb-REE-Fe ore and dolomite-type Nb-REE-(Fe) ore, niobium-bearing minerals are represented by columbite, while niobium mineralization in aegirine-type Nb-REE-Fe ore is characterized by pyrochlore and aeschynite. The major niobium-bearing mineral in the riebeckite -type Nb-REE-(Fe) ore and fluorite-type (banded) Nb-REE-Fe ore is aeschynite, and major niobium-bearing mineral in biotite-type Nb-REE-Fe ore and diopside-type niobium ore is fergusonite. The μ-XRF results and SEM observations display that columbite contains dolomite, magnetite and monazite inclusions and show obvious genetic links with apatite. Columbite, apatite and magnetite in massive Fe-REE-Nb ore and dolomite-type Nb-REE-(Fe) ore occur at same mineral generation, both having magmatic origins. Pyrochlore from aegirine-type Fe-REE-Nb ore also showsclose genetic relationship with apatite, which is formed by fractional crystallization during the magmatic stage of carbonatite. Aeschynite in fluorite-type (banded) Fe-REE-Nb ore, riebeckite-type Nb-REE-(Fe) ore, and fergusonite in biotite-type Fe-REE-Nb ore and diopside-type niobium ore are large in grain size and have hydrothermal origins. Moreover, intensive Nb mineralization in a series of ores related to fluoritization and alkali-metasomatism demonstrates the critical role of hydrothermal process in niobium enrichment in the Bayan Obo deposit. Fluid-rock interaction leads to the generation of alteration minerals, such as fluorite, biotite and aegirine, and contributes to a slash of K, Na and/or F in hydrothermal fluids, facilitating precipitation of niobium-bearing minerals. By using scanning electron microscope (SEM), X-ray energy dispersive analysis (EDS), Micro-XRF spectral analysis (μ-XRF) and TESCAN Intergrated Mineral Analysis (TIMA), detailed mineralogical study on niobium occurrence and typical niobium mineral compositions in various types of Fe-REE-Nb ores was conducted to provide an important reference for mineral processing and niobium prospecting and give a deeper understanding of the niobium anomalous enrichment mechanism of the Bayan Obo Fe-REE-Nb deposit.
In the complex fluid environment of subterranean rocks, some mineral components are easily hydrated, which hinders the accumulation and utilization of hydrocarbon. However, the nature and ...distribution of these key substances remain unclear. This study aims to provide a fresh perspective on the substances that impede the storage and extraction of hydrocarbon of the world's largest conglomerate oilfield. Using a variety of qualitative, semi-quantitative, and quantitative methods, including X-ray diffraction, secondary electron imaging, elemental spectroscopy, and Tescan-Integration-Mineral-Analyzer (TIMA), our experimental results show: (1) For the first time, water-sensitive clay minerals on the surfaces of gravel particles in tight conglomerates in China have been identified. Although the matrix composition contains less than 4.2% clay minerals on average, certain gravels contain over 72.7% clay minerals. These clay minerals are primarily composed of smectite, which is highly water sensitive, followed by chlorite, which poses significant challenges to hydrocarbon extraction; (2) The distribution of clay minerals on a single gravel surface is relatively uniform, enabling their interaction with fracturing fluid and exacerbating reservoir degradation. The total content of the illite-smectite mixture in the conglomerate can reach approximately 12%, with skeleton particles (gravel) containing more than 30% of this mixture. There are significant differences in the degree of clayiness among different types of gravel, which can be classified as high clayey, medium clayey, or low clayey. The evenly distributed illite-smectite mixed layer on the gravel surface allows complete contact with the fracturing fluid, resulting in severe reservoir damage; (3) Gravel particles with a size range of 8.88 μm–10.73 μm contain the highest concentration of illite-smectite mixture, which is identified as a major factor contributing to reservoir damage.
•The storage and mobility of hydrocarbon in the subsurface are intricately linked to mineralogy.•The illite-smectite mixtures significantly impede the oil exploitation in tight conglomerates.•The proportion of illite-smectite mixture on skeleton particles, commonly referred to as gravel, can exceed 30%.•Gravels ranging in size from 8.88 μm to 10.73 μm exhibit the highest concentration of illite-smectite mixture.
This study aims to shed light on the elemental and mineralogical mechanisms controlling the storage and flow performances of tight conglomerates. This is achieved through the application of Field ...Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectrometer (EDS), TESCAN Integrated Mineral Analyzer (TIMA), and geophysical logging data.
The findings suggest that augmenting the Mg and CaO content in silicates can markedly enhance the storage capacity of tight conglomerates within the Upper Wuerhe Formation. Chlorite exerts a positive influence on the evolution of reservoir porosity, whereas an escalation in Na content does not foster the development of reservoirs with superior physical attributes. A reduction in the chemical index of alteration (CIA) facilitates the creation of a more expansive pore space, while an elevation in the index of component variation (ICV) augments porosity and diminishes mud content, albeit it may also curtail oil content. It is pertinent to note that an increase in ICV is not invariably advantageous. The emergence of orthoclase results in a decrease in porosity and an enhancement in permeability, whereas the progression of kaolinite adversely affects reservoir porosity.
The conclusion may yield significant insights for hydrocarbon exploration in these regions, as well as in reservoirs exhibiting analogous lithologies.
•The porosity of the conglomerate increases with Mg and the chlorite content.•Element and mineral properties determine the physical properties.•Geophysical and geochemical data can be integrated to study pores.
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•The total rare earth elements contents for the high ash coal samples was ≥ 225 ppm.•LREEs exhibited a greater association with the mineral matter.•HREEs manifest a greater affinity ...for the organic fraction.•HREEs were distributed with kaolinite dispersed in cleats of the carbon matrices.•A Coutlook ≥ 0.88 for both coals suggests a potential promising REE source.
Conventional deposits of rare earth elements (REEs) cannot meet the high demand for REEs globally. Therefore, the prospecting of REEs from alternative sources like high ash coal is vital. In this study, coal discard and “Run of Mine” (ROM) coal were studied to evaluate the abundance and association of REEs in these materials. The TESCAN Integrated Mineral Analyzer (TIMA) and X-ray diffractometer (XRD) techniques were employed to determine the mineralogy of the coal samples. TIMA was further utilized to investigate the REE associations and distributions, whilst the inductively coupled plasma-mass spectrometry (ICP-MS) was used to quantify the amount of REEs in the coal samples. Quantitative analysis results revealed that the total REE content in the coal discard and ROM coal was above 225 ppm. Furthermore, the results show that the dominant REE-bearing minerals in the discard and ROM coal samples were kaolinite, pyrite, and hematite. In addition, the heavy REEs (HREEs) displayed a strong affinity for the organic macerals and were enriched in the ROM coal. The encouraging results of significantly light REEs (LREEs) relative to HREEs in both coals suggest they are viable prospects for REE extraction. Hydrometallurgical leaching is therefore recommended to assess the potential for REE recovery from these sources.
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•Co-existing pyrite and calcite with uranium minerals play a significant role in ISL of uranium.•Gypsum produced by pyrite and calcite in CO2 + O2 environment disadvantages the ...leaching of uranium.•Secondary hexavalent uranium minerals will be produced in the ore layer of a neutral environment.
Oxidative weathering of pyrite, a widespread iron sulfide mineral, is crucial for the uranium mineralization in sandstone-hosted uranium deposits and the ore utilization leaching under manual intervention. To understand the behavior of pyrite under CO2 + O2 leaching conditions in sandstone-hosted uranium deposits, samples of uranium ore from the mineralized zone of the Qianjiadian IV uranium deposit located in the lower section of the Yaojia Formation were collected for this study. The stirring leaching experiment was carried out through the processes of the pyrite-bearing uranium ore samples thinned before and after the reaction, followed by an optical microscopic study and the TESCAN Integrated Mineral Analyzer analysis, and finally, the thermodynamic simulation by making use of PHREEQC3.0.
The results revealed the following: (1) The dissolution particles of pyrite become smaller, which may increase the porosity of the ore layer and the exposure ratio of uranium minerals. And more soluble pyrite with a high free surface will be more competitive with uranium minerals for the consumption of O2. (2) The ion (Fe2+) produced by the dissolution of pyrite will be oxidized to Fe3+ by excess O2 (4 mol), which provides an oxidant for the oxidation of uranium minerals, and the generated SO42- will combine with the Ca2+ released from calcite to form a permanent precipitate of gypsum, which may block pores and cover the uranium ore. (3) Pyrite and calcite will consume O2 and CO2 in the injection system, thus jointly inhibiting the leaching of uranium minerals. After the injection of excessive CO2 and O2, the concentration of Ca2+, SO42-, Fe3+, UO22+, and HCO3– in the system will continue to accumulate, resulting in the secondary precipitation of calcite, co-precipitation of gypsum, iron minerals, colloids, and hexavalent uranium minerals, resulting in plugging pores and seriously affecting the effective leaching of uranium.
This study contributes to the understanding of the behavior of pyrite during uranium recovery through CO2 + O2 leaching. It also contributes to the understanding of quantitative uranium mineralization in sandstone-hosted uranium deposits and process parameters in in-situ leaching (ISL) of uranium.
Tima (Niger-Congo, Sudan) has two morphological means to express contrast: focus marking and selective marking. We take the distribution of both marking options and their interaction as evidence for ...a broad approach to contrast, the latter being a gradient phenomenon rather than a categorical one. We show for Tima that exhaustivity and unexpectedness play a role in determining the strength of the contrast, with the selective marker and focus marker occurring with weaker and stronger types of contrast respectively. While the selective marker signals the existence of a set of alternatives singling out one alternative, the focus marker requires that the information under focus is either exhaustive or unexpected.
The collection of representative modal mineralogy data as well as textural and chemical information on statistically significant samples is becoming essential in many areas of Earth and material ...sciences. Automated Scanning Electron Microscopy (ASEM) systems provide an ideal solution for such tasks. This paper presents the methods and techniques used in the recently developed TESCAN Integrated Mineral Analyzer (TIMA-X) with Version 1.5 TIMA software. The benefits from the use of a fully integrated quantitative energy-dispersive X-ray spectrometry (EDS) and an advanced statistical approach to ASEM systems are demonstrated. Typically, the system can handle more than 500,000 X-ray events per second. Using a common spectral total of 1000 events this represents the acquisition of 500 spectra per second. A number of measurement modes is available to make the most effective use of these spectra depending on the application. For a back-scattered electrons (BSE) map combined with EDS data with spatial resolution of 10 µm, this represents the high-resolution measurement of c. 1 cm2 of a thin section or a polished rock surface in 30 minutes. A patented X-ray spectrum clustering algorithm that lowers the chemical detection limit is described and an example of its use is shown. The modal and textural (liberation, association, size etc.) data produced are statistically robust and provide information across a broad range of Earth and material sciences. A comparison with some other available instruments is also provided together with a number of case studies.
For many years, the most common acid practice for sandstone acidizing is based on mud acid and dolomite formations using hydrochloric acid. During various stages of sandstone acidizing, different ...acids react with different minerals, and interactions of minerals with acids are an origin for precipitation reactions, which can be possibly deleterious as they may reduce reservoir permeability. During this research, the effects of chelates on pore size distribution, mineralogy, and grain size distribution have been investigated. Various chelates (GLDA, HEDTA, EDTA) were examined to react with different Berea Sandstone samples at a temperature of 180 °F and under 1000 psi confining pressure. Experimental techniques and analysis like Tescan Integrated Mineral Analysis (TIMA), were implemented in this research to understand the effect of chelates on Berea Sandstone. These results are related to elemental mass, element deportment, mineral mass, mineral locking, grain size distribution, and particle size distribution of the core samples reacted with different chelating agents. It has been found that all the chelating agents are effective in increasing the porosity and dissolving the cations from the Berea sandstone core sample. HEDTA proved to be more effective in dissolving quartz as compared to other chelates. GLDA proved to be more effective in the dissolution of rutile and zircon minerals. The significance of this research is the application of environment-friendly chelating agents to sandstone formation. Moreover, the detailed mineral analysis revealed that the most number of particles were dissolved by HEDTA.
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