Inorganic Affinity Research Articles

Mineralogy and Geochemistry of Rare Earth Elements in Carboniferous-Permian Coals at the Eastern Margin of the Ordos Basin.

This article used Carboniferous-Permian coals from the Jungar, Hedong, and Weibei Coalfields in the east of the Ordos Basin as research samples. Characteristics of coal quality, petrology, mineralogy, and geochemistry were analyzed by proximate analysis, inductively coupled plasma mass spectrometry, X-ray fluorescence spectroscopy, X-ray diffraction analysis, scanning electron microscopy-energy spectrum analysis, and incident light microscope. The enrichment regulations, distribution patterns, and occurrences of REY (rare earth element and yttrium) in coal under different geological conditions were compared. Geological significance and the influence of REY were then discussed. The average REY of Permian coal in the eastern margin of the basin is 127.9 μg/g, CC = 1.87, and the average REY of Carboniferous coal is 117.49 μg/g, CC = 1.72, which are within the normal enrichment range. The inorganic affinity of REYs in the study area is strong and mainly occurs in clay minerals and detrital phosphates and correlates well with LREY. The Permian coal sedimentary environment is more oxidized than the Taiyuan formation, and the Carboniferous coal sedimentary environment is noticeably more affected by marine water. With an increasing degree of coalification, the concentration of rare earth elements (REE) in high-rank coal vitrinite is lower than that in inertinite. In contrast, the concentration of REEs in low-rank coal is the opposite. This is because the oxygen-containing functional groups that can combine with REEs in vitrinite reduce significantly, resulting in the loss of trace elements into other forms. The provenance of the northern and central regions of the study area is mainly sedimentary rocks, granite, alkaline basalt, and continental tholeiite, while the southern region is mainly granite and sedimentary rocks.

A comparative evaluation of enrichment of trace elements in South African and Australian coals using SRXRF

In this study, coals imported from South Africa and Australia were characterized and quantified by an accelerator based X-ray emission technique viz., Synchrotron Radiation X-ray Fluorescence (SRXRF). Twelve trace metallic analytes (V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Rb, Sr, and Pb) and four minor elements (K, Ca, Ti, and Fe) were quantified by SRXRF. Elements of environmental concern, V, Cr, Co, Sr, and Pb were found to be enriched with respect to Clarke's world coal values. Correlation analysis reveals that most of the enriched trace elements in both the studied coals have organic affinity rather than inorganic affinity except Cr. Elements were clustered into three groups by hierarchical cluster analysis based on their chemical affinities.

Elemental composition and mineralogy of NW Venezuelan Guasare coals: Provenance study and role of illite in methane sorption capacity

A series of coal seams (groups 4 to 11) of Paleocene age in the Marcelina Formation have been open pit exploited in two mines (Paso Diablo and Mina Norte) in the Guasare Coalfield (NW Venezuela). An investigation has been conducted on the elemental composition, mineralogy, and coalbed methane (CBM) in Guasare coals. For this study, 46 core coal samples of 16 seams (groups 2 to 7) were collected from 16 exploratory boreholes that were drilled in both mines. It was also considered unpublished proximate-ultimate and gross calorific data of other 66 coals of 31 seams intersected in most of these wells. The coals under study showed low ash yields (3.4 wt % on average) and were classified as high volatile bituminous A. Mean values of trace element and lanthanide (REE) contents in Marcelina coals generally indicate depletion compared to average values for world hard coals. The statistical evaluations indicate that elements (except Se) show inorganic affinity or intermediate association and mixed mode of occurrence. La/Sc, Th/Sc, La/Co, and Th/Cr ratios support a felsic or metamorphic felsic source for the mineral matter present in Marcelina coals. Most coal samples exhibited similar normalized REE patterns, showing light REE enriched, as well as negative Ce and Eu anomalies. The comparison of REE patterns to those of some nearby granitoids suggests that Marcelina coals received a supply of sediments from theses granitic source rocks. The mineralogical compositions of representative coal samples are notably similar, kaolinite and quartz were noted as the major mineral species in all coal seams. The measured gas volumes available for CBM production from Marcelina seams vary approximately between 5 and 11 cm3/g. Variation in the illite content has an appreciable positive effect on gas adsorption capacity of Guasare coals. Lastly, a numerical model of the gas generative potential of the coals in the Marcelina Formation was also developed.

Enrichment of critical elements (Li-Ga-Nb-Ta-REE-Y) in the coals and host rocks from the Daping Mine, Yudongnan Coalfield, SW China

Critical elements in coals and host rocks have attracted much attention due to their growing demand and rising economic significance. This research reports new data of elevated critical elements and mineralogical characteristics of the coals and host rocks from the Daping Mine, Yudongnan Coalfield, neighboring to the previously reported coal-hosted Li and rare earth elements plus yittrium (REY) ore deposit of the Donggou Mine in the same coalfield. The coal in the Daping Mine is mainly a medium-volatile bituminous coal and characterized by a low-ash yield (Ad = 13.08–30.32 %, 19.65 % on average) and a high-sulfur content (1.75–9.25 %, 3.43 % on average). Critical elements including Li, Ga, Nb, Ta, REY are enriched in the coal. Minerals in the Daping coal are mainly clay minerals (including illite, mixed layer of illite/smectite (I/S), kaolinite, and chamosite) and pyrite, and to a lesser extent, calcite, anatase, and marcasite, with traces of zircon, celestite, and baddeleyite. Lithium is mainly associated with illite, and Ga, Nb, Ta, and REY also have an inorganic affinity. The terrigenous materials of the Daping coal were from the intermediate-felsic rocks at the top of the Kangdian Upland rather than the basalts. Hydrothermal solutions also make a great contribution to the enrichment of critical elements and minerals. High-temperature solutions (>200 °C) may be responsible for the weakly negative Eu anomalies. The coal ashes in the Daping Mine have significant concentrations of Li2O (2583 ppm on average), Ga (83.5 ppm on average), (Nb, Ta)2O5 (143 ppm on average), and REO (oxides of REY, 1125 ppm on average), all of which are higher than their respective cut-off grades. Moreover, the floor strata are enriched in these critical elements. Thus, the coal ashes and floor strata are potential resources for extraction of these critical elements.

Effects of Magmatic Fluids in Coals of São Pedro da Cova Coalfield, Douro Carboniferous Basin, Portugal: Insights from Inorganic Geochemistry

The Douro Carboniferous Basin (DCB), aged from Gzhelian, is an important coal-bearing basin occurring in Northern Portugal. While the coals and the sedimentary sequence of the DCB have been deeply studied, the inorganic geochemical data are scarce. This study intends to provide major and trace element contents and discuss their modes of occurrence and origins using a set of twenty-four coal samples from the São Pedro da Cova Coalfield taken from different sectors/outcrops. Thus, an integrated approach using petrographic, geochemical, both organic and inorganic, and mineralogical data was used to achieve these purposes. The main results demonstrated that these coals are anthracite A and vitrinite is the main organic component. Most of the elements have inorganic affinities and are associated with aluminosilicates, while the other elements have affinities with sulfides. Illite and muscovite are the main phyllosilicates occurring in these coals and pyrite is the most common sulfide. However, cinnabar, together with phosphates (fluorapatite, monazite, xenotime and gorceixite), were also identified. The enrichment of most elements as well as a heterogenous rare earth elements (REE) distribution pattern in the tectono-sedimentary unit (TSU) samples are related to magmatic fluids. On the other hand, on the Eastern Outcrop (EO), a tectonic slice, the subparallel trend of the REE distribution patterns, and a depletion of all the elements are related to the sedimentary contribution. The occurrence of cinnabar and gorceixite epigenetic mineralizations is interpreted as the action of a porphyry intrusion identified in this area of the DCB, between the TSU B1 and TSU D1.

Silicon and aluminum in Bulgarian coals

The presence and distribution of Si and Al in 19 Bulgarian coal basins and deposits, belonging to 8 coal provinces, were studied. Coals are of different rank (lignite to anthracite) and age (Late Carboniferous to Pliocene). The presence of both studied major elements depends strongly on: i) their concentration within the basin’s provenance; ii) the extent of terrigenous supply; iii) environmental acidity during peat formation; and iv) the presence and composition of epigenetic mineralization within the coal seams. Because of the presumed abundant terrigenous supply, the concentrations of both Si and Al are higher than the world average for most of the studied coals. Exceptions are the Maritsa-West, Burgas, Staniantsi, Oranovo, Chukurovo and Pernik Basins, for which reduced terrigenous supply can be suggested. For most of the basins, both Si and Al demonstrate good positive correlation with the ash yields, thus arguing for predominant inorganic affinity. Relatively low Si/Al ratios (typically <2) and good positive correlation between Si and Al (ro>0.6) imply the predominant role of the clay mineral assemblages as the main source of the elements in coal. Quartz is presumed to have dominant role only in Maritsa-West Basin. Poorer or negative correlations with the ash yields in part of the studied basins (i.e. Svoge, Maritsa-West, Sofia, Burgas and Dobrudzha Basins) suggest either mixed or predominantly organic affinity of the elements. Release of Si and Al from the clay minerals during the peat formation/diagenesis and subsequent formation of organo-metallic complexes is considered to responsible for such affinity.

Silicon and aluminum in Bulgarian coals

The presence and distribution of Si and Al in 19 Bulgarian coal basins and deposits, belonging to 8 coal provinces, were studied. Coals are of different rank (lignite to anthracite) and age (Late Carboniferous to Pliocene). The presence of both studied major elements depends strongly on: i) their concentration within the basin’s provenance; ii) the extent of terrigenous supply; iii) environmental acidity during peat formation; and iv) the presence and composition of epigenetic mineralization within the coal seams. Because of the presumed abundant terrigenous supply, the concentrations of both Si and Al are higher than the world average for most of the studied coals. Exceptions are the Maritsa-West, Burgas, Staniantsi, Oranovo, Chukurovo and Pernik Basins, for which reduced terrigenous supply can be suggested. For most of the basins, both Si and Al demonstrate good positive correlation with the ash yields, thus arguing for predominant inorganic affinity. Relatively low Si/Al ratios (typically <2) and good positive correlation between Si and Al (ro>0.6) imply the predominant role of the clay mineral assemblages as the main source of the elements in coal. Quartz is presumed to have dominant role only in Maritsa-West Basin. Poorer or negative correlations with the ash yields in part of the studied basins (i.e. Svoge, Maritsa-West, Sofia, Burgas and Dobrudzha Basins) suggest either mixed or predominantly organic affinity of the elements. Release of Si and Al from the clay minerals during the peat formation/diagenesis and subsequent formation of organo-metallic complexes is considered to responsible for such affinity.

Geochemistry of Carboniferous–Permian Coal from the Wujiawan Mine, Datong Coalfield, Northern China: Modes of Occurrence, Origin of Valuable Trace Elements, and Potential Industrial Utilization

This paper provides new geochemical data focusing on valuable elements in the coal, parting, and floor samples in the No. 5 coal seam of the Taiyuan Formation from the Wujiawan mine, Datong coalfield, northern China. The minerals mainly consist of kaolinite, calcite, and pyrite, as well as trace amounts of quartz and illite. The No. 5 coal is enriched in Li, Ga, high field strength elements (HFSEs), and rare earth elements and yttrium (REY) when compared with world hard coals. Of particular interest is the high average concentration of Li (67.66 μg/g), which is around seven times higher than the value for world hard coals. Lithium, Ga, and HFSEs have strong inorganic affinities, whereas REY have organic affinities. The main carrier of Li, Ga, and HFSEs is aluminosilicate minerals, while REY appear to occur with organophosphorus. These HFSEs are enriched, both in the parting and in the adjacent coal samples. This suggests that these elements are likely to leach out during the diagenetic process. The distribution patterns of REY, along with the ratio of Al2O3/TiO2 and the figure of Zr/TiO2 vs. Nb/Y are suggestive of their derivation from felsic parent material. In the northern and eastern part of the Datong coalfield, there are several regions where the Li content is higher than the mineable grade, in particular in the northern Datong coalfield where there is a mine with an Li content of 294.6 μg/g. This is significantly higher than the mineable grade. Therefore, there is a potential for financially viable recovery of Li in these coals of the Datong coalfield.

Geochemistry of Carboniferous coals from the Laoyaogou mine, Ningwu coalfield, Shanxi Province, northern China: Emphasis on the enrichment of valuable elements

This paper provides new geochemical data focussing on valuable elements and their origins in the coals from the Laoyaogou mine, Ningwu coalfield, Shanxi Province, northern China. Kaolinite, pyrite, calcite, and boehmite are the main minerals, along with a small amount of illite and anatase, present in the coals studied.The studied coals are enriched with Li, Ga, Zr, Zn, Hf, Sr, Nb, Sn, Th, and REY, especially the case of high average concentration of Li (163.42 μg/g) which is more than ten-times higher than that in world hard coals. Zirconium and Hf, the average concentrations of which are more than five-times higher than those in world hard coals. Lithium, Ga, Zr, Hf, and Th have strong inorganic affinities, whereas Sr and REY have organic affinities. The main carrier of Li in the No. 5 Coal is kaolinite, illite, and boehmite. Gallium, Zr, Hf, and Th probably have the same origin and are largely associated with kaolinite and Ti/Ca-bearing minerals which originate from the source region. In Shanxi Province, the main coalfields are enriched in several valuable elements (e.g. Li, Ga, Zr, Hf, and Th), especially the high average content of Li in the Ningwu coalfield (116 μg/g) and the Qinshui Basin (110 μg/g). The Laoyaogou coals and the coals from the main coalfields in Shanxi Province have economic significance as hidden treasures of the coals themselves and in their by-products.

Factors controlling the occurrence and distribution of iron in Bulgarian coals

Coal of varying age (Upper Carboniferous to Pliocene) and coalification rank (lignite to anthracite) from nineteen coal-bearing basins and deposits, belonging to 8 coal-bearing provinces from Bulgaria, were examined for the occurrence and distribution of Fe. For the majority of the coals, the average Fe concentrations vary from 1.1 to 10.2 wt% and are higher than the World’s average. An exception exists only for Karlovo and Dobrudzha Basins, where slight depletion of Fe (<1 wt%) was established. On contrary, carbonaceous shales from the majority of the basins show Fe depletion in comparison to the Clarke values for clays. Based on the negative correlations with the ash yields, organic affinity of the element can be suggested for most of the studied coals. An exception exists for the Burgas Basin, for which predominantly inorganic affinity of the element can be suggested, whereas for Stanyantsi, Samokov, Bobov Dol, Dobrudzha and Svoge Basins mixed organic/inorganic affinity of Fe can be presumed. The element most probably predominantly occurs in the form of organometallic compounds, especially in the coals that formed in preferentially acidic peat-forming environment. Nevertheless, small contribution from biogenic iron cannot be excluded. The mineral form of Fe is probably mainly associated with sulfides, carbonates, and sulfates, although the presence of Fe oxides, silicates and hydroxides is also established. The analysis of Fe occurrence and its organic/inorganic affinity in Bulgarian coals reveal the following controlling factors: i) Fe concentration within the basin’s provenance; ii) the type (i.e. terrigenous or groundwater) of element supply; and iii) environmental conditions during peat-formation.

Distribution of major and trace elements in the Kovin lignite (Serbia)

A geochemical and mineralogical study was performed on lignite samples from the Upper Miocene Kovin deposit, hosting three coal seams. The Kovin lignite is characterized by high moisture content, medium to high ash yield, medium to high sulphur content and a relatively low gross and net calorific value. The mineralogical composition, and major and trace element contents were determined by X-ray diffraction, scanning electron microscopy with energy dispersive Xray spectroscopy (SEM-EDS) analyses, and inductively coupled plasma optical emission spectrometry (ICP-OES). The most abundant minerals in all lignite samples from the three coal seams are clays (illite/smectite), silicates (quartz, plagioclase), sulphates (gypsum/anhydrite) and carbonate (calcite). The other iron-rich minerals are sulphides, oxides and hydroxides (pyrite, magnetite, haematite, and limonite). In general, mineral matter in the matrix coal consists of illite/ smectite and quartz, while xylite-rich coals, apart from illite/smectite, have a higher content of sulphates and Fe-oxide/hydroxide minerals. The lignite from the Kovin deposit is enriched in As, Cd, Co, Cr, Cu, Ga, Li, Mn, Mo, Ni, Pb, V, Zn, Gd, Tb, Er and Lu in comparison with the Clarke values for brown coals. The statistical analysis of bulk compositional data shows inorganic affinity for the majority of the major and trace elements and possible association with pyrite, illite/ smectite and calcite.

Modes of occurrence and partitioning behavior of trace elements during coal preparation—A case study in Guizhou Province, China

Coal preparation technology is expected to play an important role in trace elements removal before coal combustion. The modes of occurrence of five trace elements (As, Se, Pb, Be, and Hg) in two coal cleaning plants in Guizhou, China, designated WJZ and ZZC, were studied using screening and float-and-sink tests. The behaviors of these trace elements when coal was cleaned were also investigated via sampling and analysis of raw coal, coal products, fresh water, and circulating water in two coal cleaning plants. Screening tests show that the content of trace elements is highest in 3–1 mm or 1–0.5 mm size fraction and they distributed mainly (more than 50%) in the +0.5 mm size fractions. Float-and-sink tests indicate that trace elements have a strong inorganic affinity and are significantly enriched, distributed in high-density fraction (+1.8 g/cm3). Over 50% of trace elements could be removed when pre-gangue removal is done with separation density of 1.8 g/cm3. The analysis of solid samples (raw coal, coal products) demonstrates that trace elements migrated mainly into gangue, and slime, enrichment of trace elements in middlings was also observed in ZZC plant. Results of water samples analysis suggest that Se, and As in coal are more likely to be released into water during coal cleaning while Be and Hg are present in a highly insoluble form in coal.

Investigating the occurrences of valuable trace elements in African coals as potential byproducts of coal and coal combustion products

There is a growing attention in valuable trace elements (TEs) in coal and coal combustion products as they can potentially be future resources of valuable TEs. Therefore, understanding the mode of occurrences of valuable TEs in coal has several advantages for their economical and industrial extractions. Since there is limited information on the affinity of valuable TEs in the structure of African coals, this study explores correlations between conventional coal properties and concentration of vanadium, yttrium, gallium and lithium as valuable TEs for a wide range of African coal samples (139 samples) from South Africa, Botswana, Egypt, Tanzania, Nigeria and Zambia by statistical methods. Statistical assessments indicated that the concentrations of Y, V, Li and Ga for these countries are higher than their value in the world coal (on average). The outcomes of assessments showed that the Li, Ga and V are associated with the mineral matter fraction (inorganic affinity) of the coal where they have significant positive correlations with ash and Al (as a major element) and potentially clay minerals are their main bearing minerals. However, statistical explorations suggested that Y may have both the organic and inorganic occurrences in the African coal samples.

In seam variation of element-oxides and trace elements in coal from the eastern Ordos Basin, China

This paper investigated the mineralogical and geochemical compositions of the upper Pennsylvanian coal from Hedong Coalfield, in the eastern Ordos basin, China, using SEM, XRD, ICP-MS, ICP-CCT-MS, DMA-80 and ISE methods. The bituminous coal samples were collected form Nos. 3 and 4 Coal, which had low ash yield and were medium volatile, and had low sulfur content and low hazardous trace elements concentrations (Be, F, As, Hg, U and Pb). Maceral compositions were dominated by vitrinite (up to 90.2%), and to a lesser extent by inertinite and liptinite, all subgroups were detected in the coal samples. Minerals included quartz, clay minerals, sulfide and other oxide minerals. SiO2 and Al2O3 were the dominant major elements-oxides in both coal seams with much higher concentrations than in Chinese coal, while other major elements-oxides (Na2O, K2O, Fe2O3, MgO) had average values compared to Chinese coal. No. 3 Coal was enriched in Li and Zr, and No. 4 Coal was enriched in Li, Be, Cu, Se, and In. Elemental occurrence was studied using statistical methods, and Li, Rb, Zr, Cs, Ba, Hf, Tl, Pb, and Th were inorganic affinities, while F, V, Cr, Ga, Ni, As, In, Ta occurred as inorganic–organic affinities and Fe and S may have occurred in pyrite. Coal facies indicators (GI, TPI, GWI, and VI) plots suggested that the two coal seams were deposited in different environments: No. 3 Coal was deposited in a wet forest swamp, while No. 4 Coal was formed in a mesotrophic to ombrotrophic environment. The geochemistry of these coal samples (Al2O3/TiO2, TiO2/Zr, Zr/Sc and Th/Sc ratios) indicated that the coal samples sediment was sourced from intermediate and felsic igneous rocks.

Occurrences of valuable trace elements in Iranian coals as potential coal combustion byproducts

ABSTRACT In Iran, coal as one of the primary energy resources mainly has just one customer (Iranian Steel Corporation); therefore, coal and production of its combustion have recently attracted much attention as promising alternative sources for valuable trace metals (VTM). Since there has been few principle exploration on occurrence modes of VTM for Iranian coal, this investigation assessed possible interactions between various coal conventional properties (proximate and ultimate analysis) and Y, Li, Ga, and V as VTM for Iranian coals. Statistical analyses indicated that on average, the contents of all these elements are higher than the general world coal ranges. Inter-correlation assessments showed that Ga and V in the samples are mainly associated with mineral matter (inorganic fracture of coal), e.g., mostly adsorbed by aluminosilicate (clay minerals) while Y and Li have a mixed organic and inorganic affinity. Strong interactions of Ga and V with inorganic fraction for samples with over 70% ash content released that host rocks of Iranian coal seams may also have the potential for the extraction of these two VTM. On the other hand, the mixed organic and inorganic affinity of Y and Li showed high possibility of their extraction from the coal combustion products. These results could be a critical key not only for geological and environmental information but also for developing possible procedures for their extraction.

Washability and Distribution Behaviors of Trace Elements of a High-Sulfur Coal, SW Guizhou, China

The float-sink test is a commonly used technology for the study of coal washability, which determines optimal separation density for coal washing based on the desired sulfur and ash yield of the cleaned coal. In this study, the float-sink test is adopted for a high-sulfur Late Permian coal from Hongfa coalmine (No.26), southwestern Guizhou, China, to investigate its washability, and to analyze the organic affinities and distribution behaviors of some toxic and valuable trace elements. Results show that the coal is difficult to separate in terms of desulfurization. A cleaned coal could theoretically be obtained with a yield of 75.50%, sulfur 2.50%, and ash yield 11.33% when the separation density is 1.57 g/cm3. Trace elements’ distribution behaviors during the gravity separation were evaluated by correlation analysis and calculation. It was found that Cs, Ga, Ta, Th, Rb, Sb, Nb, Hf, Ba, Pb, In, Cu, and Zr are of significant inorganic affinity; while Sn, Co, Re, U, Mo, V, Cr, Ni, and Be are of relatively strong organic affinity. LREE (Light rare earth elements), however, seem to have weaker organic affinity than HREE (Heavy rare earth elements), which can probably be attributed to lanthanide contraction. When the separation density is 1.60 g/cm3, a large proportion of Sn, Be, Cr, U, V, Mo, Ni, Cd, Pb, and Cu migrate to the cleaned coal, but most of Mn, Sb and Th stay in the gangue. Coal preparation provides alternativity for either toxic elements removal or valuable elements preconcentration in addition to desulfurization and deashing. The enrichment of trace elements in the cleaned coal depends on the predetermined separation density which will influence the yields and ash yields of the cleaned coal.

The Petrography, Mineralogy and Geochemistry of Some Cu- and Pb-Enriched Coals from Jungar Coalfield, Northwestern China

The petrological, geochemical, and mineralogical composition of the Carboniferous-Permian coal deposit in the Jungar coalfield of inner Mongolia, Northwestern China, were investigated using optical microscopy and field emission scanning electron microscopy in conjunction with an energy-dispersive X-ray spectrometer (SEM-EDX), as well as X-ray powder diffraction, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The Jungar coal is of high volatile C/B bituminous quality with 0.58% vitrinite reflectance and has a low sulfur content of 0.70% on average. Inertinite (mineral-free basis) generally dominates in coal from the lower part of the Shanxi formation, and vitrinite is the major maceral assemblage in the coal from the Taiyuan formation, which exhibits forms suggesting variation in the sedimentary environment. The Jungar coal is characterized by higher concentrations of copper (Cu) in No. 6 coal, at 55 μg/g, and lead (Pb) in No. 4 coal at 42 μg/g. Relative to the upper continental crust, the rare earth elements (REE) in the coal are characterized by light and medium–heavy REE enrichment. The minerals in the Jungar coal are mainly kaolinite, dickite, pyrite, calcite, siderite, quartz, and, to a lesser extent, gypsum and K-feldspar. The enrichment and occurrence of the trace elements, and of the minerals in the coal, are attributed to the fragmental parent rock during diagenesis and coalification. The main elements with high enrichment factors, Cu and Pb, overall exhibit a notably inorganic sulfide affinity and a weak organic affinity. Primary and epigenetic sedimentary environment and the lithology of the terrigenous parent rock are the key factors that influence the occurrence and formation of Cu and Pb in coal. The depositional environment is more influential in the formation of Cu than Pb in coal. Lead is more easily affected by the terrigenous factors than Cu when they are under a similar depositional environment.

Meso- and microporosity of the subbituminous kM2 coal seam (Soma, Turkey) and its relationship with coal characteristics

This study focuses on meso- and microporosity of the subbituminous kM2 coal seam and its relation to coal characteristics. The coal seam is being mined in an underground coal mine at the Eynez sector in the Soma Basin (Western Turkey). The analysed coal samples are characterized by low moisture (avg. 8.2%, on air-dry basis) and total S content (avg. 1.5%, on dry basis), and moderate ash yield (avg. 26.1%, on dry basis). The predominant maceral group is huminite, in which telohuminite is the dominant maceral subgroup (up to 57.1vol.%, on whole-coal basis), whereas liptinite and inertinite maceral groups occur in low but variable proportions. Mineralogically, the samples are composed of quartz, clay minerals (kaolinite and illite), carbonates, pyrite, and rarely feldspars and gypsum. Statistical and SEM-EDX analyses indicate that the majority of elements have inorganic affinity, particularly the aluminosilicate minerals. The specific surface area and volume of mesopores, and average mesopore size determined by low pressure N2 adsorption, range widely throughout the studied seam section. Micropore characteristics, analysed by low-pressure CO2 adsorption, demonstrate that micropores are abundant, and specific surface area and volume of micropores vary widely. Surface area and volume of mesopores are slightly higher in the lower part of the seam, whereas the opposite was observed for surface area and volume of microspores. These trends may imply that hydrostatic pressure has little impact upon mesopore characteristics, although increased ash yields in the lower part of the seam suggest that minerals are the major contributor of coal mesopores. Furthermore, total C contents and huminite macerals, particularly telohuminite, display positive correlations with micropore characteristics. Thus, the variations in the microporosity are mainly correlated with the proportion of organic matter (macerals) in the analysed samples. The contents of aluminosilicate-affiliated elements display moderate to strong positive correlations with surface area and volume of mesopores, and total S and B contents display weak positive correlations with surface area and volume of micropores. The element B likely precipitated from porewater or intra-seam solutions during coalification and was absorbed by macerals having abundant microporosity. The abundance of micropores along with frequent disseminated pyrite crystals within the reactive macerals (telohuminite group) and higher total S contents in the upper parts of the seam could increase the risk of self-heating. Therefore, care should be taken to use caution when mining the upper part of the seam.

Coal characteristics, palynology, and palaeoenvironmental interpretation of the Yeniköy coal of Late Oligocene age in the Thrace Basin (NW Turkey)

The Yeniköy coal field is located in a narrow area between the Black Sea coast and the Istranca (Standrja) Mountain in the Thrace Basin. The aims of this study are to characterize coal petrographical, mineralogical, palynological, geochemical, and sedimentological properties of the Yeniköy coal deposit and to reconstruct palaeoenvironmental conditions during peat accumulation. A total of 9 coal samples collected from the coal seam section are almost entirely composed of xylite-rich lithotype, and are characterized by low ash yield (7.9–21.1%, average 13.6%; on dry basis) and high total S contents (1.0–3.7%, average 2.2%; on dry basis). The macroscopic features, maceral composition, and coal facies suggest that the peat was accumulated under mesotrophic anoxic conditions, and the peat-forming vegetation consisted mainly of arboreal species (e.g. Cupressaceae, Ulmus, Carya, Zelkova, Alnus, Pterocarya and Quercus). The low HI values of the analysed samples are presumably related to presence of xylite-rich lithotype rather than the dominance of herbaceous plant and/or low preservation of organic matter in the palaeomire. Even though, relatively B-enrichments, high total S contents, and weak anomalies of some REY (e.g. Y, Ce, and Gd) in the analysed samples could refer possible sea water influence into palaeomire in the study area during Late Oligocene; the sedimentological and palynological (freshwater algaes: Pediastrum, Spirogyra, and Mougeotia) data that indicate the palaeomire was located within a delta plain environment where small freshwater lakes and/or ponds developed. The statistical analysis and SEM-EDX data show the vast majority of elements in the analysed coal samples have inorganic affinity. The major elements Al, K, and enriched elements like B, V, Cr, Hg, and U seem to be affiliated with aluminosilicate minerals, whereas Fe, Ni, and As have probably sulphide affinity. The detrital presences of apatite crystals as detected by SEM-EDX analysis indicate that REY have mainly phosphate affinity in the analysed samples. Vertical distributions of the elements and ash yields suggest that the detrital input ratio was changeable and controlled some elemental enrichment during peat accumulation. These variations could be related to development of and fluvial conditions in the study area which interrupted peat-accumulation several times during Late Oligocene.

Relationship between trace elements and macerals in Huanglong Jurassic coal

ABSTRACTThis study is the detailed publication concerning the origins of trace elements in Huanglong Jurassic coal. Forty-two coal samples were collected from Huanglong Jurassic coalfield. Twenty-two elements, including U, B, F, Hg, Be, Cd, Cr, Cu, Mn, Mo, Ni, Pb, V, Zn, Ba, Co, Ga, Sr, As, Se, Cl, and P, were determined. The element profiles were compared with the organic petrography, and the statistical analysis was also carried out to provide preliminary information for origins of the trace elements. The following conclusions were obtained: Cd, Cr, Cl, Ni, Zn, Co, Ga, Sr, As, Se, and B show inorganic affinity. Hg, V, Be, Cu, Pb, and F show generally vitrinite affinity, suggesting that their origins are associated with parenchymatous and woody tissues of roots, stems, barks, and leaves composed of cellulose and lignin. U shows inertinite affinity, which indicated that wood and leaf tissue weakly altered by decay or by biochemical alteration are the main origins of U. P, Mn, Mo, and Ba show overall mixed affinities, indicating the complex of biological origins.