Next Article in Journal
Geochemical Characterization of Bauxite Deposits from the Abruzzi Mining District (Italy)
Previous Article in Journal
Selective Fabrication of Barium Carbonate Nanoparticles in the Lumen of Halloysite Nanotubes
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Minerals
Volume 8
Issue 7
10.3390/min8070297
minerals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Mineralogical and Geochemical Characteristics of Trace Elements in the Yongdingzhuang Mine, Datong Coalfield, Shanxi Province, China

by
Yue Yuan
1,2,3,
Shuheng Tang
1,2,3,*,
Songhang Zhang
1,2,3 and
Ning Yang
1,2,3
1
School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China
2
Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering, China University of Geosciences, Beijing 100083, China
3
Coal Reservoir Laboratory of National Engineering Research Center of CBM Development & Utilization, China University of Geosciences, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Minerals 2018, 8(7), 297; https://doi.org/10.3390/min8070297
Submission received: 11 May 2018 / Revised: 4 July 2018 / Accepted: 7 July 2018 / Published: 11 July 2018
Browse Figures
Versions Notes

Abstract

:
Fifteen samples of No. 4 coal from the Yongdingzhuang Mine in Datong Coalfield were tested for their elemental compositions, modes of occurrence, and mineralogical compositions, using X-ray powder diffraction, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, and scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer. The samples have low sulfur content (0.63%). The major minerals are kaolinite and quartz, followed by pyrite and anatase. Compared with averages for the Chinese coals, the percentages of SiO2 (15.11%), TiO2 (0.7%), and Al2O3 (10.39%) are much higher. In No. 4 coals, Li (62.81 μg/g), Be (6.94 μg/g), Zr (235 μg/g), Ga (17.04 μg/g), F (165.53 μg/g), Tl (1.93 μg/g), and Hg (0.34 μg/g) are some potentially valuable and toxic trace elements with higher concentrations than Chinese coals and World hard coals. Lithium and F mainly have kaolinite associations. With the exception of kaolinite, Li, and F also partly occur in anatase, gorceixite and goyazite. Beryllium largely occurs in anatase; gallium is mainly associated with kaolinite and to a lesser extent, with gorceixite and goyazite; zirconium is associated with kaolinite, gorceixite and goyazite; and thallium and Hg occur in in pyrite. Potentially valuable elements (including Al, Li, Ga, and Zr) might be recovered as value-added byproducts from coal ash. Toxic elements (e.g., Be, F, Tl, and Hg) might have potential adverse effects to the environment and human health during coal processing. In addition, the distribution patterns of rare earth elements and yttrium (REY) indicate that the REY in No. 4 coals originated from the granite of Yinshan Oldland, and natural waters or hydrothermal solutions that may circulate in coal basins.

1. Introduction

China is the major consumer of coal worldwide, accounting for 50% of the total annual world coal consumption [1] and coal utilization will continue to play a leading role in energy consumption in the future [2]. Due to potentially hazardous compositions of coal, both the environment and human health are tremendously threatened by the pollution generated through both coal production and utilization [3,4]. In recent decades, an increasing number of studies have focused on relevant studies [5,6,7], detailing the abundances, elemental compositions, and occurrence modes of various trace elements in coal, including toxic (e.g., F, As, Hg, and Pb) [8,9] and valuable elements (e.g., Ge, Ga, Al, Nb, Zr, and rare earth elements) [10,11,12]. The trace elements can provide not only geologic information about depositional conditions of coal, coal-bearing sequences, and regional tectonic history [13,14,15], but also practical information for potential industrial utilization of rare metals (e.g., Ge, Ga, and Al) which can be industrially utilized if they are enriched to the levels exceeding economic grades [16,17].
The Datong Coalfield is one of the largest coal producers of China and is located in northern Shanxi Province, which is adjacent to Shaanxi Province, Hebei Province, and the Inner Mongolia Autonomous Region (Figure 1). Many studies have been conducted on the geochemical characteristics of the Ordos Basin and the Ningwu Basin, which are adjacent to the Datong Coalfield [18,19]. However, few previous studies have been carried out about the geochemical characteristics on the coals in the Datong Coalfield. This paper primarily reports the mineralogical compositions, geochemical characteristics and origin of the trace elements from the Yongdingzhuang Mine in the Datong Coalfield. In order to investigate the potential for industrial utilization of the valuable elements and potential threats of the toxic elements, this paper also focuses on the concentrations and modes of occurrence of these valuable and toxic elements [20].

2. Geological Setting

The Datong Coalfield is located to the south of the Yinshan Oldland and stretches 50 km long (N-S) and 30 km wide (W-E), covering a total area of 1900 km2 [21]. It is bound to the west by the Pingwang-Emaokou fault, to the east by the Lvliang mountain syncline, and to the north by the Hongtao mountain syncline. Due to Caledonian tectonic movement, the Ordovician Majiagou Formation has been extensively weathered, leading to erosion of the Upper Ordovician, the Silurian, Devonian, and the Lower Carboniferous strata. The coals in the Datong Coalfield began to accumulate sediments during the Late Palaeozoic in part of the North China Craton. Consequently, the strata were assigned to the Benxi, Taiyuan, Shanxi, Shihezi, and Shiqianfeng Formations. The faults in the northern coalfield provided channels for magma intrusion. The lamprophyre intrusions, which occurred during the Indosinian epoch in the north of the coalfield, resulted in thermal contact metamorphism and silicification between coal seams [21].
The Shanxi Formation has a total thickness of 20–80 m and is mainly composed of conglomerate, sandstone, siltstone, mudstone, and four coal seams identified as Nos. 1, 2, 3, and 4 coal, respectively, from top to bottom. The thickness of the coal seams ranges between 0.16 and 10.63 m (Figure 2). According to previous research, the Shanxi Formation was deposited in fluvial facies [22].

3. Samples and Methods

Fifteen samples, consisting of two partings and 13 coal benches with a total thickness of 1.15 m from top to bottom, were collected from No. 4 coal in the Yongdingzhuang Mine following the Chinese Standard Method GB 482-2008 [23]. The samples were cut into sections of 10 cm width and 10 cm depth and immediately stored in plastic bags to prevent contamination and oxidation. All samples were ground to 80-mesh and 200-mesh prior to geochemical analysis.
The 80-mesh samples were used to analyze both the mineralogical composition and distribution. The mineralogical composition was determined via microscopy (Leica DM 2500P microscope by Leica Microsystems, Solms, Germany). A scanning electron microscope (HITACHI UHR FE-SEM, SU8220, HITACHI, Tokyo, Japan) equipped with an energy-dispersive X-ray spectrometer (SEM-EDS, HITACHI, Tokyo, Japan) was used to study the mineral distribution of the coal and the distribution patterns of several elements of interest.
Low-temperature ashes were used for the 200-mesh samples and performed on an EMITECH K1050 plasma asher (Quorum, Ashford, UK), with the temperature maintained below 150 °C. X-ray diffraction (XRD, Rigaku, Tokyo, Japan) analyses on the low-temperature ashes were performed via Ni-filtered Cu-Kα radiation and a scintillation detector. XRD patterns were recorded over a 2θ interval from 10° to 70°, at a step size of 0.01°.
All 200-mesh samples were ashed at a temperature of 815 °C and the residues were used to determine the concentrations of major-element oxides (SiO2, TiO2, Al2O3, Fe2O3, MgO, CaO, MnO, Na2O, K2O, and P2O5) by X-ray fluorescence spectrometry (XRF) (Thermo ADVANT XP+, Thermo Fisher, Waltham, MA, USA). Trace elements, including REY, except for As, Se, Hg, and F, were determined via inductively coupled plasma mass spectrometry (ICP-MS) [24]. For ICP-MS, 200-mesh samples were digested using an UltraClave Microwave High Pressure Reactor (Milestone, Sorisole, Italy). The basic load for the digestion tank was composed of 330 mL distilled H2O, 30 mL 30% H2O2, and 2 mL 98% H2SO4. The initial nitrogen pressure was set to 50 bars and the highest temperature was set to 240 °C, which lasted for 75 min. The reagents for the 50 mg sample digestion were 5 mL 40% HF, 2 mL 65% HNO3, and 1 mL 30% H2O2. Multi-element standards (Inorganic Ventures: CCS-1, CCS-4, CCS-5 and CCS-6) were used for the calibration of trace element concentrations [24]. Arsenic and Se were analyzed via ICP-MS with collision/reaction cell technology (ICP-CCT-MS) [25]. Fluorine was determined via pyrohydrolysis combined with an ionselective electrode (ISE) based on the ASTM method [26]. Mercury was determined using a Milestone DMA-80 Hg analyzer (Milestone, Sorisole, Italy) [27].

4. Results

4.1. Proximate Analysis

Bench thickness, forms of sulfur and proximate analysis of the No. 4 coal seam of the Yongdingzhuang Mine are listed in Table 1.
The No. 4 coals from Yongdingzhuang Mine are considered as a medium ash coal, with an average ash yield value of 20.76% (ranging from 9.82% to 48.67%), according to the Chinese National Standard (GB/T15224.1-2010, 2011, 10.0–20.00% for low ash coal, 20.0–30.00% for medium ash coal, and 30.0–40.00% for high ash coal) [28].
The moisture content of No. 4 coals ranges from 0.95% to 1.84%, averaging 1.46%, indicating that No. 4 coals are low moisture coals in accordance with the MT/T 850–2000 [29] (<5% for low moisture coal, 5% to 15% for medium moisture coal, and >15% for high moisture coal).
The volatile matter content of No. 4 coal seam ranges from 16.07% to 35.94%, with a mean of 27.45% suggesting that this coal is a medium volatile coal according to the MT/T 849-2000 [30] (20.01–28.00% for medium volatile coal, 28.01–37.00% for medium-high volatile coal, 37.01–50.00% for high volatile coal, and >50.01% for super high volatile coal).
The No. 4 coals are considered as low sulfur coals, with total sulfur contents ranging from 0.18% to 1.97%, averaging 0.70%, based on the Chinese National Standard (GB/T 15224.2-2010, 2011) [31] (<0.5% for ultra-low sulfur coal, 0.51–0.9% for low sulfur coal, and 0.9–1.50% for medium sulfur coal). Total sulfur consists of inorganic sulfur (including pyritic sulfur, 0.15–0.96%, 0.33% on average; sulfate sulfur, 0.01–0.02%, 0.01% on average) and organic sulfur (0.01–1.65%, 0.36% on average).
In summary, the No. 4 coals of the Yongdingzhuang Mine are characterized by medium ash, low moisture, medium volatile, and low sulfur coals.

4.2. Mineralogical Composition

The mineralogical composition of the coal samples from No. 4 coal of the Yongdingzhuang Mine is primarily characterized by kaolinite and quartz and, to a lesser extent, by pyrite and anatase, based on the SEM-EDS and XRD analyses (Figure 3).
Clay minerals are commonly detected in coals, including kaolinite, illite, chlorite and montmorillonite. Based on both XRD and SEM-EDS, kaolinite was found to be the most abundant mineral and mainly occurs as lumps and infillings of macerals (Figure 4A,B). Two main occurrences of kaolinite have been found in samples, one as disseminated particles in collodetrinite and the other as cell-fillings in fusinite. Filling fusinite indicates that kaolinite may indicate formation via authigenic processes (Figure 4A) [32]. Part of the kaolinite shows dissemination in collodetrinite, which is suggestive of a syngenetic origin (Figure 4B) [32,33].
Quartz is distributed as detrital grains in macerals throughout samples, along with vein quartz in coals (Figure 4C). Detrital grains with round edges have a terrigenous detrital origin, indicating transportation over a long distance from the sediment source region (Figure 4D) [34,35]. Furthermore, epigenetic quartz predominately occurs as vein quartz.
Pyrite mainly occurs as fracture-filling and discrete crystals in No. 4 coals. It can be deduced that discrete crystals are related to a syngenetic origin (Figure 5A) [36]. However, fracture-filling pyrite was deposited from migrating solutions, after compaction of the peat into coals, suggesting an epigenetic origin (Figure 5B) [37]. Anatase occurs as detrital grains in collodetrinite, indicating a syngenetic origin (Figure 5A,B) [36,38].

4.3. Geochemistry

4.3.1. Major Elements

The concentrations of major oxides in the No. 4 coals are listed in Table 2, including average values, LOI (loss on ignition), and concentration coefficients (CC = the ratio of an average elemental concentration in the investigated coal/the average concentrations for either world coals or Chinese coals) [38]. The concentrations for major oxides are as follows: SiO2 (11.14%), Al2O3 (7.16%), TiO2 (0.67%), Fe2O3 (0.60%), MgO (0.03%), K2O (0.03%), CaO (0.10%), P2O5 (0.01%), Na2O (0.0028%), and MnO (0.0008%).
Compared with the average values for Chinese coals [20], TiO2 is slightly enriched (2 < CC < 5) in No. 4 coals, while the Al2O3 and SiO2 concentrations are close to the average Chinese coal values (0.5 < CC < 2). The remaining major oxides are depleted (CC < 0.5). In general, Al2O3 and SiO2 are the most abundant element oxides in all samples. The ratios of the SiO2/Al2O3 range from 1.24 to 2.00 (average 1.54), which are higher than those of average Chinese coal (1.42) [20] and the theoretical ratio of kaolinite (1.18). This is due to the relatively high concentration of free silicon in the coal, which was mainly found in the form of quartz [39,40].

4.3.2. Trace Elements

The concentrations of 32 trace elements determined in the No. 4 coal seam samples from the Yongdingzhuang Mine are listed in Table 3, along with the CC values.
Based on the enrichment classification of Dai et al. [38] and compared with the corresponding averages for world hard coals [41], only Zr (235 μg/g) is enriched, showing a CC value above 5 (CC = 6.53). Fluorine (CC = 1.51), V (CC = 1.12), Cr (CC = 1.55), Ni (CC = 1.58), Zn (CC = 1.21), As (CC = 0.76), W (CC = 1.48), and U (CC = 1.84) are relatively close to the world hard coal values (0.5 < CC < 2). Rubidium (CC = 0.06), Sr (CC = 0.11), Cs (CC = 0.15), Ba (CC = 0.40), and Bi (CC = 0.44) are depleted. The concentrations of the remaining trace elements are slightly elevated (2 < CC < 5) (Figure 6A).
Compared to average Chinese coals [20], Be (CC = 3.29), Sc (CC = 2.06), Cu (CC = 2.94), Ga (CC = 2.40), As (CC = 2.28), Zr (CC = 2.63), Zn (CC = 2.78), Sb (CC = 3.64), W (CC = 2.37), Hg (CC = 2.30), Tl (CC = 4.62), Pb (CC = 2.02), and Th (CC = 3.78) are slightly enriched in the investigated coals. Rubidium (CC = 0.12), Sr (CC = 0.08), Cs (CC = 0.14), Cd (CC = 0.44), and Ba (CC = 0.37) are depleted and the remaining elements are similar to those of average Chinese coals (Figure 6B). Note that almost all the trace elements have higher concentrations in partings (YDZ4-4 and YDZ4-8) than those in coal benches.

5. Discussion

5.1. Elemental Associations

Affinity and cluster analyses among elements are effective indirect methods to analyze elemental modes of occurrence [42,43]. Correlation of the element concentrations with ash yield may provide preliminary information on their organic or inorganic affinities [44]. In this paper, all elements were classified by the correlation between their ash yields and elemental concentrations, demonstrating either inorganic or organic affinity (Figure 7). All of these elements were then divided into five groups according to their correlation coefficients with their ash yields [45].
Group 1 includes Na2O, Al2O3, SiO2, P2O5, K2O, Li, F, Sc, Rb, Nb, In, Cs, Ba, Hf, Ta, Bi, Th, and U, all of which have a strong correlation with the ash yield (rash = 0.7–1.0). The correlation coefficients between ash yield as well as Al2O3 and SiO2 are 0.99 and 1.00, respectively, indicating silicate and aluminosilicate associations (especially clay minerals) as major minerals in the coal samples. Additionally, Li, F, Sc, Rb, Nb, In, Cs, Ba, Hf, Ta, Bi, Th, and U also show high correlation coefficients with Al2O3 and SiO2 (Table 4), indicating an aluminosilicate affinity (mainly in kaolinite). Moreover, Li, F, Sc, Rb, Cs, In, Ba, Bi, and Th have a strong correlation (r > 0.7) with P2O5 (Table 4), which is likely due to phosphate affinity [27,46].
Group 2 consists of TiO2, Ga, Sr, Cd, W, Pb, and REY. These elements have a lesser but still high inorganic affinity, with correlation coefficients ranging between 0.4 and 0.69. Furthermore, all of these elements have a relatively strong affinity to Al2O3 and SiO2, suggesting high affinity to silicate and aluminosilicate associations in the coals.
Group 3 includes Be, Cr, Se, and Zr, which have correlation coefficients with ash yield ranging from 0.20 to 0.39. These elements have similar correlation coefficients to ash yield as well as Al2O3 and SiO2, which suggest aluminosilicate affinity.
Group 4 includes MgO, Cu, and Zn. Among these elements, MgO has high correlation coefficients with CaO and pyritic sulfur, indicating that MgO probably occurs in carbonate minerals and pyrite. Moreover, Cu and Zn both have inorganic and organic affinity, expressed by slightly weak correlation with ash yield.
Group 5 includes Fe2O3, CaO, MnO, Ni, Cu, Co, Ni, As, Mo, Sb, Hg, and Tl. Stibium is associated with the organic matters, which is due to its negative correlation with ash yield. In addition, MnO, Ni, Mo, Co, and As occur in carbonate minerals, demonstrated by high affinity to CaO. Furthermore, Ni, As, Mo, Co, Hg, and Tl are positively correlated with pyritic sulfur. Arsenic, Hg, Co, and Tl have high correlation coefficients with either sulfate or organic sulfur. In summary, these elements are combined with pyritic, sulfate and organic sulfur in coals.

5.2. Selected Elements

5.2.1. TiO2 and Al2O3

Aluminum and Ti are regarded as essentially immobile elements due to their low solubility of oxides and hydroxides in low temperature aqueous solutions [47]. Therefore, the ratios between Al2O3 and TiO2 should be close to the characteristics of their parent rocks [47,48]. The different ratios of Al2O3/TiO2 represent different types of parent rocks. Ratios of Al2O3/TiO2 ranging from 3 to 8 indicate mafic source rocks, 8–21 for intermediate source rocks, and 21–70 for felsic igneous rocks [47,48,49,50,51,52]. The ratio of the No. 4 coal seam samples ranges from 4.36 to 44.50 (18.96 on average), indicating that the sediments of the parent rocks have felsic or intermediate geochemical characteristics.

5.2.2. Zirconium

The concentration of Zr (235 μg/g) is significantly higher than World hard coals (36 μg/g) [41] and Chinese coals (89.50 μg/g) [20]. Zircon is generally thought to be the main mode of occurrence of Zr in most coals [50,53,54]. In studied area, the positive correlation coefficient of Zr-ash (r = 0.36), Zr-Al2O3 (r = 0.35) and Zr-SiO2 (r = 0.39) display that kaolinite may contain Zr but is not high. In addition, Zr has also partly occurs in gorceixite and goyazite, expressed by correlation with P2O5 (r = 0.39), Sr (r = 0.45) and Ba (r = 0.40).

5.2.3. Beryllium

Compared to Chinese coals (2.11 μg/g) [20] and World hard coals (2 μg/g) [41], Be (6.94 μg/g) is enriched in No. 4 coals. Many scholars have stated that beryllium has organic and clay mineral associations in most coals [50,54]. In No. 4 coals, Be has positive correlation with ash yield (r = 0.31), which indicates that Be has inorganic affinity. The high correlation coefficient for Be-TiO2 (r = 0.86), but low correlation coefficients for Be-Al2O3 (0.19) and Be-SiO2 (0.36), suggest that Be is mainly associated with anatase and to a lesser extent, with clay minerals.

5.2.4. Strontium and Ba

Both Sr and Ba show significantly positive correlation with the ash yield (rash = 0.60 and 0.97, respectively), indicating an inorganic association. Strontium and Ba have high correlations with Al2O3 (r = 0.52 and 0.92, respectively) and SiO2 (r = 0.64 and 0.98, respectively), which point to aluminosilicate affinity (mainly in clay minerals) [45]. Moreover, the correlation coefficients of Sr-P2O5 (r = 0.73) and Ba-P2O5 (r = 0.92) display that gorceixite and goyazite may also be the carrier of Sr and Ba. In addition, both of Sr and Ba have high correlation coefficients with TiO2 (r = 0.64 and 0.78, respectively), indicating that Sr and Ba may also occur in anatase. In terms of geochemical properties, Sr/Ba can reflect the sedimentary environment of coal formation. The average Sr/Ba ratio can represent marine sediment (r > 1) and terrestrial sediment (r < 1) [15]. In the studied area, the ratios of Sr and Ba range from 0.09 to 0.37 (0.21 on average), suggesting a terrestrial sedimentary environment.

5.2.5. Lithium

Compared to average Chinese coals [20] and world hard coals [41], Li is relatively enriched in No. 4 coal samples (52.11 μg/g on average). It should be noted that Li concentrations in the partings (132.30 μg/g on average) are typically higher than those of coal benches. Li is positively correlated with ash yield (r = 0.99), Al2O3 (r = 0.99), and SiO2 (r = 0.97), suggesting that Li is associated with silicate and aluminosilicate minerals (mainly as kaolinite) [50]. In previous studies, the supply of sediment to the Datong Coalfield has been determined to originate from the Yinshan Oldland, located to the north of the studied area, which is mainly composed of moyite with an enrichment of Li. This is most likely the dominant source of Li [51]. In addition, the high correlation coefficients of Li-P2O5 (r = 0.91), Li-Sr (r = 0.52) and Li-Ba (r = 0.93) point to that Li may partly has association with gorceixite and goyazite. Furthermore, the high correlation coefficient of Li-TiO2 shows that anatase may also be the carrier of Li. In No. 4 coals, Li largely occurs in kaolinite, followed by anatase, gorceixite and goyazite.

5.2.6. Thallium and Hg

Compared to both average Chinese coal [20] and world hard coal [41], Tl is relatively enriched in the No. 4 coal (2.17 μg/g on average). Moreover, Hg (0.37 μg/g on average) has a higher concentration than that in both Chinese coals (0.16 μg/g) [20] and world hard coals (0.10 μg/g) [41]. Thallium and Hg are negatively associated with ash yield, indicating that they occur in organic matter in the coal. Furthermore, the correlation coefficients of Tl-Sp (r = 0.47) and Hg-Sp (r = 0.60) indicate that Tl and Hg occur as sulfide minerals (pyrite) in the coal. In addition, Tl and Hg have high correlation coefficients with sulfate (r = 0.81 and 0.69, respectively) and organic sulfur (r = 0.87 and 0.80, respectively) [51,52].

5.2.7. Gallium

The Yongdingzhuang coals have a higher Ga (15.75 μg/g) concentration than Chinese coals (6.55 μg/g) [20] and world hard coals (6 μg/g) [41]. Gallium may predominantly occur as inorganic matter in coals (rGa-ash = 0.62). Due to its similar geochemical characteristics with Al, Ga could isomorphously substitute for Al in Al-bearing minerals [33,36]. Therefore, kaolinite is the main carrier of Ga, based on the positive correlation between Ga-Al2O3 (r = 0.63) and Ga-SiO2 (r = 0.62) [53]. Additionally, the correlation coefficients of Ga-P2O5 (r = 0.55), Ga-Sr (r = 0.33) and Ga-Ba (r = 0.60) point to that gorceixite and goyazite may also incorporate a small proportion of Ga.

5.2.8. Fluorine

The concentration of fluorine in No. 4 coals (123.54 μg/g on average) is higher than that in Chinese coals (130 μg/g) [20] and world hard coals (80 μg/g) [41]. The high correlation coefficient between F and ash yield (r = 0.96) indicates an inorganic affinity. Fluorine is significantly positively correlated with Al2O3 (r = 0.95) and SiO2 (r = 0.95), indicating a close relationship between F and kaolinite. Additionally, the correlation coefficients of F-P2O5 (r = 0.91), F-Sr (r = 0.64), and F-Ba (r = 0.94) indicate that F also occurs in gorceixite and goyazite [36,51]. Moreover, F is positively correlated with TiO2 (r = 0.58), which is suggestive that anatase is also one of the carriers of F. And thus, F largrly occurs in kaolinite and to a lesser extent, in anatase, gorceixite and goyazite.

5.3. Rare Earth Elements and Yttrium

5.3.1. Geochemical Characteristics of REY

The REY concentration in these coals ranges from 57.74 to 282.78 μg/g (149.09 μg/g on average), much higher than both average Chinese coal (135.89 μg/g) [20] and world hard coal (68.27 μg/g) [41]. The parting samples YDZ4-4 (339.88 μg/g) and YDZ4-8 (144.76 μg/g) have relatively higher concentrations than the other samples. In general, the REY concentration in the coal bench samples underlying partings (YDZ4-4) is higher than other samples, which are probably due to leaching, as previously reported by Crowley et al. [55] and Dai et al. [40]. However, the REY concentration of parting (YDZ4-8) is lower than that of the underlying and overlying coal benches.
Based on Seredin-Dai’s classification [56], the REY were divided into three types: light (L-REY including La, La, Ce, Pr, Nd, and Sm), medium (M-REY including, Eu, Gd, Tb, Dy, and Y), and heavy (H-REY including, Ho, Er, Tm, Yb, and Lu). The concentration of LREY (34.4–219.25 μg/g, 92.65 μg/g on average) is much higher than that of MREY (16.76–58.51 μg/g, 31.25 μg/g on average) and HREY (3.15–8.85 μg/g, 5.32 μg/g on average) (Table 5). In the studied area, the correlation coefficient between REY and ash yield (r = 0.68) indicates that REY may occur as inorganic matter in coals. Additionally, the correlation coefficients of REY-Al2O3 (r = 0.58), REY-SiO2 (r = 0.70), and REY-P2O5 (r = 0.65) suggest that REY occur in silicate and aluminosilicate or phosphate minerals.

5.3.2. Patterns of REY

In general, to investigate the fractionation of REY concentrations in coal, the REY should be normalized by standard materials that have similar origins to coal [55,56]. As a result, it is advisable to use the UCC (Upper Continental Crust) as the standard reference for normalization rather than chondrite [56,57,58].
All of the coal samples are characterized by no pronounced or weak negative Ce anomalies (δCe = CeN/CeN * ranging from 0.78 to 1.0, average of 0.92) [58] and no pronounced and weak negative Eu anomalies (δEu = EuN/EuN * ranging from 0.80 to 1.04, average of 0.92) (Figure 8) [59]. Three types of coal benches were identified: L-type (L-REY; LaN/LuN > 1), M-type (MREY; LaN/SmN < 1, GdN/LuN > 1), and H-type (H-REY; LaN/LuN < 1) [56].
The REY enrichment patterns can be characterized as H-type in most coal benches (YDZ4-2, YDZ4-3, YDZ4-12, and YDZ4-15). Coal samples with similar distribution patterns include YDZ4-5, YDZ4-7, YDZ4-10, YDZ4-13, and YDZ4-14 and can be characterized as M-H type enrichment. The remaining coal samples are characterized as L-type enrichment as well as two partings (YDZ4-4 and YDZ4-8). The L-type enrichment generally reflects a terrigenous origin [56]. The H-type enrichment is probably due to the injection of hydrothermal solutions, while the M-type is possibly related to natural waters [56]
In the parting sample YDZ4-8, Ce shows a slight positive Ce anomaly (δCe = 1.08) with a low concentration of REE, which is due to groundwater leaching [40,55]. Cerium is the only rare earth element that can be oxidized to Ce4+ and could have been precipitated in-situ, leading to high Ce and low REE concentration [51].
Dai showed that positive Eu anomalies could be caused by over estimation of Eu during the ICP-MS analysis due to interference from BaO or BaOH [58]. If Ba/Eu is > 1000, the interfered Eu is highly elevated. This indicates that when samples contain Ba/Eu less than 1000, the interference of Ba on Eu can be ignored [60]. Although No. 4 coals have high correlation coefficient between Ba and Eu (r = 0.60), low Ba/Eu value (24.50–108.77, 71.16 on average) may indicate that Eu anomalies in these samples are not caused by the interference of Ba.
As previously reported, coals with input of felsic or felsic-intermediate terrigenous materials usually display distinct negative Eu anomalies [58]. Furthermore, the ratio of Al2O3/TiO2 (18.96 on average) also indicates that the input of the No. 4 coals is felsic or felsic-intermediate terrigenous materials. And thus, the Eu in No. 4 coal would be expected to have negative anomalies because the sediment source region is mainly of felsic to intermediate materials [58]. The partings (including YDZ4-4 and YDZ 4-8) have negative Eu anomalies with L-type enrichment, indicating that partings originated from felsic or felsic-intermediate terrigenous materials [56,58]. The coal bench samples, including YDZ4-1, YDZ4-6, YDZ4-9 and YDZ4-11, have no pronounced or weak negative Eu anomalis with L-type enrichment, which is due to that the input of the coals mainly originated from felsic or felsic-intermediate terrigenous materials and to a lesser extent, from mafic terrigenous materials [56,58,61]. This may be due to that the mafic terrigenous materials are characterized by positive Eu anomalies which overprinted the negative Eu negative anomalies caused by input of the felsic or felsic-intermediate terrigenous materials [56,58,61]. In addition, the samples include YDZ4-2, YDZ4-3, YDZ4-5, YDZ4-7, YDZ4-10, YDZ4-12, YDZ4-13, YDZ4-14, and YDZ4-15, showing no pronounced or weak negative Eu anomalies with H- and M-H type enrichment. In these samples, Eu dispalys no pronounced or weakly negative anomalies, probably due to the injection of hydrothermal solutions that is characterized by positive Eu anomalies, which overprinted the negative Eu anomalies inherited from the terrigenous materials of the sediment source region [56,58,62].
In conclusion, the REY originated from the felsic or felsic-intermediate terrigenous materials (granite of Yinshan Oldland), and the natural waters or hydrothermal solutions that may circulate in coal basins [61,62,63].

6. Conclusions

The geochemical and mineralogical characteristics of the coal seam No. 4 of the Yongdingzhuang Mine are summarized below:
(1)
The No. 4 coal samples of the Yongdingzhuang Mine have a medium ash yield content (average 20.76%), a low moisture content (average 1.46%), a medium-high volatile content (average 27.45%), and a low sulfur content (average 0.70%).
(2)
The mineralogical compositions are mainly kaolinite and quartz with minor amounts of pyrite and anatase. Kaolinite occurs in the form of infillings in fusinite and disseminations in collodetrinite, suggesting syngenetic and early diagenetic authigenic origin. In addition, quartz occurs primarily as detrital grains derived from the source region.
(3)
The ratio of Al2O3 and TiO2 in coal seam No. 4 ranged from 4.36 to 44.50 (18.96 on average), indicating that sediments formed by weathering of the parent rocks, which mainly had felsic or intermediate geochemical characteristics. The ratio of Sr and Ba ranged from 0.09 to 0.37 (0.21 on average), clearly suggesting a terrestrial sedimentary environment.
(4)
Compared to both average Chinese coals and average world hard coals, REY in the No. 4 coal seam have higher concentration. The REY mainly occurs as inorganic matter in the ash yield, which is consistent with its strong correlation with ash yield. Furthermore, no pronounced or negative Ce anomalies and weak negative or positive Eu anomalies demonstrate that the REY originated from granite of Yinshan Oldland and natural waters or hydrothermal solutions that may circulate in coal basins.
(5)
Al2O3 and SiO2 are prevailing abundant major oxides in No. 4 coals, with higher SiO2/Al2O3 (1.54), compared to average Chinese coals, with a large proportion of SiO2 in the form of free silica within coals. With regard to valuable elements, the concentrations of Al, Li, Ga, Zr, Nb, Ta, Hf, Th, and REY were slightly higher than those of average world hard coals. In some coal seams, the concentrations of these elements reached industrial levels and are thus economical to extract. Furthermore, As, Hg, Be, F, U, Pb, Se, Cr, Cd, Ni, and Tl are the main hazardous trace elements in No. 4 coals. Moreover, the Be, Tl, Hg and Pb are slightly higher than in average world hard coals, which is a concern for human and environmental health during combustion and utilization. In terms of the mode of occurrence, Li, F, Cr, Ga, Se, Cd, Zr, Pb, Nb, Ta, and Hf occur as inorganic matter in clay minerals. Cobalt, Ni, As, Tl, and Hg have a strong correlation with sulfur, suggesting a occurrence in sulfide minerals. Lithium and F also occur in anatase, gorceixite and goyazite. Beryllium has affinity to anatase; gallium is mainly associated with kaolinite and to a lesser extent, with gorceixite and goyazite; zirconium also occurs as inorganic matter in ncluding kaolinie, gorceixite and goyazite. These elements and minerals should be further investigated in future studies.

Author Contributions

Y.Y. designed the experiments and performed both SEM-EDS and XRD. S.T. guided the experiments and analyzed the data. S.Z. and N.Y. analyzed the experimental data. Y.Y. wrote the bulk of this paper. All authors participated in writing this paper.

Funding

This research was funded by the National Key Basic Research Program of China (No. 2014CB238901) and the Key Program of the National Natural Science Foundation of China (No. 41330317).

Acknowledgments

We are particularly grateful for the anonymous reviewers for providing useful suggestions and comments.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. BP. BP Statistical Review of World Energy June 2014; BP: London, UK, 2014. [Google Scholar]
  2. Dai, S.F.; Finkelman, R.B. Coal geology in China: An overview. Int. Geol. Rev. 2018, 60, 531–534. [Google Scholar] [CrossRef]
  3. Tian, H.Z.; Lu, L.; Hao, J.M.; Gao, J.J.; Cheng, K.; Liu, K.Y.; Qin, P.P.; Zhu, C.Y. A review of key hazardous trace elements in Chinese coals: Abundance, occurrence, behavior during coal combustion and their environmental impacts. Energy Fuels 2013, 27, 601–614. [Google Scholar] [CrossRef]
  4. Tang, S.H.; Sun, S.L.; Qin, Y.; Jiang, Y.F.; Wang, W.F. Distribution characteristics of sulfur and the main harmful trace elements in China’s Coal. Acta Geol. Sin. Engl. Ed. 2008, 82, 722–730. [Google Scholar]
  5. Hower, J.C.; Rimmer, S.M.; Bland, A.E. Geochemistry of the blue gem coal bed, Knox County, Kentucky. Int. J. Coal Geol. 1991, 18, 211–231. [Google Scholar] [CrossRef]
  6. Kolker, A.; Finkelman, R.B. Potentially hazardous elements in coal: Modes of occurrence and summary of concentration data for coal components. Coal Prep. 1998, 19, 133–157. [Google Scholar] [CrossRef]
  7. Dai, S.F.; Yang, J.Y.; Ward, C.R.; Hower, J.C.; Liu, H.D.; Garrison, T.M.; French, D.; O’Keefe, J.M.K. Geochemical and mineralogical evidence for a coal-hosted uranium deposit in the Yili Basin, Xinjiang, northwestern China. Ore Geol. Rev. 2015, 70, 1–30. [Google Scholar] [CrossRef]
  8. Dai, S.F.; Zeng, R.S.; Sun, Y.Z. Enrichment of arsenic, antimony, mercury, and thallium in a Late Permian anthracite from Xingren, Guizhou, Southwest China. Int. J. Coal Geol. 2006, 66, 217–226. [Google Scholar] [CrossRef]
  9. Kolker, A.; Senior, C.; van Alphen, C.; Koenig, A.; Geboy, N. Mercury and trace element distribution in density separates of a South African Highveld (#4) coal: Implications for mercury reduction and preparation of export coal. Int. J. Coal Geol. 2017, 170, 7–13. [Google Scholar]
  10. Seredin, V.V.; Dai, S.F.; Sun, Y.Z.; Chekryzhov, I.Y. Coal deposits as promising sources of rare metals for alternative power. Appl. Geochem. 2013, 31, 1–11. [Google Scholar] [CrossRef]
  11. Dai, S.F.; Finkelman, R.B. Coal as a promising source of critical elements: Progress and future prospects. Int. J. Coal Geol. 2018, 186, 155–164. [Google Scholar] [CrossRef]
  12. Dai, S.F.; Yan, X.Y.; Ward, C.R.; Hower, J.C.; Wang, X.B.; Zhao, L.; Ren, D.Y.; Finkelman, R.B. Valuable elements in Chinese coals: A review. Int. Geol. Rev. 2018, 60, 590–620. [Google Scholar] [CrossRef]
  13. Dai, S.F.; Ward, C.R.; Granham, I.T.; French, D.; Hower, J.C.; Zhao, L.; Wang, X.B. Altered volcanic ashes in coal and coal-bearing sequences: A review of their nature and significance. Earth Sci. Rev. 2017, 175, 44–74. [Google Scholar] [CrossRef]
  14. Dai, S.F.; Chekryzhov, I.Y.; Seredin, V.V.; Nechaev, V.P.; Granham, I.T.; Hower, J.C.; Ward, C.R.; Ren, D.Y.; Wang, X.B. Metalliferous coal deposits in East Asia (Primorye of Russia and South China): A review of geodynamic controls and styles of mineralization. Gondwana Res. 2016, 29, 60–82. [Google Scholar] [CrossRef]
  15. Wang, A. Discriminant effect of sedimentary environment by the Sr/Ba ratio of different existing forms. Acta Sedimentol. Sin. 1996, 3, 297–304. [Google Scholar]
  16. Dai, S.F.; Wang, P.P.; Ward, C.R.; Tang, Y.G.; Song, X.L.; Jiang, J.H.; Hower, J.C.; Li, T.J.; Seredin, V.V.; Wagner, N.J.; et al. Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–CO2-mixed hydrothermal solutions. Int. J. Coal Geol. 2015, 152, 19–46. [Google Scholar] [CrossRef]
  17. Hower, J.C.; Granite, E.J.; Mayfield, D.B.; Lewis, A.S.; Finkelman, R.B. Notes on contributions to the science of rare earth element enrichment in coal and coal combustion by-products. Minerals 2016, 6, 32. [Google Scholar] [CrossRef]
  18. Dou, G.M. Datong Coalfield Carboniferous-Permian Coal Seam Occurrence Characteristics and Control Effects; Taiyuan University of Technology: Taiyuan, China, 2013; (In Chinese with English abstract). [Google Scholar]
  19. Liu, B.J.; Lin, M.Y. Enrichment mechanism of lithium in coal seam No. 9 of the Pingshuo mining district, Ningwu coalfield. Geol. Explor. 2014, 50, 1070–1075, (In Chinese with English abstract). [Google Scholar]
  20. Dai, S.F.; Ren, D.Y.; Chou, C.-L.; Finkelman, R.B.; Seredin, V.V.; Zhou, Y.P. Geochemistry of trace elements in Chinese coals: A review of abundances, genetic types, impacts on human health, and industrial utilization. Int. J. Coal Geol. 2012, 94, 3–21. [Google Scholar] [CrossRef]
  21. Liu, D.N.; Zhou, A.C.; Chang, Z.G. Geochemistry characteristics of major and rare earth elements in No. 8 raw and weathered coal from Taiyuan Formation of Datong Coalfield. J. China Coal Soc. 2015, 40, 422–430, (In Chinese with English abstract). [Google Scholar]
  22. Liu, D.N.; Zhou, A.C.; Ma, M.L. Coal facies characteristics of No. 5 coal seam in Baidong Mine Area, Datong Coalfield. Coal Geol. China 2011, 23, 1–4, (In Chinese with English abstract). [Google Scholar]
  23. China Coal Research Institute. GB/T 482-2008. Sampling of Coal Seams; Chinese National Standard; General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2008. (In Chinese)
  24. Dai, S.F.; Wang, X.B.; Zhou, Y.P.; Hower, J.C.; Li, D.H.; Chen, W.M.; Zhu, X.W.; Zou, J.H. Chemical and mineralogical compositions of silicic, mafic, and alkali tonsteins in the Late Permian coals from the Songzao Coalfield, Chongqing, Southwest China. Chem. Geol. 2011, 282, 29–44. [Google Scholar] [CrossRef]
  25. Li, X.; Dai, S.F.; Zhang, W.G.; Li, T.; Zheng, X.; Chen, W.M. Determination of As and Se in coal and coal combustion products using closed vessel microwave digestion and collision/reaction cell technology (CCT) of inductively coupled plasma mass spectrometry (ICP-MS). Int. J. Coal Geol. 2014, 124, 1–4. [Google Scholar] [CrossRef]
  26. ASTM. Standard Test Method for Total Fluorine in Coal and Coke by Pyrohydrolytic Extraction and Ion Selective Electrode or Ion Chromatograph Methods; Standard D5987-96, 2002; ASTM International: West Conshohocken, PA, USA, reapproved 2007.
  27. Dai, S.F.; Hower, J.C.; Ward, C.R.; Guo, W.M.; Song, H.J.; O’Keefe, J.M.K.; Xie, P.P.; Hood, M.M.; Yan, X.Y. Elements and phosphorus minerals in the middle Jurassic inertinite-rich coals of the Muli Coalfield on the Tibetan Plateau. Int. J. Coal Geol. 2015, 144, 23–47. [Google Scholar] [CrossRef]
  28. China Coal Research Institute. GB/T 15224.1-2010, Classification for Quality of Coal, Part 1; General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2011. (In Chinese)
  29. China Coal Science Research Institute. MT/T850-2000, Classification for Total Moisture in Coal; Chinese National Standard; General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2000. (In Chinese)
  30. China Coal Research Institute. MT/T849-2000, Classification for Volatile Matter of Coal; Chinese National Standard; General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2000. (In Chinese)
  31. China Coal Research Institute. GB/T 15224.2-2010, Classification for Quality of Coal, Part 2; General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2011. (In Chinese)
  32. Ward, C.R. Minerals in bituminous coals of the Sydney Basin (Australia) and the Illinois Basin (U.S.A.). Int. J. Coal Geol. 1989, 13, 455–479. [Google Scholar] [CrossRef]
  33. Dai, S.F.; Jiang, Y.F.; Ward, C.R.; Gu, L.D.; Seredin, V.V.; Liu, H.D.; Zhou, D.; Wang, X.B.; Sun, Y.Z.; Zou, J.H.; et al. Mineralogical and geochemical compositions of the coal in the Guanbanwusu Mine, Inner Mongolia, China: Further evidence for the existence of an Al (Ga and REE) ore deposit in the Jungar Coalfield. Int. J. Coal Geol. 2012, 98, 10–40. [Google Scholar] [CrossRef]
  34. Kang, J.; Li, X. Modes of occurrence of minerals in the Carboniferous coals from the Wuda Coalfield, northern China: With an emphasis on apatite formation. Arabian J. Geosci. 2016, 9, 606. [Google Scholar] [CrossRef]
  35. Yang, N.; Tang, S.H.; Zhang, S.H.; Chen, Y.Y. Modes of occurrence and abundance of trace elements in Pennsylvanian coals from the Pingshuo Mine, Ningwu Coalfield, Shanxi Province, China. Minerals 2016, 6, 40. [Google Scholar] [CrossRef]
  36. Dai, S.F.; Zou, J.H.; Jiang, Y.F.; Ward, C.R.; Wang, X.B.; Li, T.; Xue, W.F.; Liu, S.D.; Tian, H.M.; Sun, X.H. Mineralogical and geochemical compositions of the Pennsylvanian coal in the Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, China: Modes of occurrence and origin of diaspore, gorceixite, and ammonian illite. Int. J. Coal Geol. 2012, 94, 250–270. [Google Scholar] [CrossRef]
  37. Querol, X.; Chinenon, S.; Lopez-Soler, A. Iron sulphide precipitation sequence in Albian coals from the Maestrazgo basin, southeastern Iberean range, northeastern Spain. Int. J. Coal Geol. 1989, 11, 171–189. [Google Scholar] [CrossRef]
  38. Dai, S.F.; Seredin, V.V.; Ward, C.R.; Hower, J.C.; Xing, Y.W.; Zhang, W.G.; Song, W.J.; Wang, P.P. Enrichment of U–Se–Mo–Re–V in coals preserved within marine carbonate successions: Geochemical and mineralogical data from the Late Permian Guiding Coalfield, Guizhou, China. Miner. Depos. 2015, 50, 159–186. [Google Scholar] [CrossRef]
  39. Xiao, L.; Zhao, B.; Duan, P.P.; Shi, Z.X.; Ma, J.L.; Lin, M.Y. Geochemical characteristics of trace elements in the No. 6 Coal seam from the Chuancaogedan Mine, Jungar Coalfield, Inner Mongolia, China. Minerals 2016, 6, 28. [Google Scholar] [CrossRef]
  40. Dai, S.F.; Ren, D.Y.; Chou, C.-L.; Li, S.S.; Jiang, Y.F. Mineralogy and geochemistry of the No. 6 Coal (Pennsylvanian) in the Junger Coalfield, Ordos Basin, China. Int. J. Coal Geol. 2006, 66, 253–270. [Google Scholar] [CrossRef]
  41. Ketris, M.P.; Yudovich, Y.E. Estimations of clarkes for carbonaceous biolithes: World average for trace element concentrations in black shales and coals. Int. J. Coal Geol. 2009, 78, 135–148. [Google Scholar] [CrossRef]
  42. Spears, D.; Zheng, Y. Geochemistry and origin of elements in some UK coals. Int. J. Coal Geol. 1999, 38, 161–179. [Google Scholar] [CrossRef]
  43. Eskenazy, G.; Finkelman, R.B.; Chattarjee, S. Some considerations concerning the use of correlation coefficients and cluster analysis in interpreting coal geochemistry data. Int. J. Coal Geol. 2010, 83, 491–493. [Google Scholar] [CrossRef]
  44. Kortenski, J.; Sotirov, A. Trace and major element concentration and distribution in Neogene lignite from the Sofia basin. Int. J. Coal Geol. 2002, 52, 63–82. [Google Scholar] [CrossRef]
  45. Dai, S.F.; Wang, X.B.; Seredin, V.V.; Hower, J.C.; Ward, C.R.; O’Keefe, J.M.K.; Huang, W.H.; Li, T.; Li, X.; Liu, H.D. Petrology, mineralogy, and geochemistry of the Ge-rich coal from the Wulantuga Ge ore deposit, Inner Mongolia, China: New data and genetic implications. Int. J. Coal Geol. 2012, 90, 72–99. [Google Scholar] [CrossRef]
  46. Yang, N.; Tang, S.H.; Zhang, S.H.; Chen, Y.Y. Mineralogical and geochemical compositions of the No. 5 Coal in Chuancaogedan Mine, Junger Coalfield, China. Minerals 2015, 5, 788–800. [Google Scholar] [CrossRef]
  47. Hayashi, K.I.; Fujisawa, H.; Holland, H.D.; Ohmoto, H. Geochemistry of ~1.9 Ga sedimentary rocks from northeastern Labrador, Canada. Geochim. Cosmochim. Acta 1997, 61, 4115–4137. [Google Scholar] [CrossRef]
  48. He, B.; Xu, Y.G.; Zhong, Y.T.; Guan, J.P. The Guadalupian–Lopingian boundary mudstones at Chaotian (SW China) are clastic rocks rather than acidic tuffs: Implication for a temporal coincidence between the end-Guadalupian mass extinction and the Emeishan volcanism. Lithos 2010, 119, 10–19. [Google Scholar] [CrossRef]
  49. Dai, S.F.; Luo, Y.B.; Seredin, V.V.; Ward, C.R.; Hower, J.C.; Zhao, L.; Liu, S.D.; Tian, H.M.; Zou, J.H. Revisiting the late Permian coal from the Huayingshan, Sichuan, southwestern China: Enrichment and occurrence modes of minerals and trace elements. Int. J. Coal Geol. 2014, 122, 110–128. [Google Scholar] [CrossRef]
  50. Finkelman, R.B. Modes of Occurrence of Trace Elements in Coal; U.S. Geological Survey Open-File Report No. OFR-81-99; U.S. Geological Survey: Reston, VA, USA, 1981; p. 301.
  51. Dai, S.F.; Li, D.; Chou, C.-L.; Zhao, L.; Zhang, Y.; Ren, D.Y.; Ma, Y.W.; Sun, Y.Y. Mineralogy and geochemistry of boehmite-rich coals: New insights from the Haerwusu Surface Mine, Jungar Coalfield, Inner Mongolia, China. Int. J. Coal Geol. 2008, 74, 185–202. [Google Scholar] [CrossRef]
  52. Duan, P.P.; Wang, W.F.; Liu, X.H.; Qian, F.C.; Sang, S.X.; Xu, S.C. Distribution of As, Hg and other trace elements in different size and density fractions of the Reshuihe high-sulfur coal, Yunnan Province, China. Int. J. Coal Geol. 2017, 173, 129–141. [Google Scholar] [CrossRef]
  53. Finkelman, R.B. Trace and minor elements in coal. In Organic Geochemistry; Engel, M.H., Macko, S.A., Eds.; Plenum: New York, NY, USA, 1993; pp. 593–607. [Google Scholar]
  54. Swaine, D.J. Trace Elements in Coal; Butterworths: London, UK, 1990. [Google Scholar]
  55. Crowley, S.S.; Stanton, R.W.; Ryer, T.A. The effects of volcanic ash on the maceral and chemical composition of the C coal bed, Emery Coal Field, Utah. Org. Geochem. 1989, 14, 315–331. [Google Scholar] [CrossRef]
  56. Seredin, V.V.; Dai, S.F. Coal deposits as potential alternative sources for lanthanides and yttrium. Int. J. Coal Geol. 2012, 94, 67–93. [Google Scholar] [CrossRef]
  57. Taylor, S.R.; McLennan, S.M. The Continental Crust: Its Composition and Evolution; Blackwell: London, UK, 1985; p. 312. [Google Scholar]
  58. Dai, S.F.; Graham, I.T.; Ward, C.R. A review of anomalous rare earth elements and yttrium in coal. Int. J. Coal Geol. 2016, 159, 82–95. [Google Scholar] [CrossRef]
  59. Bau, M.; Dulski, P. Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa. Precambrian Res. 1996, 79, 37–55. [Google Scholar] [CrossRef]
  60. Yan, X.Y.; Dai, S.F.; Graham, I.T.; He, X.; Shan, K.H.; Liu, X. Determination of Eu concentrations in coal, fly ash and sedimentary rocks using a cation exchange resin and inductively coupled plasma mass spectrometry (ICP-MS). Int. J. Coal Geol. 2018, 19, 152–156. [Google Scholar] [CrossRef]
  61. Scott, C.T.; Deonarine, A.; Kolker, A.; Adams, M.; Holland, J.F. Size distribution of rare earth elements in coal ash. In Proceedings of the World of Coal Ash Conference, Nashville, TN, USA, 5–7 May 2015. [Google Scholar]
  62. Hower, J.C.; Eble, C.F.; O’Keefe, J.M.K.; Dai, S.F.; Wang, P.P.; Xie, P.P.; Liu, J.J.; Ward, C.R.; French, D. Petrology, palynology, and geochemistry of Gray Hawk Coal (Early Pennsylvanian, Langsettian) in Eastern Kentucky, USA. Minerals 2015, 5, 592–622. [Google Scholar] [CrossRef]
  63. Seredin, V.V. Rare earth elements in germanium-bearing coal seams of the Spetsugli Deposit (Primor’e Region, Russia). Geol. Ore Depos. 2005, 47, 238–255. [Google Scholar]
Minerals 08 00297 g001 550
Figure 1. Location map of both the Datong Coalfield and the Yongdingzhuang Mine [18].
Figure 1. Location map of both the Datong Coalfield and the Yongdingzhuang Mine [18].
Minerals 08 00297 g001
Minerals 08 00297 g002 550
Figure 2. General stratigraphic sequence of the Datong Coalfield.
Figure 2. General stratigraphic sequence of the Datong Coalfield.
Minerals 08 00297 g002
Minerals 08 00297 g003 550
Figure 3. X-ray diffraction (XRD) pattern of coal sample YDZ4-11 K, Kaolinite; Q, Quartz; Py, Pyrite; An, Anatase.
Figure 3. X-ray diffraction (XRD) pattern of coal sample YDZ4-11 K, Kaolinite; Q, Quartz; Py, Pyrite; An, Anatase.
Minerals 08 00297 g003
Minerals 08 00297 g004 550
Figure 4. Kaolinite and quartz in the No. 4 coal. (A) Kaolinite in fusinite (reflected light) (500×); (B) kaolinite in collodetrinite (reflected light) (500×); (C) crystalline quartz (SEM, secondary electron image); (D) quartz in collodetrinite (reflected light) (500×).
Figure 4. Kaolinite and quartz in the No. 4 coal. (A) Kaolinite in fusinite (reflected light) (500×); (B) kaolinite in collodetrinite (reflected light) (500×); (C) crystalline quartz (SEM, secondary electron image); (D) quartz in collodetrinite (reflected light) (500×).
Minerals 08 00297 g004
Minerals 08 00297 g005a 550Minerals 08 00297 g005b 550
Figure 5. Pyrite and anatase in coals. (A) Pyrite in collodetrinite (oil immersion reflected light) (500×); (B) pyrite in fusinite (reflected light) (500×); (C) crystalline anatase (SEM, secondary electron image); and (D) energy dispersive X-ray spectrometry (EDS).
Figure 5. Pyrite and anatase in coals. (A) Pyrite in collodetrinite (oil immersion reflected light) (500×); (B) pyrite in fusinite (reflected light) (500×); (C) crystalline anatase (SEM, secondary electron image); and (D) energy dispersive X-ray spectrometry (EDS).
Minerals 08 00297 g005aMinerals 08 00297 g005b
Minerals 08 00297 g006 550
Figure 6. Concentration coefficients of trace elements in No. 4 coal; (A) normalized by average concentrations in the world hard coals; (B) normalized by the average concentration in the Chinese coals.
Figure 6. Concentration coefficients of trace elements in No. 4 coal; (A) normalized by average concentrations in the world hard coals; (B) normalized by the average concentration in the Chinese coals.
Minerals 08 00297 g006
Minerals 08 00297 g007 550
Figure 7. Concentration variations of trace elements and rare earth elements and yttrium (REY) as well as ash yield of the No. 4 coals.
Figure 7. Concentration variations of trace elements and rare earth elements and yttrium (REY) as well as ash yield of the No. 4 coals.
Minerals 08 00297 g007
Minerals 08 00297 g008a 550Minerals 08 00297 g008b 550
Figure 8. REY distribution patterns in the coal and partings, normalized to the upper continental crust (UCC); (A) pattern of LREE in coals; (B) pattern of MREE in coals; (C) pattern of HREE in coals; (D) pattern of LREE in partings.
Figure 8. REY distribution patterns in the coal and partings, normalized to the upper continental crust (UCC); (A) pattern of LREE in coals; (B) pattern of MREE in coals; (C) pattern of HREE in coals; (D) pattern of LREE in partings.
Minerals 08 00297 g008aMinerals 08 00297 g008b
Table
Table 1. Bench thickness (cm), proximate, and forms of sulfur (%) of No. 4 coal samples from the Yongdingzhuang Mine.
Table 1. Bench thickness (cm), proximate, and forms of sulfur (%) of No. 4 coal samples from the Yongdingzhuang Mine.
SampleThickness (cm)MadAdVdafSt.dSp.dSs.dSo.d
YDZ4-1201.714.4733.431.350.960.010.38
YDZ4-2201.5613.631.160.510.300.010.19
YDZ4-3201.849.8230.611.100.740.010.35
YDZ4-4100.7483.1918.350.100.090.010.00
YDZ4-5101.6612.935.940.620.180.010.43
YDZ4-6101.2948.6716.070.180.160.010.01
YDZ4-7101.2839.324.130.200.180.010.01
YDZ4-850.9561.2119.430.200.170.010.02
YDZ4-9201.2827.4628.530.430.200.010.21
YDZ4-10201.5512.4326.871.020.200.010.80
YDZ4-11201.3911.8925.681.970.310.021.65
YDZ4-12151.3620.2323.920.560.150.010.40
YDZ4-13151.3119.5821.680.370.330.010.03
YDZ4-14151.3320.5521.890.350.250.010.09
YDZ4-15101.5512.5132.140.530.340.010.18
AVE-1.46 20.76 27.45 0.70 0.33 0.01 0.36
M, moisture; A, ash yield; V, volatile matter; ad, air-dry basis; d, dry basis; daf, dry and ash-free basis; St, total sulfur; Sp, pyritic sulfur; Ss, sulfate sulfur; So, organic sulfur.
Table
Table 2. Concentration of major oxides in No. 4 coal (%) (Recalculated from the dry ash basis to the whole-coal basis).
Table 2. Concentration of major oxides in No. 4 coal (%) (Recalculated from the dry ash basis to the whole-coal basis).
SampleLOISiO2TiO2Al2O3Fe2O3MgOCaOMnONa2OK2OP2O5SiO2/Al2O3
YDZ4-185.537.490.184.571.280.070.290.00320.00480.020.0131.64
YDZ4-286.46.520.175.001.180.070.260.00140.00210.040.0061.30
YDZ4-390.186.120.163.080.140.030.120.0011bdl0.010.0041.99
YDZ4-416.8148.540.8032.270.500.120.090.00120.00730.620.0611.50
YDZ4-587.17.000.125.340.230.020.050.00030.00020.030.0051.31
YDZ4-651.3327.001.6619.390.260.020.06bdl0.00670.070.0351.39
YDZ4-760.721.730.9815.980.320.020.060.00070.00950.050.0441.36
YDZ4-838.7933.351.0026.110.260.020.07bdl0.01030.060.0241.28
YDZ4-972.5414.760.3911.650.350.020.090.00050.00590.040.0131.27
YDZ4-1087.576.100.154.930.970.020.090.00020.00220.010.0041.24
YDZ4-1188.115.300.274.072.080.010.050.00040.00250.010.0051.30
YDZ4-1279.7712.001.336.220.450.010.050.0009bdl0.030.0141.93
YDZ4-1380.4211.671.406.100.210.010.050.0005bdl0.020.0131.91
YDZ4-1479.4512.491.386.250.220.010.050.0006bdl0.020.0132.00
YDZ4-1587.496.600.584.960.170.010.050.00020.00200.020.0061.33
AVE79.7411.140.677.160.600.030.100.00080.00280.030.011.54
Chinese coal 1-8.470.335.984.850.221.230.0150.160.190.091.42
CC-1.322.031.200.120.140.080.050.020.160.11-
LOI, loss on ignition; 1, Dai, et al. (2012) [20]; nd, not detected; bdl, below detected limit; CC, concentration coefficients between Chinese coal and No. 4 coal.
Table
Table 3. Concentrations of trace elements in the No. 4 coal from the Yongdingzhuang Mine (μg/g) (on whole-coal basis).
Table 3. Concentrations of trace elements in the No. 4 coal from the Yongdingzhuang Mine (μg/g) (on whole-coal basis).
ElementsLiBeFScVCrCoNiCuZnGaAsSeRbSrZr
YDZ4-121.273.84928.1526.103431.1064.2052.3034.3016.9024.332.470.8011.60306
YDZ4-212.505.53779.0117.4028.1016.4030.2057.4026.6013.401.712.870.689.40182
YDZ4-37.912.39965.0819.8014.9017.9027.6046.3021.1018.2015.071.321.169.46267
YDZ4-490.602.835505.9324.5048.604.3725.9018.2020.8025.201.291.4724.90116152
YDZ4-520.602.76964.91361420.5026.4058.2027.70221.533.941.229.60355
YDZ4-61928.302671750.8037.302.4024.4058.303131.201.685.422.8612.50330
YDZ4-71457.442481637.3024.901.8814.103424.4018.800.823.131.8718.50268
YDZ4-81746.153279.2629.5014.202.7914.1018.4022.8026.301.022.401.8810.80218
YDZ4-985.604.831687.5323.8013.7010.8018.9047.3029.2013.201.582.991.3611.50200
YDZ4-1026.705.23834.6715.1015.8016.9024.7016.9012.707.168.682.870.342.86108
YDZ4-1117.805.75684.0317.9021.2027.4029.3053.4028.1010.1018.522.380.309.26151
YDZ4-1238.8010.8010010.2036.3038.208.732254.4039.2010.803.403.681.1813.60191
YDZ4-1342.2013.201521251.30478.492472.7054.9013.501.736.550.9215.20242
YDZ4-1438.3011.80961145.8041.407.9821.9061.1057.5013.801.835.900.7112.80238
YDZ4-1528.808.33637.8331.1011.4011.9022.3056.8053.5015.701.374.740.828.12217
AVE52.116.94123.549.0331.4426.3014.0326.9251.4733.8615.756.333.711.0911.11235
World 1142823.702817617162868.301.301810036
Chinese 231.802.111304.3835.1015.407.0813.7017.5041.406.552.783.799.2514089.50
CC 33.723.471.512.441.121.552.341.583.221.212.630.762.860.060.116.53
CC 41.643.290.952.060.901.711.981.972.940.822.402.280.980.120.082.63
ElementsNbMoCdInSbCsBaHfTaWHgTlPbBiThU
YDZ4-113.10110.140.081.400.0834.305.290.411.330.794.6530.900.248.073.52
YDZ4-25.577.420.080.100.920.0632.803.860.391.260.120.6214.500.318.242.17
YDZ4-39.2012.700.120.100.980.1937.505.600.332.440.865.2731.500.287.793.22
YDZ4-431.401.800.080.1712.303.053265.702.963.040.170.4732.601.63263.54
YDZ4-512.808.340.150.121.130.1734.208.270.421.140.310.7756.100.2810.205.11
YDZ4-644.803.760.160.270.430.631439.792.993.030.080.2250.901.4030.806.98
YDZ4-722.702.190.130.200.340.321247.501.691.590.050.1060.100.9723.904.64
YDZ4-826.201.310.110.160.270.281808.511.612.220.080.2439.500.4615.204.29
YDZ4-98.081.930.100.140.520.1772.106.200.530.790.210.76260.2210.403.17
YDZ4-103.507.110.060.070.420.0320.802.410.230.420.462.9119.800.175.091.49
YDZ4-114.635.640.100.138.460.0325.203.350.350.731.179.8213.200.265.251.40
YDZ4-1223.402.680.090.120.320.1477.605.031.391.610.221.2118.200.4321.803.36
YDZ4-13252.790.100.1710.200.1072.206.531.691.830.180.5625.600.5925.203.93
YDZ4-1429.502.400.110.209.070.0765.106.912.092.190.180.5426.600.5924.703.86
YDZ4-1516.903.500.100.115.610.12344.690.770.730.150.7823.900.507.372.69
AVE16.865.500.110.143.060.1659.455.801.021.470.372.1730.560.4814.523.50
World 142.100.200.041.001.101501.200.300.990.100.5891.103.201.90
Chinese 29.443.080.250.050.841.131593.710.620.620.160.4715.10.793.842.43
CC 34.222.620.553.483.060.150.404.843.411.483.683.743.400.444.541.84
CC 41.791.780.442.783.640.140.371.561.652.372.304.622.020.613.781.44
1 Ketris and Yodvich (2009) [41]; 2 Dai et al. (2012) [20]; 3 CC = concentration in investigated coals/world hard coals; 4 CC = concentration in investigated coals/Chinese coals.
Table
Table 4. Correlation coefficients between the concentration of each element in coal and ash yield or selected elements.
Table 4. Correlation coefficients between the concentration of each element in coal and ash yield or selected elements.
Correlation with Ash Yield
rash = 0.7–1.0: Na2O (0.73) **, Al2O3 (0.99) **, SiO2 (0.99) **, P2O5 (0.92) **, K2O (0.88) **, Li (0.99) **, F (0.96) **, Sc (0.87) **, Rb (0.88) **, Nb (0.75) **, In (0.86) **, Cs (0.87) **, Ba (0.97) **, Hf (0.71) **, Ta (0.80) **, Bi (0.88) **, Th (0.77) **, U (0.74) **
rash = 0.4–0.69: TiO2 (0.67) *, Ga (0.62) *, Sr (0.60) *, Cd (0.48), W (0.53), Pb (0.60) *, REY(0.68)
rash = 0.2–0.39: Be (0.31), Cr (0.34), Se (0.36), Zr (0.36)
rash = −0.2–0.19: MgO (−0.19), Cu (0.00), Zn (−0.01)
rash < −0.2: Fe2O3 (−0.34), CaO (−0.27), MnO (−0.27), Co (−0.73) *, Ni (−0.34), As (−0.43), Mo (−0.55), Sb (−0.25), Hg (−0.54), Tl (−0.47)
Correlation with aluminosilicate
rAl-Si = 0.7–1.0: P2O5, K2O, Li, F, Sc, Rb, Nb, In, Cs, Ba, Hf, Ta, Bi, Th, U
rAl-Si = 0.4–0.69: TiO2, Na2O, Ga, Se, Cd, W, Pb, REY
rAl-Si = 0.2–0.39: Be, Cr, Se, Zr
rAl-Si < 0.2: MgO, CaO, MnO, Fe2O3, Co, Ni, Cu, Zn, As, Mo, Sb, Hg, Tl
Correlation with carbonate
rCa > 0.7: MgO (0.98) **, MnO (0.86) **, Ni (0.77) **
rCa = 0.5–0.69: Co (0.53), Mo (0.60) *,
rCa = 0.35–0.69: As (0.49)
Correlation with sulfur
rs > 0.7: Fe2O3 (0.79) **, Co (0.87) **, As (0.89) **, Hg (0.96) **, Tl (0.97) **
rpyritic sulfur >0.7: MnO (0.81) **, Ni (0.82) **, As (0.79) **, Mo (0.74) **
rpyritic sulfur = 0.5–0.69: MgO (0.60) *, CaO (0.67) *, Co (0.63) *, Hg(0.60) *
rpyritic sulfur = 0.35–0.49: Tl (0.47)
rsulfate sulfur > 0.7: Tl (0.81) **
rsulfate sulfur = 0.5–0.69: Hg (0.69) **
rsulfate sulfur = 0.35–0.49: Co (0.46), As (0.46)
rorganic sulfur > 0.7: Hg (0.80) **, Tl (0.87) **
rorganic sulfur = 0.5–0.69: Co (0.66) *, As (0.60) *
Correlation with phosphate
rp > 0.7: Li (0.91) **, F (0.91) **, Sc (0.89) **, Rb (0.79) **, Sr (0.73) **, Cs (0.76) **, In (0.77) **, Ba (0.92) **, Bi (0.85) **, Th (0.74) **
rp = 0.5–0.69: V (0.55), Ga (0.55), Nb (0.68) *, Cd (0.50), Hf (0.64) *, Pb (0.67) *, U (0.68) *
rp = 0.35–0.49: Be (0.39), Cr (0.35), Zr (0.39), W (0.48)
Correlation coefficients between selected elements
Li: Li-Na2O (0.77) **, Li-P2O5 (0.91) **, Li-TiO2 (0.60) *, Li-K2O (0.86) **, Li-F (0.96) **, Li-Ga (0.64) *, Li-Sr (0.52), Li-Ba (0.93) **, Li-Hf (0.68) *, Li-Ta (0.75) **, Li-Th (0.69) **, Li-U (0.72) **
Zr: Zr-Rb (0.63), Zr-Cd (0.94), Zr-Hf (0.85)
Be: Be-TiO2 (0.86), Be-Sr (0.48), Be-Ba (0.44)
Sr: Sr-P2O5 (0.73) **, Sr-TiO2 (0.64)*, Sr-F (0.64) *, Sr-Ba (0.73) **, Sr-Ta (0.62) *, Sr-Hf (0.61) *, Sr-Th (0.75) **, Sr-U (0.56) *
Ba: Ba-TiO2 (0.78) *, Ba-Na2O (0.60), Ba-K2O (0.82) **, Ba-F (0.94) *, Ba-Ga (0.60) *, Ba-Hf (0.74) **, Ba-Ta (0.87) **, Ba-Th (0.87) **
Tl: Tl-Fe2O3 (0.74), Tl-As (0.86) **, Tl-Hg (0.98) **
Hg: Hg-Co (0.81) **, Hg-Fe2O3 (0.66), Hg-As (0.91) **
Ga: Ga-K2O (0.69) **, Ga-F(0.63) **, Ga-Rb (0.85) **, Ga-Zr (0.86) **, Ga-Nb (0.64) *, Ga-Cs (0.87) **, Ga-Cd (0.89) **, Ga-Hf (0.85) **, Ga-U (0.89) **
F: F-Na2O (0.73) **, F-K2O (0.82) **, F-P2O5 (0.91) **, F-Rb (0.88) **, F-Nb (0.66) *, F-In (0.80) **, F-Hf (0.94) **, F-Ta (0.73) **, F-Th (0.72) **, F-U (0.75) **
** Correlation is significant at the 0.01 level (two-tailed); * Correlation is significant at the 0.05 level (two-tailed).
Table
Table 5. Concentration and geochemical parameters of REY in No. 4 coal (on whole-coal basis).
Table 5. Concentration and geochemical parameters of REY in No. 4 coal (on whole-coal basis).
ElementsYDZ4-1YDZ4-2YDZ4-3YDZ4-4YDZ4-5YDZ4-6YDZ4-7YDZ4-8YDZ4-9YDZ4-10YDZ4-11YDZ4-12YDZ4-13YDZ4-14YDZ4-15AVE
La55.3011.607.94100.007.3556.1028.2028.0036.9016.4015.9026.7030.3028.708.6625.39
Ce94.0022.8013.90146.0012.20104.0058.2058.6062.7034.4030.7056.2067.5064.4019.8049.29
Pr11.102.891.8216.701.6611.006.885.396.594.813.166.318.437.542.355.73
Nd42.4012.608.4944.607.1139.8026.4018.1024.6021.7012.0022.3030.2029.409.4922.04
Sm7.312.722.256.262.038.356.093.174.044.412.294.416.005.872.114.45
Eu1.400.500.440.670.421.331.140.570.730.880.440.881.181.180.510.85
Gd6.642.892.294.132.077.475.303.053.693.542.234.205.495.642.314.14
Td1.010.600.430.560.381.351.110.640.650.600.370.821.121.090.460.77
Dy5.554.292.562.872.297.236.053.413.433.362.294.855.925.862.924.35
Y27.0025.8013.5014.0011.6037.3032.8018.8017.0016.7012.8035.0044.8040.9022.1025.95
Ho0.930.910.510.530.431.321.140.700.660.510.430.931.271.180.600.83
Er2.772.871.491.521.153.262.971.881.661.471.192.973.223.131.762.30
Tm0.420.520.300.250.190.590.540.310.290.240.190.460.570.530.310.40
Yb2.712.941.571.591.213.233.071.921.671.291.202.693.283.031.772.28
Lu0.380.450.250.200.170.450.400.220.220.200.160.410.450.440.280.33
∑LREY210.1152.6134.4313.5630.35219.25125.77113.26134.8381.7264.05115.92142.43135.9142.4192.65
∑MREY41.634.0819.2222.2316.7654.6846.426.4725.525.0818.1345.7558.5154.6728.331.25
∑HREY7.217.694.124.093.158.858.125.034.53.713.177.468.798.314.725.32
∑REY258.9294.3857.74339.8850.26282.78180.29144.76164.83110.4985.36169.13209.72198.8975.43149.09
δCe0.860.900.830.800.800.950.951.080.910.880.980.990.961.001.000.92
δEu0.990.790.890.620.970.780.880.810.881.030.940.930.910.931.040.92
LaN/SmN1.130.640.532.400.541.010.691.321.370.561.040.910.760.730.620.81
GdN/LuN1.490.550.771.761.021.411.121.151.431.521.150.861.041.080.701.09
LaN/LuN1.570.280.345.390.461.340.751.341.810.891.040.700.720.700.330.84
TypeLHHLM-HLM-HLLM-HLHM-HM-HH-
N. values normalized by the average REY concentration of Upper Continental Crust. δCe = CeN/CeN * = 2CeN/(LaN + PrN) [57]. δEu = EuN/EuN * = EuN/(0.67 × SmN + 0.33 × TbN) [58].

Share and Cite

MDPI and ACS Style

Yuan, Y.; Tang, S.; Zhang, S.; Yang, N. Mineralogical and Geochemical Characteristics of Trace Elements in the Yongdingzhuang Mine, Datong Coalfield, Shanxi Province, China. Minerals 2018, 8, 297. https://doi.org/10.3390/min8070297

AMA Style

Yuan Y, Tang S, Zhang S, Yang N. Mineralogical and Geochemical Characteristics of Trace Elements in the Yongdingzhuang Mine, Datong Coalfield, Shanxi Province, China. Minerals. 2018; 8(7):297. https://doi.org/10.3390/min8070297

Chicago/Turabian Style

Yuan, Yue, Shuheng Tang, Songhang Zhang, and Ning Yang. 2018. "Mineralogical and Geochemical Characteristics of Trace Elements in the Yongdingzhuang Mine, Datong Coalfield, Shanxi Province, China" Minerals 8, no. 7: 297. https://doi.org/10.3390/min8070297

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop