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Article

Mineralogy and Geochemistry of the Lower Cretaceous Coals in the Junde Mine, Hegang Coalfield, Northeastern China

by
Yingchun Wei
1,2,
Wenbo He
2,
Guohong Qin
3,*,
Anmin Wang
2 and
Daiyong Cao
1
1
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, China
2
College of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083, China
3
School of Geographic Sciences/Hebei Key Laboratory of Environmental Change and Ecological Construction, Hebei Normal University, Shijiazhuang 050024, China
*
Author to whom correspondence should be addressed.
Energies 2022, 15(14), 5078; https://doi.org/10.3390/en15145078
Submission received: 21 June 2022 / Revised: 8 July 2022 / Accepted: 11 July 2022 / Published: 12 July 2022
(This article belongs to the Special Issue Advances in Exploration, Development and Utilization of Coal and Coal-Related Resources)
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Abstract

:
Hegang coalfield is one of the areas with abundant coal resources in Heilongjiang Province. Characteristics of minerals and geochemistry of No. 26 coal (lower Cretaceous coals) from Junde mine, Hegang coalfield, Heilongjiang province, China, were reported. The results showed that No. 26 coal of Junde mine is slightly enriched in Cs, Pb, and Zr compared with world coals. The minerals in No. 26 coal of Junde mine primarily include clay minerals and quartz, followed by calcite, siderite, pyrite, monazite, and zircon. The diagrams of Al2O3–TiO2, Zr/Sc–Th/Sc, Al2O3/TiO2–Sr/Y, and Al2O3/TiO2–La/Yb indicate that the enriched elements in No. 26 coal were mainly sourced from the Late Paleozoic meta-igneous rocks in Jiamusi block. The volcanic ash contribution to No. 26 coal seems very low. Sulfate sulfur indicating oxidation/evaporation gradually decreases during No. 26 coal formation.

1. Introduction

Coal is considered an important source of critical metals [1,2]. The critical metals in coal have become a research hotspot in recent years due to their potential economic significance [2,3] and the geological implications for coal basins [4,5]. Coals with the significant economic value of critical element production are usually called ‘metalliferous coal’ [2,6] or ‘coal-hosted rare-metal deposit’ [7]. More recently, further studies have paid close attention to the occurrence and recovery methods from these coals [8,9,10,11,12,13,14,15,16,17,18,19].
Heilongjiang Province, Northeastern (EN) China, has a vast territory and rich resources. In terms of coal resources, the Hegang coalfield is rich [20,21]. Although there has been much literature focusing on coal geochemical and mineralogical characteristics in China, these works are mainly concentrated in the coals in southwestern and northern China [13,22,23,24,25,26,27,28,29]. In Heilongjiang province, a few studies [30,31] have been carried out about coal-bearing sequences in the Hegang coalfield. Previous investigations have shown that the Hegang coalfield was affected by three periods of tectonic stress and accompanied by multiple periods of volcanic activity, which had an impact on coal quality in the coal basin [32]. There are still two problems to be solved about coal geochemistry in the Hegang coalfield: (1) did the volcanic activity influence the element enrichment in the coals? (2) The occurrence modes and the provenance of elements in the Palaeogene coal-bearing seams have been deeply studied recently in Jilin province [33,34,35,36], neighboring the Heilongjiang province. Is the provenance of trace elements in Hegang coals the same as in the coals from Jilin Province [33,35]? Further investigation of these issues has important theoretical and economic value for improving the comprehensive utilization efficiency of coal measures mineral resources.
To address this issue, we study the minerals and elements characteristics of No. 26 coal in the Hegang coalfield. We also discussed the geological factors influencing element enrichment.

2. Geological Setting

Junde mine is situated in Hegang coalfield, Heilongjiang Province (Figure 1). Geologically, the Hegang coalfield is located on the Jiamusi block inside the Central Asian Orogenic Belt between the Chinese plate and the Siberia plate, and is generally characterized as a semi-covered monoclinic structure dipping eastward. The Hegang coalfield is an important part of the Mesozoic-Cenozoic basin group in the east of Heilongjiang. There are mainly fault structures in the Hegang coalfield, and there are relatively gentle folds in the local area, accompanied by multiple volcanic structures. Proterozoic, Mesozoic and Cenozoic strata developed in the study area [37,38].
The major coal-bearing formation in the Hegang coalfield is the Lower Cretaceous Chengzihe Formation. The Lower Cretaceous Chengzihe Formation consists of gray-white conglomerate, coarse and fine sandstone, gray-yellow medium sandstone, dark gray siltstone, mudstone, coal seams, and tuff. In Hegang coalfield, 36 coal seams are minable or partially minable, which are divided into four coal bearing groups from top to bottom. The first coal seam group includes coal seams No. 1 and No. 2, which are unstable. The second coal seam group includes coal seams No. 3~22. The third coal seam group, including coal seams No. 23~26, is mainly developed in the south of the coalfield, and its thickness gradually thins or even pinches out to the north. The fourth coal seam group includes coal seams No. 27~32.
No. 26 coal, as the main mining seam in Junde mine from Hegang coalfield, is the main research object of this paper. The thickness of No. 26 coal is about 2.9 m, deposited in continental facies [37,38].

3. Sampling and Analytical Techniques

Ten samples were obtained in No. 26 coal in Junde mine, Hegang Coalfield, which include one roof sample, eight coal samples, and one floor sample (Figure 2). From top down, eight coal samples are identified as JD-26-01 to JD-26-08 (Figure 2B). The roof and floor are identified as JD-26-R and JD-26-F, respectively (Figure 2B). All samples are fresh, without pollution and oxidation.
According to ASTM D3173-11, D3174-11 and D3175-11(2011) [39,40,41], the coal samples collected from Junde mine were tested for the proximate analysis. The macerals were obtained based on the ICCP System 1994 (ICCP, 1998, 2001) [42,43] and Pickel, Kus [44]. The total sulfur content was obtained by ZCL-3 automatic sulfur analyzer, and the contents of various sulfur forms in the samples were obtained according to ASTM D3177-02(2011) and ASTM D2492-02(2012) [45,46]. These analyses were made at the Société Générale de Surveillance S.A-China Stand Science and Technology Group Corporation (SGS-CSTC) Standards Technology Service Corporation.
Based on SY/T 5163-2010, the minerals were identified by X-ray diffractometer. The morphology of minerals was observed by the scanning electron microscopy (SEM) with an energy dispersive X-ray spectrometer (EDS). The working distance was 8.4–11.4 mm, and beam voltage is 15.0 kV during the SEM operation. These experiments were conducted at the Beijing Center for Physical and Chemical Analysis (BCPCA).
The cleaned samples used for the geochemical analysis were crushed and ground to less than 200-mesh size using a tungsten carbide ball mill. The Major Oxides contents were obtained using X-ray fluorescence spectrometry (XRF; PANalytical Axios). The trace elements were obtained by the inductively coupled plasma mass spectrometry (ICP-MS, ELEMENT XR). Before ICP-MS analysis, samples were digested by using an UltraClave Microwave High Pressure Reactor (Milestone, Milan, Italy). Multi-element standards (Inorganic Ventures: CCS-1, CCS-4, CCS-5, and CCS-6; GBW07103, GBW07104) were used for trace element concentrations calibration. More method details can be seen in [47]. XRF analyses and the ICP-MS analyses were performed at the China National Nuclear Corporation (CNNC) Beijing Research Institute of Uranium Geology.
In our study, concentration coefficients (CC) proposed by [48] is adopted. CC = ratio of the element contents in the coals/clays to average contents in worldwide coals/clays. On this basis, the concentrations of elements can be classified into six categories, i.e., unusually enriched (CC > 100), significantly enriched (10 < CC < 100), enriched (5 < CC < 10), slightly enriched (2 < CC < 5), normal (0.5 < CC < 2), and depleted (CC < 0.5).

4. Results

4.1. Coal Characteristics and Coal Petrology

As shown in Table 1, the ash yield and total sulfur of Junde coals is 8.6–17.6% (13.0% on average) and 0.54–0.72%, (0.62% on average). The contents above show that No. 26 coals are characterized by low ash and low sulfur based on GB15224.1-2010 and GB15224.2-2010 [49,50]. In addition, sulfur in coal occurs mainly in organic and pyritic sulfur. Sulfate sulfur increases with depth.
The vitrinite (84.8 vol.% on average) is the most abundant macerals in No. 26 coal (Table 2). It is composed mainly of collotelinite (Figure 3A–C,E,I) and collodetrinite (Figure 3A,D,I), and to a lesser extent, by telinite (Figure 3H), with a few corpogelinite and virtrodetrinite. The collodetrinite is usually in matrix form, embedded in quartz (Figure 3B), clay minerals (Figure 3D,I), calcite (Figure 3E), or fracture-filling pyrite (Figure 3G).
The inertinite (8.2 vol.% on average) is the second most abundant macerals in No. 26 coal in the Junde mine (Table 2). It primarily consists of semifusinite (Figure 3D), inertodetrinite, and fusinite (Figure 3F,H), with small amounts of micrinite. In the majority of cases, the cell walls of fusinite and semifusinite are swollen and not intact, indicating the existence of degradation [51,52] (Figure 3D,F,H).
The liptinite (2.2 vol.% on average) is mainly represented by sporinite (1.4 vol.% on average), with trace amounts of cutinite (0.3 vol.% on average), bituminite (0.3 vol.% on average), resinite (0.2 vol.% on average), and suberinite (0.1 vol.% on average).

4.2. Geochemical Features

4.2.1. Major Oxides (MEO)

Table 3 shows the MEO percentages of studied coals and the average value of Chinese coals. The MEO in studied coals are primarily composed of SiO2 (average 7.63%), Al2O3 (average 2.95%) and Fe2O3 (average 1.62%). By comparison with the average values of Chinese coals [22], the percentages of MnO and K2O are a bit higher, while the content of other MEO is near or below (Figure 4). Value of SiO2/Al2O3 of No. 26 coals (average 2.65) exceeds that of Chinese coals [22] and the theoretical figure of SiO2/Al2O3 of kaolinite, probably because a high content of quartz existed in the studied coals (Figure 3B,D).

4.2.2. Trace Elements

Compared to the average figures for world hard coals [53], the trace elements Cs (CC, 3.58), Pb (CC, 2.05) and Zr (CC, 2.04) are slightly enriched in No. 26 coals. Cr, Cd, Ba, Sr, Cu and Bi are depleted (Table 4, Figure 5A).
By comparison with the average figures for world clays [54], the roof sample is slightly enriched in Er (CC, 2.92), Pb (CC,2.78), Bi (CC, 2.37), Yb (CC,2.32), Lu (CC, 2.23), Ho (CC, 2.11), and Dy (CC, 2.08). Other elements are normal or depleted (Figure 5B). In floor sample, only Pb (CC, 2.23) and Bi (CC, 2.19) are slightly enriched, and other elements are normal or depleted (Figure 5C).
In addition, from the vertical section of No. 26 coal seams, the contents of Cs, Pb, and Zr in coal near the host rocks (roof and floor) outclass those in the middle coal seams (Figure 6).
Energies 15 05078 g005 550
Figure 5. CC [48] of trace elements in (A) coals, (B) the roof, and (C) the floor in the Junde mine. Average concentration of trace elements of world hard coals is used to normalize the corresponding element concentration in studied coal samples [53]. Average concentration of trace element of world clays is used to normalize the corresponding element concentration in the studied roof and floor samples [54].
Figure 5. CC [48] of trace elements in (A) coals, (B) the roof, and (C) the floor in the Junde mine. Average concentration of trace elements of world hard coals is used to normalize the corresponding element concentration in studied coal samples [53]. Average concentration of trace element of world clays is used to normalize the corresponding element concentration in the studied roof and floor samples [54].
Energies 15 05078 g005
Table
Table 4. Concentrations of trace elements in Junde mine samples, on a whole coal basis (μg/g).
Table 4. Concentrations of trace elements in Junde mine samples, on a whole coal basis (μg/g).
SampleLiBeScCrCoNiCuZnGaRbSrYNbMoUCdInCsBaLaCe
JD-26-R223.413695.520 32 83 29 221 217 51 19 0.565.4 0.110.0918 221 58 122
JD-26-01194.34.14.97.111 3.4 32 11 65 52 29 11 1.3 2.0 0.140.08 13 51 28 52
JD-26-027.531.554.310 4.5 16 4.3 16 42 6.7 4.6 0.830.89 0.04 0.02 2.0 47 6.4 14
JD-26-03161.71.46.61.49 5.4 21 6.4 16 35 6.3 4.5 1.3 0.98 0.03 0.02 2.0 66 9.9 22
JD-26-04231.62.9141.7162.8 43 9.3 55 27 126.8 1.1 2.2 0.15 0.03 7.235 42 72
JD-26-054.81.11.14.52.4212.4 22 4.2 5.9 23 6.5 4.7 0.91 0.86 0.06 0.03 0.45 28 8.5 17
JD-26-064.60.620.874.81.75.73.6 57 4.1 5.1 27 4.8 8.1 1.6 0.56 0.11 0.02 0.58 27 6.0 12
JD-26-078.11.31.75.92.8103.7 19 4.5 4.4 31 6.7 3.9 1.81.1 0.05 0.02 0.42 34 7.8 19
JD-26-08171.92.6104.1146.2 43 6.7 1727 9.0 6.8 1.5 1.7 0.06 0.05 3.4 55 15 34
JD-26-F594.37.4314.41348 65 23 1249727 16 0.99 4.9 0.22 0.07 24 10469 138
Average- coal13 1.9 2.0 7.0 3.2 12 4.0 32 6.3 23 33 10 6.3 1.3 1.3 0.08 0.03 3.6 43 15 30
world coal a121.63.9165.11316235.8141108.43.72.22.40.220.0311501123
world clay b54315110194936891613324031111.64.30.910.06134604875
SamplePrNdSmEuGdTbDyHoErTmYbLuTaTlPbBiThVSbZrHf
JD-26-R1353 9.61.5 8.3 1.4 9.2 1.9 5.6 0.845.8 0.871.6 1.1 39 0.922 ----
JD-26-015.9 23 4.1 0.40 3.6 0.68 4.2 0.86 2.5 0.42 2.6 0.4411.7 0.49634 0.2449.3 12 2.2 2057.0
JD-26-021.5 5.9 1.1 0.18 1.0 0.19 1.1 0.21 0.59 0.11 0.74 0.11 0.260.29 7.0 0.08 2.2 14.81.8 40 0.98
JD-26-032.4 8.6 1.6 0.18 1.3 0.23 1.1 0.23 0.730.11 0.78 0.13 0.420.35 14 0.16 3.2 16.50.39 46 1.3
JD-26-047.7 26 4.1 0.62 3.8 0.53 2.6 0.41 1.3 0.20 1.2 0.1680.53 0.57 8.5 0.33 3.9 20.90.57 441.3
JD-26-052.0 7.2 1.3 0.16 1.1 0.20 1.1 0.23 0.65 0.12 0.70 0.11 0.26 0.25 4.9 0.07 2.5 5.7 0.31 66 1.5
JD-26-061.4 5.4 1.0 0.11 0.84 0.16 0.88 0.17 0.50 0.08 0.48 0.08 0.61 0.32 4.3 0.071.6 9.5 0.48 70 1.5
JD-26-072.2 9.0 1.7 0.22 1.4 0.24 1.2 0.25 0.77 0.12 0.690.13 0.24 0.54 14.60.23 2.4 13 0.90 47 1.1
JD-26-083.5 14 2.5 0.352.1 0.34 1.9 0.35 0.94 0.161.0 0.17 0.48 1.2 39 0.43 4.7 29 1.0 72 1.8
JD-26-F14.6 50 7.9 1.1 7.2 1.1 5.3 0.89 2.5 0.41 2.6 0.391.4 0.89 31 0.83 14 64 1.5 1223.0
Average-coal3.3 12 2.2 0.281.9 0.321.7 0.340.990.161.0 0.170.550.516 0.23.7 15 0.9573 2.0
world coal a3.5 1220.472.70.322.1 0.540.930.311.0 0.20.280.637.8 0.973.3 250.92361.2
world clay b103681.25.80.834.4 0.91.9 0.52.5 0.391.41.3140.38141201.3 1905
a, averages of world coals [53]; b, averages of world clay [54]; -, no test or no result.

4.2.3. Rare Earth Elements and Yttrium (REY)

REY geochemical classification adopted in our study is according to [55]. Previous studies have shown that because of interference of BaO or BaOH, the Eu content measured in coal by ICP-MS based on quadrupole should be carefully used to identify the positive Eu anomaly [56,57]. In our study, the Ba/Eu values (56 to 370, average of 185), and the relation degree of Ba and Eu in coal samples are low (Figure 7), indicating that Ba concentration has no interference with Eu content.
The contents of REY of No. 26 coal in the Junde mine (from 34.1 μg/g to 174.6 μg/g, average 80.6 μg/g; Table 5) slightly exceed those in the world’s hard coal [53], but below those in Chinese coals [22] and the upper continental crust [58].
The REY contents in host rocks (roof and floor) are about four times that of coals (Table 5). Additionally, REY contents of the roof (340.9 μg/g) and the floor (327.8 μg/g) are well above those of average world clays [54] and the upper continental crust [58].
According to [55], the features of REY in No. 26 coals from Junde mine are LREY enrichment, with obviously negative Eu (Figure 8A), and, in the upper coal bench only, by HREY enrichment with obviously negative Eu, and positive Y anomalies. Correspondingly, the feature of REY of the roof is HREY enrichment like the top coal sample, while the feature of REY of the floor is LREY enrichment, like other coal samples (Figure 8B).

4.3. Mineralogy

Based on X-ray diffraction experiment (XRD) results (Figure 9), clay minerals and quartz are the chief minerals in the Junde coals, and after them calcite, siderite, and pyrite. Some monazite and zircon were detected in No. 26 coal by SEM-EDS. The minerals in the floor and roof are primarily clay minerals, quartz, potassium feldspar, and plagioclase.

4.3.1. Clay Minerals

Clay minerals in No. 26 coals primarily occur as massive lumps (Figure 10A,B) and cell-fillings (Figure 3C), indicating authigenic and terrigenous origins. Kaolinite, illite/smectite formation (I/S), and illite have been detected in Junde coals.

4.3.2. Quartz

In No. 26 coals, some quartz occurs as fine-grained particles (Figure 10C,D), indicating a syngenetic detrital origin. A lot of quartz in the studied coals has sharp edges Figure 3B,D and Figure 10A) and indicates the influence of high temperature and volcanic activity [35,59,60].

4.3.3. Pyrite

Some pyrite in No. 26 coal is in the form of discrete crystals (Figure 3B,D and Figure 10E), suggesting an authigenic origin. In addition, fracture fillings pyrite has also been found (Figure 3A,G and Figure 10F), suggestive of an epigenetic origin [61].

4.3.4. Carbonate Minerals

Calcite and siderite are the major carbonate minerals. Calcite generally occurs as plates (Figure 10G) and crack fillings (Figure 10H), suggesting an authigenic origin and epigenetic origin, respectively. Additionally, the siderite occurs as fracture-fillings cutting through the kaolinite (Figure 10I), indicating an epigenetic origin.

4.3.5. Other Minerals

Zircon (Figure 11) and monazite (Figure 12) were observed in No. 26 coal. Zircon occurs as corroded-crystal (Figure 11A), hexagon (Figure 11B) or incomplete quadrilateral bipyramid (Figure 11C), while monazite occurs mainly as nearly circular individual particles (Figure 12).

5. Discussion

5.1. Sediment Source

The value of Al2O3/TiO2 is commonly used to infer the sediment source (including coal deposits) [62,63]. The value of Al2O3/TiO2 in Junde coals varies from 26 to 45 (average 22.6) (Figure 13A), suggesting source rocks during No. 26 coal formation in Junde mine are primarily felsic rocks. This conclusion can also be evidenced by the diagrams of Zr/Sc—Th/Sc (Figure 13B), which have been proved a useful provenance indicator for coal deposits [64,65].
The No. 26 coals in the study area and the Fuqiang coals from the Hunchun Coalfield [33] have similar Cs-Pb-Zr enrichment characteristics. The provenance in Fuqiang coals is Mesozoic and Paleozoic igneous and metamorphic rocks [33]. To further explore the terrigenous supply of No. 26 coal, a comparison about Sr/Y, La/Yb, and Al2O3/TiO2 values of Junde coals with the local (the Jiamusi block) rocks of Neoproterozoic, Late Paleozoic, Mesozoic and Cretaceous ages [66,67,68,69] is shown in Figure 14. Figure 14 indicates that the source material of the Junde mine mainly comes from the Late Paleozoic igneous rocks from Jiamusi block. In addition, the REY patterns of No. 26 coal are akin to those of the Late Paleozoic igneous rocks with negative Eu anomalies (Figure 15). Sun et al. have also determined that detrital zircons of Mesozoic and Paleozoic ages predominate in sandstones of the Chengzihe Formation [70]. Those zircons are shaped similarly to the zircons described in this study (Figure 11A–C). Therefore, the terrigenous components in No. 26 coal from Junde mine were mainly derived from the Late Paleozoic meta-igneous rocks in local block.

5.2. Sedimentary Environment

The value of Sr/Ba has been widely used to identify the depositional environment of sedimentary rocks and coals [71,72]. Generally, coals with Sr/Ba ratio greater than 1 and less than 1 was formed in the environment of seawater and freshwater intrusion, respectively. However, we should be cautious when using this indicator, because the content of Sr and Ba in terrigenous clastic minerals (especially feldspar) may cause misjudgment of the sedimentary environment [73,74]. In the present study, feldspar content is so low that it is not detected by XRD. Thus, Sr/Ba ratio is used to roughly distinguish sedimentary environment in this study. Sr/Ba value of No. 26 coal seam from Junde mine varies from 0.48 to 1.01, and the average Sr/Ba value of the coal seam is 0.81, suggestive of a primarily fresh-water affected process of No. 26 coal.
Because NE China is abundant with Cu porphyry ores [75] that may be eroded and consequently changing the ratio in terrigenous sediments, Sr/Cu ratio is not suitable to infer the sedimentary environment. The relationship of sulfur and the environment has been widely recognized [72]. In the Junde mine, sulfate sulfur increases with depth (Figure 16), which indicate oxidation/evaporation gradually decreases during No.26 coal formation.

5.3. Influence of Volcanic Ash

It is generally believed that the Eu anomaly in coal does not originate from the weathering process during the transportation of metals from provenance to coal forming peat, but is inherited from rocks in the source areas [56]. Eu anomalies characteristics of No. 26 coal from Junde mine (including roof and floor) resembles those of felsic volcanic rocks.
Previous studies suggested that the crystalline habit and morphology of terrigenous detrital zircons are quite different from those of igneous detrital zircons [76]. The characteristics of the former are tetragonal bipyramids with relatively short prisms, and the length width ratio (c/a values) is about two [77], while the feature of the latter is long and well-developed, with a c/a value of more than 2.5 [77]. In the present study, the ratio of c/a in the zircon found in No. 26 coal (Figure 11C) is > 2.5, indictive of a pyroclastic origin. Another possibility that its angular and elongated shapes may evidence just short transportation by relatively quiet water streams cannot be ruled out.
A large number of sharp-edged quartz particles were observed in No. 26 coal (Figure 3B,D and Figure 10A), indicating a volcanic origin rather than a terrigenous clastic origin [35,59,60].
Although zircon and some high-T quartzs have been found in the No. 26 coals, the vermicular kaolinite/chlorite particles that commonly indicate volcanic ash have not been found. Thus, the volcanic ash contribution to No. 26 coal seems very low, if occurred. This conclusion is consistent with [70].

6. Conclusions

The characteristics of minerals and elements of No. 26 coal from Junde mine, Hegang coalfield, northeastern China, were studied. The main conclusions are summarized as follows.
(1)
The No. 26 coal of Junde mine is slightly enriched in Cs, Pb, and Zr. From the vertical section of No. 26 coal seams, the contents of Cs, Pb, and Zr in the coal samples near the host rocks (roof and floor) outclass those in the middle coal seams.
(2)
The minerals in Junde coals mainly include clay minerals and quartz, followed by calcite, siderite, pyrite, monazite, and zircon.
(3)
The terrigenous components in No. 26 coal from Junde mine were derived from the Late Paleozoic meta-igneous rocks in the Jiamusi block evidenced by Sr/Y, La/Yb, and Al2O3/TiO2 ratios, Zr/Sc—Th/Sc plot, and negative Eu anomalies.
(4)
The No. 26 coal from the Junde mine was affected by fresh water during coal formation. Sulfate sulfur indicate oxidation/evaporation gradually decreases during No. 26 coal formation.
(5)
The volcanic ash contribution to No. 26 coal seems very low, if occurred.

Author Contributions

Y.W.: Methodology, Data curation, Writing-original draft. W.H.: Data curation, Writing-original draft. G.Q.: Methodology, Data curation, Writing-original draft. A.W.: Supervision. D.C.: Conceptualization, Supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This work was funded by the National Key Research and Development Plan of China (2021YFC2902004), National Natural Science Foundation of China (41972174 and 42072197), and Science Foundation of Hebei Normal University (L2021B25).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Available from Yingchun Wei and corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. (A,B) Site of the Hegang coalfield. (C) Location of the Junde mine.
Figure 1. (A,B) Site of the Hegang coalfield. (C) Location of the Junde mine.
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Figure 2. (A) The strata histogram (modified after [38]) and (B) sampling profile from Junde mine, Hegang coalfield.
Figure 2. (A) The strata histogram (modified after [38]) and (B) sampling profile from Junde mine, Hegang coalfield.
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Figure 3. Coal petrology characteristics in No. 26 coal. (A) Collotelinite, collodetrinite, and pyrite in sample JD-26-01; (B) Collotelinite, clay, quartz, and pyrite in sample JD-26-01; (C) Collotelinite and clays in sample JD-26-04; (D) Collodetrinite, semifusinite, quartz, pyrite and clay minerals in sample JD-26-04; (E) Collotelinite and calcite in sample JD-26-05; (F) Fusinite in sample JD-26-07; (G) Pyrite in in sample JD-26-07; (H) Telinite and Fusinite in sample JD-26-07; (I) Collodetrinite, collotelinite and clays in sample JD-26-08. T—telinite; CT—collotelinite; CD—collodetrinite; F—fusinite; SF—semifusinite.
Figure 3. Coal petrology characteristics in No. 26 coal. (A) Collotelinite, collodetrinite, and pyrite in sample JD-26-01; (B) Collotelinite, clay, quartz, and pyrite in sample JD-26-01; (C) Collotelinite and clays in sample JD-26-04; (D) Collodetrinite, semifusinite, quartz, pyrite and clay minerals in sample JD-26-04; (E) Collotelinite and calcite in sample JD-26-05; (F) Fusinite in sample JD-26-07; (G) Pyrite in in sample JD-26-07; (H) Telinite and Fusinite in sample JD-26-07; (I) Collodetrinite, collotelinite and clays in sample JD-26-08. T—telinite; CT—collotelinite; CD—collodetrinite; F—fusinite; SF—semifusinite.
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Figure 4. Concentration coefficient (CC) of MEO in No. 26 coals.
Figure 4. Concentration coefficient (CC) of MEO in No. 26 coals.
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Figure 6. Variations of Hf, Cs, and Pb contents in the Junde mine.
Figure 6. Variations of Hf, Cs, and Pb contents in the Junde mine.
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Figure 7. (A) Correlation diagram of Eu and Ba contents in coals, roof, and floor samples. (B) Magnification of relationship between Eu and Ba in coal samples from Junde mine.
Figure 7. (A) Correlation diagram of Eu and Ba contents in coals, roof, and floor samples. (B) Magnification of relationship between Eu and Ba in coal samples from Junde mine.
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Figure 8. REY characteristics for (A) coal samples, (B) roof and floor samples in Junde mine. REY contents were normalized by UCC.
Figure 8. REY characteristics for (A) coal samples, (B) roof and floor samples in Junde mine. REY contents were normalized by UCC.
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Figure 9. XRD patterns of No. 26 coals of Junde mine. (A) Sample JD-26-02; (B) sample JD-26-04; (C) sample JD-26-05; (D) sample JD-26-08.
Figure 9. XRD patterns of No. 26 coals of Junde mine. (A) Sample JD-26-02; (B) sample JD-26-04; (C) sample JD-26-05; (D) sample JD-26-08.
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Figure 10. Minerals in samples from Junde mine (SEM, SE mode). (A) Kaolinite and quartz in sample JD-26-05; (B) Kaolinite and siderite in sample JD-26-06; (C) Siderite and quartz in sample JD-26-04; (D) Quartz in sample JD-26-05; (E) Pyrite in sample JD-26-04; (F) Pyrite in sample JD-26-05; (G) Calcite in sample JD-26-04; (H) Fracture-filling calcite in sample JD-26-05, Reflected light, oil immersion; (I) Siderite and kaolinite in sample JD-26-06.
Figure 10. Minerals in samples from Junde mine (SEM, SE mode). (A) Kaolinite and quartz in sample JD-26-05; (B) Kaolinite and siderite in sample JD-26-06; (C) Siderite and quartz in sample JD-26-04; (D) Quartz in sample JD-26-05; (E) Pyrite in sample JD-26-04; (F) Pyrite in sample JD-26-05; (G) Calcite in sample JD-26-04; (H) Fracture-filling calcite in sample JD-26-05, Reflected light, oil immersion; (I) Siderite and kaolinite in sample JD-26-06.
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Figure 11. Zircon in samples from Junde mine. (A) Sample JD-26-03; (B) Sample JD-26-05; (C) Sample JD-26-06. (D) EDS spectrum of Spot 1 in Figure 11C.
Figure 11. Zircon in samples from Junde mine. (A) Sample JD-26-03; (B) Sample JD-26-05; (C) Sample JD-26-06. (D) EDS spectrum of Spot 1 in Figure 11C.
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Figure 12. Monazite in samples from Junde mine. (A) Sample JD-26-04; (B) Sample JD-26-06; (C) Sample JD-26-07; (D) EDS spectrum of Spot 1 in Figure 12C.
Figure 12. Monazite in samples from Junde mine. (A) Sample JD-26-04; (B) Sample JD-26-06; (C) Sample JD-26-07; (D) EDS spectrum of Spot 1 in Figure 12C.
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Figure 13. Plot of (A) TiO2 vs. Al2O3 and (B) Zr/Sc vs. Th/Sc for coal samples from the Junde mine.
Figure 13. Plot of (A) TiO2 vs. Al2O3 and (B) Zr/Sc vs. Th/Sc for coal samples from the Junde mine.
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Figure 14. Comparison of (A) Al2O3/TiO2 vs. Sr/Y and (B) Al2O3/TiO2 vs. La/Yb between the studied samples, and the local (the Jiamusi block) rocks of Neoproterozoic, Late Paleozoic, Mesozoic and Cretaceous ages [66,67,68,69].
Figure 14. Comparison of (A) Al2O3/TiO2 vs. Sr/Y and (B) Al2O3/TiO2 vs. La/Yb between the studied samples, and the local (the Jiamusi block) rocks of Neoproterozoic, Late Paleozoic, Mesozoic and Cretaceous ages [66,67,68,69].
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Figure 15. Characteristics of REY of (A) Late Paleozoic rocks, (B) Early Cretaceous rocks, (C) the Neoproterozoic rocks, and (D) Mesozoic rocks in the Jiamusi block [66,67,68,69].
Figure 15. Characteristics of REY of (A) Late Paleozoic rocks, (B) Early Cretaceous rocks, (C) the Neoproterozoic rocks, and (D) Mesozoic rocks in the Jiamusi block [66,67,68,69].
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Energies 15 05078 g016 550
Figure 16. Regularity of the variation of sulfate sulfur in the Junde samples.
Figure 16. Regularity of the variation of sulfate sulfur in the Junde samples.
Energies 15 05078 g016
Table
Table 1. Proximate analysis and sulfur contents (%) of coals from Junde mine.
Table 1. Proximate analysis and sulfur contents (%) of coals from Junde mine.
SampleMadAdVdafTotal Sulfur Pyritic SulfurSulfate Sulfur Organic Sulfur
JD-26-013.112.636.20.540.270.040.23
JD-26-022.413.437.20.570.020.050.50
JD-26-032.417.538.80.570.020.070.48
JD-26-042.212.138.60.720.430.080.20
JD-26-052.38.637.30.580.310.070.20
JD-26-062.39.737.90.660.330.090.24
JD-26-071.912.438.30.620.350.130.14
JD-26-082.217.641.10.700.440.140.11
Mad—air-dry basis moisture; Ad—dry basis ash yield; Vdaf—dry and ash-free basis volatile matter.
Table
Table 2. Coal petrology characteristics of No. 26 coals (Vol.%).
Table 2. Coal petrology characteristics of No. 26 coals (Vol.%).
SampleVitriniteInertiniteLiptiniteMineral
TCTCDVDCGT-VFSFMicIDT-ISpCutSubResBitT-LClaysSulfide MineralsCarbonate MineralsSilica MineralsTotal Minerals
JD-26-0111.1 38.7 26.6 0.5 1.0 77.9 0.5 14.6 - 2.0 17.1 0.5 0.5 --0.5 1.5 0.5 1.0 1.5 0.5 3.5
JD-26-0219.2 29.8 31.8 0.5 0.5 81.8 0.5 7.6 - 1.0 9.1 1.5 --0.5 -2.0 2.5 -3.5 1.0 7.1
JD-26-0310.5 37.1 38.1 -1.9 87.6 1.9 3.8 -1.9 7.6 1.0 0.5 ---1.4 2.4 --1.0 3.3
JD-26-048.0 40.3 34.3 1.0 2.0 85.6 0.5 4.5 0.5 1.0 6.5 1.5 --0.5 0.5 2.5 2.5 0.5 1.0 1.5 5.5
JD-26-0511.0 49.8 27.8 - 3.8 92.3 -3.4 -0.5 3.8 1.0 0.5 ---1.4 -0.5 1.9 -2.4
JD-26-0615.1 40.6 31.8 - 3.7 91.2 1.0 4.7 0.5 -6.3 0.5 -0.5 --1.0 0.5 -1.0 -1.6
JD-26-079.5 39.5 35.0 - 2.0 86.0 3.0 5.0 -0.5 8.5 1.0 0.5 -0.5 -2.0 1.5 -1.0 1.0 3.5
JD-26-086.6 26.5 39.8 - 3.1 76.0 0.5 4.1 -2.0 6.6 4.6 ---1.0 5.6 4.6 -5.6 1.5 11.7
Notes: T—telinite; CT—collotelinite; CD—collodetrinite; CG—corpogelinite; VD—Virtrodetrinite; T-V—total vitrinites; F—fusinite; SF—semifusinite; Mic—micrinite; ID—inertodetrinite; T-I—total inertinites; Sp—sporinite; Cut—cutinite; Res—resinite; Sub—suberinite; Bit—bituminite; T-L—total liptinites; -, no test or no result.
Table
Table 3. The concentration of MEO in No. 26 coals, on a whole coal basis (%).
Table 3. The concentration of MEO in No. 26 coals, on a whole coal basis (%).
SampleLOISiO2TiO2Al2O3Fe2O3 MgOCaOMnONa2OK2OSiO2/Al2O3Al2O3/TiO2
JD-26-0187.41 7.35 0.08 2.99 0.99 0.22 0.56 0.03 0.03 0.33 2.4636.93
JD-26-0286.65 7.75 0.08 3.01 1.41 0.22 0.49 0.04 0.04 0.3 2.5739.15
JD-26-0382.47 10.94 0.11 4.76 1.04 0.15 0.09 0.01 0.05 0.38 2.342.61
JD-26-0487.93 7.64 0.06 2.63 1.32 0.12 0.07 0.02 0.03 0.16 2.945.15
JD-26-0591.37 4.8 0.05 1.64 1.68 0.16 0.11 0.04 0.02 0.11 2.9329.92
JD-26-0690.35 5.44 0.07 1.85 1.76 0.16 0.14 0.07 0.03 0.14 2.9328.48
JD-26-0787.64 7.52 0.1 2.88 1.38 0.16 0.07 0.05 0.04 0.16 2.6128.1
JD-26-0882.38 9.56 0.15 3.83 3.35 0.25 0.06 0.14 0.04 0.25 2.525.96
Average 7.63 0.09 2.95 1.62 0.18 0.20 0.05 0.04 0.23 2.65 34.54
China a 8.470.335.984.850.221.230.020.160.191.4218.12
Notes: LOI, loss on ignition; a, concentration of MEO in Chinese coals [22].
Table
Table 5. REY geochemical parameters for the studied samples from the Junde mine.
Table 5. REY geochemical parameters for the studied samples from the Junde mine.
SampleLREYMREYHREYREYLaN/LuNLaN/SmNGdN/LuNEuN/EuN *CeN/CeN *δY
JD-26-R255.1 70.9 15.0 340.9 0.99 1.07 0.73 0.72 1.17 1.33
JD-26-01112.6 37.5 6.8 157.0 0.96 1.24 0.63 0.43 1.06 1.67
JD-26-0228.6 9.2 1.8 39.6 0.90 1.01 0.74 0.66 1.15 1.57
JD-26-0344.4 9.0 2.0 55.4 1.13 1.14 0.73 0.53 1.19 1.35
JD-26-04151.9 19.5 3.3 174.6 3.72 1.80 1.73 0.70 1.05 1.47
JD-26-0536.1 9.0 1.8 46.9 1.16 1.18 0.75 0.55 1.11 1.40
JD-26-0626.0 6.8 1.3 34.1 1.09 1.05 0.78 0.48 1.11 1.39
JD-26-0739.6 9.7 2.0 51.2 0.92 0.82 0.81 0.57 1.21 1.32
JD-26-0869.7 13.7 2.7 86.0 1.34 1.09 0.92 0.64 1.23 1.27
JD-26-F279.5 41.6 6.7 327.8 2.67 1.57 1.40 0.66 1.14 1.52
Notes: Units for REYs: μg/g; REY = LREY + MREY + HREY; Calculation formula for LREY, MREY, HREY, EuN/EuN *, CeN/CeN *, δY are according to [56].
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Wei, Y.; He, W.; Qin, G.; Wang, A.; Cao, D. Mineralogy and Geochemistry of the Lower Cretaceous Coals in the Junde Mine, Hegang Coalfield, Northeastern China. Energies 2022, 15, 5078. https://doi.org/10.3390/en15145078

AMA Style

Wei Y, He W, Qin G, Wang A, Cao D. Mineralogy and Geochemistry of the Lower Cretaceous Coals in the Junde Mine, Hegang Coalfield, Northeastern China. Energies. 2022; 15(14):5078. https://doi.org/10.3390/en15145078

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Wei, Yingchun, Wenbo He, Guohong Qin, Anmin Wang, and Daiyong Cao. 2022. "Mineralogy and Geochemistry of the Lower Cretaceous Coals in the Junde Mine, Hegang Coalfield, Northeastern China" Energies 15, no. 14: 5078. https://doi.org/10.3390/en15145078

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