mineralogical and geochemical responses of coal to igneous

International Journal of Coal Geology 124 (2014) 11–35

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International Journal of Coal Geology

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Mineralogical and geochemical responses of coal to igneous intrusion inthe Pansan Coal Mine of the Huainan coalfield, Anhui, China

Jian Chen a,b,1, Guijian Liu b,⁎, Hui Li b, Bin Wu b

a School of Earth and Environment, Anhui University of Science and Technology, Huainan, Anhui 232001, Chinab CAS Key Laboratory of Crust–Mantle Materials and Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China

⁎ Corresponding author. Tel.: +86 551 63603714; fax:E-mail addresses: [email protected] (J. Chen), lgj@

[email protected] (H. Li), [email protected] (B1 Tel.: +86 15855510413 (mobile).

0166-5162/$ – see front matter © 2014 Elsevier B.V. All rihttp://dx.doi.org/10.1016/j.coal.2013.12.018

a b s t r a c t
a r t i c l e i n f o
Article history:Received 16 August 2013Received in revised form 31 December 2013Accepted 31 December 2013Available online 11 January 2014

Keywords:MineralTrace elementIgneous intrusionCoalHuainan coalfield

The Huainan coalfield, where magma is commonly intruded into the coal measures in the northern section,(e.g., the Zhuji, Dingji, Pansan, and Panbei mines), is the largest energy base in eastern China.To investigate the mineralogical and geochemical responses of coal to igneous intrusion, minerals, majorand trace elements in sandstone, thermally-altered coal, igneous rock, sandy mudstone, and unalteredcoal samples were collected from a representative profile of the No. 1 Coal of the Pansan Coal Mine. Thesamples were analyzed using an optical microscope, powder X-ray diffraction, scanning electron micros-copy in conjunction with X-ray energy dispersive spectroscopy, X-ray fluorescence, inductively coupledplasma atomic emission spectrometry and mass spectrometry. The results indicated that the thick silltransformed from mafic rocks at the bottom, via intermediate rocks in the middle to felsic rocks at thetop of the profile. The moisture, total sulfur, and carbon contents of the coal increased, whereas volatilematter, hydrogen, and nitrogen decreased during contact metamorphism caused by igneous intrusion.Epigenetic minerals (i.e., dolomite, quartz, and pyrite) occurred in the thermally-altered coals. Threestages of hydrothermal fluids (i.e., Ca-, Mg-, and Fe-rich; Si-rich; and Fe- and/or H2S-rich solutions)were identified. Iron, Ca, S, Si, Mg, Zn, Cd, and Pb were transported into the thermally-altered coal byhydrothermal fluids. The concentrations of Co and Ni in the thermally-altered coal increased in relationto the increase of ash yields that were caused by contact metamorphism, whereas the B in the coal wasvolatilized. Manganese is directly related to the intrusive magma. Phosphorus, Ge, and Sr might be intro-duced into the coal by groundwater; however, K, Na, Ga, and Ba were leached out. Titanium, Sc, Cr, V, Cu,Zr, Nb, and rare earth elements and yttrium (REY) in the coals originated from terrigenous input andwere not influenced by igneous intrusion.

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1. Introduction

Due to the relative weakness of coal compared to host rocks(i.e., sandstone and mudstone) in coal-bearing strata, coalbeds areprone to be emplaced by igneous rocks in six patterns (Fig. 1): cut-incoalbed by dike, cut-through coalbed by dike, coalbed roof intrusionby sill, coalbed floor intrusion by sill, middle coalbed intrusion by sill,and double intrusions through the roof and floor by sills.

Igneous intrusion into a coalbed can result in contactmetamorphismof the coal, which produces large amounts of natural coke, causes botheconomic and safety issues in coal exploitation, exploration, and devel-opment of coalbed methane (Cooper et al., 2007; Dai and Ren, 2007;Golab and Carr, 2004; Yao and Liu, 2012).

+86 551 63621485.ustc.edu.cn (G. Liu),. Wu).

ghts reserved.

Igneous intrusion may also lead to physical and chemical changesof organic matter in coal, including the formation of mosaic and vesic-ular structures (Crelling and Dutcher, 1968; Jiang et al., 2011; Singhet al., 2007, 2008, 2013; Yao and Liu, 2012), enhancement of vitrinitereflectance and carbon contents, and a decrease in volatile matterand hydrogen (Jiang et al., 2011; Karayigit and Whateley, 1997;Singh et al., 2008; Yao et al., 2011), the production of deposited carbonand carbon spherulites (Crelling and Dutcher, 1968; Singh et al., 2007,2008), and the formation of anisotropic components (Singh et al.,2008; Yao et al., 2011).

The inherentminerals in coalmay be altered or destroyed because ofthe heat, fluid, and gas introduced by the igneous intrusion. Epigeneticminerals may be deposited during the circulation of hydrothermalfluids derived from igneous activities (Cressey and Cressey, 1988;Dai and Ren, 2007; Goodarzi and Cameron, 1990; Querol et al., 1997;Yao and Liu, 2012; Yao et al., 2011). For example, the diaspore andammonian illite in theAdaohai coalswere derived from thedehydrationof gibbsite and the interaction of kaolinite with nitrogen released fromcoal organic matter during metamorphism, respectively (Dai et al.,

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Fig. 1. Six patterns of igneous intrusion in coal measure. I: cut-in coalbed by dike; II: cut-through coalbed by dike; III: coalbed roof intrusion by sill; IV: coalbed floor intrusion bysill; V: middle coalbed intrusion by sill; VI: double intrusions through the roof and floorby sills; modified from Yao and Liu (2012).

12 J. Chen et al. / International Journal of Coal Geology 124 (2014) 11–35

2012a). Epigenetic carbonates (e.g., siderite, ankerite, dolomite, calcite,magnesite, dawsonite, and many others) fill the fractures and vesiclesof the altered coals (Dai et al., 2012a; Golab and Carr, 2004; Golabet al., 2006; Karayigit and Whateley, 1997; Querol et al., 1997; Singhet al., 2008). Epigenetic pyrite is commonly precipitated in the porousnatural coke (Dai and Ren, 2007; Finkelman et al., 1998; Kisch andTaylor, 1966; Querol et al., 1997, 2001; Singh et al., 2007).

Finally, igneous intrusion can geochemically modify the coal,which leads to the enrichment or depletion of some trace elementsin the thermally-altered coals. This is evidenced by the following:high concentrations of platinum group elements in some Late Permiancoals from the western Guizhou (Dai et al., 2003); B, F, Cl, Br, Hg, As,Co, Cu, Ni, Pb, Sr, Mg, Ca, Mn, and Zn in the altered Fengfeng-Handancoal (Dai and Ren, 2007); Mn in the Fuxin coal (Querol et al., 1997);increased Hg in the altered Adaohai coal (Dai et al., 2012a), and theNos. 5 and 7 coals from the Huaibei coalfield (Zheng et al., 2008).The following provide evidence of the thermally-altered coals outsideof China: Mn, Sr, Ag, Hg, Cu, and Zn in the Pitkin bituminous coalof the USA (Finkelman et al., 1998); Sc, Ti, V, Cr, Ga, Zr, and Hf inthe Upper Hunter Valley altered coal of Australia (Golab and Carr,2004); Mn and V in the Penarroya anthracite of Spain (Suarez-Ruizet al., 2006); rare earth elements in some coals (Seredin and Dai,2012); and F in some Palaeogene coals from Bulgaria (Eskenazyet al., 2013).

The Huainan coalfield, which is located in the northern AnhuiProvince (Fig. 2a), is the largest energy base in eastern China. In northernHuainan, such as the Zhuji, Dingji, Pansan, and Panbei mines, igneousrocks are commonly intruded in coal measures (Fig. 2b). Sun et al.(2010a) and Chen et al. (2011) investigated the geochemistry of traceelements in coals from the Zhujimine and from the entire Huainan coal-field. However, only Sun et al. (2010b) and Yang et al. (2012) reportedthe coal quality and rare earth elements of the igneous intrusion-influenced coal in the Zhuji Coal Mine. Therefore, a systematic studyon the mineralogical and geochemical responses of coal to igneousintrusion in the Pansan Coal Mine of the Huainan coalfield is of bothacademic and practical significance.

This paper presents an investigation of the characteristics ofthe intrusive rocks, coal quality changes, minerals, major elementoxides, certain trace elements (B, Mn, Sr, Zr, Ba, Sc, V, Cr, Co, Ni, Cu,Zn, Ga, Ge, Nb, Cd, and Pb), and REY (rare earth elements and yttrium)in typical samples (e.g., roof sandstone, thermally-altered coal, igne-ous rock, sandy mudstone, and unaltered coal) from the igneousintrusion-influenced No. 1 Coal in the Pansan Coal Mine of the Huainancoalfield.

2. Geological setting

The Pansan Coal Mine was built in 1979 and operated in 1992. It islocated in the north-central region of the Huainan coalfield (Fig. 2b).The mine is 9.6-km in length (E–W), 5.8-km in width (N–S), and coversan area of 56 km2. Its production capacity is 3 Mt per year, and itsexploitable reserves are 542 Mt.

The Pansan Coal Mine is situated in the west of the south flank ofthe Panji anticline (Fig. 2b). The coal measure is generally a monoclinicstructure that strikes NWW–SEE, and it has dips that range from5 to 10°.

The coal-bearing sequences are mainly composed of the lateCarboniferous Taiyuan Formation, the early Permian Shanxi andLower Shihezi Formations, and the late Permian Upper ShiheziFormation (Fig. 3). Detailed information on these formations wasdiscussed by Chen et al. (2011). Seven mineable and stable coalbeds(Nos. 13-1, 11-2, 8, 7-1, 5, 4-2, and 4-1) are located in the PansanCoal Mine.

Igneous intrusion widely developed in the northern section of theHuainan coalfield, specifically in the Zhuji, Dingji, Pansan, and Panbeimines. In the Pansan Coal Mine, igneous intrusion is mainly present inthe north, which approaches the axis of the Panji anticline (Fig. 2b).The Nos. 8, 4-2, 4-1, 3, and 1 coalbeds were influenced by the igneousintrusion to various extents.

The igneous rocks were emplaced in the coal-bearing strata duringthe Sichuan Period (135–52 Ma: the late Yanshanian Movement) ofthe early Cretaceous, which is approximately 118 Ma (Miao et al.,2012). The intrusive rocks mainly consist of syenite porphyry andlamprophyre.

The local mineable unstable No. 1 Coal, which was the coal mostaffected by igneous rock emplacement in the Pansan Coal Mine, occursin the lower part of the Shanxi Formation (Fig. 3). The thickness ofNo. 1 Coal ranges from 0.28 to 8.00 m (with an average of 2.92 m).Two carbonaceous mudstone partings, sandstone roof, and mudstonefloor are commonly associated with the No. 1 Coal. Igneous intrusionswere predominantly in the forms of roof (pattern III in Fig. 1) or middle(pattern V in Fig. 1) coalbed intrusions by sills.

3. Sampling and methods

To investigate the mineralogical and geochemical responses of coalto the igneous intrusion in the Pansan Coal Mine, 27 samples werecollected from roof sandstone, thermally-altered coals, igneous rocks,sandy mudstone partings, and mixtures from the contact areas ofa representative core profile of the 13w27 borehole (Fig. 4). In thisborehole, a thick sill was emplaced in the upper part of the No. 1Coal (pattern V in Fig. 1), which was separated by a sandy mudstoneparting (with a thickness of 1.24 m), and the sill was divided intotwo splits (with thicknesses of 0.34 m and 27.42 m, respectively).Correspondingly, the coalbed was correspondingly divided into foursubseams (Fig. 4). Four metamorphic zones were distinguished fromthe unaltered area to the intrusion/coke contact: normal coal, cokedcoal, natural coke, and mixed coke rock (Yao et al., 2011). However,as disclosed from the logging information of the 13w27 borehole, allof the coals with thicknesses of 2.02 m and 1.68 m (separated by a0.44 m mudstone parting) in the lower section were thermally-altered. Unfortunately, all of the core samples deeper than sample1327-1 were abandoned by the driller. One borehole coal sample,which approached the roof of the No. 1 Coal and was not influencedby igneous intrusion in an adjacent borehole (15E7) in the PansanCoal Mine, was also obtained for a comparison. Information on thesamples is listed in detail in Table 1. Two samples (1327-22 and1327-20) from the sharp contact areas of the igneous rock andthermally-altered coal were subdivided into two parts according totheir lithologies to clearly illustrate the geochemical variation amongthe rocks.

Fig. 2. Locations of the Huainan (a) in China and the Pansan Coal Mine (b) in Huainan.

13J. Chen et al. / International Journal of Coal Geology 124 (2014) 11–35

Bulk samples were air dried, sealed in polyethylene bags to preventcontamination and oxidation, and ground to pass a 200 mesh sievefor chemical analysis. The coal quality parameters (i.e., Aad, Mad, Vdaf,Cad, Had, Nad, and St, d) of the thermally-altered coals and unalteredcoal were determined in accordance with the Chinese NationalStandards (Aad, Mad, and Vdaf with GB/T 212-2008, Cad, Had, and Nad

with GB/T476-2001, and St,d with GB/T214-2007, respectively) andwith the same procedures as the ASTM standards (D3174-04, D3173-

03, D3175-02, D3178-89, and D3177-02), except for small temperaturedifferences (815 ± 10 °C and 700–750 °C for Aad, 105–110 °Cand 104–110 °C for Mad, and 600–850 °C and 500–900 °C for Cad andHad determination with the Chinese National Standards and ASTMstandards).

The losses on ignition (LOIs) were determined at 1075 °C by thegravimetric method that is based on the Chinese National Standard(GB/T3257.21-1999).

image of Fig.�2

Upp

er S

hihe

zi F

orm

atio

n

Low

er S

hihe

zi F

orm

atio

n

Shan

xi F

orm

atio

n

3

4-14-2

5

11-1

11-2

6

7-1

7-2

8

9-1

9-2

1

Coal

Siltstone

Finesandstone

Mediumsandstone

Coarsesandstone

QuartzSandstone

Fine sandstonewith siderite

Sandymudstone

Ooliticmudstone

Claystone

CarbonaceousShale

13-120

m

Early Permian

Middle Permian

Late Permian

Fig. 3. Generalized stratigraphic columns of the Permian coal measures in the Huainancoalfield (from Chen et al. (2011)).

817.04817.98

848.06

852.20

846.02

818.32818.60

846.82

272625242322212019181716151413121110987654321

Depth/m Sample No.

Upper sill split

Lower sill split

Subseam 1

Subseam 2

Subseam 3

Subseam 4

Sandy mudstoneMudstone

Thermally-altered coalIgneous rock

Fine sandstoneCoarse sandstone

Legend

Fig. 4. Sampling profile of the No. 1 Coal in the Pansan Coal Mine. The prefixion of sampleNo. was omitted.


The minerals were characterized and determined by an optical mi-croscope, powder X-ray diffraction (XRD), and a scanning electronmicroscopy in conjunction with X-ray energy dispersive spectroscopy(SEM-EDS). Aliquots of the powdered samples were analyzed withan 18-kW rotating anode XRD diffractometer. The data were recordedover a 2θ interval of 3–60° and a step size of 0.02°. Thin sectionsof each borehole sample, which were perpendicular to the coalbed,were prepared for optical microscopy and SEM-EDS observations. Forthe samples 1327-22 and 1327-20 from the sharp contact areas, onethin section in each borehole sample that transects both the igneousrock and thermally-altered coal was prepared. All of the thin sectionswere carbon coated in the high vacuum Cressington 208C sputteringcoater. Optical characterizations of the minerals were performedin three optical modes (i.e., reflected, plane polarized, and crossedpolarized lights) using a Nikon DS Ri1 microscope. Furthermore, theminerals and elements therein occurred were analyzed by a cold fieldemission scanning electron microscope (SEM, JSM-6700F) combinedwith an X-ray energy dispersive spectrometer (EDS, INCA, Si (Li)detector).

Before the major element oxides determination, the thermally-altered coals, unaltered coal, and sandymudstoneswere ashed to a con-stant weight at 550 °C to remove organic carbon; the results wererecalculated to a whole rock basis. The major element oxides, includingSiO2, Al2O3, Fe2O3, MnO, TiO2, CaO, K2O, SO3, P2O5, Na2O, and MgO ofthe powdered samples were determined by X-ray fluorescence spec-trometry (XRF, XRF-1800).

An acidicmixture ofHNO3:HCl:HF (3:1:1) (using amicrowave oven)was applied to the powdered samples. The elemental concentrationsin the resultant solution (e.g., B, Mn, Sr, Zr, and Ba) were measured byinductively coupled plasma atomic emission spectrometry (ICP-AES,Optima 7300 DV), whereas Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, Nb, Cd, La,Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu, and Pb weremeasured by inductively coupled plasma mass spectrometry (ICP-MS,Thermo X Series 2).

The standard reference material GBW07406 (GSS-6, soil) was ran-domly allotted, prepared, and determined to estimate the precision of

image of Fig.�3

Table 1Information on samples from the No. 1 Coal in the Pansan Coal Mine.

Sample No. Depth/m Description Sample No. Depth/m Description

1327-27 816.54 Sandstone 1327-13 846.05 Thermally-altered coal and igneous rock from contact area1327-26 817.04 Thermally-altered coal and sandstone from contact area 1327-12 846.35 Thermally-altered coal1327-25 817.09 Thermally-altered coal 1327-11 846.65 Thermally-altered coal1327-24 817.59 Thermally-altered coal 1327-10 846.90 Sandy mudstone1327-23 818.03 Igneous rock 1327-9 847.10 Sandy mudstone1327-22 818.23 Thermally-altered coal and igneous rock from contact area 1327-8 847.30 Sandy mudstone1327-21 818.33 Thermally-altered coal 1327-7 848.05 Thermally-altered coal and mudstone from contact area1327-20 818.58 Thermally-altered coal and igneous rock from contact area 1327-6 848.15 Thermally-altered coal1327-19 818.88 Igneous rock 1327-5 848.45 Thermally-altered coal1327-18 819.18 Igneous rock 1327-4 848.70 Thermally-altered coal1327-17 837.80 Igneous rock 1327-3 848.85 Thermally-altered coal1327-16 844.05 Igneous rock 1327-2 849.05 Thermally-altered coal1327-15 845.05 Igneous rock 1327-1 849.34 Thermally-altered coal1327-14 845.55 Igneous rock 1571 901.00 Unaltered coal


the results. As listed in Table 2, all of the determined values are withinthe ranges of the certified reference values.

4. Results and discussion

4.1. Characteristics of intrusive rocks

Megascopically, the igneous rocks have a pale-gray color, a crypto-crystalline texture, and a massive structure. Fracture-filled pyritesare predominantly in the contact areas of the igneous rocks andthermally-altered coal in the upper part of the sill.

Microscopically, the igneous rocks from the central part of the lowersill split are compact, and the crystalline forms of the feldspars are intactand semi-oriented (Fig. 5g). The amygdaloidal structure was alsopresent (Fig. 5g). However, the feldspars in the rocks from the marginsof the lower sill split and the entire upper sill split were altered andkaolinized (Fig. 5a, d, e, f, h, i, and j). The pores and fractures werewell-developed (filled by quartz and pyrite veins or disseminatedby massive pyrite patches) in the rocks that were adjacent to thethermally-altered coals (Fig. 5a, d, and j). At the joints of the igneousrocks and thermally-altered coal (Subseam 2 in Fig. 4), thick epigenetic

Table 2Comparison of determined values to reference values of the standard reference material GSS-6

Majorelementoxides

SiO2 Al2O3 Fe2O3 MnO TiO2 C

Determinedvalues

56.77 21.40 8.03 0.18 0.75 0

Certifiedvalues

56.93 ± 0.18 21.23 ± 0.16 8.09 ± 0.13 0.187 ± 0.011 0.732 ± 0.02 0

Traceelements

B Sc V Cr Mn C

Determinedvalues

53.4 16.6 140 75.9 1395 6

Certifiedvalues

57 ± 5 15.5 ± 0.9 130 ± 7 75 ± 6 1450 ± 82 7

Traceelements

Sr Y Zr Nb Cd B

Determinedvalues

31.7 17.6 231 27.4 0.11 1

Certifiedvalues

39 ± 4 19 ± 2 220 ± 14 27 ± 2 0.13 ± 0.03 1

Traceelements

Eu Gd Tb Dy Ho E

Determinedvalues

0.40 3.21 0.66 3.76 0.67 2

Certifiedvalues

0.66 ± 0.04 3.4 ± 0.3 0.61 ± 0.08 3.3 ± 0.3 0.69 ± 0.05 2

Units for major element oxides and trace elements are wt.% and mg/kg, respectively.

pyrite layers (up to 2 mm) (Fig. 5b and c) that originated from hydro-thermal fluids were precipitated.

The contents of major element oxides in rock and coal samples arepresented in Table 3. The major element oxides are dominated by SiO2

and Al2O3 (Table 3), indicating that feldspar and quartz were the mainminerals in the igneous rocks. The high Fe2O3 content was related tothe disseminated massive pyrite (Fig. 5a and d).

The nine intrusive rocks from the bottom of the lower sill split tothe upper sill split exhibit an increase in acidity that correlates withthe rise of the SiO2 content (Table 3). Furthermore, according to thebenchmarks of the SiO2 content, the intrusive rocks can be dividedinto three categories: mafic sample 1327-14; intermediate samples1327-15, 1327-16, 1327-17, and 1327-18; and felsic samples 1327-19,1327-202, 1327-222, and 1327-23. Thus, a transition occurs frommafic rocks in the bottom of the lower sill split, via intermediate rocksto the upper of the lower sill split, to felsic rocks in the top of thelower sill split and entire upper sill split. Based on the total alkali–silicadiagram of the intrusive rocks (Fig. 6) and the lithology classificationproposed by Middlemost (1994), sample 1327-14 is gabbro, sample1327-15 is located on the boundary of diorite and granodiorite, samples1327-16 and 1327-17 are monzonite, and samples 1327-18, 1327-19,

.

aO K2O SO3 P2O5 Na2O MgO

.19 1.67 0.071 0.143 0.15 0.31

.22 ± 0.03 1.70 ± 0.06 0.065 ± 0.011 0.139 ± 0.014 0.19 ± 0.02 0.34 ± 0.05

o Ni Cu Zn Ga Ge

.77 55.6 389 92.6 27.8 3.08

.6 ± 1.1 53 ± 4 390 ± 14 97 ± 6 30 ± 3 3.2 ± 0.4

a La Ce Pr Nd Sm

04 34.5 63.8 5.17 20.8 3.61

18 ± 14 30 ± 2 66 ± 6 5.8 ± 0.6 21 ± 2 3.8 ± 0.4

r Tm Yb Lu Pb

.24 0.32 2.48 0.43 323

.2 ± 0.3 0.40 ± 0.06 2.7 ± 0.4 0.42 ± 0.05 314 ± 13


1327-202, 1327-222, and 1327-23 are granodiorite. These results coin-cide with Bowen's reaction series for igneous crystallization (Haldarand Tisljar, 2014): the temperature and pressure decrease, while thesilica minerals from the lower part of the lower sill split to the upperpart of the lower sill split and upper sill split increase.

4.2. Changes in coal quality

The volatile matter and hydrogen contents decrease, whereasthe ash yields and elemental carbon increase during the igneous

Fig. 5.Micrographs of igneous rocks of the Pansan CoalMine. a: 1327-23; b: 1327-22; c–d: 1327light; e–j: crossed polarized light.

metamorphism of coal (Ghosh, 1967; Jiang et al., 2011; Karayigit andWhateley, 1997; O'Keefe et al., 2013; Singh et al., 2008; Yao et al.,2011). Moreover, Querol et al. (1997) observed a two-fold increase insulfur content of the diabase-influenced coal samples from the Fuxinbasin, Liaoning province in northeast China.

The results of the proximate and ultimate analyses of the thermally-altered coals and unaltered coal in the No. 1 Coal are tabulated inTable 4. Overall, the moisture, total sulfur, and carbon contents werehigher in the thermally-altered coals than in the unaltered coal, where-as the volatile matter, hydrogen, and nitrogen exhibited the opposite

-20; e: 1327-19; f: 1327-18; g: 1327-17; h: 1327-16; i: 1327-15; j: 1327-14; a–d: reflected

Fig. 5 (continued).


trend. The enhancedmoisture of the thermally-altered coalswas relatedto the well-developed pores and fractures, which facilitated water ad-sorption. The high sulfur content was associated with the epigeneticpyrite of hydrothermal origin. Contact metamorphism induced theloss of volatile matter, hydrogen, and nitrogen; however, it induced

Table 3Contents of major element oxides in sandstone, igneous rocks, thermally-altered coals, sandy m

Sample no. SiO2 Al2O3 Fe2O3 MnO TiO

1327–27 91.5 2.88 0.46 0.031 0.0

1327–26 18.0 3.13 42.4 0.012 0.3

1327–25 10.3 3.61 2.17 0.131 0.1

1327–24 9.81 3.56 3.83 0.169 0.1

1327–23 74.4 10.5 4.42 0.014 0.3

1327–222 73.1 12.2 3.57 0.016 0.3

1327–221 20.9 4.19 1.65 0.012 0.1

1327–21 26.8 3.67 0.70 0.039 0.1

1327–201 17.9 4.28 1.28 0.021 0.1

1327–202 71.4 11.7 5.03 0.143 0.3

1327–19 70.6 13.4 4.56 0.147 0.3

1327–18 64.6 16.0 4.96 0.152 0.4

1327–17 59.8 16.6 5.53 0.139 0.4

1327–16 57.2 17.4 5.04 0.144 0.4

1327–15 63.0 18.0 2.30 0.082 0.4

1327–14 46.2 15.2 4.60 0.229 0.3

1327–13 7.94 4.21 1.95 0.124 0.0

1327–12 13.9 6.24 0.49 0.036 0.5

1327–11 4.51 2.12 1.44 0.035 0.0

1327–10 60.6 22.4 0.73 0.003 1.0

1327–9 61.8 21.8 0.57 0.003 1.0

1327–8 56.4 24.5 0.82 0.003 1.0

1327–7 56.6 24.6 1.08 0.003 1.0

1327–6 6.56 2.80 0.29 0.005 0.1

1327–5 2.18 1.12 0.85 0.004 0.0

1327–4 3.29 2.34 0.19 0.001 0.0

1327–3 3.57 1.28 1.00 0.012 0.1

1327–2 3.21 2.45 0.97 0.012 0.1

1327–1 5.40 3.21 1.28 0.008 0.1

1571 31.6 20.4 1.05 0.002 0.5

Shading colors in Tables 3, 4, 6, and 7, i.e., light gray, light blue, yellow, blue, and gray, are admudstones, and unaltered coal, respectively.

the gain of carbon. According to the classification of ASTM D388-12(2012), all of the thermally-altered coals were anthracite, whereas theunaltered coal was high volatile A bituminous in rank.

The vertical variations of coal quality parameters in the profile ofthe No. 1 Coal are illustrated in Fig. 7. The moisture, total sulfur, and

udstones, and unaltered coal (units: wt.%; on whole rock basis).

2 CaO K2O SO3 P2O5 Na2O MgO

7 1.01 0.67 0.31 0.043 0.04 0.45

6 0.31 0.33 14.4 0.234 0.17 0.45

1 9.20 0.09 0.34 0.017 0.25 5.06

0 11.9 0.09 4.36 0.019 0.14 6.54

8 0.69 0.16 3.86 0.098 0.04 0.16

9 0.72 0.12 3.05 0.096 0.06 0.20

6 0.49 0.11 0.62 0.050 0.09 0.22

6 1.70 0.14 0.99 0.052 0.10 0.83

8 0.71 0.18 0.76 0.054 0.07 0.33

9 0.68 1.67 2.19 0.078 0.08 0.35

9 0.72 1.67 1.58 0.074 0.08 0.39

3 0.95 3.46 1.27 0.091 0.19 0.47

2 1.08 5.80 0.39 0.118 3.31 0.59

3 2.18 5.79 0.20 0.098 1.86 1.21

5 1.19 5.28 0.24 0.100 0.95 0.62

3 8.13 2.18 3.32 0.087 0.12 4.57

6 8.17 0.05 4.21 0.009 0.17 4.53

4 2.08 0.40 0.42 0.057 0.23 1.31

6 2.29 0.04 3.28 0.006 0.14 1.22

6 0.08 1.49 0.20 0.044 0.24 0.35

5 0.08 1.44 0.02 0.046 0.41 0.35

8 0.09 1.74 0.02 0.046 0.42 0.44

8 0.39 1.92 0.14 0.054 0.47 0.51

4 0.44 0.14 1.12 0.009 0.05 0.23

6 0.33 0.02 0.77 0.005 0.04 0.16

7 0.16 0.03 0.47 0.014 0.09 0.05

2 1.19 0.06 3.10 0.013 0.01 0.55

1 1.23 0.06 2.77 0.022 0.08 0.60

6 0.66 0.11 0.66 0.023 0.08 0.30

4 0.07 0.66 0.15 0.040 0.31 0.26

ded to differentiate sandstone, mixed samples from contact areas, igneous rocks, sandy

image of

Unlabelled image

Fig. 6. Total alkali–silica diagram of igneous rocks of the Pansan Coal Mine. Lithologyclassification was based on the nomenclature proposed by Middlemost (1994).

Table 4Proximate and ultimate analyses, and losses on ignition of sandstone, igneous rocks, thermally

Items Aa, d Mad Vdaf

1327—27 — — —

1327—26 74.61 — —

1327—25 37.10 1.01 5.06

1327—24 47.97 0.66 3.59

1327—23 — — —

1327—222 — — —

1327—221 29.60 — —

1327—21 37.34 1.64 7.82

1327—201 27.49 — —

1327—202 — — —

1327—19 — — —

1327—18 — — —

1327—17 — — —

1327—16 — — —

1327—15 — — —

1327—14 — — —

1327—13 33.68 2.16 4.78

1327—12 27.93 1.63 6.83

1327—11 15.13 1.13 3.97

1327—10 90.69 — —

1327—09 90.10 — —

1327—08 87.58 — —

1327—07 89.37 — —

1327—06 12.15 1.97 3.90

1327—05 5.65 2.26 3.03

1327—04 6.87 2.20 3.78

1327—03 11.97 2.14 6.21

1327—02 11.54 2.13 7.31

1327—01 13.24 1.92 4.96

Minimum — 0.66 3.03

Maximum — 2.26 7.82

Average — 1.74 5.10

1571 56.93 1.48 39.08

“–”: not determined; A: ash yield; M: moisture; V: volatile matter; St: total sulfur; C: carbon; Hbasis. The LOIs of thermally-altered coals and sandy mudstones were determined at 1075 °C, w


hydrogen contents in the thermally-altered coals from the uppersubseams (Subseams 1 and 2 in Fig. 4) are relatively lower than thosein the altered coals from the lower subseams (Subseams 3 and 4). How-ever, volatilematter, carbon, and nitrogen exhibit a uniformdistributionin this profile.

4.3. Mineralogical responses

4.3.1. Variation of ash yieldsAlthough the pyrite, siderite, and clay minerals (kaolinite, illite/

smectite) may be altered during the ashing process at temperaturesas low as 370 °C (Ward et al., 2001), the ash yield is conventionallydetermined at 815 °C; nonetheless, it reflected the overall level of theminerals in coal.

The ash yields of the thermally-altered coals, which can directlyreflect the general change of the minerals, increased as a result of thevolatilization, release,migration of organicmatter, and the precipitationof hydrothermal and epigenetic minerals in the vesicles and fracturesdue to igneous intrusion.

-altered coals, sandy mudstones, and unaltered coal (units: %).

St,ad Cad Had Nad LOIs

— — — — 0.83

— — — — 3.35

0.40 87.07 1.46 1.26 14.96

0.96 75.17 1.35 1.61 37.25

— — — — 4.43

— — — — 4.74

— — — — 2.03

0.20 93.40 1.33 1.29 32.56

— — — — 2.78

— — — — 4.62

— — — — 4.14

— — — — 4.57

— — — — 2.03

— — — — 4.78

— — — — 2.90

— — — — 15.14

1.86 92.19 2.40 1.25 19.14

0.55 92.88 1.55 1.31 20.00

0.31 91.87 1.53 1.18 15.34

— — — — 4.31

— — — — 10.05

— — — — 0.52

— — — — 4.16

0.48 94.71 1.81 1.05 16.01

0.77 94.40 1.71 1.01 4.42

0.61 93.91 2.04 1.12 23.66

0.93 92.27 2.22 1.24 51.98

0.79 91.81 2.49 1.26 47.66

1.54 91.56 2.56 1.25 5.33

0.20 75.17 1.33 1.01 —

1.86 94.71 2.56 1.61 —

0.78 90.94 1.87 1.24 —

0.26 75.83 5.95 2.40 0.48

: hydrogen; N: nitrogen; LOI: loss on ignition; ad: on air dry basis; daf: on dry and ash freehich were previously ashed at 550 °C to remove organic matter.

Unlabelled image

1327-11327-21327-31327-41327-51327-61327-71327-81327-9

1327-101327-111327-121327-131327-141327-151327-161327-171327-181327-19

1327-2021327-201

1327-211327-2211327-222

1327-231327-241327-251327-261327-27

1571

0 1 2

Igneous rock

Igneous rock

Sandy mudstone

Thermally-altered coal




SandstoneUnaltered coal

Mad / %

Sam

ple

No.

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1327-2021327-201

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1327-231327-241327-251327-261327-27

1571

0 10 20 30 40




Unaltered coal

Igneous rock

Igneous rock

Sandy mudstone


Sandstone

Vdaf / %

Sam

ple

No.

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1327-2021327-201

1327-211327-2211327-222

1327-231327-241327-251327-261327-27

1571

0.0 0.5 1.0 1.5 2.0




Igneous rock

Igneous rock

Sandy mudstone



St,ad / %

Sam

ple

No.

Fig. 7. Vertical variations of coal quality parameters of thermally-altered coals and unaltered coal of the Pansan Coal Mine. M: moisture; V: volatile matter; St: total sulfur; C: carbon;H: hydrogen; N: nitrogen; ad: on air dry basis; daf: on dry and ash free basis.


1327-11327-21327-31327-41327-51327-61327-71327-81327-9

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1571

0 20 40 60 80 100




Igneous rock

Igneous rock

Sandy mudstone



Cad / %

Sam

ple

No.

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1327-2021327-2011327-21

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1571

0 2 4 6




Igneous rock

Igneous rock

Sandy mudstone



Had / %

Sam

ple

No.

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1327-2021327-2011327-21

1327-2211327-2221327-231327-241327-251327-261327-27

1571

0 1 2




Igneous rock

Igneous rock

Sandy mudstone



Nad / %

Sam

ple

No.

Fig. 7 (continued).


1327-11327-21327-31327-41327-51327-61327-71327-81327-9

1327-101327-111327-121327-131327-141327-151327-161327-171327-181327-19

1327-2021327-2011327-21

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1571

0 20 40 60 80 100




Unaltered coal

Sandy mudstone

Igneous rock

Igneous rock

Sandstone

Ash yields / %

Sam

ple

No.


Fig. 8. Vertical variation of ash yields of thermally-altered coals and unaltered coal of the Pansan Coal Mine.


The vertical trend indicates that the ash yields (Fig. 8) decreaseas the distance from the sill increases. For example, samples from1327-13 to 1327-10, and from 1327-24 to 1327-25 display aweakeningcontact metamorphism with an increasing distance from the intrusion.The ash yields of the sandy mudstones and thermally-altered coalsrange from 87.58% to 90.69% (89.46% on average) and from 5.65% to47.97% (21.84% on average) (Table 4), respectively. The unalteredcoal that approaches the roof of the No. 1 Coal (see Section 3) has anash yield of 56.93%, probably suggesting that it has an abundant terrig-enous input. The ash yields of the thermally-altered coals underlyingthe sandy mudstone parting were lower than those of the overlyingsamples. Therefore, the impact of the contact metamorphism of the in-trusive sill on the coal was reduced by the parting. Although the sedi-mentary rocks that are rich in organic matter generally have lowerthermal conductivities than other rock types (Cercone et al., 1996),the 1.24 m sandy mudstone parting, which is relatively deprived

1327-11327-21327-31327-41327-51327-61327-71327-81327-9

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1327-2021327-2011327-21

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1571

0 20

Thermally

Sandy mudstone

Igneous rock

Igneous rock

Therm

Sandstone

Sam

ple

No.

Unaltered coal

Fig. 9. Vertical variation of losses of ignition of roc

of organic matter (with an average ash yield of 89.46%), effectivelyweakened the thermal effect of the thick intrusive sill by acting as aninsulating layer.

4.3.2. Vertical variation of LOIsLoss on ignition is applied widely in rock analyses to measure the

total volatiles (i.e., H2O, CO2, F, Cl, S, etc.) (Lechler and Desilets, 1987).Carbonate minerals in coal, such as siderite, magnesite, calcite, dolo-mite, and ankerite, are decomposed in nitrogen at 480, 620, 820, 760,and 690 °C, respectively (Dubrawski and Warne, 1987). Therefore, it isreasonable to assume that the LOIs of the pre-ashed thermally-alteredcoals and sandy mudstones identified at 1075 °C could reflect the con-tent of carbonates.

As displayed in Table 4 and Fig. 9, the LOIs of the thermally-alteredcoals (averaging 21.07%) are significantly higher than those of theigneous rocks (averaging 5.26%) and unaltered coal (0.48%); thus,

40 60


-altered coal


ally-altered coal

LOI / %

k and coal samples of the Pansan Coal Mine.


more carbonate minerals could have occurred in the thermally-alteredcoals. During the igneous intrusion, the plentiful vacuoles, pores, andfractures provided spaces for the precipitation of Fe-bearing dolomite(Fig. 10), which was attributed to the precipitation of hydrothermalfluids, and/or to the reaction of CO2 in the volatiles accompanying theintrusion or CO2 from the thermally-altered coal with material fromthe intrusion (Dai and Ren, 2007). Additionally, the dehydration ofhalloysite (Al2Si2O5(OH)4·2H2O) in the thermally-altered coals fromSubseam 4 (samples 1327-7 to 1327-1, Table 5) is an alternative reason

Fig. 10. Fe-bearing dolomite in thermally-altered coals of theNo. 1 Coal in the Pansan CoalMineof the square area in panel (a) and whole panel (d); c and f: X-ray EDS spectrograms of spots

for the high LOIs. Moreover, the relatively high LOI of igneous rocksample 1327-14 is related to dolomite (Table 5). The presence of onlykaolinite and quartz (Table 5) are responsible for the low LOI of theunaltered coal. Finally, the presence of quartz alone (Fig. 11) causes alow LOI in the roof sandstone.

4.3.3. Evolution of minerals in No. 1 CoalRegarding the minerals identified by XRD (Table 5), more species of

minerals occurred in the thermally-altered coal than in unaltered coal.

. a–c: 1327-2; d–f: 1327-7; a and d: reflected light; b and e: secondary electron SEM imagesnoted in panels (b) and (e).

Table 5Minerals in sandstone, igneous rocks, thermally-altered coals, sandy mudstones, and un-altered coal identified by XRD.

SampleNo. Minerals

1327-27 Quartz1327-26 Pyrite, quartz1327-25 Quartz, clinochlore, and dolomite1327-24 Quartz, dolomite, and anhydrite1327-23 Quartz, orthoclase1327-222 Kaolinite, amesite, quartz, and kaolinite–montmorillonite1327-221 Quartz, pyrite, and kaolinite1327-21 Quartz, microcline1327-201 Quartz, anatase, and kaolinite1327-202 Quartz, orthoclase1327-19 Quartz, orthoclase, microcline, and kaolinite1327-18 Quartz, orthoclase, and kaolinite1327-17 Orthoclase,microcline, anorthoclase, albite, quartz, Sanidine, and kaolinite1327-16 Sanidine, orthoclase, and clinochlore1327-15 Kaolinite, quartz, sanidine, and orthoclase1327-14 Dolomite, sanidine, kaolinite, quartz, and clinochlore1327-13 Quartz, dolomite, and orthoclase1327-12 Akermanite, kaolinite, quartz, and clinochlore1327-11 Dolomite, clinochlore, muscovite, kaolinite1327-10 Kaolinite, quartz, and clinochlore1327-9 Kaolinite, quartz, and halloysite1327-8 Quartz, kaolinite, and muscovite1327-7 Halloysite, muscovite, clinochlore, and quartz1327-6 Dolomite, muscovite, kaolinite, quartz, and halloysite1327-5 Kaolinite, quartz, halloysite, gypsum, and pyrite1327-4 Kaolinite, quartz, and muscovite1327-3 Dolomite, kaolinite, halloysite, and quartz1327-2 Dolomite, kaolinite, and halloysite1327-1 Kaolinite, quartz, and halloysite1571 Kaolinite, quartz


Kaolinite and quartz dominate the unaltered coal (Fig. 12), whereas ka-olinite, quartz, dolomite, and pyrite are dominant in the thermally-altered coals (Table 5). Clinochlore, originated from the weatheredbiotite, was observed in the andesite sill-influenced coal in the Yangoumine of Jiangxi province, southeast China (Querol et al., 2001). Thehalloysite in the Newcastle coal of the Sydney basin was attributed tothe alteration of fine pyroclastic debris under swampy or soil-formingconditions (Ward, 1989). Therefore, the clinochlore and halloysite inthe Pansan thermally-altered coals may be a result of the alteration ofaluminosilicate in the coal. Furthermore, the dolomite and pyrite inthe Pansan thermally-altered coals were likely deposited by the hydro-thermal fluids as proposed by Dai et al. (2012a), Karayigit andWhateley(1997), and Querol et al. (2001).

Based on the vertical distribution of theminerals in the profile of theNo. 1 Coal (Fig. 13), different sub-horizons generally contained variousepigenetic minerals, including Fe-bearing dolomite, quartz, and pyrite.

Fig. 11.Minerals in roof sandstone of the No. 1 Coal in the Pansan

Massive pyrite, even thick pyrite layers, were exclusively associatedwith the contact joint of two rocks, i.e., sandstone and thermally-altered coal (Fig. 13a) and igneous rock and thermally-altered coal(Fig. 13c and e), which indicate a delayed and intensive Fe- and/orH2S-rich hydrothermal fluid and limited space for pyrite precipitation.The dispersive massive pyrite, inter-developed with the Fe-bearingdolomite (Fig. 13i and k) or kaolinite (Fig. 13j and l), was probably de-rived from the combination of clay- and hydrothermal fluid-sourcedFe and scarce H2S in the volatiles released from the coal. The distinctlysharp contact of the fracture-filled quartz in the thermally-altered coaland massive pyrite in the igneous rock (Fig. 13c and e), in addition tothe coexistence of quartz and pyrite stingers in the sandy mudstone(Fig. 13h), implied that two minerals had different origins and forma-tion stages. Quartz was confined to the thermally-altered coal layersthat are adjacent to the sill (Fig. 13b, c, d, e, and g), the bottom ofthe lower sill split (Fig. 13f), and the sandy mudstone parting(Fig. 13h). Interestingly, a hexagonal quartz crystal was observed ina quartz vein in the thermally-altered coal (Fig. 13d), which suggeststhat sufficient spaces existed to circulate the Si-rich hydrothermalfluid and crystal growth. Fe-bearing dolomite, which prevailed inthe thermally-altered coals from the lower part of the profile, weredeposited from the reaction of Ca-, Mg-, and Fe-rich hydrothermalfluid with CO2 in the volatiles that were derived from magma or coalmetamorphism.

Based on the occurrence of the minerals in the typical profile of theNo. 1 Coal of the Pansan Coal Mine, three hydrothermal fluids stageswith different compositions were differentiated: Ca-, Mg-, and Fe-rich; Si-rich; and Fe- and/or H2S-rich fluids stages. The Ca-, Mg-, andFe-rich fluid first flowed into the No. 1 Coal through the fully devel-oped fractures that formed by the squeezing motion of the intrusionor by the contraction during the cooling process of the thermally-altered coal. The intensity of the fluid was relatively weak, and itmainly penetrated into the lower part of the seam (corresponding tothe formation of Fe-bearing dolomite) (Fig. 13i–k). Then, the Si-richfluid entered the upper part of the seam, which was accompaniedby the deposition of quartz in the upper section (Fig. 13b–h). Finally,the Fe- and/or H2S-rich fluid flowed into the seam where no otherspaces (other than the juncture of two rocks), which acted as achannel for fluid circulation and an area for mineral deposition(corresponding to the precipitation of thick pyrite layers) (Figs. 5b–d,and 13a, c, and e).

4.4. Geochemical responses

4.4.1. Major element oxidesThe major element oxides in the thermally-altered coals are SiO2

(averaging 9.87 wt.%), Al2O3 (3.14 wt.%), Fe2O3 (1.24 wt.%), TiO2

(0.15 wt.%), CaO (2.49 wt.%), K2O (0.11 wt.%), SO3 (1.51 wt.%), P2O5

Coal Mine. a: X-ray diffractogram; b: crossed polarized light.

image of Fig.�11

Fig. 12.Minerals in unaltered coal of the No. 1 Coal in the Pansan Coal Mine. a: reflected light; b and d: secondary electron SEM images of the square areas in panel (a); c and e: X-ray EDSspectrograms of spots noted in panels (b) and (d).


(0.03 wt.%), Na2O (0.10 wt.%), and MgO (1.34 wt.%). The SiO2, Al2O3,and CaOwere dominant, whichwere related to the kaolinite, epigeneticquartz and Fe-bearing dolomite.

CaO and MgO distinctly enrich in the thermally-altered coals ofthe No. 1 Coal in the Pansan Coal Mine, compared with those in the un-altered coal, the Huainan No. 1 coal (Chen et al., 2011), Huainan coals(Chen et al., 2011), Chinese coals (Dai et al., 2012b), and world hardcoals (Ketris and Yudovich, 2009) (Fig. 14b). Fe2O3 was also moreconcentrated in the thermally-altered coal than in the unaltered coal.The CaO, MgO, and Fe2O3 enrichments were associated with the Fe-bearing dolomite and pyrite of hydrothermal origins (Figs. 10 and 13).Moreover, a slightly elevated SiO2 content in the thermally-alteredcoals compared with that in the Huainan No. 1, Huainan, Chinese, andworld coals (Fig. 14a). The elevated SiO2 content was probably resultedfrom the Si-rich hydrothermal fluid and was due to the increase of ashyields induced by contact metamorphism. The low contents of Al2O3

and TiO2 in the thermally-altered coal (Fig. 14a, b) were related tosparse terrigenous input of the No. 1 Coal in the Huainan coalfield,which was consistently influenced by brackish water (Chen et al.,2011). The low K2O, Na2O, and P2O5 contents in the thermally-alteredcoal (Fig. 14b, c) may have resulted from groundwater leaching (a dis-cussion follows).

SiO2 is enriched in roof sandstone, followed by sandy mudstoneparting (Fig. 15a), in accordance with the observation of the abundantquartz (Table 5 and Fig. 11). The CaO, MgO, Fe2O3, and SO3 contentsin the thermally-altered coal were comparable to those in the igne-ous rock, but significantly higher than those in the unaltered coal(Fig. 15b), further substantiating their hydrothermal origins. TheAl2O3, TiO2, K2O, Na2O, and P2O5 contents in the thermally-alteredcoal were lower than those in the igneous rock and unaltered coal(Fig. 15a–c), implying that the igneous intrusion did not exert animpact on these major element oxides in the coal.

4.4.2. Trace elements and REYThe concentrations of trace elements and REY in the rock and

coal samples of the No. 1 Coal in the Pansan Coal Mine are listed inTables 6 and 7.

The boron concentrations in the thermally-altered coals range from3.29 to 29.16 mg/kg, with an average of 10.82 mg/kg. Goodarzi andSwaine (1994) set the benchmarks of B for freshwater-influenced(b50 mg/kg), moderately brackish water-influenced (50–110 mg/kg),and brackish water-influenced (N110 mg/kg) coals. Based on thesebenchmarks, the No. 1 Coal in the Pansan Coal Mine was deposited in afreshwater-influenced environment, which contradicts the conclusions

image of Fig.�12


of Chen et al. (2011). However, the ratios of Sr/Ba in the thermally-altered coals vary from 0.28 to 5.72 (averaging 2.76). Only the Sr/Ba ofsample 1327-6 is smaller than 1. Thus, the No. 1 Coal has a marinewater-influenced depositional environment. Boron generally exhibits astrong organic affinity in coal (Dai et al., 2004; Newman et al., 1997;Pires et al., 1997; Sun et al., 2010a; Swaine, 1992; Zhou et al., 2010;Zhuang et al., 2003); the low B concentration in the No. 1 Coal was prob-ably due to its volatilization and releasing during the metamorphismthat was caused by the sill intrusion, but the B was enriched in theFengfeng-Handan altered coals (ascribed to hydrothermal solution)

Fig. 13. Evolution of minerals in rock and coal samples of the No. 1 Coal in the Pansan Coal Mih: 1327-8; i: 1327-7; j: 1327-4; k and l: 1327-1; under reflected light, except for panel (j), wh

(Dai and Ren, 2007). Strontium and Ba are commonly associated withminerals in coal (Dai et al., 2005, 2008; Eskenazy, 2009; Iordanidis,2002; Ward, 2002), which can be stable and non-volatile during activi-ties of igneous intrusion.

The thermally-altered coals of the PansanNo. 1 Coal are significantlyenriched in Mn and Sr, as compared with the unaltered coal, HuainanNo. 1 coal (Chen et al., 2011), Huainan coals (Chen et al., 2011), Chinesecoals (Dai et al., 2012b), and world hard coals (Ketris and Yudovich,2009) (Fig. 14d). These results are related to the Fe-bearing dolo-mite (containing the Mn detected by the X-ray EDS in Fig. 13j) of

ne. a: 1327-26; b: 1327-25; c: 1327-22; d: 1327-21; e: 1327-20; f: 1327-14; g: 1327-13;ich is a secondary electron SEM imagine.

image of Fig.�13

Fig. 13 (continued).


hydrothermal origins and, in particular, to theMn-rich intrusivemagma(Fig. 15g). Querol et al. (1997) also reported that Mn was enriched byone or two orders of magnitude in the diabase-influenced coal com-pared with the unaffected coal from the Fuxin basin in northeastChina. The elevated concentrations of Ca,Mg, Fe,Mn, and Sr in the Pitkincokewere attributed to the carbonates that were derived from the reac-tion of CO and CO2 during the coking of coal with fluids from the intru-sion (Finkelman et al., 1998). However, Sr was not detected in thecarbonates using X-ray EDS (see the 4.4.3 section). The concentrationsof Pb, Sc, and La in the thermally-altered coal and unaltered coal werehigher than those of the Huainan No. 1, Huainan, Chinese, and worldcoals (Fig. 14e and f), which might relate to the increased ash yields.The concentrations of Zr, Ba, V, Zn, Nd, Cr, Co, Ni, Cu, Ce, Y, Nb, Pr, Sm,Gd, Cd, Ge, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu in the thermally-alteredcoal are comparable to those in the unaltered, Huainan No. 1, Huainan,Chinese, and world coals (Fig. 14d–g), which suggests that igneousintrusion has little or no effect on these elements in the coal.

Regarding the changes of trace elements and REY in various rocksand thermally-altered coals (Fig. 15d–g), the igneous rocks containthe highest concentrations of Ge, Cd, Sc, Nb, Ga, Mn, Zr, Ba, and REY.Igneous intrusion exhibits little to no influence on Ge, Cd, Sc, Cr, Nb,V, Zn, Zr, Ba, and REY concentrations in the thermally-altered coal,which is located between the igneous rock and unaltered coal. Therelative enrichment of Cr, Co, Ni, and V in the sandy mudstone partingand in the unaltered coal adjacent to the roof of the No. 1 Coal(Fig. 15e and f), indicates a terrigenous input. The Sr increase in thematerials as follows: unaltered coal b sandy mudstone b igneousrock b sandstone b thermally-altered coal (Fig. 15g), which may elimi-nate the possibility of a terrigenous input. The Ga andMn decrease fromthe igneous rock, through the thermally-altered coal, to the unalteredcoal (Fig. 15f and g), suggesting a potential igneous source. Consideringthe enrichment of Pb in the thermally-altered coal and unaltered coal(Fig. 15f), it is difficult to conclude its origin from the general concentra-tion comparison.

Yang et al. (2012) delineated that the REE concentrations of igneousintrusion-affected coals were not distinctly different from those of the

unaltered coals in the Zhuji Coal Mine (Fig. 2) of the Huainan coalfield.However, Huang et al. (2000) stated that the distribution pattern ofthe REE would be markedly changed due to igneous intrusion.

The geochemical parameters of REY in rock and coal samplesof the No. 1 Coal are listed in Table 7. The REY concentrations ofthe thermally-altered coals range from 24.3 to 352 mg/kg, with amean of 107 mg/kg, remarkably lower than that of the unaltered coal(274 mg/kg). The (La/Lu)N, (La/Sm)N, and (Gd/Lu)N averages of thethermally-altered coals are 1.90, 1.39, and 1.26, respectively, whichare similar to those of the unaltered coal (2.20, 1.10, and 1.62, respec-tively). Thus, the two coal types may have similar distribution patternsand sources of REY.

The Upper Continental Crust-normalized REY patterns of the rockand coal samples in the profile of the No. 1 Coal are presented inFig. 16. The results indicated that the patterns of roof sandstone 1327-27, igneous rocks 1327-222 and 1327-202, thermally-altered coals1327-221 and 1327-201, and unaltered coal 1571 are similar. In partic-ular, the patterns are characterized by the enrichment of REY than thosein the Upper Continental Crust, and significant negative anomalies ofCe and Eu.

The REY concentration of the roof sandstone 1327-27 is 176 mg/kg,higher than that of the thermally-altered coal (107 mg/kg) but lowerthan that of the unaltered coal (274 mg/kg). The roof sandstonedisplayed significant negative anomalies of Ce and Eu. The Ce negativeanomaly usually correlated with the marine water influence (Liu et al.,2000) and redox conditions (Cressey and Cressey, 1988; Huang et al.,2000) of the depositional environment. The Eu anomaly (both positiveand negative) generally inherits the source rocks' chemical composition(Dai et al., 2013, 2014; Seredin andDai, 2012). Igneous rock samples, in-cluding 1327-23, 1327-19, 1327-18, 1327-17, 1327-16, 1327-15, and1327-14, presented a similar distribution pattern, characterized by asignificant enrichment of LREY (La, Ce, Pr, Nd, and Sm) and a positiveCe anomaly. However, the REY distribution patterns of the twosubdivided igneous rock samples, 1327-222 and 1327-202, resemblethose of roof sandstone 1327-27 and thermally-altered coals 1327-221 and 1327-201, rather than those of the bulk igneous rocks. The

image of


REY concentrations of thermally-altered coal samples 1327-221 and1327-201 are 352 mg/kg and 276 mg/kg, respectively, approximatelytwo times that of the roof sandstone (176 mg/kg, Table 7) and muchlower than the concomitant igneous rocks 1327-222 and 1327-202;this suggests that the igneous material was added to and/or contami-nated the thermally-altered coal. The negative Ce anomaly in coal canbe caused by low temperature hydrothermal fluids (Dai et al., 2004,

0

7

14

21

28

35

Con

tent

s / w

t.%

Oxides

Unaltered coal Pansan thermally-altered coal Huainan No. 1 coal (Chen et al., 2011) Huainan coals (Chen et al., 2011) Chinese coals (Dai et al., 2012b)World coals (Ketris and Yudovich, 2009)

SiO2 Al2O3

a

0.0

3.5

7.0

Con

tent

s / w

t.%

Oxides


Fe2O3 TiO2 CaO K2O Na2O MgO

b

0.0

0.4

0.8

1.2

Con

tent

s / w

t.%

Oxide

Una

ltere

d co

al

Pan

san

ther

mal

ly-a

ltere

d co

al

Hua

inan

No.

1 c

oal (

Che

n et

al.,

201

1)

Hua

inan

coa

ls (

Che

n et

al.,

201

1)

Chi

nese

coa

ls (

Dai

et a

l., 2

012b

)

Wor

ld c

oals

(K

etri

s an

d Y

udov

ich,

200

9)

P2O5

c

Fig. 14. Comparison of elemental contents of the Pansan thermally-altered coals to those of unc: b0.1 wt.%; d: N100 mg/kg; e: 50–100 mg/kg; f: 10–50 mg/kg; g: b10 mg/kg.

2011, 2013) and oxygen-bearing groundwater (Huang et al., 2000).Therefore, the significant negative Ce anomalies of the igneous rocksamples 1327-222 and 1327-202 and thermally-altered coals 1327-221 and 1327-201 were probably attributed to the Fe- and/or H2S-richhydrothermalfluid and/or groundwater.Moreover, the REY distributionpattern of igneous rock 1327-23 from the middle of the upper sill splitnearly resembles those of the igneous rocks from the lower sill split,

B Mn Sr Zr Ba0

80

160

240

320

400

Con

cent

ratio

ns /

mg/

kg

Elements


d

V Zn Nd Pb La0

25

50

75

100

Con

cent

ratio

ns /

mg/

kg

Elements


e

Sc Cr Co Ni Cu Ga Ce Y Nb Pr Sm Gd0

25

50

Con

cent

ratio

ns /

mg/

kg

Elements

Unaltered coal

Pansan thermally-altered coal

Huainan No. 1 coal (Chen et al., 2011)

Huainan coals (Chen et al., 2011)

Chinese coals (Dai et al., 2012b)

World coals (Ketris and Yudovich, 2009)

f

altered, Huainan No. 1, Huainan, Chinese, and world coals. a: N7.0 wt.%; b: 0.1–7.0 wt.%;

image of Fig.�14

Cd Ge Eu Tb Dy Ho Er Tm Yb Lu0.0

2.5

5.0

7.5

10.0

Con

cent

ratio

ns /

mg/

kg

Elements


g



highlighting its poorly developed fractures and relatively weak hydro-thermal fluid influence (Fig. 5a).

Almost all of the thermally-altered coals (1327-25, 1327-24, 1327-21, 1327-12, 1327-11, 1327-5, 1327-4, 1327-3, 1327-2, and 1327-1),sandy mudstones, and mixture samples (1327-26 and 1327-7) shareda similar pattern that was relatively horizontal.

Sample 1327-26, collected from the contact area of the roof sand-stone and thermally-altered coal, displays a similar REY distributionpattern to that of the thermally-altered coals (i.e., the sample wasdominated by thermally-altered coal).

The REY distribution pattern of thermally-altered coal 1327-21differs from that of thermally-altered coals 1327-221 and 1327-201. Inparticular, the Fe- and/or H2S-rich hydrothermal fluid did not impact1327-21 (Fig. 13d) in themiddle of the Subseam2 (Fig. 4) (with a thick-ness of 28 cm).

The REY concentrations of the sandy mudstones range from 111 to176 mg/kg, with an average of 139 mg/kg, slightly higher than that ofthe thermally-altered coal (107 mg/kg). Additionally, the sandy mud-stones have similar REY distribution patterns to the thermally-alteredcoals, suggesting that they have a common REY source (terrigenousinput).

For thermally-altered coal sample 1327-6 close to the sandy mud-stone parting, the appreciable enrichment of HREY was probably de-rived from the overlying sandy mudstone parting and was related tothe stronger organic affinity of HREY than LREY (Beaton et al., 1991;Dai et al., 2012a, 2013; Eskenazy, 2009; Huang et al., 2000).

4.4.3. Sources of elements in No. 1 CoalTo better understand the influence of igneous rock, hydrothermal

fluid, terrigenous input, and groundwater on elements in the No. 1Coal of the Pansan Coal Mine, the vertical distribution of the elementalcontents in the profile was plotted (Fig. 17).

Because of the epigenetic pyrite precipitated from Fe- and/or H2S-rich hydrothermal fluid, Fe2O3 and SO3 were enriched in the samplesadjacent to the contact areas (e.g., samples 1327-26, 1327-24, and1327-23).

The Mn concentration reaches its maximum in the igneous rocks,especially in the lower sill split. However, the concentrations decreasein Subseams 1 and 3 as the distance increases from the lower andupper sill splits. The Mn concentration was low in the thin uppersill split (0.34 m), probably related to leaching during the alteration.The remarkable difference of the Mn concentrations in the thermally-altered coals that were separated by the sandy mudstone partingsuggests that the parting acted as an insulator for both heat and

chemical materials. In summary, the Mn in the thermally-altered coalwas directly related to the intrusive magma.

Because more terrigenous detritus occurred in the sandy mudstoneand unaltered coal, the decrease in the TiO2 from the sandy mudstone,through the unaltered coal, to the thermally-altered coal suggests a ter-rigenous Ti input.

The diminishing trends of CaO and MgO in Subseams 1 and 3 coin-cide with the Ca-, Mg-, and Fe-rich hydrothermal fluid origins.

K2O and Na2O, which were related to feldspar and kaolinite,were concentrated in the lower sill split and to a lesser extent thesandymudstone. The relatively high K2O contents in the roof sandstoneand unaltered coal and the decreasing tendency from samples 1327-27to 1327-25 suggests that the input was terrigenous and that the K2O inthe thermally-altered coal was not influenced by the igneous intrusion.The single-peak distributions of the K2O and Na2O in the lower sill splitand the low contents in the upper sill split suggests that the K and Nawere leached out by groundwater.

The P2O5 content is highest in the igneous rocks. The sandy mud-stones, thermally-altered coals, and unaltered coal are depleted inP2O5, ruling out the possibility of igneous and terrigenous input. Itcould be proposed that the maximum P2O5 in the mixture of thethermally-altered coal and sandstone (sample 1327-26) could betransported by groundwater.

With the exception of their contents in the roof sandstone, the verticaltendencies of SiO2 and Al2O3 were similar, both enriched in the igneousrock and sandy mudstone parting. The SiO2 and Al2O3 were related toquartz and feldspar in the igneous rock and to detrital quartz andkaolinite in the sandy mudstone parting. The more frequent SiO2 enrich-ment, comparedwith Al2O3, indicating the excessive Si in quartz (in addi-tion to aluminosilicate). The ratio of SiO2/Al2O3 for the unaltered coal was1.55, higher than the value of kaolinite (1.17) (Newman et al., 1997). Thisstoichiometrically confirmed the existence of free SiO2 (Fig. 12a, d, and e).

Scandiumwas enriched in the lower sill split. However, the reducedconcentrations in the upper sill split and in the upper part of the lowersill split may indicate themobility of Sc during alteration. The high con-centrations of Sc in the sandymudstone and Subseam 1 near the roof ofthe No. 1 Coal reveal its terrigenous origin.

The sandy mudstone parting and unaltered coal were abundant inthe terrigenous-sourced Cr and V. The small variations of Cr and V inthe thermally-altered coals and igneous rocks implied only a weak orno impact of the igneous intrusion on the Cr and V in the coal.

The Co and Ni concentrationswere low in the igneous rocks, where-as the concentrations were high in the sandymudstone parting and un-altered coal (i.e., reflecting terrigenous inputs). The analogous verticaldistributions of Co and Ni to ash yields, i.e., higher in the upperthermally-altered coal layers (Subseams 1 and 2) than in the lowerlayers (Subseams 3 and 4), suggests that the increased Co and Ni inthe thermally-altered coals were a result of the increased ash yieldsduring contact metamorphism.

Copper was enriched in the sandy mudstone parting, whereas theconcentrationwas low in the igneous rocks (i.e., reflecting a terrigenoussource). The high ash yield (37.34%, Table 4) may be the cause of thehigh Cu concentration in thermally-altered coal 1327-21.

Zinc exhibited a uniform distribution in the profile, except for theenrichment at the contact area of the thermally-altered coal and lowersill split; thus, the hydrothermal fluid might introduce the Zn intothe coalbed. Because Zn is highly concentrated in the unaltered coal,the geochemical background of Zn in the No. 1 Coal may be dominatedby terrigenous materials.

The Ga in the upper sill split and upper part of the lower sill splitcould have been leached out by groundwater. The vertical variationsof Ge and Sr reveal maximum values of sample 1327-26 in the contactarea of the roof sandstone and thermally-altered coal, which may beintroduced by groundwater.

Zirconium and Nb concentrations were highest in the intrusiverocks, indicating an igneous source. The sandy mudstone parting


also had high concentrations of Zr and Nb that may originatefrom terrigenous detritus. The Zr and Nb in the thermally-alteredcoals are not influenced by igneous intrusion due to their lowconcentrations.

Cadmium, which was concentrated in the igneous rocks andmixture samples from the contact areas (e.g., samples 1327-26 and

0

20

40

60

80

100

Con

tent

s / w

t.%

Oxides

Igneous rock Thermally-altered coal Unaltered coalSandstoneSandy mudstone

SiO2 Al

2O

3

a

0

1

2

3

4

5

Con

tent

s / w

t.%

Oxides


Fe2O3 TiO2 CaO K2O SO

3Na

2O MgO

b

0.00

0.02

0.04

0.06

0.08

0.10

0.12

Con

tent

s / w

t.%

Oxide


P2O5

c

Fig. 15. Comparison of major and trace elements in various rocks and thermally-altered coalse: 10–50 mg/kg; f: 50–200 mg/kg; g: N200 mg/kg.

1327-13), may be associated with epigenetic pyrite of hydrothermalorigin.

The Ba displayed an even vertical distribution in the profile, with theexception of the bottom of the lower sill split. Therefore, Ba could beleached out by groundwater in the upper sill split and the top of thelower sill split.

Ge Cd Eu Tb Dy Ho Er Tm Yb Lu0

2

4

6

8

10

Con

cent

ratio

n / m

g/kg

Elements


d

B Sc Cr Co Ni Cu Y Nb Pr Sm Gd

0

10

20

30

40

50

Con

cent

ratio

n / m

g/kg

Elements


e

V Zn Nd Ga Pb0

20

40

60

80

100

120

140

160

Con

cent

ratio

n / m

g/kg

Elements


f

of the Pansan Coal Mine. a: N5.00 wt.%; b: 0.10–5.00 wt.%; c: b0.10 wt.%; d: b10 mg/kg;

Mn Sr Zr Ba La Ce0

200

400

600

800

1000

1200

1400

1600

Con

cent

ratio

n / m

g/kg

Elements


g


Table 6Concentrations of trace elements in sandstone, igneous rocks, thermally-altered coals, sandy m

Sample no. B Sc V Cr Mn Co Ni Cu

1327–27 25.1 2.57 11.4 7.16 194 1.33 2.40 1.94

1327–26 54.1 15.1 29.7 25.2 81.5 31.5 16.4 15.3

1327–25 19.4 10.4 27.2 14.9 1300 11.3 11.2 9.97

1327–24 29.2 13.4 23.9 13.5 1806 11.5 11.3 17.3

1327–23 14.1 8.31 25.8 15.4 77.8 1.80 1.57 26.5

1327–222 3.58 4.84 4.36 6.23 73.8 1.61 1.53 2.85

1327–221 11.5 3.32 9.07 12.0 62.3 15.0 13.2 16.4

1327–21 10.1 6.82 24.9 20.8 326 14.7 12.6 42.0

1327–201 8.48 3.27 7.35 7.10 126 14.9 12.5 10.7

1327–202 14.2 7.98 4.64 3.99 1289 0.94 0.46 11.5

1327–19 31.0 15.4 29.0 16.7 1198 0.84 0.62 4.73

1327–18 47.3 19.4 15.7 17.7 1363 0.64 2.86 7.42

1327–17 27.6 18.0 28.5 14.7 1293 0.52 0.04 6.36

1327–16 45.4 23.6 22.7 17.6 1388 0.66 0.72 5.74

1327–15 21.5 13.0 20.4 16.4 701 0.49 0.72 6.74

1327–14 43.9 20.1 25.1 28.5 2046 2.84 4.38 9.69

1327–13 28.2 6.76 13.0 7.80 1279 3.44 6.94 5.85

1327–12 13.3 6.30 20.8 16.3 325 1.33 4.04 6.57

1327–11 9.20 3.79 18.3 7.05 362 8.03 11.1 6.29

1327–10 28.6 11.7 93.2 49.2 6.93 11.6 14.3 17.3

1327–9 31.2 14.6 70.8 40.3 5.76 13.4 15.0 11.8

1327–8 18.2 12.1 80.9 35.9 3.87 8.87 12.9 12.5

1327–7 20.3 11.6 77.5 38.8 2.55 13.3 18.7 17.3

1327–6 4.69 8.53 8.15 7.13 35.6 2.17 5.38 5.90

1327–5 3.83 2.44 7.95 5.22 27.0 0.79 2.91 4.77

1327–4 3.29 2.02 6.78 4.06 5.67 0.35 1.65 4.80

1327–3 10.4 5.13 16.2 7.26 110 2.53 4.72 9.03

1327–2 8.91 5.00 25.6 11.3 110 3.57 5.53 12.1

1327–1 8.41 5.30 25.6 13.8 66.2 5.45 8.90 15.7

1571 28.5 6.71 73.9 27.7 6.68 6.12 15.7 11.8


The Pb was high in the upper thermally-altered coal layers(Subseams 1 and 2), especially in the samples from the contact areas(i.e., 1327-26, 1327-221, and 1327-201). The Pb was derived from thehydrothermal fluid.

All REY depict similar vertical distribution patterns in the profile: thehighest enrichment was in the intrusive rocks, followed by the unal-tered coal, and lowest in the thermally-altered coals. These elementslikely had a common terrigenous input and it seems that igneous intru-sion did not affect the REY in the No. 1 Coal.

5. Conclusions

In this study, a comprehensive investigation of the mineralogy andgeochemistry of the roof sandstone, thermally-altered coal, igneousrock, sandy mudstone, and unaltered coal from a representative profilein the No. 1 Coal of the Pansan Coal Mine was conducted. The conclu-sions of the research are as follows.

The thick sill was transformed from the mafic rocks at the profilebottom via the intermediate rocks in the middle to the felsic rocks at

udstones, and unaltered coal (units: mg/kg; on whole rock basis).

Zn Ga Ge Sr Zr Nb Cd Ba Pb

44.0 1.57 0.40 220 16.8 1.47 0.07 59.7 5.59

9.36 5.87 7.76 2085 106 10.4 1.14 98.6 374

63.3 8.78 0.39 323 46.4 4.91 0.23 76.8 120

83.6 8.51 0.92 345 47.7 4.91 0.27 81.1 86.4

75.5 18.9 1.10 314 662 38.2 1.00 40.6 6.77

67.1 2.53 2.53 178 698 40.3 0.72 10.7 26.5

133 2.27 1.31 255 45.1 5.67 0.12 75.8 180

156 16.6 0.23 434 47.2 5.63 0.32 159 46.7

23.8 1.98 0.79 228 50.4 6.27 0.06 71.1 132

50.5 2.78 3.59 182 785 41.2 0.81 54.7 19.0

71.9 20.5 1.19 137 744 40.5 0.99 54.6 2.45

7.26 30.4 1.18 206 1026 47.5 1.15 267 4.59

65.1 165 1.34 131 410 46.5 0.65 3300 4.72

18.6 118 1.43 127 987 49.8 1.20 2325 2.83

8.85 53.9 0.92 80.3 884 51.3 1.06 755 1.91

145 175 1.21 130 653 31.6 1.33 3780 3.31

519 28.2 0.32 216 86.0 2.40 1.41 790 3.70

13.1 13.1 0.14 531 81.2 13.3 0.18 169 3.88

21.6 10.0 0.25 216 28.0 2.35 0.19 121 3.21

84.0 27.7 0.12 123 231 18.9 0.44 211 3.31

70.8 20.8 0.22 187 165 20.3 0.23 281 4.78

15.6 18.7 0.47 151 140 19.4 0.17 276 3.94

37.1 31.1 0.19 314 167 21.1 0.23 482 4.82

23.8 16.2 0.09 124 23.3 3.63 0.04 435 0.52

7.25 2.93 0.11 184 12.3 1.33 0.02 77.2 0.54

14.2 2.52 0.03 101 18.1 2.11 0.06 61.9 0.50

9.83 5.35 0.17 189 55.8 3.53 0.24 93.4 56.9

4.01 8.33 0.16 509 52.4 3.26 0.15 89.0 1.62

5.69 9.60 0.20 190 46.8 4.64 0.17 85.5 1.75

102 5.02 0.68 66.7 127 8.62 0.27 161 51.0

Table 7Concentrations and parameters of REY in sandstone, igneous rocks, thermally-altered coals, sandy mudstones, and unaltered coal.

Sample no. La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu REY LREY MREY HREY LaN/LuN LaN/SmN GdN/LuN

1327–27 67.7 20.2 12.2 45.8 7.13 0.39 4.14 0.44 2.76 11.6 0.55 1.48 0.21 0.96 0.22 176 153 19.3 3.42 3.08 1.44 1.46

1327–26 53.9 116 12.8 47.4 8.36 1.46 7.25 0.74 3.19 12.7 0.52 1.56 0.18 1.17 0.19 267 238 25.4 3.63 2.78 0.98 2.90

1327–25 11.2 22.6 2.47 8.96 1.75 0.44 1.86 0.28 1.69 8.63 0.33 0.98 0.13 0.83 0.13 62.2 46.9 12.9 2.40 0.86 0.97 1.11

1327–24 10.8 21.5 2.42 8.96 1.76 0.45 1.93 0.29 1.79 10.0 0.35 1.04 0.13 0.86 0.15 62.5 45.5 14.5 2.53 0.73 0.93 1.01

1327–23 177 333 32.1 105 14.8 3.13 15.2 1.26 6.96 25.8 1.27 4.05 0.54 3.76 0.60 724 662 52.3 10.2 2.95 1.81 1.96

1327–222 622 137 94.0 312 37.5 1.77 27.3 2.83 17.6 73.8 3.26 10.6 1.45 7.64 1.04 1350 1203 123 24.0 5.98 2.52 2.03

1327–221 179 33.0 23.0 69.6 8.50 0.40 5.80 0.62 4.38 22.2 0.86 2.73 0.37 1.87 0.26 352 313 33.4 6.09 6.94 3.19 1.75

1327–21 32.5 60.2 5.69 16.4 2.30 0.58 2.73 0.24 1.58 7.15 0.31 0.96 0.13 0.86 0.13 132 117 12.3 2.39 2.49 2.14 1.62

1327–201 122 30.2 19.9 63.2 7.33 0.38 5.28 0.58 4.07 17.4 0.80 2.52 0.34 1.69 0.23 276 243 27.7 5.57 5.30 2.53 1.77

1327–202 340 175 57.7 196 23.5 0.93 19.4 1.89 12.3 45.5 2.44 8.36 1.22 6.55 0.91 892 792 80.0 19.5 3.74 2.20 1.65

1327–19 160 430 30.0 97.2 13.7 2.51 13.8 1.11 6.32 23.8 1.18 3.83 0.52 3.66 0.58 788 730 47.6 9.77 2.75 1.76 1.84

1327–18 183 522 33.4 106 14.5 2.61 15.4 1.37 7.31 30.1 1.41 4.63 0.64 4.54 0.80 928 859 56.8 12.0 2.29 1.91 1.49

1327–17 115 264 23.6 77.4 10.7 3.20 10.8 1.15 4.88 21.1 0.88 2.76 0.36 2.53 0.44 538 490 41.1 6.97 2.60 1.62 1.90

1327–16 198 551 36.5 116 16.2 3.85 16.6 1.49 7.81 32.9 1.47 4.75 0.65 4.69 0.78 993 918 62.7 12.3 2.54 1.85 1.65

1327–15 177 444 32.5 103 13.5 2.65 13.8 1.29 6.13 26.6 1.17 3.82 0.52 3.60 0.59 830 770 50.4 9.70 2.99 1.98 1.81

1327–14 195 460 38.8 125 17.9 5.14 19.4 1.44 7.94 27.5 1.38 4.13 0.51 3.60 0.62 909 837 61.4 10.2 3.14 1.65 2.43

1327–13 17.6 29.3 3.04 10.7 1.99 0.83 2.66 0.29 1.98 8.70 0.37 1.00 0.12 0.81 0.14 79.5 62.6 14.5 2.44 1.27 1.34 1.49

1327–12 15.5 31.0 3.40 11.9 2.33 0.49 2.21 0.23 1.60 7.12 0.32 1.02 0.15 1.03 0.15 78.4 64.1 11.7 2.66 1.01 1.01 1.11

1327–11 7.47 16.3 1.84 6.96 1.71 0.48 2.21 0.30 2.19 12.8 0.47 1.44 0.20 1.31 0.20 55.9 34.2 18.0 3.62 0.37 0.66 0.84

1327–10 18.8 43.9 5.22 19.2 3.59 0.73 3.24 0.49 2.44 9.98 0.47 1.47 0.22 1.42 0.21 111 90.7 16.9 3.79 0.90 0.79 1.20

1327–9 31.7 72.9 8.30 30.5 5.72 1.15 5.11 0.51 3.74 11.0 0.71 2.20 0.31 2.11 0.32 176 149 21.5 5.64 1.01 0.84 1.26

1327–8 23.2 52.5 5.93 21.4 4.00 0.85 3.51 0.53 2.57 11.8 0.49 1.49 0.21 1.46 0.25 130 107 19.3 3.90 0.95 0.88 1.11

1327–7 50.9 106 12.1 41.4 5.99 1.27 5.66 0.50 3.89 11.6 0.75 2.40 0.33 2.31 0.35 246 217 22.9 6.15 1.46 1.29 1.26

1327–6 7.20 15.0 1.77 6.53 1.53 0.54 1.93 0.29 2.48 14.1 0.59 2.00 0.30 2.14 0.35 56.7 32.0 19.3 5.38 0.21 0.72 0.43

1327–5 11.3 25.4 2.23 7.45 1.28 0.29 1.26 0.12 0.72 3.31 0.13 0.38 0.05 0.30 0.05 54.2 47.6 5.70 0.91 2.49 1.33 2.16

1327–4 4.47 10.3 0.94 3.18 0.58 0.12 0.58 0.10 0.49 2.79 0.09 0.29 0.04 0.27 0.04 24.3 19.5 4.08 0.74 1.10 1.17 1.11

1327–3 11.2 23.4 2.44 8.50 1.72 0.39 1.82 0.22 1.59 6.76 0.32 0.98 0.14 0.94 0.14 60.6 47.3 10.8 2.52 0.79 0.99 1.00

1327–2 19.5 35.7 3.52 11.6 2.21 0.48 2.31 0.27 1.79 7.51 0.35 1.04 0.14 0.97 0.14 87.6 72.6 12.4 2.65 1.37 1.34 1.25

1327–1 17.5 36.1 3.81 13.0 2.46 0.50 2.40 0.30 1.96 8.37 0.38 1.16 0.16 1.08 0.16 89.3 72.8 13.5 2.94 1.09 1.08 1.16

1571 85.3 32.3 19.1 72.1 11.8 0.63 8.08 1.10 8.20 25.3 1.54 4.71 0.65 3.27 0.39 274 221 43.3 10.6 2.20 1.10 1.62

Unit for REY content is mg/kg, on whole rock basis. The division of REY, i.e., LREY (La, Ce, Pr, Nd, and Sm), MREY (Eu, Gd, Tb, Dy, and Y), and HREY (Ho, Er, Tm, Yb, and Lu), is based onSeredin and Dai (2012). REY are normalized by Upper Continental Crust (Rudnick and Gao, 2003) when LaN/LuN, LaN/SmN, and GdN/LuN are calculated.


the profile top. Due to the igneous intrusion, the moisture, total sulfur,and carbon contents of the coal increased, whereas the volatile matter,hydrogen, and nitrogen decreased. The sandy mudstone parting actedas an effective insulating layer to weaken the thermal and chemicaleffects of the sill.

Three stages of hydrothermal fluids were distinguished: Ca-, Mg-,and Fe-rich fluid, Si-rich fluid, and Fe- and/or H2S-rich fluid. Iron, Ca, S,Si, Mg, Zn, Cd, and Pb were carried into the thermally-altered coalthrough hydrothermal fluids. The concentrations of Co and Ni in thethermally-altered coal increased alongwith the ash yields due to contactmetamorphism; the B in the coalwas volatilized. TheMnwas directly re-lated to the intrusive magma. The P, Ge, and Sr might be introduced intothe coal by groundwater; however, K, Na, Ga, and Ba were leached out.The Ti, Sc, Cr, V, Cu, Zr, Nb, and REY in the coals originated from terrige-nous input anddid not suffer from the influence of the igneous intrusion.

Acknowledgments

This work was supported by the National Key Basic Research Pro-gram of China (No. 2014CB238903), the National Natural Science Foun-dation of China (Nos. 41173032 and 41373110), and the Creative

Project of the Huainan Mining Industry (Group) Co. Ltd. Special thanksare given to Prof. Shifeng Dai and two anonymous reviewers for theiruseful suggestions and comments.

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Fig. 16. Upper Continental Crust-normalized REY patterns of rock and coal samples of the No. 1 Coal in the Pansan Coal Mine. The data of the Upper Continental Crust were cited fromRudnick and Gao (2003).


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0 50 100 0Ash yield / %

20

Fe2O3 / wt.%40 0

MnO / wt.%0.1

TiO2 / wt.%0 0.3 0.6 0.9 1.2 0 3

CaO / wt.%6 9 12 0 2

K2O / wt.%4 6

MgO / wt.%0 2 4 632014

Al2O3 / wt.%217010050

SiO2 / wt.%00.20.10

P2O5 / wt.%SO3 / wt.%1612840

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0 20 40 60B / mg/kg

0 10Sc / mg/kg

20 0 25 50 75 100V mg/kg

0 20 40Cr / mg/kg

0 500 100015002000Mn / mg/kg

0 7 14 21 28Co / mg/kg

35

0 5 10 15 20Ni / mg/kg

0 15 30 45Cu / mg/kg

0 200 400 600Zn / mg/kg

0 40 80 120 160Ga / mg/kg

0 2 4 6Ge / mg/kg

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Fig. 17. Vertical distributions of ash yields and elemental contents in the profile of the No. 1 Coal in the Pansan Coal Mine. The prefixion of sample No. was omitted.


0 20 40 60Y / mg/kg

80 0 300 600 900Zr / mg/kg

1200 0 20 40Nb / mg/kg

60 0 0.4 0.8 1.2Cd / mg/kg

1.6 0 800 16002400

Ba / mg/kg32004000 0 150 300 450 600

La / mg/kg

Ce / mg/kg0 200 400 600 0 25 50 75 100

Pr / mg/kg0 70 140 210

Nd / mg/kg280 350 0 7 14 21 28

Sm / mg/kg35 42 0 2 4

Eu / mg/kg6 0 6 12 18

Gd / mg/kg24 30

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0 0.6 1.2 1.8 2.4

Tb / mg/kg3.0 0 4 8 12 16

Dy / mg/kg0 0.7 1.4 2.1 2.8

Ho / mg/kg3.5 0 4 8

Er / mg/kg12

0 0.4 0.8 1.2 1.6

Tm / mg/kg0 2 4 6 8

Yb / mg/kg0 0.4 0.8

Lu / mg/kg1.2 0 80 160 240

Pb / mg/kg320 400

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mineralogical and geochemical responses of coal to igneous

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