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Geochemistry of rare earth and other trace elements in Chinese oil shale.

1. Introduction

Oil shale (OS), from which shale oil may be generated, is a fine-grained sedimentary rock containing aquatic organisms derived organic matter called kerogen (about 5-50%). Oil shale is classified as sapropelic coal with rich minerals, and is considered as a solid fossil fuel with a low heat value. In many countries, oil shale is a major source of energy. Its estimated reserves in China are approximately 2 x [10.sup.12] tons, which is equivalent to 80 billion tons shale oil. This amount is just next to the United States', Brazil's and Estonia's, ranking fourth in the world [1]. At present, China's discovered reserves of OS are about 32 x [10.sup.12] tons and are chiefly distributed over 55 deposits located in the provinces of Jilin, Guangdong and Liaoning. Hence, the exploitation and utilization of oil shale has been an important part of Chinese national energy development strategies [2].

Coal and oil shale as fossil fuels contain various trace elements besides major elements. Most trace elements are present in all coals at exceedingly low levels, less than 1 mg/g, some even less than 1 [micro]g/g. The emission of potentially toxic trace elements during the utilization of coal and oil shale may cause environmental pollution. The researchers throughout the world have systematically studied the distribution of trace elements in coal [3-6]. Despite the relatively late start, also in China the corresponding investigations have been carried out [7-10].

Rare earth elements (REEs) are trace elements which carry important information about the origin, source, evolution and original environment of rock. Compared with trace elements in coal, REEs in coal have been studied more extensively and more resultfully by Chinese scientists Wang et al. [11], Dai et al. [12] and Liu et al [13].

At the same time, there are but few investigations on the enrichment and distribution characteristics of trace elements and REEs in Chinese oil shale. Fu et al. [14, 15] and Zhao [16] studied the content of trace elements and REEs in oil shale from northern Tibet, China. Fu et al. [15] and Bai et al. [17] also investigated the modes of occurrence of trace elements and REEs in oil shale respectively from Huadian and Wangqing, by the sequential chemical extraction procedure. The study on trace elements in oil shale may contribute to reflecting the original environment of oil shale, to promoting the rational utilization of usable elements and to decreasing environmental pollution with hazardous elements during a comprehensive utilization of oil shale.

In this work, the contents of trace elements and REEs in oil shale samples from several mineral areas of China were determined by inductively coupled plasma mass spectrometry (ICP-MS). The distribution and enrichment of trace elements were also analyzed. The results of the study will serve as a foundation for a further exploration and utilization of oil shale.

2. Materials and methods

For the study, 22 oil shale samples were chosen, including one sample from Beitaizi (JH-10) and Wangqing (JW), four from Gonglangtou (JH-6-JH-9) and Meihekou (JM-1-JM-4), and five from Dachengzi (JH-1-JH-5) in Jilin province; one sample from Dongning (HDN), Liushuhe (HLH) and Dayingzi (LK), and two from Jinbaotun (JL-1, JL-2) in Heilongjiang province; and two from Xinjiang (X-1, X-2) in Xinjiang province.

The content of trace elements in oil shale was measured by ICP-MS at the Testing Center of Jilin University. ICP-MS as a highly sensitive technique is capable of determining a wide range of metals and also nonmetals at concentrations below one part in [10.sup.12] (trillion). Used in trace elemental analysis, it has several advantages over atomic absorption techniques, such as high speed, precision and sensitivity. However, determination of lower concentrations is more prone to be disrupted by trace contaminants in the lab ware and reagents used.

3. Results and discussion

3.1. Trace elements content in oil shale

Table 1 presents data on the content of trace elements in oil shale determined in this work. From the table it can be seen that the content of most trace elements ranges from 1 to 50 [micro]g/g, but some elements are present at a concentration of less than 1 [micro]g/g or more than 50 [micro]g/g. At the same time, individual samples differ in trace element content, which displays a relatively high enrichment degree, in particular, in sample LK.

The range and average values of the concentration of trace elements in Chinese oil shale samples are shown in Table 2. For comparison, the average concentration of trace elements in Estonian oil shale [4] and Chinese coal [18], as well as Clarke value in oil shale [19], and crustal abundance [20] are given.

A comparison of the average contents and content ranges of trace elements in oil shale (OS) with those in Chinese coal (C) is illustrated in Figures 1 and 2, respectively. As shown in Figure 1, the average content of Ba, Cr, Cs, Cu, Ga, Ni, Ta, Tl, V and Zn in oil shale is two times higher than those in Chinese coal. However, the average content of As, B, Cd, Mo, Sb, Se and Hg in oil shale is significantly lower, while that of other elements is mostly the same. As can be seen from Figure 2, compared with the content range of trace elements in Chinese coal, the content of Be, B, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Ba, Ta, W, Tl, Th and U in oil shale samples is close to the upper limit. The Cs content is a little higher than the upper limit in Chinese coal. The content of Ge, Sr, Sn and Sb is within the content range, and that of Se, Mo, Cd, Hg and P is close to the lower limit in coal.

Aunela-Tapola et al. [3] reported the content of several trace elements in Estonian and US Green River oil shales, and found that Mn, Cu, Zn, As, V and Cr were present in Green River oil shale at higher concentrations. Meanwhile, the content of Cu, Ni, Co, V, Cr and Mn in Chinese oil shale is quite high. Accordingly, Mn, Zn, V, Cu and Cr in Chinese Huadian oil shale, Estonian oil shale and US Green River oil shale show a high enrichment degree unlike those in Chinese coal. Furthermore, the released amount of trace elements from Estonian oil shale is greater than from Chinese coal. In addition, the fact that trace elements are constantly detected in the moss within a radius of 1-30 km around the oil shale fired power plant suggests that their release in the process of oil shale combustion may eventually exert a negative influence on the surrounding environment.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

3.2. Enrichment degree of trace elements in oil shale

The variation of the content of trace elements in the Earth's crust and in all oil shale samples is illustrated in Figure 3. It is clearly seen that the corresponding curves for all oil shale samples and crustal abundance are similar. Hence, the distribution of trace elements in oil shale is primarily influenced by the geochemical cycling of elements, and elements with a higher abundance in the Earth's crust, such as Ti, Ba, Sr, Mn, etc., have an elevated content in oil shale as well.

[FIGURE 3 OMITTED]

The enrichment factor (EF) is a measure of the enrichment degree of trace elements in sediment. It enables analyzing the environmental impacts of heavy metals, both nature- and human-derived. It is necessary that some elements should be considered as reference (or standard) elements. EF equals the content ratio of elements to reference elements in oil shale samples divided by such a ratio in the Earth's crust as shown in Equation (1):

EF = [[([C.sub.i]/[C.sub.n]).sub.os]/[([C.sub.i]/[C.sub.n]).sub.BG]], (1)

where [C.sub.i] is the concentration of element i, [C.sub.n] is the concentration of a reference element, and OS and BG denote oil shale and background, respectively.

Generally, a standard element, such as Al, Ti, Sc, Zr, etc., should have stable geochemical properties. In this paper, Ti is considered as a standard element, and its crustal abundance as a background value. Usually, EF < 1 signifies "poverty", 10 > EF > 1 "normal", and EF > 10 "enrichment". According to such a rule, Cs in oil shale samples is of high "enrichment", Hg belongs to "poor", and other elements are "normal".

3.3. Rare earth elements in oil shale

The measured contents of rare earth elements in oil shale samples are presented in Table 3. A comparison shows the REEs content ranges in oil shale to be the same as those in Chinese coal. REEs ranged from La-Eu as light rare earth elements (LREEs) to Gd-Lu as heavy rare earth elements (HREEs). The average content of LREEs in oil shale samples is twice higher than that in Chinese coal, and the HREEs abundance is 1-1.5 times higher. Compared with Chinese coal, in oil shale the enrichment degree of LREEs is higher than that of HREEs. The average content of REEs in Chinese oil shale is nearly equal to that in North American shale composite (NASC). The HREEs content in samples JM-1-JM-4 is high and that of LREEs low. However, the REEs content in JH-7 is abnormally low. This is due to that JH-7 originated from the bottom of the eleventh floor of Huadian mine area. As established by XRD, its organic content is high, and REEs in Huadian oil shale mainly exist in the inorganic mineral part [21]. This is why the REEs concentration in sample JH-7 is relatively low.

The geochemical parameters of REEs can reflect their characteristics, representing the degree of enrichment and source. LREE/HREE is the ratio of LREE to HREE contents, and [La.sub.N]/[Yb.sub.N] is the ratio of chondrite-normalized elements. [delta][Eu.sub.N] and [delta][Ce.sub.N] are anomalies of Eu and Ce by chondrite-normalized values as shown in Equations (2) and (3), respectively [22]:

[delta][Eu.sub.N] = [Eu.sub.N]/[([Sm.sub.N] x [Gd.sub.N]).sup.1/2] (2)

[delta][Ce.sub.N] = [Ce.sub.N]/[([La.sub.N] x [Pr.sub.N]).sup.1/2], (3)

where [Eu.sub.N], [Sm.sub.N], [Gd.sub.N], [Ce.sub.N], [La.sub.N] and [Pr.sub.N] denote the chondrite-normalized values of elements.

The geochemical parameters of REEs in Chinese oil shale are given in Table 4. As seen, the average [SIGMA]REE of REEs is 171.20 [micro]g/g, [SIGMA]LREE is 153.70 [micro]g/g and EHREE is 117.51 [micro]g/g. Meanwhile, these values are approximately equal to those in NASC. The average value of LREE/HREE is 8.76 [micro]g/g, and LaN/YbN is 10.22 [micro]g/g, which indicates that the content of LREEs in oil shale is much higher than that of HREEs. The fractional degree of HREEs and LREEs is remarkable, representing a distinct LREE-enriched pattern.

The average [SIGMA]REE in Chinese coal is 87.45 [micro]g/g, which is higher than that in oil shale and world coals calculated by Valcovic and in American coal proposed by Finkelman [23]. It is clear that the enrichment degree of REEs in oil shale is much higher than that in coal.

The average [SIGMA]REE in Huadian oil shale samples is 156.28 [micro]g/g, [SIGMA]LREE 140.31 [micro]g/g, [SIGMA]HREE 15.97 [micro]g/g, LREE/HREE 12.6 [micro]g/g, and LaN/YbN is 10.28 [micro]g/g. In addition, the average LREE/HREE in oil shale samples of Meihekou is 12.97 [micro]g/g, while LaN/YbN is 19.5 [micro]g/g. Such values indicate that Meihekou oil shale is highly REEs-enriched. The fractional degree of HREE and LREE is remarkable, and exhibits a distinct LREEs-enriched pattern because of the sedimentary environment and climate change.

3.4. Distribution pattern of REEs

The geochemical characteristics of REEs are reflected by their distribution pattern data. The standardization based on chondrite, which reflects the differentiation degree of the sample and characteristics of the source region in comparison with pristine terrestrial materials, is one of the approaches to the study of the distribution pattern of REEs in shale sediment. The standardization distribution data on oil shale is shown in Figure 4, and relative calculated results are presented in Table 3. From Figure 4 it can be seen that the REEs distribution patterns of samples are similar as their curves all lean to the right. Additionally, the standardization value decreases gradually from La to Lu, and the corresponding curve assumes a V shape. At Eu, the distribution pattern of La-Eu (LREEs) is characterized by a steep curve and Gd-Lu (HREEs) by a gentle curve, which implies that the diagenetic environment of oil shale samples is similar. The similarity of REEs distribution shows that their source has been the same during the formation of oil shale, and suggests that REEs in oil shale have a close connection with terrigenous clastic rocks, and the supply of terrestrial material has been stable.

[FIGURE 4 OMITTED]

4. Conclusions

The content of trace elements in oil shale ranges from 1 to 50 [micro]g/g, some being present at a concentration < 1 and > 50 [micro]g/g. The elements with a higher abundance in the Earth's crust have an elevated content in oil shale as well. Comparison shows that the content of Be, B, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Ba, Ta, W, Tl, Th, U and Cs in oil shale samples is slightly higher than the upper limit in Chinese coal, while that of Se, Mo, Cd, Hg, Pb is close to the lower limit in coal. The EF of elements in oil shale with Ti as a standard element and the crustal abundance as a background value indicates that oil shale is highly enriched with Cs, non-enriched with HG, while the enrichment degree of other elements is normal.

Compared with Chinese coal, the enrichment degree of light REEs in oil shale is higher than that of heavy ones. An average content of REEs in oil shale is approximately equal to that in NASC. The similarity of REEs distribution indicates that the source of REEs is the same during the formation of oil shale, and suggests that REEs in oil shale have a close connection with terrigenous clastic rock, and the supply of terrestrial material has been stable.

In this paper, the enrichment characteristics of trace elements and REEs in different Chinese oil shale samples have been analysed. The current work will lay the foundation for a further study on the occurrence of trace elements in oil shale, as well as their transformation. The study is also of great significance for the development of green oil shale industry from both the theoretical and practical point of view.

doi: 10.3176/oil.2014.3.06

Acknowledgements

The authors are grateful for the financial support from the National Natural Science Foundation of China (No. 50876018) and the Ministry of Education of the People's Republic of China within the Program for Changijang Scholars and Innovative Research Team in University (IRT 13052). We also thank the Testing Center of Jilin University, China, for providing the service of testing samples by using ICP-MS.

REFERENCES

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Received October 31, 2013

WANG QING (a) *, BAI JINGRU (a), GE JIANXIN (a), WEI YAN-ZHEN (a), LI SHUYUAN (b)

(a) Northeast Dianli University, Jilin 132012, China

(b) China University of Petroleum, Beijing 102249, China

* Corresponding author: e-mail rlx888@126.com
Table 1. Content of trace elements in oil shale

Content, w [micro] g/g         Trace elements

[greater than or equal to]     Ba, Mn, Sr, Ti
  100
[greater than or equal to]     V, Cr, Zn
  50-100
[greater than or equal to]     Cu, Li, Ni, Ga, Y, B, Pb, Co, Th, Cs,
  1-50                           Be, Ge, As, Sn, Ta, Re, Tl, U, W
[greater than or equal to]     Mo, Pd, Ag, Sb
  0.1-1
[greater than or equal to]     Hg, Te, Cd
  0.1

Table 2. Content of trace elements in different oil shale samples
and Chinese coal, w [micro] g/g

Element   Chinese oil shale       Estonian oil shale   Clarke [19]
                                  average value [4]

          Range        Average
                       value

Be        1.5-4.8      2.5        94                   3
B         2-253        47         55                   10
Ti        907-7382     3200       -                    4600
V         19-475       92         22                   130
Cr        20-130       60         15.5                 90
Mn        57-4811      1060       306                  850
Co        3.1-24.4     14         2.7                  19
Ni        5-139        38         13.2                 68
Cu        9-270        41         6.7                  45
Zn        11-290       94         76                   95
Ga        9.4-28       20         -                    19
Ge        0.6-3.3      1.9        -                    1.6
As        0.6-10       2          18.8                 13
Se        0.05-0.3     0.1        -                    0.6
Sr        46-810       280        168                  300
Y         10-64        27                              26
Mo        0.6-11.3     1.9        4.9                  2.6
Cd        0.01-0.4     0.1        0.3                  0.8
Sn        0.6-3.2      2          -                    6
Sb        0.1-5        0.9        0.4                  1.4
Cs        1.8-16.5     10         -                    5
Ba        109-719      440        59                   580
Ta        0.45-15.7    2.3        -                    80
W         0.6-48.4     4.3        -                    71.8
Hg        0.00-0.12    0.02       -                    0.4
Tl        0.38-4.1     1.3        0.43                 1.4
Pb        6-38         16         27.3                 20
Th        2.6-22       11         -                    12
U         1.1-11.5     4          2.18                 3.7

Element   Chinese coal [18]       Crustal abundance [20]

          Range        Average    Range        Average
                       value                   value

Be        0.1-6        2          1.3-2        1.73
B         10-250       63         10-13        11.3
Ti        16-4201      528        5400-9590    6250
V         2-100        21         110-180      143
Cr        2-50         12         71-200       127
Mn        4-109        77         774-1549     1090
Co        1-20         7          23-26        24.7
Ni        2-65         14         75-89        81.3
Cu        1-50         13         45-63        56
Zn        2-106        35         65-94        76.3
Ga        1-20         9          15-18        16.7
Ge        0.5-10       4          1.4-2.0      1.6
As        0.4-10       5          1.9-2.2      2.6
Se        0.1-11       2          0.075-0.10   0.0883
Sr        27-3000      136        215-480      382
Y         0.5-22       8          19-40        27.7
Mo        1-15         4          1.0-2.0      1.43
Cd        0.01-3       0.2        0.15-0.20    0.177
Sn        0.4-5        2          1.7-4.0      2.9
Sb        0.1-10       2          0.2-0.7      0.507
Cs        0.1-3        1          1.0-1.4      1.23
Ba        13-400       82         390-600      463
Ta        0.06-4       0.7        1.2-2.0      1.6
W         0.1-9        2          0.4-1.1      1.13
Hg        0.01-1       0.15       0.057-0.17   0.103
Tl        0.1-1        0.4        0.48-1.0     0.727
Pb        10-47        13         12-16        14
Th        0.5-15       6          5.8-10       7.6
U         0.5-10             3          1.7-2.5      2.07

Table 3. Content of rare earth elements (REEs) in different oil shale
samples and coal, w [micro] g/g

Sample \ REE        La      Ce      Pr      Nd      Sm      Eu

JH-1                24.46   41.90   5.59    19.67   3.33    0.72
JH-2                29.95   51.77   6.86    24.42   4.17    0.90
JH-3                23.92   40.77   5.55    19.57   3.40    0.76
JH-4                34.67   59.84   7.75    26.35   4.54    0.96
JH-5                38.53   67.68   8.52    28.35   4.77    0.96
JH-6                26.17   44.45   6.01    22.29   3.81    0.86
JH-7                12.83   21.60   3.02    10.96   1.88    0.42
JH-8                57.32   103.2   12.73   43.20   7.26    1.45
JH-9                45.62   91.67   11.39   40.19   6.83    1.42
JH-10               55.88   102.9   13.64   52.00   9.35    2.12
JL-1                35.00   64.66   8.47    29.90   5.27    1.05
JL-2                30.93   58.85   7.80    27.83   4.85    1.01
JM-1                52.93   93.22   11.46   37.90   6.35    1.26
JM-2                74.11   135.0   16.63   57.36   9.74    1.99
JM-3                57.32   107.4   13.60   47.87   7.90    1.57
JM-4                64.40   117.2   14.27   47.38   7.95    1.56
JW                  30.86   64.22   6.88    26.61   4.97    1.18
HDN                 33.27   56.60   7.74    27.86   5.17    0.91
HLH                 22.31   37.08   5.11    18.16   3.21    0.71
LK                  41.66   73.35   10.90   41.73   7.66    1.62
X-l                 19.76   35.31   4.89    18.29   3.35    0.72
X-2                 25.34   44.56   6.22    22.86   4.21    0.90
Max                 74.11   135     16.63   57.36   9.74    2.12
Min                 12.83   21.6    3.02    10.96   1.88    0.42
Average             38.06   68.78   8.87    31.40   5.45    1.14
Chinese coal        17.79   35.06   3.76    15.03   3.01    0.65
Chondrite           0.315   0.813   0.115   0.597   0.192   0.0722
Crustal abundance   39      43      5.7     26      6.7     1.2
NASC                31.50   66.50   7.90    27.00   5.90    1.18

Sample \ REE        Gd      Tb       Dy      Ho       Er      Tm

JH-1                3.22    0.51     2.60    0.51     1.51    0.25
JH-2                4.00    0.63     3.19    0.63     1.86    0.31
JH-3                3.27    0.50     2.58    0.51     1.53    0.25
JH-4                4.14    0.66     3.34    0.65     1.92    0.32
JH-5                4.15    0.64     3.37    0.64     1.92    0.33
JH-6                4.24    0.67     3.46    0.69     2.08    0.34
JH-7                1.88    0.30     1.64    0.33     1.05    0.17
JH-8                6.24    1.00     5.14    0.99     2.89    0.49
JH-9                5.90    0.96     5.02    0.95     2.79    0.48
JH-10               11.32   1.87     10.16   2.17     6.46    1.08
JL-1                5.09    0.83     4.42    0.87     2.67    0.45
JL-2                4.63    0.75     4.12    0.81     2.39    0.41
JM-1                5.40    0.82     3.73    0.66     1.93    0.31
JM-2                8.61    1.34     6.05    1.05     3.00    0.48
JM-3                6.72    1.05     4.94    0.92     2.70    0.44
JM-4                6.64    1.01     4.67    0.84     2.43    0.40
JW                  4.61    0.78     3.75    0.76     2.15    0.31
HDN                 6.24    1.10     6.78    1.53     4.72    0.82
HLH                 3.57    0.57     3.01    0.62     1.83    0.28
LK                  8.64    1.49     8.51    1.87     5.70    0.99
X-l                 3.54    0.58     3.28    0.66     1.99    0.33
X-2                 4.52    0.75     4.07    0.81     2.42    0.40
Max                 11.32   1.87     10.16   2.17     6.46    1.08
Min                 1.88    0.3      1.64    0.33     1.05    0.17
Average             5.30    0.86     4.45    0.89     2.63    0.44
Chinese coal        3.37    0.517    3.141   0.731    2.081   0.335
Chondrite           0.259   0.0473   0.325   0.0723   0.213   0.0333
Crustal abundance   6.7     1.1      4.1     1.4      2.7     0.3
NASC

Sample \ REE        Yb      Lu

JH-1                1.42    0.28
JH-2                1.74    0.36
JH-3                1.44    0.28
JH-4                1.83    0.41
JH-5                1.89    0.43
JH-6                1.89    0.36
JH-7                1.01    0.21
JH-8                2.79    0.63
JH-9                2.65    0.59
JH-10               5.79    1.02
JL-1                2.61    0.55
JL-2                2.31    0.48
JM-1                1.67    0.32
JM-2                2.46    0.49
JM-3                2.41    0.45
JM-4                2.15    0.42
JW                  1.96    0.30
HDN                 4.58    0.90
HLH                 1.43    0.26
LK                  5.76    1.09
X-l                 1.99    0.43
X-2                 2.34    0.51
Max                 5.79    1.09
Min                 1.01    0.21
Average             2.46    0.49
Chinese coal        1.975   0.323
Chondrite           0.208   0.0323
Crustal abundance   2.7     0.8
NASC

Table 4. Geochemical parameters of rare earth elements (REEs) in
different oil shale samples and coal

           [sigma]                   LREE    [La.sub.N]/  [delta]
Sample     REE      LREE     HREE    HREE    Y[b.sub.N]   [Eu.sub.N]

JH-1       105.97   95.67    10.30   9.29    11.37        0.68
JH-2       130.79   118.07   12.72   9.28    11.37        0.68
JH-3       104.33   93.97    10.36   9.07    10.97        0.70
JH-4       147.38   134.11   13.27   10.11   12.51        0.68
JH-5       162.18   148.81   13.37   11.13   13.46        0.67
JH-6       117.32   103.59   13.73   7.54    9.14         0.66
JH-7       57.30    50.71    6.59    7.69    8.39         0.69
JH-8       245.33   225.16   20.17   11.16   13.57        0.67
JH-9       216.46   197.12   19.34   10.19   11.37        0.69
JH-10      275.76   235.89   39.87   5.92    6.37         0.64
JL-1       161.84   144.35   17.49   8.25    8.85         0.63
JL-2       147.17   131.27   15.90   8.26    8.84         0.66
JM-1       217.96   203.12   14.84   13.69   20.93        0.66
JM-2       318.31   294.83   23.48   12.56   19.89        0.67
JM-3       255.29   235.66   19.63   12.01   15.71        0.67
JM-4       271.32   252.76   18.56   13.62   19.78        0.66
JW         149.34   134.72   14.62   9.21    10.40        0.76
HDN        158.22   131.55   26.67   4.93    4.80         0.49
HLH        98.15    86.58    11.57   7.48    10.30        0.65
LK         210.97   176.92   34.05   5.20    4.78         0.62
X-1        95.12    82.32    12.80   6.43    6.56         0.65
X-2        119.91   104.09   15.82   6.58    7.15         0.64
Average    171.20   153.70   17.51   8.78    10.22        0.65
Max        334.90   294.96   39.94   7.39    8.45         0.62
Min        57.30    50.71    6.59    7.69    8.39         0.69
Chinese    87.77    75.30    12.15   6.20
coal
Chondrite  3.29     2.10     1.19    1.77    1.00         1.00
Crustal    141.40   121.60   19.80   6.14    9.54         0.55
abundance
NASC       160.12   139.98   20.14   6.95    7.00           0.66

           [delta]      [La.sub.s]/   [delta]      [delta]
Sample     [Ce.sub.N]   [Yb.sub.s]    [Eu.sub.S]   [Ce.sub.s]

JH-1       0.84         1.62          1.03         0.85
JH-2       0.85         1.62          1.03         0.86
JH-3       0.83         1.57          1.07         0.84
JH-4       0.85         1.79          1.04         0.87
JH-5       0.87         1.92          1.01         0.89
JH-6       0.83         1.31          1.00         0.84
JH-7       0.81         1.20          1.05         0.82
JH-8       0.89         1.94          1.01         0.91
JH-9       0.94         1.62          1.05         0.95
JH-10      0.87         0.91          0.97         0.88
JL-1       0.88         1.26          0.95         0.89
JL-2       0.89         1.26          1.00         0.90
JM-1       0.89         2.99          1.01         0.90
JM-2       0.90         2.84          1.02         0.91
JM-3       0.90         2.24          1.01         0.91
JM-4       0.91         2.82          1.01         0.92
JW         1.03         1.48          1.16         1.05
HDN        0.83         0.68          0.75         0.84
HLH        0.81         1.47          0.98         0.82
LK         0.81         0.68          0.93         0.82
X-1        0.84         0.94          0.98         0.85
X-2        0.83         1.02          0.97         0.84
Average    0.88         1.46          0.99         0.89
Max        0.90         1.21          0.95         0.91
Min        0.81         1.20          1.05         0.82
Chinese
coal
Chondrite  1.00         0.14          1.52         1.01
Crustal    0.68         1.36          0.84         0.68
abundance
NASC         0.99               1.00              1.00     1.00

REE--rare earth element; LREE--light rare earth element; HREE--high
rare earth element.
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Author:Qing, Wang; Jingru, Bai; Jianxin, Ge; Yan-Zhen, Wei; Shuyuan, Li
Publication:Oil Shale
Article Type:Statistical data
Geographic Code:9CHIN
Date:Sep 1, 2014
Words:5442
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