Geochemistry of trace elements of Tertiary coals of India

International Journal of Coal Geology, 20 ( 1992 ) 99-113

99

Elsevier Science Publishers B.V., Amsterdam

Geochemistry of trace elements of Tertiary coals of India K.N. Mukherjee a, N.R. Dutta a, D. Chandra b and Mahendra P. Singhc ~Coal Wing, Geological Survey oflndia, Calcutta, India bDepartment of Applied Geology, Indian School of Mines, Dhanbad 826004, India "Department of Geology, Benaras Hindu University, Varanasi 221005, India (Received January 3, 1989; revised version accepted August 21, 1991 )

ABSTRACT Mukherjee, K.N., Dutta, N.R., Chandra, D. and Singh, M.P., 1992. Geochemistry of trace elements of Tertiary coals of India. Int. J. Coal Geol., 20: 99-113. Forty-one coal samples from seven Tertiary basins of the Himalayas, representing coalfields of the States of Assam (sub-bituminous), Meghalaya (lignitous to sub-bituminous ), and Jammu and Kashmir (low volatile bituminous to semi-anthracite) have been spectrographically analyzed. The trace elements analysed were Ge, Ni, Co, Cu, Pb, Mo, Zr, Mn, Cr, Ba, Ga, V, Sr, B, Nb, Sn, La and Y. There are differences in trace element concentrations between the Eocene coals of northeastern and northwestern India. A significant difference also exists between the Eocene and Oligocene coals of northeastern India. The results show that some of the elements are significant for the identification and correlation of the coal seams. The element Cr can be used as a marker or index element for the Oligocene coals of the Makum and Dilli-Jeypore coalfields of northeastern India, and Mn for the Eocene coals of Meghalaya of northeastern India. The interpretation of organic/inorganic association of the trace elements indicates that elements such as Ni, Co, Ba, V, Sr, Cr, Y, Ge and Nb are associated with the organic fractions. Pb and Cu show affinity with both the organic matter and sulphides. Mn shows affinity with the organic matter and mineral matter, while Ga is exclusively related to the mineral matter. Further, it has been revealed that the Eocene and Oligocene coals of northeastern India originated under marine conditions. In contrast, the Eocene coals of northwestern India give significant evidence of a high influx of fresh water during coal development and show parity with the fluviolacustrine coals of Lower Gondwana, so far as the concentrations of the trace elements are concerned.

INTRODUCTION

The first major attempt at trace element studies of Indian coals was made by Rishi ( 1970 ) followed by Mukherjee and Ghosh ( 1976 ); Mullick and Ahmad (1979); Chandra et al. (1981), Mukherjee et al. (1982a,b and 1988); Singh et al. ( 1983, 1985 ) and Pareek and Bardhan ( 1985 ). In recent years considerable emphasis has been laid on the analysis of the stratigraphy, structure/tectonics and resource potential of the Tertiary coal 0166-5162/92/$05.00

© 1992 Elsevier Science Publishers B.V. All rights reserved.

K.N. MUKHERJEE ET AL.

100

7,z°

8B"

s,o °

i

9,6 °

/

[KALAKOT&METKAI ..f" 3~

3ooQ,.._L=2,qO.MS

-

/"" JAMhtU ~ ./"

/'t

./" "~

./

f"

.32°

SCALE "~

.J

./

.~.f'~

?

• D E L H I ".,,

~~ Y, P, O ~ E J J ~,;._, "~i~IBRUGARH~

"'~..IW DARRANGIRI

~..

ANDI ~ . " ~

. . . . . . . . ""c~ "

• ,..^~.

I MAKUM)

~,.3~-t~-,.~S_H.IL LO~ G ' .~/ "B ' ANG~-"l ~ a ~

/ ...... ~

;

-24°

OMBAY 16. ARABIAN

SEA \\

~

4s°

f IMADRAS

8c. 7~o

8 ~)o

8,Bo

Fig. 1. The Tertiarycoalfieldsof India studied in this investigation. basins of India. However, so far, no systematic study on the assessment and distribution of the trace elements in this coal has been made. To bridge this gap, a study has been made of the occurrence, distribution and organic/inorganic affinity of eighteen trace elements: Ge, Ni, Co, Cu, Pb, Mo, Zr, Mn, Cr, Ba, Ga, V, Sr, B, Nb, Sn, Y and La in Tertiary coals from northeastern and northwestern India. The location of the coalfields is shown in Fig. 1. In addition, the impact of the occurrence and distribution of these elements on the palaeo-environment has been evaluated. METHOD OF STUDY

Collection o f samples

For the purpose of this investigation coal samples were collected from seven Tertiary coal basins in northeastern and northwestern India (Table 1 ). The

101

GEOCHEMISTRY OF TRACE ELEMENTS OF INDIAN COALS

TABLE 1 Details of coal samples collected for trace element study Coalfield basin

State

Age

Seam/Seam Number

Assam

Oligocene

Seam III (20' seam) Seam I ( 100' seam) Seam VI Seam IV Seam III Darrangiri seam Seam A Seam B Seam C Seam IV Seam III Seam II Seam I

Number of samples analysed

Coalfields of northeast India Makum

4 6

Dilli-Jeypore

Assam

Oligocene

West Darrangiri Siju

Meghalaya Meghalaya

Eocene Eocene

Langrin

Meghalaya

Eocene

Jammu and Kashmir Jammu and Kashmir

Eocene

Lower seam

3

Eocene

Lower seam

3

1 1 2 14 1 1 1 1 1 1 1

Coalfields of north west India Kalakot Metka

samples were taken from measured depths/heights with respect to the roof or floor of a seam. Therefore, every sample represents a definite stratigraphic position. Necessary precautions were taken to avoid any superficial contamination while collecting the samples. The quantity of each sample was reduced to 500 g by the coning and quartering method.

Laboratory work Powdered coal samples were ashed at 450°C in an electric furnace with controlled air flow for oxidation. The ash was ground thoroughly in an agate mortar, mixed with an equal quantity of carbon and arced in a Jarrell ash 3.4 m Ebert grating spectrograph using D.C. excitation at 14 Amp in graphic necked electrodes (National, SPKL 4200). Synthetic standards were used, which were prepared from a synthetic silicate base simulating the coal ash composition. The base was thoroughly sintered before use. Standards of the various concentrations were prepared by the solid dilution technique using the synthetic base. The total energy m e t h o d of quantitative spectrographic

102

K.N.MUKHERJEEETAL.

analysis described by Bastron et al. (1960) was followed. The overall coefficient of variation for all the elements is considered as +_ 15%. RESULTS AND DISCUSSION

West Darrangiri coalfield (Meghalaya) In the Darrangiri seam, studied both in the Mining Hill and Bonkhandi blocks, separated only by about 1 km, some trace element concentrations show a wide variation (Table 2), these are: Ge (229-395 ppm), Pb (110-280 ppm), Mn (290-483 ppm), Cr (66-106 ppm). Other elements, such as Cu (23-33 ppm), Ba ( 147-162 ppm), Ni (42-64 ppm,) and Sr ( 105-120 ppm), show a small variation. The Ge concentration (299-395 ppm) in the Eocene coals of the West Darrangiri coalfield is significantly higher than the Permian coals of Peninsular India ( 5-96 ppm) (Mukherjee et al., 1988 ) and the Oligocene coals of Upper Assam (40-72 ppm). Such high Ge values were also recorded by earlier workers (Banerjee et al., 1972). The profiles based on the element concentrations have revealed similar but non-identical (Figs 2a and b) relations between two different but nearby places in the same seam. There is enrichment of many elements, such as Cu, Pb, Mo, V, Cr, Zr, Ga and Sr, either in the roof or floor zone or at both marginal sections, due to adsorption and enrichment of these elements through surface water and groundwater (Table 3 ).

Siju coalfieM (Meghalaya) In three shaly coal/carbonaceous shale samples collected from closely spaced (within 50 m) outcrops (Table 2), coal sample (B) shows a comparatively lower ash content (23.6%), and is not enriched with regard to Ni, Co, Cu, Pb, Ba, V and Sr. This suggests that these elements are associated mainly with the organic fractions as organic metallic compounds and possibly as chelates. This has also been shown by workers on American and Australian coals (Clark and Swaine, 1962; Ruch et al., 1974; and Kuhn et al., 1980; Ward, 1980). Ge (less than 5 ppm), Ni (20-40 ppm), Co (15-25 ppm), Cu (less than 10-80 ppm), Mo (less than 5 ppm) and Ga (less than 10-15 ppm) have low concentrations in almost all the samples analysed. Only V ( 500 ppm ) and Ba (400 ppm) have fairly high concentrations in the coaly horizon (seam B). The profiles based on the trace element concentrations (Figs 2c,d and e) exhibit a wide variation between Seam B and the carbonaceous shale/shale horizons (Seams A and C). The "vanadium peak" in Seam B is a significant deviation (Fig. 2d) from almost all the other seams studied in the various coalfields of Meghalaya.

Barsora Barsora Barsora Barsora

Langrin

Valley Valley Valley Valley

Between 101 and 102 km milestones from Demra to Baghmara

Siju

IV Ill ll 1

A B C 0.3 0.5 1.3 0.6

0.5 0.6 0.6 52.3 4.8 21.6 7.1

67.2 23.6 81.9

2.1 3.7

Darrangiri 2.1 Darrangiri 3.0

Mining Hill Block Ronkhandi Block

West Darrangiri

Coal seam Thickness Ash (m) (%)

Coalfield/area/block

< < < <

5 5 5 5

<5 <5 <5

229 395

Ge

90 20 21 30

20 40 25

64 42

Ni

80 < 10 < 10 29

15 25 15

51 25

Co

800 25 34 30

<10 80 5

23 23

Cu

Coal ash analysis ( p p m )

< 10 < 10 16 24

<5 50 <10

280 110

Pb

Results of spectrographic analysis of Eocene coals of Meghalaya (lignitous to s u b - b i t u m i n o u s )

TABLE 2

5 5 15 <5

<5 <5 <5

13 <5

Mo

80 80 115 90

70 60 60

57 88

Zr

300 400 180 350

200 90 90

483 290

Mn

130 70 122 75

40 150 130

106 66

Cr

80 60 118 80

30 400 40

147 162

Ba

14 7

66 25

V

< 10 200 <10 30 63 142 12 50

<10 40 15 500 10 140

Ga

70 100 373 75

<10 150 60

105 120

Sr

O uz

o

z

7~

o

z

t"

,H

o

ill

Darrangiri seam (Ronkhandi Block )

Darrangiri seam (Mining Hill BlockWorking Quarry)

Seam

Bottom

Top

Bottom

Top

0.6 0.6 0.6 0.6 0.6

0.3 0.3 0.3 0.3 0.3 0.3 0.3

(m)

Sample thickness Cu 25 20 5 20 5 15 70 5 5 5 80 70

200 450 200 150 250 100 250 225 200 250 700 600

2.2 1.8 1.3 1.7 2.4 2.0 3.0 3.4 4.7 2.8 2.8 4.9

50 40 10 200 250

900 600 250 150 < 10 25 25

Pb

5 5 <5 <5 <5

50 20 5 5 <5 <5 <5

Mo

Coal ash analysis (ppm) Ge

Ash (%) 400 100 40 40 20 40 100 70 60 60 60 80

30 30 20 20 25

Cr

170 100 60 50 20 30 30

V

60 70 60 50 200

70 60 50 50 40 50 80

Zr

25 25 25 25 25

< 10 80 60 80 20 70 40

Co

Details of spectrographic analyses of Darrangiri seam along vertical section, West Darrangiri coalfield, Meghalaya

TABLE 3

50 40 40 40 40

70 60 60 90 30 80 60

Ni

200 200 300 500 250

800 700 650 650 80 250 250

Mn

10 15 <10 < 10 15

40 15 < 10 < 10 < 10 <10 10

Ga

170 100 90 300 150

250 200 170 200 20 80 110

Ba

50 50 50 200 250

200 200 70 70 < 10 40 150

Sr

E,

GEOCHEMISTRY OF TRACE ELEMENTS OF INDIAN COALS

WEST DARRANGIRI COALFIELD 500Cu PbMnCr

1+60~

A

V Ni Co

Cu PbMnCr V Ni Co

West Dtarrangiri Mining Hill Block

ISlaU

COALFIELD ILANGRIN COALFIELD

Cu PbMnCr

200 . 100~

E L,20]-

V Ni Co

1II\ Siju L (e' Seam-A

Cu PbMn [r V Ni Co

200L" J~

It'' Longrin (f)

o-~

220

~

105

~+00r 200 L

160

z 120

l+O

~ Seam- III Longrin (g)

Siju (d) 60

60

200_

_ $eom-II tin (hi

100 t-

o

,or 100 60

,o' 0

ot,u 200=100

\ a Langrin (i)

°°t. / 2O

Fig. 2. Frequency curves, based on trace element concentration, in the Eocene coal seams of Meghalaya.

Langrin coalfieM(Meghalaya) Samples from four coal seams in the Barsora area belonging to this field were collected and analysed (Table 2). The results show very low Ge (less than 5 p p m ) , Pb ( 10-24 p p m ) , Mo (5-6 p p m ) and Ga ( 10-63 p p m ) concentrations. In the youngest (Seam IV) the m a x i m u m concentrations of Cu (800 p p m ) , V (200 p p m ) and Ni (90 p p m ) occur. These high concentrations at the top of the coaly horizon suggest changes in the nature and type of the coal-forming plants with time, apart from the role of surface and ground water in the elements' enrichment, because Ni, Cu and V show stronger affinities with organic matter. Moreover, extremely high concentrations o f C u (800 p p m ) also suggests m a x i m u m enrichment of sulphide minerals in this seam due to its intermediate character and partial association with sulphide minerals (Kuhn et al., 1980 ). The next older seam in succession (Seam I II ), with an ash content of 4.8% shows the highest concentration of Mn (400 p p m ) . This m a x i m u m Mn concentration with low ash indicates its possible associ-

106

K.N. MUKHERJEE ET AL.

ation with organic matter. Previously Mn had been interpreted as being associated with the inorganic fraction by a number of workers. The elemental profiles (Figs. 2g, h and i) show a nearly similar pattern except for seam IV (Fig. 2f), which shows a aximum enrichment in Cu.

Makum coalfield (Assam) In the Oligocene coals (Table 4 ) very high concentrations of Cu (948-1264 ppm), Ni (504-754 ppm), Cr (1169-1641 ppm) and Ba (783-1110 ppm) have been found with very low ash percentages (2.6-8.8). This strongly suggests their association with the organic coal fraction. At the same time, Mn is practically negligible in this belt. Besides Mn, Ge (69-72 ppm), Co (18-77 ppm ), Y (22 ppm ) and Nb (negligible) also have low values. The elemental profiles show high peaks for Cr, Cu and Ni but very low values for Mn (Figs. 3a and b). This indicates that the Makum coals are geochemically different from the Meghalaya coals.

Dilli-Jeypore coalfieM (Assam) Four coal seams were studied, one (Seam III ) from Dilli colliery and three (Seams III, IV and VI) from Jeypore colliery. Like the Makum coals, the coals from this belt also have quite high values (not as high as in Makum; Table 4) of Cr (800-1000 ppm) and Cu (300-400 ppm). However, an usually high Nb ( 150-450 ppm) accumulation compared to the negligible amount of this element in the Makum belt was observed (Table 4 ). The concentration of other elements such as Ge (40-60 ppm), Co (20-50 ppm), V (200-600 ppm), is more-or-less similar in both coalfields (Table 4). Coal seam III in Dilli colliery, having a very low content (2.7%), has the highest values of Cr, V, and Nb. This again suggests the association of these elements with organic matter. The profiles of elemental concentration indicate high Cr-Cu-V-Ni and low Mn peaks (Figs. 3c-f ) which are more-or-less similar to those of the Makum coals and are significantly different from those of Meghalaya coals.

Kalakot coalfield (Jammu) The majority of the elements, B, Cu, Co, Cr, Ga, Mo, Ni, Pb, Sn and Y, show low concentrations, between 5 and 30 ppm. Mn ( 80-250 ppm ), Sr ( 50130 ppm) and Zr (70-150 ppm) have, however, moderate values (Table 5 ).

ND = not determined.

Jeypore Colliery (Quarry No. 6 ) Jeypore Colliery (Incline No. 7) Jeypore Colliery (Incline No. 7) Dilli Colliery

Dilli-Jeypore

TirapQuarry Bhahmanadi Quarry

Makblm TirapQuarry (Ledo)

Coalfield/area/Block

1.5

1.5

0.9

1.8

IV

III

III (?)

21.0

4.6

Thickness (m)

VI

III (20' seam ) I(100' seam )

Coalseam

2.6

24.4

4.2

18.5

2.6

8.8

Ash (%)

60

40

50

40

69

72

Ge

450

200

150

450

754

504

Ni

40

30

20

50

77

18

Co

300

150

300

400

948

1264

Cu

Coal ash analysis (ppm)

200

160

80

250

174

126

Zr

<5

<5

<5

<5

ND

ND

Mn

1000

500

400

400

300 800

700

II10

783

Ba

800

1169

1641

Cr

R e s u l l s o f s p e c t r o g r a p h i c a n a l y s e s o f O l i g o c e n e c o a l s ~ o m t h e c o a l f i e l d s o f U p p e r A s s a m(sub-bituminous)

TABLE4

600

400

200

500

209

533

V

40

20

<30

<30

<30

<30

-

22

50

-

La 22

<20

Y

40

30

200 450

110

40

198

82

Pb

150

450

ND

ND

Nb

E,

©

©

z

m

m

m

,.H

,< ©

,--]

K.N. MUKHERJEEET AL.

108

MAKUM COALFIELD

DILLI-JEYPORE COALFIELD

I

Cu PbMnCr V Ni Co

Cu PbMnCr V NiC0 Hokum

1800~

Seam4111000 (a) 800 -

1L,00I'120017

,OoOoE /

Cu PbMnCr V Ni Co JeyporeColliery Dilli Colliery eam-Ill 800

i 6ool

600 t,O0 t,00 200 100

200 i 100 60

200 t100 t

\

t,0 0

20

2O @ z o m I-oc I-,,-

0

1200 Hokum

8°°f

1000 -

z i,iJ i_1 z o Ld

~ = . ~Dilli-Jey S p°r e m-VI 800600

(dl

1 60

t~00 ,.

0

200 -

~ ~0 0

,00L--

OoF

I "~"'

\

Fig. 3. Frequency curves, based on trace element concentration, in the Oligocene coal seams o f Assam.

Metka coalfield (Jammu) Similar trends to the low concentrations found in the Kalakot coalfield are observed here for B, Cu, Co, Ga, Nb, and Y. In general, the coals of this field are comparatively more enriched in all the elements studied than those of Kalakot. This is especially true for Zr, V, Sr, Cr and Ba (Table 5 ).

109

GEOCHEMISTRY OF TRACE ELEMENTSOF INDIAN COALS TABLE 5

Results of spectrographic analyses of Eocene coals of the Kalakot and Metka coalfields, Jammu (low volatile bituminousoosemi-anthracite) coalfield Thick- Ash Coal ash analysis (pprn) hess (%) (m) B Ba Cu Co Cr Ga La

Mn

Mo Ni Nb Pb Sn

Kalakot

1.1

16.5 10 20 10 10 25 10 ND 250 5 22.7 20 50 10 10 30 10 ND 80 5 31.1 10 25 10 10 25 10 ND 110 5

Metka

0.8

37.0 10 90 15 30 60 10 15 33.8 15 80 15 25 90 10 15 31.0 30 90 20 30 80 10 15

Sr

V

10 15 15 10 50 30 10 20 20 ND 130 50 10 15 15 ND 60 35

60 ND 30 20 60 ND 35 20 100 5 40 20

Y

Zr

15 70 20 150 15 80

20 ND 280 130 25 200 45 ND 160 150 20 200 35 ND 190 150 30 230

ND = not determined.

Depositional environment The coalfields of northeastern India, particularly, Makum, Dilli-Jeypore, and Langrin show, on the basis of distribution and concentration of specific trace element assemblages, significant indications of the possible effects of marine transgression during the coal-forming periods. The basin analyses by various geoscientists have also corroborated these observations. According to Chandra et al. ( 1980, 1983 ), the total sulphur content in the coal seams of northeastern India increases from the base to the top of a seam. The authors also noticed a general upward increase in sulphur content in the sequence of seams. Chandra et al., ( 1983 ) stated that, in a basin, pH values decreased with depth; that is, alkalinity increased from the bottom to the surface. As a result, the sulphur content was highest at the top of a sequence because the alkaline condition is conducive to the deposition of sulphide. Such an upward increase of elements such as Pb, Mn and V (Table 3 ) is also observed by this study in the Darrangiri seam in the Mining Hill block of the West Darrangiri coalfield. In the adjacent Ronkhandi block, although a moreor-less similar trend is found for V, no distinct trend for Mn and Pb could be seen (Table 3 ). Further, a gradual increase in the total sulphur content was observed by Chandra et al. (1983) in the coals of Meghalaya from West to East within the basin of deposition, due to the increasing marine influence of the peat forming swamps of Khasi and Jaintia Hills (i.e. Langrin coalfield) in the eastern part of the Meghalaya as compared to the Garo Hills in the west (West Darrangiri, Siju coalfields). We have found similar accumulation trends for Cu (80-800 ppm), Zr (88-115 ppm) and Zn ( 150-373 ppm). This suggests that, possibly, the marine environment also contributed to the deposition of these chalcophile (Cu and Zn) and lithophile (Zr) elements, as in the case of sulphide in the Meghalaya basin from west to east. Further, exception-

Ni

<5

229 395 <15

42 64 20 40 20 90

69 72 40 60 <5 395

Total range

Metka

Kalakot

Eocene coalfields of Jamrnu

Total Range

Dilli-Jeypore

Makum

10 10 30 40 10 40

504 754 150 450 20 754

10 10 25 30 10 30

18 77 20 50 < 10 80

25 51 15 25 <10 80

Co

OligocenecoalfieldsofupperAssam

Langfin

SOu

West Darrangiri

Eocene coalfields of Meghalaya

Ge

10 10 15 20 10 20

948 1264 150 400 5 1264

23 33 5 80 25 800

Cu

15 20 20 45 15 45

82 198 30 110 <5 280

110 280 <5 150 <10 24

Pb

-

5

5 5 5

<5 13

-

-

<5 5

<5 13 <5

Mo

70 150 200 280 70 280

126 174 80 250 57 250

57 88 60 70 30 115

Zr

80 150 60 100 60 150

<5 483

<5

-

290 483 90 200 180 400

Mn

25 30 60 90 25 90

1169 1641 300 1000 40 1641

66 106 40 150 70 130

Cr

20 50 80 90 20 90

783 1110 400 700 30 1110

147 162 30 400 60 118

Ba

Coal belt/coalfield Minimum and maximum concentrations of trace elements (ppm)

10 10 10 10 10 10

< 10 63

-

-

7 14 < 10 15 < 10 63

Ga

30 50 130 150 30 150

209 533 200 600 25 600

25 66 40 500 30 200

V

15 20 20 30 15 30

22 22 <20 50 <20 50

Y

15

15 15

> 30 <30

La

10

10

Sn

10 20 10 30 10 30

B

50 130 160 280 50 280

< 10 373

105 120 < 10 150 70 373

Sr

70 150 200 230 70 230

Zn

15 20 20 20 15 20

150 450 150 450

Nb

Variation in the trace element content (in coal ash) among Eocene coals of Meghalaya, Oligocene coals of Upper Assam, and Eocene coals of Jammu

TABLE 6

r-

z

GEOCHEMISTRY OF TRACE ELEMENTS OF INDIAN COALS

111

ally high concentrations of Cu, Cr, V, and Ni in the coals of Assam indicate marine influence during coal formation and also support the views of Nicholls (1968) on the British coals and of Potter et al. (1963) for the depositional environments of argillaceous sediments. The low average concentrations of Cu, Cr, V, Ni and B (Table 6) in the Tertiary coals of northwestern India (Jammu) indicate a high influx of fresh water during the formation of these coals. This view is further supported by the close similarity of Jammu coals with the fluvio-lacustrine Lower Gondwana coals of India with respect to the concentrations of Cu, Cr, V, Ni and Ga, which are good indicators of palaeo-environments. CONCLUSIONS

Trace element data reveal a recognisable difference in their concentrations and distribution between the coals of the northeast and northwest Tertiary coal basins of India, and also between the Eocene coals of Garo-Khasi Hills of Meghalaya and the Oligocene coals of Upper Assam, particularly of Makum (Table 6 ). In general, the Eocene coals, both of northeastern and northwestern India, show lower elemental concentrations than the Oligocene coals of Upper Assam (Table 6 ). Of the two areas, the Eocene coals of northwestern India are the poorer (Table 6 ). The Oligocene coals of Upper Assam (the Makum and Dilli-Jeypore coalfields) show higher concentrations of, for example, Cr, Cu, Ni, Zr, and Ba, than the Eocene coals of Meghalaya. It has been observed that an increase or decrease in the percentage of ash over a section of the coal seam corresponds with a decrease or increase, respectively, usually of the concentrations of elements such as Ba, Cu, Ge, Zr and Pb. High concentrations of one element in all the coal seams of a particular coalfield can be significant for the identification and correlation of the coal seams. The results show that, for the Oligocene coals of the Makum and DilliJeypore coalfields, Cr can be used as marker or Index element because it shows significantly high peaks for all the seams analysed. Likewise, for west Darrangiri, and the Siju and Langrin coals of Meghalaya (apart from Seam IV, Langrin coalfield, Fig. 2f ) Mn gives the highest peaks for all the coal seams. The inorganic/organic association of trace elements has been interpreted on the basis of the variation in the concentration of trace elements with respect to ash content in coal samples of a particular seam. The results indicate that Ni, Co, Ba, V, Sr, Cr, Y, Ge and Nb are associated with organic matter, whereas Cu and Pb are associated with both organic matter and sulphides. Mn shows its affinity with organic matter and mineral matter, Ga exclusively with mineral matter. Further, the concentrations and distribution of trace elements in the Eocene

I 12

K.N.MUKHERJEEETAL.

and Oligocene coals of northeastern India indicate marine conditions, whereas the Eocene coals of northwestern India show freshwater influence.

REFERENCES Banerjee, N.N., Rao, H.S. and Lahiri, A., 1972. Germanium in Indian Coals. Ind. J. Technol., 12: 353-368. Bastron, H., Barnett, P.R. and Murata, K.J., 1960. Method for the quantitative spectrochemical analysis of rocks, minerals and other materials. U.S. Geol. Surv. Bull., 1084G: 165-181. Chandra, D., Chadhuri, S.G. and Ghosh, S., 1980. Distribution of sulphur in coal seams with special reference to the Tertiary coals of North Eastern India. Fuel, 59 ( 5 ): 357-359. Chandra, D., Samsuddin, A.K. and Banerjee, K.C., 1981. Trace element studies of G.III coal seam of Korba coalfield, M.P., in relation to pollution problem due to gasification for the production of fertilizers. Sci. Cult., 47: 299-301. Chandra, D., Mazumdar, K. and Basumallick, S., 1983. Distribution of sulphur in the Tertiary coals of Meghalaya, India. Int. J. Coal. Geol., 3: 63-75. Clark, M.C. and Swaine, D.J., 1962. Trace elements in coal. I. New South Wales Coals. C.S.I.R.O. Div. Coal Res. Tech., North Ryde, Australia, Commun. 45. Kuhn, J.K., Fiene, F.L., Cahill, R.A., Gluskoter, H.J. and Shimp, N.F., 1980. Abundance of trace and minor elements in organic and mineral fractions of coal environment. Geol. Notes (88), State Geol. Surv. Div., Urbana, II1., 67 pp. Mukherjee, B. and Ghosh, A., 1976. Distribution and behaviour of trace elements in some Permian coals of India. Ind. Mineral., 17: 23-30. Mukherjee, K.N., Pal, J.C., Dutta, N.R. and Raja Rao, C.S., 1982a. Geochemical and trace elements studies of coal seams of Tertiary coalfields in north-eastern India. Rec. Geol. Surv. India, 112: 1-12. Mukherjee, K.N., Rajo Rao, C.S., Chowdhury, A.N., Pal, J.C. and Das, M., 1982b. Trace element studies in the Major Tertiary and Gondwana coalfields of India. Bull. Geol. Surv. India, 49:1-115. Mukherjee, K.N.,Dutta, N.R., Chandra, D., Pandalai, H.S. and Singh, M.P., 1988. A statistical approach to the study of the distribution of trace elements and their organic/inorganic affinity in Lower Gondwana coals of India. Int. J. Coal Geol., 10: 99-108. Mullick, A.U. and Ahmed, S., 1979. Analytical studies on Indian coals with special reference to their ash and mineral contents. J. Min. Met. Fuel, 27 (5): 148-152. Nicholls, G.D., 1968. The geochemistry of coal bearing strata. In: D. Murchison and T.S Westoll (Editors), Coal and Coal-bearing Strata. Elsevier, New York, pp. 269-307. Pareek, H.S. and Bardhan, B., 1985. Trace elements and their variations along seam profiles of certain coal seams of Middle and Upper Barakar Formations (Lower Permian) in East Bokaro coalfield, district Hazaribagh, India. Int. J. Coal Geol., 5:281-314. Potter, P.E., Shimp, N.F. and Witters, J., 1963. Trace elements in marine and fresh water argillaceous sediments. Geochem. Cosmochim. Acta, 27: 669-694. Reynolds, R.C., 1972. Boron: Elements and Geochemistry. In: R.W. Fairbridge (Editor), The Encyclopedia of Geochemistry. In: R.W. Fairbridge (Editor), The Encyclopedia of Geochemistry and Environmental Sciences. Van Nostrand Reinhold, New York, pp. 88-90. Rishi, M.K., 1970. Germanium and other minor elements in the coals of Umaria, M.P.J. Geol. Soc. India, 11: 85-87. Ruch, B.R., Gluskoter, H.J. and Shimp, N.F., 1974. Occurrence and distribution of potentially volatile trace elements in coal. A final report. Illinois State Geol. Surv. Environmental Geol. Note 72, 96 pp. Singh, R.M., Singh, M.P. and Chandra, D., 1983. Occurrence, distribution and probable source

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of the trace elements in Ghugus coals, Wardha Valley, districts Chandrapur and Yeotmal, Maharashtra, India. Int. J. Coal. Geol., 2:371-381. Singh, M.P., Singh, R.M. and Chandra, D., 1985. Environmental and health problems due to geochemical alterations associated with trace elements in coals, Ghugus coalfield, Wardha Valley, Maharashtra. Q.J. Geol. Min. Metall. Soc. India, 57: 99-103. Walker, C.T., 1972. Boron Geochemistry and Environmental Sciences. Van Nostrand Reinhold, New York, pp. 90-92 Ward, C., 1980. Mode of occurrence of trace elements in some Australian coals. Coal Geol., 2(2): 77-88.