petro-chemical characterization and evolution of vastan lignite, gujarat, india
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Petro-chemical characterization and evolution of Vastan Lignite, Gujarat, India
Prakash K. Singh a,⁎, M.P. Singh a, Alok K. Singh b
a Coal & Organic Petrology Lab, Department of Geology, Banaras Hindu University, Varanasi-221005, Indiab Research & Development Division, Tata Steels Ltd., Jamshedpur, India
a b s t r a c ta r t i c l e i n f o
Article history:Received 1 May 2009Received in revised form 7 January 2010Accepted 8 January 2010Available online 15 January 2010
Keywords:MaceralsMicrolithotypesLignitePaleomireVastan
The present paper entails the results of the chemical and petrological studies carried out on VastanLignites of Gujarat. Petrographically there is an unambiguous dominance of huminite group of maceralsover the liptinite and inertinite groups and is chiefly represented by telohuminite and detrohuminite.Ulminite dominates among telohuminite while attrinite and densinite mainly contribute to detrohuminite.Liptinite and inertinite groups are recorded comparatively in small concentrations. Argillites are the maininorganic component while the carbonates and sulphides contribute meagerly to the total mineral mattercontent.Chemically these lignites are characterized by high moisture content with moderately high volatile matterand variable ash contents. The fixed carbon and the elemental carbon show a moderate concentration. Thesulphur content is more in the Lower seam with an average content of 1.59%.The study reveals that these lignites originated under moderate to high water cover in limnic environmentswith evidences supporting anaerobic decay of the organic matter with a loss of structural components ofvegetal matter to a lesser extent. Moreover, the influx of fresh waters raised the pH of the paleomire whichwas further raised by carbonate rich surface water and was responsible for high sulphur content in some ofthe sections.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
Lignite, more commonly known as brown coal in most of thecountries in the world, is a low calorific fossil fuel. It predominantlyoccurs in countries like Germany, Australia, Russia, U.S.A., China andCanada. The global lignite resources are estimated to be over1025 billion tonnes andnearly one third are located inAsia (Thielemannet al., 2007).
In India, lignite has a distinctive occurrence, age, and depositionalfeatures with a strong paleogeographic control. The Tertiary coals ofthe country contribute only around 1% of total Indian coal reserve andare of two types, i.e. sub-bituminous and lignite. While the sub-bituminous coal occurs in northeastern India, lignite occurs inwestern, northwestern and southern India. The major Tertiary coalproducing states of India are Assam, Arunachal Pradesh, Nagaland,and Meghalaya. Lignite deposits are found in the Eocene (Jammu andKashmir, Gujarat and Rajasthan), Miocene (Neyvelli, Tamil Nadu) andPlio-Pleistocene (Nichahom, Jammu and Kashmir) ages. The Geolog-
ical Succession of important lignite bearing horizons of India is asfollows:
International Journal of Coal Geology 82 (2010) 1–16
⁎ Corresponding author. Tel.: +91 9935819700.E-mail address: [email protected] (P.K. Singh).
Geological age Age(in my)
Important localities References
Early Pleistocene toLate Pliocene
15 Lignite in the Karewaformation of KashmirValley, Jammu andKashmir
Pareek, 1970
Miocene 30 1. Lignite in theCuddalore series ofsouth Arcot, Chennai,Tamil Nadu
1. Navale and Mishra,1980; Pareek, 2004
2. Lignites of Kerala 2. Shukla et al., 2000;Pareek, 2004
Oligocene to LateEocene
45 Lignite in the BarailSeries in Nazira, Assam
Mishra and Ghosh, 1996
Middle Eocene Lignite in Palana,Rajasthan
Pareek, 2004
Early Eocene 1. Coal in Jaintia Seriesof Assam
1. Mishra and Ghosh(1996)
2. Jammu Coalfields 2. Singh and Singh (1995)3. Lignites ofBhavnagar,Matanomadh, Vastanand Panandhro ofGujarat
3. Balasubramanyan,2006; Saxena, 1979;Singh and Singh, 2005;Sahni et al., 2006.
0166-5162/$ – see front matter © 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.coal.2010.01.003
Contents lists available at ScienceDirect
International Journal of Coal Geology
j ourna l homepage: www.e lsev ie r.com/ locate / i j coa lgeo
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The lignite deposits of the country occur widely as subsurfacedeposits and vary in their lateral and vertical extents, structuraldisposition, multiplicity of seams, quality, and associated overburden.Over two third of the total Indian lignites come from Neyveli,Tamilnadu.
It is believed that 55 million years ago Vastan suffered multipletransgressions being located at sea shore at Indian Plate Margin and allalong this Plate margin occur coal and lignite deposits like Vastan, in
other parts of Gujarat, Rajasthan, Jammu and Kashmir and Pakistan(Joshi, 2007). Sahni et al. (2006) have studied the regional subconti-nental distribution of the Lower Eocene coals and lignites of Gujarat andRajasthan. They believe that the Lower Tertiary coal measures wereformed on the Indian Platemargins as a result of the gradual withdrawalof the Neotethys in Pakistan, Western India (Gujarat and Rajasthan),Northern India (Jammu, Shimla, Solan) and Northeastern India(Meghalaya). While investigating the sedimentological and
Fig. 1. Geological map around Vastan area.After Rana et al., 2004.
2 P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
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paleontological records of the lignite bearing sediments of Vastan, theycollected several benthic foraminifera, Nummulites burdigalensis andassigned an Early Eocene age to these sediments. Garg et al. (2008) havestudied the dinoflagellate cyst assemblage from various levels of thelignite bearing sediments of Vastan LigniteMine and they have assignedan age ranging from late Thanetian (Late Paleocene) to middle Ypresian(Early Eocene) to this succession.
Floral similarities can be seen in these lignite-coal depositsand indicate an amiable warm climate required for the luxuriantfloral growth (Joshi, 2007). Mandal and Guleria (2006) carried outpalynological investigations of these lignites and recorded richassemblages of pollen-spores, algal–fungal remains and dinoflagellatecysts. Based on these fossil records they have suggested the deposition
of Vastan lignite during Early Eocene in deltaic condition underbrackish water influence with the prevalence of humid tropicalcondition. Singh and Singh (2005) have carried out petrologicalstudies of adjacent, Early Eocene lignite deposit of Gujarat (Panandhrolignites of Kachchh basin). They have suggested lagoonal conditions offormation of Panandhro lignites where increased microbial activitiesexisted under highly anaerobic and relatively elevated pH conditionsof mire near the existing shore line.
2. Geological setting
The Vastan opencast lignite mine is situated 60 kmNE of Surat and29 km ENE of Kim town (latitude 21°25′47″N, longitude 73°07′30″E
Fig. 2. Megascopic profiles of the two Vastan lignite showing various bands.Litholog is after Sahni et al., 2006.
3P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
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Table 1Maceral composition (with mineral matter) of Lower seam of Vastan Lignite, Gujarat.
Macerals B-1% B-2% B-3% B-4% B-5% B-6%
Huminite Textinite-A 0.00 0.16 0.00 0.00 0.00 0.00Textinite-B 0.48 2.30 1.52 6.24 3.80 2.79Ulminite-A 7.68 29.34 52.19 41.54 52.64 37.11Ulminite-B 9.44 40.49 14.81 25.62 18.48 9.85Attrinite 25.76 3.93 6.90 5.09 7.76 19.54Densinite 22.56 9.84 7.74 8.37 8.09 9.20Phlobaphinite 0.16 0.33 0.17 0.49 0.17 0.16Pseudo-phlobaphinite 5.12 6.39 2.69 3.94 1.32 4.93Levi-gelinite 0.00 0.16 0.00 0.00 0.00 0.00Pori-gelinite 0.00 0.00 0.00 0.00 0.00 0.00
Liptinite Microtenuisporinite 0.00 0.16 0.17 0.16 0.00 0.00Microcrassisporinite 0.00 0.00 0.00 0.00 0.00 0.00Megatenuisporinite 0.00 0.00 0.00 0.00 0.00 0.00Megacrassisporinite 0.00 0.00 0.00 0.00 0.00 0.00Microtenuicutinite 0.00 0.16 0.17 0.00 0.00 0.00Microcrassicutinite 0.00 0.00 0.00 0.00 0.00 0.00Megatenuicutinite 0.00 0.00 0.00 0.00 0.00 0.00Megacrassicutinite 0.00 0.00 0.00 0.00 0.00 0.00Resinite 0.00 0.33 0.34 0.82 0.17 0.16Suberinite 0.48 0.33 0.51 0.49 0.17 0.16Liptodetrinite 0.16 0.16 0.34 0.33 0.17 0.16
Inertinite Micrinite 0.00 0.00 0.00 0.00 0.00 0.00Macrinite 0.00 0.00 0.00 0.00 0.00 0.00Pyrosemifusinite 0.00 0.00 0.00 0.00 0.00 0.00Degradosemifusinite 0.16 0.16 0.00 0.00 0.17 0.00Pyrofusinite 0.96 0.00 1.68 0.82 0.66 0.49Degradofusinite 1.28 0.16 0.67 0.16 0.17 0.16Funginite 0.80 0.49 1.01 1.48 0.33 0.49Secretinite 0.00 0.00 0.17 0.00 0.00 0.00Inertodetrinite 1.44 0.16 2.02 0.49 0.99 1.15
M. matter Sulphide 0.48 1.15 0.84 0.16 1.65 2.30Carbonates 4.00 0.33 0.67 0.00 0.66 0.16Argillaceous 19.04 3.44 5.39 3.78 2.64 11.17Total 100.00 100.00 100.00 100.00 100.00 100.00
Table 2Maceral composition (m. m. f. basis) of Lower seam of Vastan Lignite, Gujarat.
Macerals B-1 B-2 B-3 B-4 B-5 B-6
Huminite Textinite-A 0.00 0.17 0.00 0.00 0.00 0.00Textinite-B 0.63 2.41 1.63 6.50 3.99 3.23Ulminite-A 10.04 30.86 56.06 43.25 55.38 42.97Ulminite-B 12.34 42.59 15.91 26.67 19.44 11.41Attrinite 33.68 4.14 7.41 5.30 8.16 22.62Densinite 29.50 10.34 8.32 8.72 8.51 10.65Phlobaphinite 0.21 0.34 0.18 0.51 0.17 0.19Pseudo-Phlobaphinite 6.69 6.72 2.89 4.10 1.39 5.70Levi-gelinite 0.00 0.17 0.00 0.00 0.00 0.00Pori-gelinite 0.00 0.00 0.00 0.00 0.00 0.00
Liptinite Microtenuisporinite 0.00 0.17 0.18 0.17 0.00 0.00Microcrassisporinite 0.00 0.00 0.00 0.00 0.00 0.00Megatenuisporinite 0.00 0.00 0.00 0.00 0.00 0.00Megacrassisporinite 0.00 0.00 0.00 0.00 0.00 0.00Microtenuicutinite 0.00 0.17 0.18 0.00 0.00 0.00Microcrassicutinite 0.00 0.00 0.00 0.00 0.00 0.00Megatenuicutinite 0.00 0.00 0.00 0.00 0.00 0.00Megacrassicutinite 0.00 0.00 0.00 0.00 0.00 0.00Resinite 0.00 0.34 0.36 0.85 0.17 0.19Suberinite 0.63 0.34 0.54 0.51 0.17 0.19Liptodetrinite 0.21 0.17 0.36 0.34 0.17 0.19
Inertinite Micrinite 0.00 0.00 0.00 0.00 0.00 0.00Macrinite 0.00 0.00 0.00 0.00 0.00 0.00Pyrosemifusinite 0.00 0.00 0.00 0.00 0.00 0.00Degradosemifusinite 0.21 0.17 0.00 0.00 0.17 0.00Pyrofusinite 1.26 0.00 1.81 0.85 0.69 0.57Degradofusinite 1.67 0.17 0.72 0.17 0.17 0.19Funginite 1.05 0.52 1.08 1.54 0.35 0.57Secretinite 0.00 0.00 0.18 0.00 0.00 0.00Inertodetrinite 1.88 0.17 2.17 0.51 1.04 1.33Total 100.00 100.00 100.00 100.00 100.00 100.00
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Table3
Maceral
compo
sition
(withmineral
matter)
ofup
perseam
ofVastanLign
ite,
Gujarat.
Macerals
A-1%
A-2%
A-3%
A-4%
A-5%
A-6%
A-7%
A-8%
A-9%
A-10%
A-11%
A-12%
A-13%
A-14%
A-15%
A-16%
A-17%
A-18%
A-19%
Hum
inite
Textinite-A
0.00
0.32
0.33
0.00
0.00
0.00
0.17
0.00
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Textinite-B
3.41
14.75
14.14
15.79
5.34
2.33
7.77
5.32
1.13
1.48
3.58
0.83
2.60
4.91
1.04
0.33
7.45
7.07
6.02
Ulm
inite-A
68.13
47.65
48.03
53.62
66.34
71.88
48.26
58.14
16.69
9.39
6.99
6.97
9.11
6.06
2.43
0.66
23.84
16.45
55.77
Ulm
inite-B
11.71
17.02
18.42
4.61
8.74
9.65
9.59
3.49
2.59
5.44
0.49
2.65
3.58
5.40
4.33
1.15
31.46
7.89
3.09
Attrinite
2.60
6.00
2.14
9.38
5.02
2.66
2.81
9.80
29.01
23.89
33.98
44.11
31.71
20.79
15.94
9.88
9.27
26.15
9.43
Den
sinite
1.95
1.94
1.97
5.10
1.29
0.83
0.66
7.31
26.74
13.84
10.24
16.92
22.60
20.62
3.81
1.65
23.68
13.32
17.40
Phloba
phinite
0.16
1.46
0.16
0.66
0.32
0.00
0.33
0.66
0.65
0.99
0.65
0.33
0.98
2.13
0.17
0.66
0.00
0.99
0.00
Pseu
do-phlob
aphinite
3.25
4.05
4.11
3.29
4.85
2.83
2.48
5.48
2.59
1.81
1.30
1.49
2.44
3.27
1.04
0.66
0.50
1.15
0.65
Levi-gelinite
0.00
0.00
0.49
0.33
0.00
0.00
0.17
0.00
0.00
0.33
0.00
0.00
0.00
0.49
0.00
0.00
0.00
0.00
0.00
Pori-gelinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Liptinite
Microtenu
ispo
rinite
0.00
0.00
0.00
0.00
0.00
0.33
0.00
0.00
0.00
0.16
0.00
0.00
0.00
0.16
0.17
0.00
0.00
0.00
0.00
Microcrassisp
orinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
aten
uisp
orinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
acrassispo
rinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Microtenu
icutinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Microcrassicu
tinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
aten
uicu
tinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
acrassicutinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Resinite
0.33
0.32
0.33
0.16
0.49
1.16
0.17
0.00
0.16
0.16
0.33
0.17
0.49
0.98
0.69
0.49
0.00
0.33
0.00
Sube
rinite
0.16
1.13
0.16
0.66
0.32
0.00
0.33
0.66
0.65
0.82
0.65
0.33
0.98
1.96
0.17
0.00
0.00
0.99
0.00
Liptod
etrinite
0.16
0.16
0.16
0.16
0.16
0.33
0.17
0.17
0.16
0.16
0.16
0.17
0.16
0.00
0.00
0.00
0.00
0.16
0.00
Inertinite
Micrinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Macrinite
0.49
0.49
0.16
0.16
0.00
0.33
0.50
0.17
0.49
0.16
0.00
0.17
0.00
0.00
0.00
0.00
0.00
0.00
0.16
Pyrosemifu
sinite
0.00
0.00
0.00
0.00
0.32
0.00
0.00
0.00
0.16
0.00
0.00
0.00
0.33
0.00
0.00
0.00
0.00
0.00
0.00
Deg
rado
semifu
sinite
0.00
0.00
0.00
0.00
0.00
0.00
0.50
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Pyrofusinite
3.25
0.65
4.11
1.15
1.46
4.33
15.04
2.66
5.35
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.33
Deg
rado
fusinite
0.49
0.81
0.49
0.66
0.49
0.50
0.33
0.66
0.32
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.33
0.49
Fung
inite
1.46
0.81
0.66
0.82
0.32
0.17
1.16
0.66
1.13
0.33
0.16
0.33
0.65
0.82
0.35
0.16
0.83
0.49
0.49
Secretinite
0.33
0.32
0.00
0.16
0.00
0.17
0.50
0.00
0.16
0.00
0.00
0.00
0.16
0.16
0.00
0.00
0.00
0.00
0.00
Inertode
trinite
0.98
0.97
2.80
2.30
1.46
1.16
5.62
1.99
6.00
0.82
0.00
0.00
0.00
0.33
0.17
0.16
0.17
0.33
0.33
Mineral
matter
Sulphide
0.00
0.00
0.00
0.00
0.16
0.33
0.00
0.66
0.16
0.33
0.16
0.83
0.33
0.00
0.52
0.00
0.00
0.16
0.00
Carbon
ates
0.33
0.65
0.49
0.33
0.65
0.33
0.00
0.83
0.65
1.98
9.27
2.82
3.74
4.75
35.88
58.65
0.33
2.14
0.49
Argillaceo
us0.81
0.49
0.82
0.66
2.27
0.67
3.47
1.33
5.02
37.89
32.03
21.89
20.16
27.17
33.28
25.54
2.48
22.04
5.37
Total
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
5P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
Author's personal copy
Table4
Maceral
compo
sition
(m.m
.f.b
asis)of
uppe
rseam
ofVastanLign
ite,
Gujarat.
Macerals
A-1%
A-2%
A-3%
A-4%
A-5%
A-6%
A-7%
A-8%
A-9%
A-10%
A-11%
A-12%
A-13%
A-14%
A-15%
A-16%
A-17%
A-18%
A-19%
Hum
inite
Textinite-A
0.00
0.33
0.33
0.00
0.00
0.00
0.17
0.00
0.17
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Textinite-B
3.45
14.92
14.33
15.95
5.51
2.36
8.05
5.47
1.20
2.48
6.11
1.11
3.43
7.21
3.43
2.08
7.67
9.35
6.39
Ulm
inite-A
68.91
48.20
48.67
54.15
68.45
72.85
50.00
59.83
17.73
15.70
11.94
9.35
12.02
8.89
8.00
4.17
24.53
21.74
59.24
Ulm
inite-B
11.84
17.21
18.67
4.65
9.02
9.78
9.93
3.59
2.75
9.09
0.83
3.56
4.72
7.93
14.29
7.29
32.37
10.43
3.28
Attrinite
2.63
6.07
2.17
9.47
5.18
2.70
2.91
10.09
30.81
39.94
58.06
59.24
41.85
30.53
52.57
62.50
9.54
34.57
10.02
Den
sinite
1.97
1.97
2.00
5.15
1.34
0.84
0.68
7.52
28.40
23.14
17.50
22.72
29.83
30.29
12.57
10.42
24.36
17.61
18.48
Phloba
phinite
0.16
1.48
0.17
0.66
0.33
0.00
0.34
0.68
0.69
1.65
1.11
0.45
1.29
3.13
0.57
4.17
0.00
1.30
0.00
Pseu
do-phlob
aphinite
3.29
4.10
4.17
3.32
5.01
2.87
2.57
5.64
2.75
3.03
2.22
2.00
3.22
4.81
3.43
4.17
0.51
1.52
0.69
Levi-gelinite
0.00
0.00
0.50
0.33
0.00
0.00
0.17
0.00
0.00
0.55
0.00
0.00
0.00
0.72
0.00
0.00
0.00
0.00
0.00
Pori-gelinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Liptinite
Microtenu
ispo
rinite
0.00
0.00
0.00
0.00
0.00
0.34
0.00
0.00
0.00
0.28
0.00
0.00
0.00
0.24
0.57
0.00
0.00
0.00
0.00
Microcrassisp
orinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
aten
uisp
orinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
acrassispo
rinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Microtenu
icutinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Microcrassicu
tinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
aten
uicu
tinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Meg
acrassicutinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Resinite
0.33
0.33
0.33
0.17
0.50
1.18
0.17
0.00
0.17
0.28
0.56
0.22
0.64
1.44
2.29
3.13
0.00
0.43
0.00
Sube
rinite
0.16
1.15
0.17
0.66
0.33
0.00
0.34
0.68
0.69
1.38
1.11
0.45
1.29
2.88
0.57
0.00
0.00
1.30
0.00
Liptod
etrinite
0.16
0.16
0.17
0.17
0.17
0.34
0.17
0.17
0.17
0.28
0.28
0.22
0.21
0.00
0.00
0.00
0.00
0.22
0.00
Inertinite
Micrinite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Macrinite
0.49
0.49
0.17
0.17
0.00
0.34
0.51
0.17
0.52
0.28
0.00
0.22
0.00
0.00
0.00
0.00
0.00
0.00
0.17
Pyrosemifu
sinite
0.00
0.00
0.00
0.00
0.33
0.00
0.00
0.00
0.17
0.00
0.00
0.00
0.43
0.00
0.00
0.00
0.00
0.00
0.00
Deg
rado
semifu
sinite
0.00
0.00
0.00
0.00
0.00
0.00
0.51
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Pyrofusinite
3.29
0.66
4.17
1.16
1.50
4.38
15.58
2.74
5.68
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.35
Deg
rado
fusinite
0.49
0.82
0.50
0.66
0.50
0.51
0.34
0.68
0.34
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.43
0.52
Fung
inite
1.48
0.82
0.67
0.83
0.33
0.17
1.20
0.68
1.20
0.55
0.28
0.45
0.86
1.20
1.14
1.04
0.85
0.65
0.52
Secretinite
0.33
0.33
0.00
0.17
0.00
0.17
0.51
0.00
0.17
0.00
0.00
0.00
0.21
0.24
0.00
0.00
0.00
0.00
0.00
Inertode
trinite
0.99
0.98
2.83
2.33
1.50
1.18
5.82
2.05
6.37
1.38
0.00
0.00
0.00
0.48
0.57
1.04
0.17
0.43
0.35
TOTA
L10
0.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
6 P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
Author's personal copy
and falls in Mangrol Taluka of Surat district, Gujarat (Survey of IndiaToposheet No: 46/G/2). The geological map of Vastan has beenprovided in Fig. 1 (Rana et al., 2004).
Vastan lignite deposit is a part of major lignite occurrences inGujarat and is of Eocene age. The subsurface lignite bearing sequenceseen in the Vastan lignite mine is referred to as the Cambay Formation
Fig. 3. Representative photomicrographs of macerals of Vastan lignite: a)pyrite occurring in association with attrinite, b) funginite, c) clustering of funginite, d) pyrite framboidsclustered together, e) and f) pyrite, g) siderite replacing ulminite and the oxidation cracks are filled up with argillaceous mineral matter, h) resinite.
7P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
Author's personal copy
Fig. 4. Representative photomicrographs of macerals of Vastan lignite: a) suberinite cell walls and phlobaphinite, b) textinite-B, c) elongated cells of fusinite where some cell lumensare filled with argillaceous mineral matter, d) levigelinite with oxidation cracks, e) ulminite-A, f) pyrite in cells of textinite, g) textinite-B where cell lumens are filled up withargillaceous mineral matter, h) clustering of corpohuminite.
8 P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
Author's personal copy
or the Cambay Shale that was deposited in a NNW–SSE trendingintracratonic graben called Cambay Basin (Fig. 1). The cambay basin isa major tertiary hydrocarbon belt extending through the Sanchor–Mehsana–Ahmedabad–Tarapur–Broach–Surat areas of Gujarat andcontinuing northwards into the Barmer region of Rajasthan (Mathuret al., 1968; Raju, 1968; Pareek, 1981; Raju and Srinivasan, 1983;Biswas, 1987; Raju and Srinivsan, 1993; Sharma, 2003).
The surface exposure of the Cambay shale occurs as a thin strip alongthe Saurashtra coast and to the east of the Gulf of Cambay (Khambhat)and comprises 75–150 m thick beds of greenish and whitish grey andblack clay/shales with lignite seams. The Vagadkhol Formation and itshomotaxial equivalentOlpad Formationdeposited over theDeccanTrapsunderlie the Cambay shale. The cambay shale is classified into a lower,older Cambay and an upper, younger Cambay shale based on electrologshift that is considered to mark an unconformity between the two units.
The Vastan mine has exposed a nearly 200 m thick muddy suc-cession directly over the Deccan traps. This succession can beinformally differentiated into three stratigraphic units — successionA, succession B and succession C. The lignite beds occur in the 45 mthick succession A. This succession consists of lignites, greenish greyshales, carbonaceous shales and shell carbonates (Garg et al., 2008).While succession B is made up of greenish grey shales with low anglediscordances, succession C comprises of reddish brown shales alongwith mud filled channels and discordances.
In Vastan mine area, the Cambay shale acquires a thickness of 20–145 m (Sahni et al., 2006) comprising alternating sequences of lignitebeds, dark grey to black and greenish grey shales and claymarls. Thereare two main lignite seams, one at the top which is referred to asUpper Lignite seam and the other one is Lower lignite seam as shownin Fig. 2 (taken from Sahni et al., 2006). There is cyclic repetition ofshell carbonate, carbonaceous shale, green shale, and lignite in thesuccession between the two main lignite seams (Garg et al., 2008).
Besides, there are several thin bands of lignites which are regardedas split seams. A fault is observed striking in NE–SW direction with athrow of 50 m towards NW.
The beds in region have a low dip of 3°–4° to NW subcroping in theEast. The strata strike in NE–SW direction. Moreover, a fault has been
observed striking in the direction of strata with a throw of 50 mtowards NW.
3. Materials and method
The lignite samples from the Lower and Upper working seamswere collected from the Vastan open cast lignite mine following Pillarsampling. For microscopic study, the samples were crushed to −18mesh size, mounted in cold medium araldite and hardener andsubsequently ground and polished. The maceral and microlithotypeanalyses were carried out with polished pellets using an incident LeitzOrthoplan Pol microscope equipped withWild Photoautomat MPS 45.The line to line and point to point spacing was kept at 0.4 mm and foreach sample more than 600 counts were taken. The methodologygiven by Stach et al., 1982 and Taylor et al., 1998 was followed and theterminologies for huminite macerals given by ICCP (2005), and that ofinertinite given by ICCP (2001) have been used.
The proximate analysis was performed taking 70 mesh size coalpowder using oven andmuffle furnace as per BIS, 2003. The elementalanalysis (C, H, N, and S) was performed by C.D.R.I, Lucknow on VarioEL-III Analyzer.
4. Results and discussion
4.1. Macroscopic characteristics
The Vastan lignites are matrix rich and the presence of xylite andcharcoal is less than 10%. While the stratified matrix rich bandsconstitute detrital humic groundmass with inclusions of plant organs,the unstratified matrix rich bands comprise of fine detrital humicgroundmass having a homogeneous appearance. Visibly, these lignites
Table 5Summary of microlithotypes of lignites/low rank coal (proposed scheme ofclassification).
Maceral composition(mineral free)
Microlithotype Maceral groupcomposition(mineral free)
Microlithotypegroup
MonomaceralTH>95% Telo Humite H>95% HumiteDH>95% Detro HumiteGH>95% Gelo HumiteS>95% Sporite L>95% LiptiteA>95% AlgiteSf>95% Semifusite I>95% InertiteF>95% FusiteID>95% Inertodetrinite
BimaceralH+S>95% Sporoclarite H+L>95% Clarite
H, LH+Cu>95% CuticoclariteH+LD>95%H+M>95% H+I>95% Huminertite
H, IH+Sf>95%H+F>95%H+ID>95%I+S>95% Sporodurite I+L>95% DuriteI+LD>95% I, L
TrimaceralH, I, L>5% Duroclarite H>I, L Trimacerite
Huminertoliptite L>I, H H, I, LClarodurite I>H, L
Table 6Microlithotype analysis of Lower seam of Vastan Lignite samples, Gujarat.
Microlithotype B-1% B-2% B-3% B-4% B-5% B-6%
Humite 58.42 91.17 84.62 87.05 91.21 86.08Liptite 0.00 0.00 0.00 0.00 0.00 0.00Inertite 0.54 0.00 0.00 0.00 0.00 0.00Clarite-H 0.27 0.51 0.19 1.21 0.18 0.00Clarite-E 0.00 0.00 0.00 0.00 0.00 0.00Huminertite-H 2.17 0.85 7.12 4.15 4.58 2.58Huminertite-I 0.00 0.17 0.19 0.00 0.00 0.00Durite-I 0.00 0.00 0.00 0.00 0.00 0.00Durite-E 0.00 0.00 0.00 0.00 0.00 0.00Carbominerite 0.00 0.00 0.00 0.00 0.00 0.00Carbargilite 35.87 5.60 6.73 7.08 3.11 10.82Carbopyrite 0.54 0.17 0.19 0.35 0.00 0.26Carbankerite 0.00 0.17 0.00 0.00 0.18 0.00Carbosilicite 0.00 0.00 0.00 0.00 0.00 0.00Carbopolyminerite 2.17 1.36 0.96 0.17 0.73 0.26Total 100.00 100.00 100.00 100.00 100.00 100.00
Table 7Microlithotype analysis (carbominerite free basis) of Lower seam of Vastan Lignitesamples, Gujarat.
Microlithotype B-1 B-2 B-3 B-4 B-5 B-6
Humite 95.13 98.35 91.86 94.21 95.04 97.09Liptite 0.00 0.00 0.00 0.00 0.00 0.00Inertite 0.88 0.00 0.00 0.00 0.00 0.00Clarite-H 0.44 0.55 0.21 1.31 0.19 0.00Clarite-E 0.00 0.00 0.00 0.00 0.00 0.00Huminertite-H 3.54 0.92 7.72 4.49 4.77 2.91Huminertite-I 0.00 0.18 0.21 0.00 0.00 0.00Durite-I 0.00 0.00 0.00 0.00 0.00 0.00Durite-E 0.00 0.00 0.00 0.00 0.00 0.00Total 100.00 100.00 100.00 100.00 100.00 100.00
9P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
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Table8
Microlitho
type
analysis
ofUpp
erseam
ofVastanLign
itesamples,G
ujarat.
Microlitho
type
A-1%
A-2%
A-3%
A-4%
A-5%
A-6%
A-7%
A-8%
A-9%
A-10%
A-11%
A-12%
A-13%
A-14%
A-15%
A-16%
A-17%
A-18%
A-19%
Hum
ite
84.21
89.29
88.85
92.54
91.58
93.04
68.91
92.64
77.40
11.11
71.15
39.31
61.84
68.97
95.92
45.83
93.14
86.92
92.39
Liptite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Inertite
0.00
0.00
0.00
0.00
0.00
0.36
1.09
0.60
0.56
0.00
0.00
0.00
1.32
0.69
0.00
0.00
0.00
0.00
0.00
Clarite-H
0.17
1.04
0.35
0.20
0.18
0.54
0.18
0.00
0.56
33.33
0.00
0.00
0.00
2.76
0.00
0.00
0.00
0.00
0.00
Clarite-E
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.66
0.00
0.00
0.00
0.00
0.00
0.00
Hum
inertite-H
13.92
5.18
8.01
4.03
2.63
3.39
22.91
3.78
13.56
22.22
0.00
0.00
0.00
0.00
0.00
4.17
0.19
0.77
1.03
Hum
inertite-I
0.34
0.17
0.17
0.00
0.18
0.36
1.45
0.40
0.56
0.00
0.00
0.00
0.00
0.00
2.04
0.00
0.00
0.00
0.00
Durite-I
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Durite-E
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Carbom
inerite
Carbargilite
1.36
3.63
2.26
3.23
4.91
1.61
4.91
1.59
6.78
22.22
25.00
55.86
33.55
26.21
2.04
41.67
6.10
10.38
6.58
Carbop
yrite
0.00
0.00
0.00
0.00
0.18
0.18
0.00
0.20
0.00
0.00
0.00
1.38
0.00
0.69
0.00
0.00
0.19
0.00
0.00
Carban
kerite
0.00
0.35
0.00
0.00
0.00
0.54
0.00
0.20
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Carbosilicite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Carbop
olym
inerite
0.00
0.35
0.35
0.00
0.35
0.00
0.55
0.60
0.56
11.11
3.85
3.45
2.63
0.69
0.00
8.33
0.38
1.92
0.00
Total
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
Table9
Microlitho
type
analysis
((mmfba
sis)of
VastanLign
itesamples,G
ujarat.
Microlitho
type
A-1%
A-2%
A-3%
A-4%
A-5%
A-6%
A-7%
A-8%
A-9%
A-10%
A-11%
A-12%
A-13%
A-14%
A-15%
A-16%
A-17%
A-18%
A-19%
Hum
ite
85.37
93.32
91.23
95.63
96.85
95.25
72.88
95.10
83.54
16.67
100.00
100.00
96.91
95.24
97.92
91.67
99.80
99.12
98.90
Liptite
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Inertite
0.00
0.00
0.00
0.00
0.00
0.37
1.15
0.61
0.61
0.00
0.00
0.00
2.06
0.95
0.00
0.00
0.00
0.00
0.00
Clarite-H
0.17
1.08
0.36
0.21
0.19
0.55
0.19
0.00
0.61
50.00
0.00
0.00
0.00
3.81
0.00
0.00
0.00
0.00
0.00
Clarite-E
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.03
0.00
0.00
0.00
0.00
0.00
0.00
Hum
inertite-H
14.11
5.42
8.23
4.17
2.78
3.47
24.23
3.88
14.63
33.33
0.00
0.00
0.00
0.00
0.00
8.33
0.20
0.88
1.10
Hum
inertite-I
0.34
0.18
0.18
0.00
0.19
0.37
1.54
0.41
0.61
0.00
0.00
0.00
0.00
0.00
2.08
0.00
0.00
0.00
0.00
Durite-I
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Durite-E
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Total
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
10 P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
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have four bands viz. (i) stratified brown coal (ii) unstratified browncoal (iii) unstratified black coal and (iv) stratified black coal.
4.2. Petrographic composition
4.2.1. Maceral compositionFor petrography, 25 composite samples were subjected to detailed
maceral and microlithotype analyses. The results of maceral analysisare shown in Tables 1–4 while that of microlithotype is furnished in
Tables 6–9. The huminite reflectance (VRr) ranges from 0.24 to 0.31 intheUpper Seamand from0.25 to 0.30 in the Lower Seam that put themunder lignite/low rank coal. These lignites are dominated by maceralsof huminite group (Figs. 3–4) and the concentration of macerals ofliptinite and inertinite groups is small. The telohuminite anddetrohuminite are the major maceral sub-groups. Ulminite is thedominating maceral among telohuminite (Fig. 4e) whereas amongdetrohuminite, both attrinite (Fig. 3a) and densinite have beenobserved. The gelohuminite is mainly represented by pseudo-phlobaphinite followed by phlobaphinite (Fig. 4a). Gelinite is literallyabsent but a few samples have recorded their presence in very smallamount (Fig. 4d). The liptinites, are represented by suberinite, (Fig.4a), resinite, sporinite, cutinite and liptodetrinite and are recorded invery small concentrations. There are several amber/fossil resin richlayers having insects preserved in them are reported in the lowermostsections of the seam (Alimohammadian et al., 2005; Kraemer andEvenhuis, 2008; Kraemer and Wagner, 2009). However, they are notuniformly distributed and under microscope they have been observedin small amount. Some of the resinites show an oval shape (Fig. 3h).Mallick et al. (2009) have carried out the pyrolytic and spectroscopicstudies of resins fromVastanmine. The cortex cell lumens of suberiniteare filledwith phlobaphinite and sometimeswith argillaceousmineralmatter. Similarly, among the inertinite group ofmacerals, the observedones are fusinite, semi-fusinite, (Fig. 4c), secretinite, inertodetriniteand macrinite. The cell lumens of fusinite are often filled up withargillaceous mineral matter. The funginites have been found to occurindividually as well as in clusters(Fig. 3b, c).
4.2.2. MicrolithotypeThe microlithotypes are useful to decipher the type of facies for
better understanding the paleodepositional conditions. Schneider(1995) has discussed the usefulness of the scheme of lignitemicrolithotypes proposed by Sontag et al. (1965) and Schneider(1980) for Central European brown coals. However, these micro-lithotype classifications are complicated. The microlithotype classifi-cation scheme (proposed) has been considered for the facies study ofVastan lignites (Table 5). The dominating microlithotype is humitewhich is followed by huminertite and clarite (Tables 6–9).
Table 10Proximate components of Vastan lignite.
SampleNo
Moisture%
Ash%
Volatilematter %
Fixedcarbon %
VM(daf)
FC(daf)
VRr
B1 15.13 17.52 47.01 20.34 69.79 30.21 0.27B2 22.31 10.95 43.42 23.32 65.05 34.95 0.3B3 23.7 6.75 30.75 38.8 44.21 55.79 0.25B4 17.33 6.57 32.01 43.91 42.06 57.94 0.28B5 17.72 5.76 33.92 42.6 44.32 55.68 0.3B6 14.94 11.92 39.96 33.18 54.63 45.37 0.29Mean 18.52 9.91 37.85 33.69 53.34 46.66 0.28A1 11.95 4.18 48.60 35.27 57.94 42.06 0.28A2 10.43 3.57 50.00 36 58.13 41.87 0.28A3 11.95 3.57 56.37 28.11 66.72 33.28 0.27A4 11.61 4.18 48.31 35.9 57.36 42.64 0.29A5 14.21 3.18 52.92 29.69 64.06 35.94 0.27A6 11.35 3.18 54.11 31.36 63.30 36.7 0.26A7 13.91 3.58 58.85 23.66 71.32 28.68 0.26A8 7.18 4.37 55.17 33.28 62.40 37.6 0.28A9 13.54 5.17 52.19 29.1 64.23 35.77 0.30A10 5.8 27.2 52.76 14.24 78.74 21.26 0.27A11 9.16 28.4 46.81 15.63 74.96 28.04 0.31A12 10.33 25.29 40.06 24.32 62.22 37.78 0.27A13 8.34 26.24 52.21 13.21 79.80 20.2 0.26A14 7.58 28.03 47.40 16.99 73.61 26.39 0.28A15 6.26 40.35 42.72 10.67 80.01 19.99 0.35A16 11.95 47.21 28.48 12.36 69.73 30.27 0.32A17 20.31 8.96 40.44 30.29 57.17 42.83 0.31A18 17.36 15.5 41.20 25.94 61.36 38.64 0.24A19 7.96 15.13 45.42 31.49 59.05 40.95 0.28Mean 11.11 15.65 48.11 25.13 66.43 33.73 0.28
Table 11Ultimate analysis of Vastan lignite.
Sample No Carbon % Hydrogen % Nitrogen % Oxygen % Sulphur % Carbon % (daf) Hydrogen % (daf) Nitrogen % (daf) Oxygen % (daf) Sulphur % (daf)
B1 44.97 5.25 0.85 28.94 2.47 66.77 7.80 1.26 20.50 3.67B2 45.78 5.19 0.91 35.77 1.40 68.59 7.78 1.36 20.17 2.10B3 46.39 5.66 0.88 39.59 0.73 66.70 8.14 1.27 22.85 1.05B4 49.21 5.48 0.84 36.13 1.77 64.66 7.20 1.10 24.70 2.33B5 44.10 4.83 0.41 43.82 1.08 57.63 6.31 0.54 34.11 1.41B6 43.34 4.79 0.48 37.37 2.10 59.26 6.55 0.66 30.67 2.87Mean 45.63 5.20 0.73 36.94 1.59 63.94 7.30 1.03 25.50 2.24A1 57.95 5.25 0.88 31.66 0.08 69.10 6.26 1.05 23.50 0.10A2 56.28 5.13 0.90 34.03 0.09 65.44 5.97 1.05 27.44 0.10A3 52.03 5.55 0.77 37.89 0.19 61.59 6.57 0.91 30.71 0.22A4 52.41 5.22 0.46 37.73 0.00 62.24 6.20 0.55 31.02 0.00A5 56.90 5.22 0.97 33.32 0.41 68.88 6.32 1.17 23.13 0.50A6 54.37 5.17 0.85 36.41 0.02 63.61 6.05 0.99 29.32 0.02A7 55.71 5.18 0.90 34.14 0.49 67.52 6.28 1.09 24.52 0.59A8 53.79 5.07 0.99 35.00 0.78 60.81 5.73 1.12 31.45 0.88A9 56.87 5.71 0.92 30.92 0.41 69.96 7.02 1.13 21.38 0.50A10 37.23 4.57 0.79 29.69 0.52 55.57 6.82 1.18 35.66 0.78A11 48.28 4.87 0.95 16.92 0.58 77.32 7.80 1.52 12.43 0.93A12 46.91 5.11 0.77 21.39 0.53 72.86 7.94 1.20 17.18 0.82A13 36.87 4.15 0.71 31.61 0.42 56.36 6.34 1.09 35.57 0.64A14 37.15 4.49 0.53 29.47 0.33 57.70 6.97 0.82 34.00 0.51A15 25.41 3.99 0.35 29.72 0.18 47.59 7.47 0.66 43.94 0.34A16 26.40 3.64 0.49 21.39 0.87 64.64 8.91 1.20 23.11 2.13A17 48.32 5.14 1.04 36.21 0.33 68.32 7.27 1.47 22.48 0.47A18 47.22 5.29 0.79 30.46 0.74 70.33 7.88 1.18 19.51 1.10A19 49.78 5.02 0.59 29.06 0.42 64.73 6.53 0.77 27.43 0.55Mean 47.36 4.94 0.77 30.90 0.39 64.45 6.86 1.06 27.04 0.59
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4.2.3. Mineral matterThe mineral matter occurs in variable quantity. It is dominated by
argillaceous mineral while sulphides and carbonates occur in lesseramounts. However, some samples do record the presence of sulphidesin noticeable amount. The sulphides are represented by pyrite whichoccurs as cavity filling (Fig. 3a), massive replacement (Fig. 3e, f) and asframboids (Fig. 3d). The framboids occur both as individual spheres aswell as in clusters. The carbonates are chiefly represented by siderites(Fig. 3g).
4.3. Chemical composition
Vastan lignite is characterized by variable ash content. The Upperseam has 3.18 to 47.21%, (av 15.65%)while the Lower seam has 5.76 to11.92%, (av 9.91%) of ash content. The moisture content is relativelyhigh (av. 18.57% in Lower seam and 11.11% in Upper seam) while thevolatile matter content is moderately high (av 37.85% in Lower seamand 48.11% in Upper seam) and fixed carbon is 33.69% in Lower seamand 25.13% in Upper seam (Table 10). The ultimate analysis (Table 11)shows that carbon ranges from 43.34 to 49.21, av 45.63% in the Lowerseam and from 25.41 to 57.95, av 47.31% in Upper seam. The Lowerseam has a little high sulphur content which varies between 0.73%and 2.47%, (av 1.59%) but has relatively low concentration (between0.02 and 0.87, av 0.39%) in Upper seam.
4.4. Paleomire of peat
Macerals are dependent on plants and environment and may beused to appreciate the characteristics of paleomire. The degree ofhumification of plant tissues and the type of vegetation can bedeciphered through Tissue Preservation Index (TPI) because of thedifference between less humified structures and strongly humifiedunstructured tissue derived macerals (Diessel, 1992). High TPI issuggestive of either a high subsidence rate of the basin or a dominanceof wood derived tissues. While low TPI advocates a low subsidencerate of the basin with enhanced humification or a predominance ofherbaceous vegetation in the paleomire (Diessel, 1992).
Gelification Index (GI) indicates the degree of gelification ofhuminite macerals and allows differentiating between gelified andungelified macerals. It is a function of water level of the mire and ahigh gelification results during high water level.
The GI and TPI given by Kalkreuth et al. (1991) and Flores (2002)for low rank coals has been followed to decipher the paleodeposi-tional conditions of Vastan lignite. The indices are as follows:
GI = ðulminite + corpohuminite + gelinite + macriniteÞ= ðsemifusinite + fusinite + inertodetrinite + textinite+ attrinite + densiniteÞ
TPI = ðtextinite + corpohuminite + fusinite + semifusiniteÞ= ðulminite + gelinite + macrinite + attrinite + densiniteÞ
The study advocates that Vastan lignite deposited in limnicenvironment under a medium to very high water cover (Fig. 5) asindicated by high GI values (0.43 to 4.59; av. 2.79 in Lower seam and
Fig. 5. Coal facies deciphered from gelification Index (GI) and the Tissue Preservation Index (TPI) in relation to depositional setting and type of mire for Vastan Lignite.After Diessel, 1992).
Table 12Details of GI, TPI, VI and GWI in Vastan lignite, Gujarat.
Sl No Sample no GI TPI GWI
1 B1 0.43 0.12 0.822 B2 4.59 0.11 0.143 B3 3.4 0.08 0.134 B4 3.41 0.14 0.15 B5 3.36 0.07 0.086 B6 1.56 0.11 0.327 Mean 2.79 0.11 0.278 A1 6.61 0.12 0.059 A2 2.78 0.3 0.0810 A3 2.75 0.33 0.0711 A4 1.82 0.29 0.0712 A5 5.33 0.15 0.113 A6 7.17 0.12 0.0514 A7 1.86 0.43 0.115 A8 2.45 0.19 0.1216 A9 0.33 0.14 0.1917 A10 0.45 0.08 1.4418 A11 0.20 0.11 2.0419 A12 0.19 0.04 1.020 A13 0.28 0.09 0.7321 A14 0.37 0.19 1.0222 A15 0.38 0.08 3.0223 A16 0.26 0.12 7.0924 A17 1.38 0.09 0.0425 A18 0.56 0.15 0.5926 A19 1.76 0.09 0.0827 Mean 1.94 0.16 0.94
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0.26 to 7.17; av. 1.94 in Upper seam, Table 12). The contention isfurther supported by another facies-critical maceral associationmodel(Fig. 6) which is modified after Mukhopadhyay (1986). The plotindicates that the Vastan lignites originated partly under mildly oxicto anoxic forest swamp with good tissue preservation and partlyunder reed marsh with increasing bacterial activity.
A model based on microlithotype composition has been suggested(Fig. 7). For this purpose, themicrolithotype analysis of lignite is carriedout (Tables 6–9) based on a proposed scheme of classification (Table 5).
This model favours the development of Vastan lignite under wet moorcondition resulting to anaerobic preservation of organic material andincreasing bacterial activity during moderate flooding. The occurrenceof framboidal pyrite in these lignites supports this contention and isindicative of sulphur bacteria and an anaerobic condition in thepaleomire. A negative correlation (r=−0.77 in the Lower seam andr=−0.52 in the Upper seam) between sulphur and gelification in theVastan lignites advocates that gelification is mainly controlled by thewet conditions prevailing in the paleomire and not by the pH conditions
Fig. 6. Ternary diagram illustrating facies- critical maceral associations in Vastan lignites and suggested peat forming environments.Modified from Mukhopadhyay (1986).
Fig. 7. Peat forming environment suggested for Vastan Lignite, based on microlithotype D— wet moor with moderate flooding and increasing bacterial activity, E— oxic moor withprolong dry condition, F — wet moor with high flooding.
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(Fig. 8a i and iii). However, there exists a positive correlation (r=0.72)between sulphur and Tissue Preservation Index (TPI) in the lower seambut a low negative correlation (r=−0.23) in the upper seam (Fig. 8a iiiand iv). Ground Water Index (GWI) as calculated for these lignitesranges from 0.08 to 0.82 in Lower seam and from 0.05 to 3.02 in Upperseam (Table 12). Sulphur maintains a positive correlation (r=0.98 inLower seam and r=0.47 in Upper seam) with Ground Water Index(GWI) in both the seams (Fig. 8a v and vi) and also with ash content(r=0.81 in the Lower seam and r=0.41 in the Upper seam) (Fig. 8b iand ii). This positive correlation between ash and sulphur is seenparticularly in the upper and lower portions of the Lower Lignite seamand is less pronounced in the middle portion of the seam. It indicatesthat theflowingwater raised the pHvalue bydiluting humic acids in theupper and lower portions. Carbonate rich surface water further raisedthe pH value and is responsible for high sulphur content.
5. Conclusions
The Vastan lignites have a complex Petrographic composition andconsist of most of the macerals of the three Maceral groups —
huminite, liptinite and inertinite. However, there is a definitedomination of huminite group of macerals over the rest two groupsand is mainly represented by telohuminite and detrohuminite.Ulminite dominates among telohuminite while attrinite and densinitecontributemainly to detrohuminite. Liptinite and inertinite groups arerecorded in small concentrations. Funginites have been recorded bothas individual and also in clusters. Among microlithotypes, humitedominates over the other ones. The inorganic components are mainlyrepresented by argillaceous mineral matter while the carbonates andsulphides are recorded in lesser concentrations. The pyrite framboidsoccur both as individual spheres and also in clusters.
Fig. 8. a) Relationship of sulphur with GI, TPI and GWI in Lower and Upper Lignite seams. b) Relationship of sulphur with Ash content and relationship between TPI and GWI in Lowerand Upper Lignite seams.
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These lignites are chemically characterized by high moisturecontent, moderately high volatile matter and variable concentrationof ash. The fixed carbon and the elemental carbon show a moderateconcentration. The sulphur content is more in the Lower seamwith anaverage content of 1.59%.
The study reveals that these lignites originated under mediumhigh water cover in limnic environment which resulted into ananaerobic preservation of the organic matter with increasing bacterialactivity. Besides, there are evidences of partly mildly oxic to anoxicforest swamp with good tissue preservation. Sulphur is seen tomaintain an increasing trend with ash content particularly in thelower and upper portion of Lower Lignite seam. This demonstratesthat the inflowing water raised the pH value of the paleomire whichwas further raised by carbonate rich surface water and wasresponsible for high sulphur content in these lignites.
Acknowledgements
The authors are thankful to the Head, Department of Geology, BHU,Varanasi, India, for extending the facilities. We sincerely thank theofficials of Vastan lignite mine for extending their help to Mr ManojKumar, our student, in collecting the lignite samples from the mine.We thank our colleague, Mr A. S. Naik, for reading the earlier versionof this paper. The financial support received from SAP, UGC,Government of India, to carryout ultimate analysis, is thankfullyacknowledged which is carried out at CDRI, Lucknow, Uttar Pradesh.
References
Alimohammadian, H., Sahni, A., Patnaik, R., Ran, R.S., Singh, H., 2005. First record of anexceptionally diverse and well preserved amber-embedded biota from LowerEocene (52 Ma) lignites, Vastan, Gujarat. Current Science 89 (8), 1328–1330.
Balasubramanyan, M. N., 2006. Geology and Tectonics of India: An overview.International Association for Gondwana Research, Memoir 9, 204 p.
BIS, 2003. Methods of test for coal and coke (2nd revision of IS: 1350). Part I, Proximateanalysis. Bureau of Indian Standard, 1–29.
Biswas, S.K., 1987. Regional tectonic framework, structure and evolution of the westernmarginal basins of India. Tectonophysics 135, 307–327.
Diessel, C.F.K., 1992. Coal Bearing Depositional Systems. Springer-Verlag, Berlin. 721p.Flores, D., 2002. Organic facies and depositional palaeoenvironment of lignites from Rio
Maior Basin (Portugal). International Journal Coal Geology 48, 181–195.Garg, R., Ateequzzaman, K., Prasad, V., Tripathi, S.K.M., Singh, I.B., Jauhri, A.K., Bajpai, S.,
2008. Age-diagnostic dinoflagellate cysts from the lignite bearing sediments of theVastan lignite mine, Surat district, Gujarat, Western India. Journal of Palaeonto-logical Society of India 53 (1), 99–105.
International Commitee forCoal and Organic Petrology, 2001. The new inertiniteclassification (I.C.C.P. System 1994). Fuel 80, 459–471.
International Committee for Coal and Organic Petrology, 2005. Classification ofhuminite (ICCP System 1994). International Journal of Coal Geology 62, 85–106.
Joshi, V.K., 2007. Pages of Past Environment entombed in a mine. www.boloji.com/environment/121.htm.
Kalkreuth,W.D.,Marchioni,D.L., Calder, J.H., Lamberson,M.N.,Naylor,R.D.,Paul, J., 1991. Therelationship between coal petrography and depositional environments from selectedcoal basins in Canada. In: Kalkreuth, W.D., Bustin, R.M., Cameron, A.R. (Eds.), RecentAdvances in Organic Petrology and Geochemistry. A Symposium honouring Dr. P.Hacquebard: International Journal of Coal Geology, vol. 19, pp. 21–76.
Kraemer, M.M.S., Wagner, R., 2009. The first psychodid (Diptera: Psychodidae:Phlebotominae) species from the Lower Eocene amber of Vastan, Gujarat, India.Zootaxa 2152, 63–68.
Kraemer, M.M.S., Evenhuis, N.L., 2008. The first keroplatid (Diptera: Keroplatidae) speciesfrom the Lower Eocene amber of Vastan, Gujarat, India. Zootaxa 1816, 57–60.
Mallick, M., Dutta, S., Greenwood, P.E., Bertram, N., 2009. Pyrolytic and spectroscopicstudies of Tertiary resin from Vastan lignite mine, Cambay basin. Western India.Geological Society of India 74, 16–22.
Mandal, J., Guleria, J.S., 2006. Palynology of Vastan lignite (Surat district), Gujarat: itsage, palaeoecology and depositional environment. Palaeobotanist 55, 51–66.
Mathur, L.P., Rao, K.L.N., Chaube, A.N., 1968. Tectonic framework of the Cambay Basin,India. Bulletin of Oil & Natural Gas Commission, India. 51, 7–28.
Mishra, H.K., Ghosh, R.K., 1996. Geology, petrology and utilization potential of someTertiary coals of the northeastern region of India. International Journal of CoalGeology. 30, 65–100.
Mukhopadhyay, P.K., 1986. Petrography of selected Wilcox and Jockson Group lignitesfrom Tertiary of Texas. In: Finkelman, R.B., Casagrade, D.J. (Eds.), Geology of Gulf CoastLignites. 1986, Annu.Meet. Geological Society of America, Coal Geology Division, FieldTrip, pp. 126–145.
Fig. 8 (continued).
15P.K. Singh et al. / International Journal of Coal Geology 82 (2010) 1–16
Author's personal copy
Navale, G.K.B., Mishra, B.K., 1980. Systematic study of organic micro-constituents of themain seam of Neyveli Lignite, south India. Geophytology 10, 245–264.
Pareek, H.S., 1970. A note on the microscopic study of Nichahom Lignite, Kashmir.Journal of Mines Metals and Fuels 18 (3), 103–104.
Pareek, H.S., 1981. Petrology of Kalol lignite, Cambay basin, Gujarat. Symposium onThree Decades of development in Petrology, Mineralogy and Petrochemistry inIndia. Geol. Surv. India, Jaipur, Abstracts, pp. 106–107.
Pareek, H. S., 2004. Progress of coal Petrology in India. Memoir, Geological Society ofIndia, 161 p.
Raju, A.T.R., 1968. Geological evolution of the Assam and Cambay Tertiary basins ofIndia. American Association of Petroleum Geology Bulletin 52 (12), 2422–2437.
Raju, A.T.R., Srinivasan, S., 1983. More hydrocarbon from well explored Cambay basin.Petroleum As & Z. 6, 25–35.
Raju, A.T.R., Srinivsan, S., 1993. Cambay basin-petroleum habitat. In: Biswas, S.K., et al.(Ed.), Proc. 2nd Seminar on Petroliferous Basins of India, Vol. 2. Indian Petroleum,Dehradun, pp. 33–78.
Rana, R.S., Kumar, K., Singh, H., 2004. Vertebrate fauna from the subsurface Cambayshale (Lower Eocene), Vastan Lignite Mine, Gujarat, India. Current Science 87(12), 1726–1733.
Sahni, A., Saraswati, P.K., Rana, R.S., Kishor, K., Singh, H., Alimohammadian, H.,Sahni, N., Rose, K.D., Singh, L., Smith, T., 2006. Temporal constraints anddepositional paleoenvironmnets of the Vastan lignite sequences, Gujarat:analogy for Cambay shale hydrocarbon source rock. Indian Journal of PetroleumGeology 15, 1–20.
Saxena, R.K., 1979. Palynology of the Matanomadh Formation in type area, north-western Kutch, India: Part 2. Systematic description of gymnospermous andangiospermous pollen grains. Palaeobotanist 26, 130–143.
Schneider, W., 1980. Mikropaliiobotanische Faziesanalyse in der Weichbraunkohle.Neue Bergbautechnik 10, 670–675.
Schneider, W., 1995. Palaeohistological studies on Miocene brown coals of CentralEurope. International Journal of Coal Geology. 28, 229–248.
Sharma, D.D., 2003. Review of coal resources in India and their exploration strategy.Journal of Geological Society of India 61, 387–402.
Shukla, M., Kumar, P., Prakash, A., Srivastava, G.P., Kumar, M., 2000. Resin embeddedinsects and other organic remains from Warkalli Formation, Kerala coast, India.Journal of Geological Society of India 56 (3), 315–319.
Singh,M.P., Singh, G.P., 1995. Petrological evolution of the Paleogene coal deposits of Jammu,Jammu and Kashnir, India. International Journal of Coal Geology 27, 171–199.
Singh, A., Singh, B.D., 2005. Petrology of Panandhro lignite deposit, Gujarat in relation topalaeodepositional condition. Journal of Geological Society of India 66, 334–344.
Sontag, E., Tzschoppe, E., Christoph, H.J., 1965. Beitrag zur mikropetrographischenNomenklatur and Analyse der Weichbraunkohle. Zeitschrift für AngewandteGeologie 11, 647–658.
Taylor, G.H., Teichmüller, M., Davis, A., Diessel, C.F.K., Littke, R., Robert, P., 1998. OrganicPetrology. Gebrüder Borntraeger, Berlin, Germany. 704 p.
Thielemann, T., Schmidt, S., Gerling, J.P., 2007. Lignite and hard coal: Energy suppliersfor world needs until the year 2100 — an outlook. International Journal of CoalGeology 72, 1–70.
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