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sanidine, and other minor phases, at pressures of 0.1
1.0 GPa, indicating discrete,
-
pressure-speci
c fractionation events. According to Coban and Flower (2006) the
Bucak silica poor
lamproites were probably generated by partial melting of
phlogopite-bearing, refractory peridotite at pressures of 1.5
'
leucite
'
2 GPa, higher than those
-
proposed for SiO
2
-saturated
1.5 GPa) from Afyon,
located to the North of this locality. The depth (total pressure) of melt segregation
probably dominates over volatile partial pressures (e.g. of CO
2
,F,H
2
O) in deter-
mining the SiO
2
-undersaturated character of the Bucak magmas.
'
phlogopite
'
lamproites (1
-
4.1.4 Potassium-Rich Lamprophyres and Lamproites
from Bokaro, Jharia and Raniganj Basins, East India
Phlogopite-bearing ma
c dykes and sills are often found to intrude
into a sedimentary rock sequence (Upper Carboniferous to middle Triassic) of the
Bokaro, Jharia and Raniganj basins located in the eastern part of India (Fig.
4.3
).
The sedimentary sequence consists of alternating rock types of sandstone and shale
along with coal-bearing seams (Lower Gondwana formation). This sequence
occupies tectonic troughs with E
c and ultrama
-
W trending fault boundaries.
4.1.4.1 Bokaro Basin
Petrological and geochemical studies of the K-rich lamproitic and lamprophyric
rocks from the east Bokaro Coal
eld of Bihar was studied by Basu et al. (1997).
They found altogether thirty dykes ranging in thickness between 0.3 and 12 m and
in strike length extending from few metres to more than 2.5 km.
Fig. 4.3 Distribution of
Gondwana basins in Damodar
valley coal
field (Ghosh and
Mukhopadhyay 1985)
88
0
84
0
86
0
25
0
25
0
Karanpura
basin
Bokaro
basin
Raniganj
basin
Ramgarh
basin
Jharia
basin
23
0
23
0
DAMODAR VALLEY
COAL BASINS
CALCUTTA
84
0
86
0
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