Page 311 - Introduction to Mineral Exploration

294 M.K.G. WHATELEY
13

Soma Lignite Basin, Turkey

Michael K.G. Whateley

13.1 INTRODUCTION data form the basis for any investigation into
the resource potential of a coal deposit.
The variables in a coal deposit (quality, thick- The quality of a coal deposit must be
ness, etc.) are a function of the geological envir- assessed. This is undertaken by sampling out-
onment. Excellent descriptions of all aspects of crops, borehole cores (Whateley 1992), mine
coal deposits and the assessment of these de- faces, etc. (section 10.1.3), and sending the coal
posits are given by Ward (1984), Scott (1987), to the laboratory. The coal is subjected to
and Whateley and Spears (1995). Coal or lignite proximate analyses to determine the moisture,
is a heterogenous, organoclastic sedimentary ash, volatile, and fixed carbon contents (Ward
rock mainly composed of lithified plant debris 1984). Additional tests which are often re-
(Ward 1984), which was deposited in layers and quested are sulfur content, calorific value (CV),
may have vertical and lateral facies changes. and specific gravity (SG). The quality of coal
These changes reflect variations in vegetation will determine the end use to which it is put,
type, climate, clastic input, plant decomposi- e.g. steam coal to be burnt in a power station
tion rates, structural setting, water table, etc. to generate electricity or metallurgical coal for
Coal originated as a wet spongy peat, which steel making, although other uses are possible.
after burial underwent compaction and Since the energy crisis caused by the OPEC
diagenesis (coalification). The coalification oil price rises which started in 1973, there has
process proceeds at different rates in different been a worldwide increase in the search for
structural settings. Coal which has been sub- alternative fossil fuels. Lignite, bituminous
jected to low pressure and temperature is re- coal, and anthracite are important sources of
ferred to as a low rank coal, such as lignite. energy. The exploration for and exploitation of
Coal which has been subjected to high pressure these fuels is important for developing coun-
and temperature is referred to as a high rank tries which wish to reduce their reliance on
coal, such as anthracite. Bituminous coal is imported oil by building coal-fired power
a medium rank coal. Thus the properties of stations at or near their own coal mines.
coal are almost entirely a reflection of the In 1982 Golder Associates (UK) Ltd (GA)
original depositional environment and dia- undertook a World Bank funded feasibility
genetic history. study of the Soma Isiklar lignite deposit in
Some of the properties of coal depend on western Turkey (Golder Associates 1983) for
the nature of the original plant material or the state-owned coal company Turkiye Komur
macerals (Stach 1982, Cohen et al. 1987). These Isletmeleri Kurumu (TKI). The lignite from the
properties are measured using microscopic Soma Mine was used as feedstock for the age-
techniques. Large scale, subsurface changes ing 44 MW Soma A Power Station. It was
are determined by studying the lithology of the the intention to increase the mine production
−1
coal and coal-bearing strata in borehole cores from 1.0 to 2.5 Mt yr , 2.0 Mt of which were
and down-the-hole geophysical logs. These to come from the expanded surface mine. The