Neogene (?) subbitu
minous carbonaceous shale deposits fro
m Chalāw, Afghanistan, were investigated through organic petrology techniques and standard coal analyses to deter
mine paleoenviron
ment and potential for resource utilization. The Chalāw deposit, approxi
mately 30 k
m southeast of Kabul, currently is exploited for brick
making and do
mestic heating and cooking. Three
multiple-bench channel sa
mples of the
mined bed at Chalāw were collected and evaluated. The presence of significant hu
minite (ranging fro
m 0.2 to 59.0 vol. % ,
mineral-inclusive basis) is suggestive of a terrestrial lignin-rich precursor plant
material. Measured reflectance values of 0.38–0.55 % indicate subbitu
minous rank. This rank suggests burial depths of approxi
mately 1500
m and
maxi
mu
m te
mperatures of approxi
mately 50 °C. Structured liptinite
macerals generally are absent except for so
me fluorescing
morphologies interpreted to be poorly-preserved root cork suberinite. Sponge spicule bioliths including ge
mmoscleres and
megascleres are co
mmon. These petrographic observations, in addition to high
mineral
matter content (33 to > 95 vol. % ),
mediu
m to high sulfur content (2.1–11.5 wt. % , dry basis; db), and the presence of co
mmon gastropod? shell frag
ments and an aragonite-needle chalk bed are consistent with, but not directly indicative of, a
marginal
marine or estuarine
mangrove depositional environ
ment. However, additional data are necessary to confir
m this hypothesis and deposition in a freshwater environ
ment cannot be ruled out at this ti
me.
Commercial-scale development and utilization of the Chalāw deposit as a thermal fuel resource may be possible using a fluidized bed combustion system which could accept the low-quality mine product currently produced. Samples examined herein contain high-ash yield (45–90 wt. % , db), high total moisture content (17–39 wt. % ), low calorific value (980–6860 Btu/lb, m,mmf), and have poor agglomerating properties (FSI = 0), consistent with fuels utilized in fluidized bed combustors. However, delineation of the extent of the deposit through field investigation will be necessary to make a quantified resource estimate for mine planning.