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Geology
Geology
Coal deposits in Mongolian were formed during the Carboniferous, Permian, Jurassic and Cretaceous periods. Permian coal deposits, such as those at Baruun Naran and Tavan Tolgoi, contain the highest quality coal and generally only occur in the southern part of Mongolia.
Most Permian sedimentary strata in southern Mongolia, including the coal-bearing rocks at Baruun Naran, are indicative of non-marine depositional environments, including fluvial and swamp facies, and were deposited in local intermontane basins.
Local Geological Setting
The Baruun Naran coal deposit is hosted in a thick sequence (>800 m) of Upper Permian clastic sedimentary rocks known as the Tavan Tolgoi Formation. This formation also hosts the adjacent large Tavan Tolgoi coking and thermal coal deposit, located approximately 20 km to Baruun Naran’s northeast.
The ENE-trending belt of Tavan Tolgoi Formation that crops out in the Baruun Naran valley represents the western continuation of the Ulaan Nuur coal basin (Baruun Naran NI 43-101 Resource Statement, June 2006).
Stratigraphy
Drilling to date has defined at least eleven major coal seams ranging from 3.8 m to 18.6 m in thickness, as well as an additional thirteen thinner or less well explored seams (Average true seam thickness for these seams ranges from 1.3 m to 18.6 m).
Trenching, geophysical data, and drilling results suggest that additional seams may occur to the west and south of the area currently being targeted at Baruun Naran.
At the nearby Tavan Tolgoi deposit, the same formation exhibits a similar stratigraphic thickness (approximately 965 m) and contains 16 coal seams.
| Baruun Naran Stratigraphic column (Tavan Tolgoi Formation) |
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Structural Geology
The dominant structural feature at Baruun Naran is a large ENE-trending fold referred to as the Baruun Naran syncline. The synclinal fold in the Baruun Naran valley is asymmetrical, with a steep northern limb and a more gently-dipping southern limb. The syncline is well defined by closely-spaced drilling and geophysical data.
Detailed drilling along grid lines as close as 150 m apart has been carried out along both limbs of the syncline over much of the eastern half of the coalfield.
Several faults have been identified on both the northern and southern flanks of the syncline, in some cases repeating large sections of the coal-bearing strata.
The combination of drilling as well as aerial and down-hole geophysical data demonstrates consistent seam correlation both across and along both flanks of the eastern end of the Baruun Naran syncline. This suggests that, whilst the sequence is strongly folded and several large faults are present, overall the strata represent a coherent sequence. Individual seams are traceable along strike for distances of over 3 km, without apparent major structural disturbance.
| Resistivity Gradient Array and coal seam traces and subcrops (plan view) |
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| Geological cross section – Section 36450 E |
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| Geological cross section – Section 33600 E |
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introduction | coal in mongolia | baruun naran | geology | coal quality | 
