Summary:
Regional Geology
The Soumber Coal Project is structurally situated along the arcuate, east-west-trending, moderately dipping Nariin Sukhait thrust fault, approximately 25 km east of the Ovoot Tolgoi Coal Mine.
The coal seams at Central Soumber, East Soumber, Biluut, and Jargalant are located within the Deliin Shand suite, which is estimated to have a thickness of up to 1,300 m in the Ovoot Khural Basin (RPM, 2013). The Deliin Shand suite is characterized by a sedimentary sequence consisting of claystones, siltstones, sandstones, conglomerates, and coal layers. These coal deposits are situated along the Nariin Sukhait thrust fault, indicating tectonic changes that have resulted in highly variable sedimentary partings and locally thick coal layers. that the drillhole interception suggested that there exists a substantial coal-bearing sequence in the central portion of the deposit, which is predominantly covered by the Quaternary and recent alluvium.
Coal-bearing Sequences
The coal seams of the Coal Project were hosted in the Deliin Shand suite, which is a sedimentary sequence consisting of intercalated claystones, siltstones, sandstones, conglomerates and coal seams. The sedimentary sequence is exposed along the trend of the Nariin Sukhait thrust fault. However, the coal-bearing sequence is largely covered by the Quaternary and recent alluvium, which makes it less accessible for direct observation. Near Soumber and Biluut concessions, the exposed sequences indicate the deposition of various geologic sequences occurred during the Permian, Triassic, Jurassic, and Quaternary periods. These sequences represent different periods of geologic history and contribute to the overall stratigraphy and geological framework of the area.
The coal-bearing sequence of the Soumber concession has a roughly rectangular shape with dimensions of approximately 12 km in length from east to west and 2 km in width from north to south. On the other hand, the coal-bearing sequence of Biluut and Jargalant field has a longer strike length of approximately 25 km.
The overburden and interburden lithotypes are mainly composed of fine to coarse-grained sediments. These lithotypes are generally moderately hard to slightly soft in texture. In the core logs, it was observed that thin zones containing pyrite and siderite exhibited relatively higher hardness compared to most rock types that do not bear coal. Below the main coal seam, there exists a distinctive red marker bed that serves as a valuable correlation tool. This red marker bed, with its characteristic color, allows an easier identification and correlation of geological layers within the deposit.
The work conducted by Norwest in 2007 at Soumber delineated a total of seven coal seams which were labeled as S6 (top) through S0 (base). Among these seams, S4 was determined to be the main seam, exhibiting a stronger continuity compared to the others and containing most of the coal resource. The S1 and S2 seams varied considerably in both thickness and quantity of in-seam partings but contribute locally to the coal resource. The S0 seam was encountered in several drill holes but did not indicate any significant coal resources. Norwest's interpretation of the coal seam sequence suggested that it repeats three times, likely due to the presence of two major east-west trending faults. These faults are believed to have caused the repetition of the sedimentary sequence, resulting in multiple occurrences of the coal seams within the deposit.
After the exploration programs conducted in 2010 and 2011, McElroy-Bryan Geological Service ("MBGS") performed a reinterpretation of the stratigraphy of the Soumber concession, which unveiled the presence of six major seams (labeled from 0 to 5) and two minor seams (labeled 6 and 7). These seams have been further divided into plies, considering the presence of stone partings within the seams. Among the identified seams, Seam 2 holds approximately 40% of the total coal resources. On average, this seam has a thickness of 5.9 m. Contrary to Norwest's interpretation, MBGS believes that the two east-west faults proposed by Norwest do not actually exist and that the seams can be correlated throughout the area using downhole geophysics, suggesting that there is no need to have these faults to explain the distribution and continuity of the coal seams.
It is worth noting that MBGS's assessment challenged the existence of the two east-west faults as interpreted by Norwest in 2007. Instead, they proposed that the coal seams can be correlated throughout the area with the assistance of downhole geophysics, suggesting that the continuity and connectivity of the seams can be established using geophysical data collected from drillholes. This re-interpretation of the stratigraphy and the proposed seam correlation throughout the area are important considerations in the understanding of the coal resources.
Coal Quality
The earlier exploration program driven by the former Soviet-Mongolian government (Dashkhoral et al., 1992) suggested that the coal was of the GJO and IGJO groups, based on the Soviet standards, equivalent to high-volatile bituminous coals using ASTM Standard D388. Generally, the coal in Nariin Sukhait region also exhibits low inherent moisture content, typically less than 2%. Low moisture content is beneficial as it reduces the energy required for drying the coal and improves its calorific value.
The coal resources in the Nariin Sukhait region are generally characterized by low ash content, low sulfur content, low inherent moisture and varying Free Swelling Index ("FSI") values, indicating both non-coking (<2 FSI) and coking coal properties (>4 FSI). The ash content is typically below 20% on an air-dried basis, indicating that the coal has a relatively low mineral content, which can be advantageous for combustion and processing purposes.
Based on the available analytical results and composite coal quality data, the coal resources rank between low to medium volatile bituminous coal in accordance with the ASTM Standard D388. The average sulfur content of the coal is less than 1%, indicating a relatively low sulfur content. Low sulfur content is desirable as it reduces the emission of sulfur dioxide (SO2) during combustion, which can have environmental and health impacts. The coal also exhibits low inherent moisture content, typically less than 2%. Low moisture content is beneficial as it reduces the energy required for drying the coal and improves its calorific value.
A number of coal seams of the East Soumber, Biluut and Jargalant concessions show an average FSI greater than 4, which indicates that some parts of the coal deposits possess metallurgical properties. However, further testing of the coking characteristics is required to definitively confirm their coking potential.