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The objective of the research was to summarize and analyze the existing and emerging methods of sustainability assessment for the territories of Ulaanbaatar City. The principle of target use of territories assumes determination of its possibilities for performance of social and economic functions on the basis of a preliminary assessment of its natural resources, value of natural objects, etc. It is important that the mandatory damage was minimal, and the planned benefits significantly exceeded them. A principle of safety assumes that any anthropogenic impact on the geological environment should not create environmentally harmful and dangerous to the habitat of the present generation and have long-term environmentally harmful consequences for future generations. Generalization and systematization of information about the state and stability of the geological environment should be consistent with the scale of the problems and the level of decision-making (global, regional, local). The results of assessments of the stability of territories can be presented in various forms, as well as the leading natural and man-made factors that affect their stability. They include quantitative, semi-quantitative and qualitative assessments. The cost criteria for evaluating the stability of territories are being widely developed at present in two main directions. The first is assessment of the risk of the impact of dangerous natural and natural-technogenic processes. The second is due to the assessment of the costs required for the construction and normal operation of natural-technical systems or objects, including their engineering protection.
The Tavantolgoi deposit, which has more than six billion tons of coal reserves, is situated in southern Mongolia. In 2018, more than 22Mt coal was produced from the deposit. During the exploration program completed in 2017, eighteen sandstone and two andesite samples for petrographical and geochemical analysis were collected from the upper part of coal-bearing Middle Permian Tavantolgoi Formation, which was intersected completely by 960 m deep bore hole. Petrographically, the sandstones are classified as litharenite reflecting relatively weak weathering intensity in source area, probably due to arid or semiarid climate conditions. Provenance analysis indicates that the sandstones are sourced from transitional arc and undissected arc that were probably formed during the closure of Paleoasian ocean between southern Mongolia and North China block. Geochemistry of major oxide and trace element result are summarized as below. CAI values from major oxides of the studied samples vary between 66.7 and 81.5 with an average of 77.0, reflecting weak to moderate intensity of weathering in source area. The plotted data on A-CN-K diagram displays that sandstones were sourced mainly from early Permian andesite and dacite, which are widely distributed around Tavantolgoi. It is also supported by Al2O3/TiO2 (avg. 19.6), TiO2/Zr (avg. 57.7) and petrographical study. C-value, indicator of paleoclimate, in the sandstone ranges from 0.15 to 1.3 with an average of 0.50, suggesting semiarid and semiarid to semimoist condition. However, some samples accumulated during the short period of arid and moist conditions. Rb/Sr and Sr/Cu of the studied samples are consistent with those of C-value. In addition, Sr/Ba (avg. 0.56), Th/U (avg. 2.8) and Ni/Co (avg. 2.0) of the samples suggest that the sandstones were deposited in paleoenvironment with fresh and oxic water.
Middle Permian Tavantolgoi coal deposit lies in southern Mongolia and has more than 6 billion tons of coal including significant tonnage of coking coal. In 2017, exploration bore holes were drilled at Borteeg, the largest syncline of the deposit. Eighteen sandstone and two andesite samples for petrographical and geochemical analysis were collected from coal-bearing sequences that were intersected by 960 m deep bore hole. The sandstones are classified as litharenite suggesting that weathering intensity in source area was weak, probably due to short transport distance coupled with relatively arid to semiarid climate conditions. Provenance analysis (Q-F-L, Qm-F-Lt, and Qp-Lvm-Lsm diagrams) suggests that the sandstones are recycled sediments derived from transitional arc and undissected arc that were formed during the closure of Paleoasian ocean between southern Mongolia and North China block. The average value of CIA for the samples is 74.1, reflecting relatively weak intensity of weathering in source area, which is consistent with the results of petrography. The plotted data on A-CN-K diagram displays that sandstones were sourced mainly from Early Permian andesite and dacite, which are widely distributed around Tavantolgoi. It is also supported by Al2O3/TiO2 (avg. 19.6) and petrographical study. To infer tectonic setting, two multi-dimensional discrimination diagrams were used. The results suggest that the tectonic setting of Tavantolgoi syncline, in which the studied sandstone was deposited, was rift.
