Abstract
ABSTRACTA geological map is an indispensable tool for understanding the structure of the Earth’s crust but high-quality geological maps are usually lacking in remote areas of mountainous Central Asia covered by vast deserts. The progress in remote sensing and geographical information system (GIS), as well as the advancement in analytical methods, have generated new challenges in producing modern geological maps in such regions. The presented 1:50,000 geological map along the Sagsai River summarizes new and more accurate geological data from the geologically interesting region at the contact of the supracrustal and deep crustal Tugrug and Tseel units forming the metamorphosed accretionary wedge on the S and SW slopes of the Mongolian Altai. These geological units are formed by the lower Palaeozoic volcano-sedimentary sequences affected by Devonian Barrovian metamorphism ranging from lower greenschist to granulite facies. This metamorphic basement was subsequently intruded by the post-orogenic late Carboniferous Sagsai Pluton. The presented map shows complex relationships between different crustal levels of the metamorphosed accretionary wedge and post-tectonic intrusion evaluated using a GIS, numerical processing of remote sensing data as well as field documentation and laboratory studies.
Highlights
A geological map is a scaled-down interpretation of the structure of a selected area of the upermost layer of the Earth’s crust, usually drawn on a topographic base
By 2003, Mongolia has been covered by geological maps at a scale of 1:200,000, while geological mapping at the scale 1:50,000 has been under way since 1990s
Even though there are available geological maps produced by foreign geological surveys (e.g. Japan, France, South Korea and the Czech Republic) only 40% of Mongolian territory is covered by maps at this scale and the maps are of variable quality
Summary
A geological map is a scaled-down interpretation of the structure of a selected area of the upermost layer of the Earth’s crust, usually drawn on a topographic base. Geological maps can be used solely for academic purposes but are essential for economic development of individual countries This is true in Central Asia, and especially in Mongolia, where the economy is based on mining and raw material exploration. We present here an example of such geological map (map sheet No L-47-85-G), which covers the drainage area of the Sagsai River between the Tseel and Tsogt districts in the SE Mongolian Altai. This Main Map demonstrates the efficiency of combined satellite imagery and field investigations in producing reliable low-cost geological maps in regions of high economic interest
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