Geology of the Gobi Altai and Tseel terranes in the central part of the Sagsai River Watershed, SE Mongolian Altai

A 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.