Gravity Field Models and the Deep Structure of the Altai-Sayan Region and Northwestern Mongolia

An EIGEN-6C4 model for the Altai-Sayan region and northwestern Mongolia constructed using data from satellite gravimetric missions and the results of ground-based measurements with absolute gravimeters and space geodesy receivers is considered. Using the EIGEN-6C4 geopotential (ETOPO1 relief), within the framework of a homogeneous crust model with the involvement of seismic exploration data on the platform part of the study area, an idea was obtained about the changes in the thickness of the earth’s crust in central Asia for the territory extending from 56° to 46° north latitude and from 80° to 100° east longitude, covering Gorny Altai, Kuznetsk Alatau, Western Sayan and Eastern Sayan, Tuva Basin, Tarbagatai Ridge (Kazakhstan), Mongolian Altai (PRC, Mongolia), Great Lakes Basin and Khangai Ridge (Mongolia). Research has shown that the depth of the Mohorovičić boundary increases from the northwest to the southeast of the territory from 40 to 55 km. For the mountainous regions in the south (Mongolian Altai, Khangai Range), the maximum crustal thickness was 55 km. For intermountain valleys and depressions (Tuva Basin, Big Lakes Basin) the depth of the Moho surface is within 45–47 km. In the north, in the flat part of the territory, the thickness of the crust is from 40 to 43 km. The differences between models constructed using gravimetric and seismic data are considered.