CRUSTAL THICKNESS IN THE BAIKAL REGION AND MONGOLIA BASED ON INTERPRETATION OF THE SATELLITE GRAVITY MODEL

The article discusses deep Earth crustal structure in the Baikal region, neighboring territory and Mongolia. The EIGEN-6C4 satellite gravity model-based Moho depth map was drawn for the territory with coordinates 43 to 61° N, 88 to 120° E. Gravity data interpretation was performed using seismic results obtained. The Bouguer EIGEN-6C4 model data interpretation was performed within the two-layer crust – mantle model with density diference 0.5·103 kg/m³. According to interpretation, Moho depth of the West Siberian Plate and Siberian Platform was estimated at 40–45 km with slight lateral variations, The depth decreases to 34–38 km near the Baikal basins. Strong lateral variations in Moho depth were obtained in mountainous areas south of the boundary going along the Main Sayan fault. The crustal thickness reaches 55–60 km in the area of active orogens (Mongolian Altai, Gobi Altai, Hangai) and decreases to 45 km in the Great Lakes Basin. The Stanovoi Range, Gobi Desert and Big Hingan have Moho depths ranging from 45 to 50 km. The southwesternmost part of the territory near Dzungaria, Tien Shan and Tuffan basin show the maximum drop of Moho from a depth of 40 km to 70 km. The Moho depth estimation error is from 2 to 4 km. The depths obtained for the Central Siberian Plateau and the Baikal basins generally correspond to the seismic data. The ground-based gravity data estimations do not contradict our results. The height anomalies of the quasigeoid model for the EIGEN-6C4 geopotential model relative to the WGS84 ellipsoid are found on the northwestern boundary of the Amur plate. The northern boundary of the Amur plate is clearly defined in the lateral distribution of the Bouguer anomalies and crustal thickness.

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