Inhomogeneities of the earth’s crust of the Aldan-Stanovoy shield along the 3-DV profile (Eastern Siberia, Russia

Abstract

Profile 3-DV (Skovorodino-Tommot) crosses in the sublatitudinal direction the Stanovoy and Aldan megablocks of the Aldan-Stanovoy shield. As the basic elements of the Earth’s crust section along the profile 3-DV, a technique was adopted for identifying regional inhomogeneities of the lithosphere based on the results of the analysis of seismic and gravimetric data with subsequent typification of their nature. According to the SRM-CMP data, in the upper part of the section (up to 35 km) of the Aldan megablock, the Yakokut and Chulman heterogeneities are distinguished, and the Stanovoy megablock — the Kalara-Dzhugdzhur heterogeneity. The Yakokut and Chulman seismic inhomogeneities in the gravitational field correspond to minima with an the amplitude of up to 25 mGal. The gravitational field of the Kalara-Dzhugdzhur heterogeneity is mosaic and reflects its block structure. It is shown that the deep structure of the Aldan megablock in the area of the 3-DV profile is determined by the Yakokut granite-gneiss dome and Chulman sublateral decompaction zone, and the upper part (0—25 km) of the Stanovoy megablock is represented by the Kalar-Dzhugdzhur structure, composed of the Stanovoy complex of rocks  and blocks of highpressure granulites. A significant (up to 10 km) increase in the thickness of the earth’s crust of the Aldan megablock is explained by the presence of the upper layer juvenile crust formed in the Paleoproterozoic as a result of regional metamorphism of igneous rocks. The Earth’s crust of the Stanovoy megablock is tectonically rebuilt for almost the entire thickness of up to 40 km during the Mesozoic collision of the Precambrian North Asian and Sino-Korean cratons. The Yakokut granite-gneiss dome, in accordance with the proposed model of the structure of the Earth’s crust of the Aldan megablock, is the ore-controlling structure of the Central Aldan gold-bearing region, and highpressure granulites of the Zverevsky block of the Kalara-Dzhugdzhur heterogeneity of the Stanovoy megablock served as a source of gold in the Chako-Berkakit ore cluster.