DEEP STRUCTURE OF THE UPPER CRUST AND MINERAGENY IN THE SIKHOTE-ALIN FRAGMENT OF THE 8-DV REFERENCE GEOLOGICAL-GEOPHYSICAL PROFILE
V.M. Solovyev1, A.S. Sal’nikov2, V.S. Seleznev3, T.V. Kashubina4, N.A. Galeva1, A.E. Shenmaier1
1Altai-Sayan Branch of the Geophysical Survey of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
3Seismological Branch of the Geophysical Survey of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, pr. Akademika Koptyuga 3, Russia
4A.P. Karpinsky Russian Geological Research Institute, St. Petersburg, Russia
Keywords: Deep seismic sounding profile, longitudinal wave, transverse wave, P-wave velocity, S-wave velocity, deep seismic section, Earth’s crust, mineragenic zone
Abstract
Results of deep seismic studies based on P- and S-wave data on a 500-km Sikhote-Alin fragment of the 8-DV reference geophysical profile are presented. Deep seismic sections of the upper crust (to depths of 15-20 km) with distributed longitudinal and transverse wave velocities are constructed. The P-wave velocity over most of the Middle Amur Basin and the East Sikhote-Alin volcanoplutonic belt varies from 4-5 km/s in the uppermost section to 5.8-6.3 km/s at depths of 7-15 km. The Sikhote-Alin orogenic belt in the section along the profile is represented by an anticlinal structure with high-velocity (up to 5.5-5.8 km/s) rocks uplifted in the center; at great depths of 10-20 km within its limits, the P-wave velocities reach 6.1-6.3 km/s. In the top of the section, the S-wave velocities within the profile as a whole are 2.7-2.9 km/s. Lower values (2.6-2.8 km/s) are observed in the center and east of the Middle Amur Depression and the eastern section of the East Sikhote-Alin volcanoplutonic belt. Higher velocities up to 3.35 km/s are observed in the central Sikhote-Alin orogenic complex. At depths of 5-15 km within the section, the S-wave velocities increase up to 3.4-3.65 km/s. The heterogeneous structure of the top of the Earth’s crust to depths of 15-20 km was identified using the P- and S-wave velocities, their ratio, and Poisson’s ratio. The profile section was used to analyze a relationship between the identified anomalies and the location of large mineragenic zones in Russian Manchuria. The correlations established earlier on the 2-DV, 3-DV, 1-SB, and East Stanovoy fragment of the 8-DV profile are confirmed using the confinement of many ore deposits to zones of lower P- and S-wave velocity ratios and Poisson’s ratio in the top of the Earth’s crust. We also substantiated the relationship between the identified surface seismic anomalies and deep (at depths of 5-20 km) roots (intermediate magmatic foci), which can be considered as ore-supplying.
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