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ASI-02 Geology and mineral resources of Northern and Central Eurasia
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Tectonics and minerageny of northeastern Eurasia in the section of the Sea-of-Okhotsk - the Long Strait geotraverse
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A.S. Yefimov, Siberian Research Institute of Geology, Geophysics and Mineral Resources (Russian Federation)
V.S. Surkov, Siberian Research Institute of Geology, Geophysics and Mineral Resources (Russian Federation)
V.S. Staroseltsev, Siberian Research Institute of Geology, Geophysics and Mineral Resources (Russian Federation)
V.L. Kuznetsov, Siberian Research Institute of Geology, Geophysics and Mineral Resources (Russian Federation)
Aleksandr Salnikov, Siberian Research Institute of Geology, Geophysics and Mineral Resources (Russian Federation)
P.N. Sobolev, Siberian Research Institute of Geology, Geophysics and Mineral Resources (Russian Federation)
A.V. Lipilin, Rosnedra (Russian Federation)
A.K. Suleimanov, Spetsgeofizika PP (Russian Federation)
N.G. Zamozhnyaya, Spetsgeofizika PP (Russian Federation)
A.G. Yakovlev, Severo-Zapad Ltd. (Russian Federation)
D.E. Zubov, NPP VIRG-Rudgeofizika CJSC (Russian Federation)
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Currently a 2-DV geotraverse (the Sea of Okhotsk - the Long Strait) has been measured by a combination of geological and geophysical studies in the northeast of Eurasia. The line intersects island-arc formations of the Coney-Murgalsk arc and structures of the Yano-Kolyma folded area including the superimposed (south to north) Okhotsk-Chukotka volcanogenic belt, Arman-Viligin synclinorium, along with Beryozovsk, Oloy, Anuy, Chaun folded zones and South-Anuy suture zone.
The main sections of the Earth's crust are identified. They are a sedimentary cover bottom, upper-lower crust boundary, crust-mantle bed and Moho discontinuity. The crust-mantle bed 4-7 (rarely more) km thick is most apparent. It is traced along the whole line with small breaks. Exceptions are some areas with highly transparent section and almost complete disappearance of the Moho discontinuity. In most of the line the Earth's crust ranges from 42 to 47 km in thickness. The exception is the extreme south of the line. There, immediately outside the town of Magadan, a minimum (35 km) thickness of the Earth's crust is observed. Further north it thickens smoothly to 55 km and then shortens smoothly to 40-45 km. P- and S-wave propagation velocities are determined: average velocities in the earth's crust and boundary velocities over the mantle surface.
The gathered data allow identifying deep structures and blocks of different types and conditions of the Earth's crust. Thus, doubling of the Moho discontinuity is revealed near the boundary between the Oloy and South-Anuy blocks.
Positions and kinematics of the largest deep-seated faults are determined. It is shown that the faults (structural sutures) are rooted in the mantle; all the deep crustal faults are confined to tectonically active zones and linked with transforms. The 2-DV geotraverse results attest to submeridional zones of tectonic-magmatic excitation, which manifest themselves in conductive and gas-geochemical anomalies, zones of seismic section transparency. It is possible that some zones are active, the others are latent and healed, though there may also be available weak conductive canals in them.
As a whole based on the analyzed structure of the deep section and regional analysis of surface geological structures we can speak about complex geodynamic environment of the territory. Thus, the contemporary structure of areas of junction of the Omolon intermediate massif and Oloy zone (block) resulted from tectonic compressive stresses with their relaxation in shear zones in a northwestward direction which is lengthwise for the Oloy zone. Geologic maps are mainly used to interpret left shear displacements. In the course of shear displacements there appeared local environments of both compression and tension.
It is revealed that familiar ore clusters are confined to deep faults being rooted in the mantle and followed by Moho fracturing. This feature can be useful for distinguishing new ore clusters.
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