NEOTECTONICS OF EASTERN GORNY ALTAI: EVIDENCE FROM MAGNETOTELLURIC DATA
I.S. Novikov1, E.V. Pospeeva2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Magnetotelluric soundings, neotectonics, Gorny Altai
Abstract
According to 2D magnetotelluric (MT) data from northeastern and southeastern Altai, numerous neotectonic faults cut the Gorny Altai territory as a whole, as well as large basins within its limits, into blocks. Large neotectonic faults are traceable depthward in MT-based cross sections as zones of very low resistivities (below 0.5 Ohm·m). The MT data generally confirm the fault geometry inferred previously from morphotectonic and geological evidence. Fault plane dips are vertical in normal and strike-slip faults and inclined in reverse faults. The nearly vertical and dipping zones of neotectonic faults crosscut a horizontal conductivity anomaly at depths of 10-15 km. The anomaly makes a natural divide between the zones of brittle crustal failure above and ductile downward pressing of material below. It may be responsible for the high tectonic and seismic activity potential of the upper lithosphere in Gorny Altai associated with growth of mountains and crust thickening. Beneath the Chuya and Kurai large basins, the conductivity anomaly occurs at a shallow depth of 10 km and has a resistivity below 10 Ohm·m.
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