Paleomagnetic evidence for post-Early Cretaceous tectonic rotation of the Sikhote-Alin Superterrane, Far East Russia

We present new Early Cretaceous paleomagnetic results from the Zhuravlevka-Amur Terrane of the Eurasian Continent, Far East Russia. Out of 34 total sites, 14 were collected from Komsomolsk-on-Amur area (50.6°N, 137.2°E) and 20 from Vaninsky area (49.1°N, 139.2°E). Thermal demagnetization reveals the presence of two interpretable magnetization components in 19 sites, with laboratory unblocking temperatures of 350°C and/or 500-580°C. The remanent directions of the low-temperature component are either parallel or anti-parallel to those obtained from the high-temperature component. Results of fold tests show that both components are secondary. Rock magnetic and reflected light microscopic observations indicate a chemical origin for both of these components, as evident from the presence of secondary pyrrhotite and magnetite. The Komsomolsk-on-Amur area provides an in-situ formation mean direction of D=127.5°, I=66.7° (k=28.2, α₉₅=9.3°, N=10 sites). When combined with the reported paleomagnetic data from Early to Middle Cretaceous accretionary wedge rocks of the Kiselevka-Manoma Terrane and the Early Cretaceous Western Sakhalin turbidite basin rocks (D=94.2° and D=57.1°, respectively), large magnitude of clockwise rotations of 66-118° is demonstrated for the eastern part of the Sikhote-Alin Superterrane with respect to Eurasia. In addition, these three landmasses maintained their E-W elongated orientations before the start of rotation, implying southward directed subduction of the oceanic plates beneath northern margins. These reconstructions of the Sikhote-Alin Superterrane provide clues on the tectonic evolution of Panthalassa Ocean.