The First Paleomagnetic Data from Permian-Triassic Rocks of Belkovsky Island (New Siberian Islands)

Abstract:

Belkovsky Island is the part of New Siberian Island (NSI) terrane for which the paleomagnetic results for O-S periods were obtained previosly [1]. Its outcrops present the Paleozoic volcanic and sedimentary sequences intruded by mafic sills and dikes. The age of formation of igneous rocks is 252±2 Ma [2], which matches to the time of Siberian trap magmatism. The study was carried out on 45 samples from two dolerite sills at the Laboratory of Geodynamics and Paleomagnetism of IPGG SB RAS. The NRM in samples ranges from 30 mA/m to 400 mA/m. AF demagnetization allowed to remove the viscouse remanent magnetization at 5-10 nT field and then only one component is isolated. 90% NRM destroys in field up to 80-100 nT, MDF is about 30 nT that suppose the presence of low coercive minerals. The site mean directions were calculated for Sill 1 (Ds=35.7°, Is=-79.7°, K=64, α95=4.2) and Sill 2 (Ds=214.2°, Is=81.4°, K=145.4, α95=4.0). Considering high paleolatitudes (70.0°-72.4°) we suppose that NSI terrane should be in North hemisphere that’s why Sill 1 formed in reversed polarity epoch and Sill 2 formed in the normal one. Taking into account this fact the VGPs were calculated for Sill 1: Plat=57.5°, Plong = 113.9°, dp/dm=8.0/7.7; for Sill 2: Plat=60.4°, Plong = 116.5°, dp/dm=7.7/7.5. To summarize we can conclude preliminarily that NSI terrane at Permian-Triassic time was located to the north from Siberia and the mafic rocks of Belkovsky Island can belong to the marginal part of P-T trap formation. The VGP position suppose significant rotation relatively to Siberia before accretion to it in J-K time and it’s most likely that in the Late Paleozoic and Early Mesozoic NSI terrane migrate in Arctic latitudes together with other fragments of Arctida.
The work was supported by grant RFBR 14-05-31399.

Leterature:

1. V. A. Vernikovsky, D. V. Metelkin, T. Yu. Tolmacheva, N. A. Malyshev, O. V. Petrov, N. N. Sobolev, and N. Yu. Matushkin, 2013. Concerning the Issue of Paleotectonic Reconstructions in the Arctic and of the Tectonic Unity of the New Siberian Islands Terrane: New Paleomagnetic and Paleontological Data. Dokl. Earth Sci. 451, 423–429.

2. Kuzmichev, A.B., Pease, V.L., 2007. Siberian trap magmatism on the New Siberian Islands: constraints for Arctic Mesozoic plate tectonic reconstructions. Journal of the Geological Society, 164, 959–968.