Lithospheric Conductors Shed Light on the Non‐Uniform Destruction of North China Craton

Abstract

AbstractLow resistivity in the continental lower crust and uppermost mantle has been commonly observed in both Phanerozoic and Precambrian areas. Given different tectonic history, these conductors could be attributed to different conductive mechanisms. The North China Craton (NCC) is one of typical craton that have suffered from extensive destruction, part of which was modified by Phanerozoic tectonic‐thermal events and the others remain stable cratonic lithosphere. We here present a high‐resolution 3‐D electrical resistivity model from the inversion of magnetotelluric data collected in 183 sites of NCC. Beneath the stable craton in the north part of Ordos Block, an E‐W trending conductor extends from lower crust to uppermost mantle, which can be attributed to the concentration of sulfides/graphite emplaced through oceanic subduction during the Paleoproterozoic assembly of Columbia. The conductors beneath the Taihang Mountains and the south part of Ordos Block also reflect ancient sutures. In contrast, the conductor in mantle beneath the south part of North China Plain (SNCP) reflects an on‐going process of craton destruction relating to the subduction of the Pacific Plate in Cenozoic. The MT data, combined with seismic radial anisotropy model suggest the lower crust and uppermost mantle beneath SNCP is anisotropic. And a significant electrical anisotropic layer with the most conductive direction along N70°W and the anisotropy factor of 6.3 is revealed in the 20–70 km depth by 2‐D anisotropic inversion. We attribute the enhanced conductivity along anisotropy direction to the accumulation of melts in sills, resulting from the upwelling of asthenosphere in Cenozoic.