Layer-Block Tectonics, a New Concept of Plate Tectonics - An Example from Nansha Micro-Plate, Southern South China Sea

Abstract

The Layer-block tectonics (LBT) is a new theory describing the layer-slip structure of lithosphere (Liu et al., 2002, 1999; Sun et al., 1991). According to this theory, a lithosphere plate, continental lithosphere plate in particular, is considered a composite of sub-plates connecting with each other horizontally and overlapping with each other vertically. The term “Layer” in the LBT emphasizes the rheological and stratifying characteristics of the lithosphere and the guiding and controlling role of mechanically “soft” layers with different deepness in the layer-slip movement of the lithosphere during the process of tectonic deformation. The term “block”, on the other hand, emphasizes the discontinuity of various types of geological bodies segmentalized by dip-slip or strike-slip movement of lithosphere in horizontal direction. We use the concept of the LTB to cover the scientific thoughts of the other tectonic theories such as the gliding of layers (Mandle and Shippan, 1981), the flake tectonics (Oxburgh, 1972), the terrane tectonics (Irwin, 1972), the capped plates (Coleman, 1977), the extensional tectonics (Wernike, 1988, 1981), and so on. The obvious different of the LBT from the these tectonic theories, even from the plate tectonics theory, is that the LBT emphasizes the geotectonic effect of multi-levels of gliding surfaces within lithosphereupper mantle including rheospheric top surface, Moho surface, mid-crust, top surface of sedimentary basement, and so on, rather than only emphasized singular Moho gliding surface in flake tectonics or the plate tectonics. The lithosphere can be divided into different layers by the characteristics of material, energy, structure, rheological and chemical stratification at different depths (Su et al., 1996; Song et al., 1996; Wang et al., 1996; Wang, 1992; Rushentsev and Trifonov, 1985; Oxburgh, 1972). These layers interrelate with each other and stack-and-piece together to form an integral lithospheric aggregate. As the manifestation of this nature of stratification, the LBT is the result of bedding layer-slip, dip-slip (both in positive and negative direction) and strike-slip (in slant direction, sinistral or dextral) of geologic bodies under tectonic forces (vertically or horizontally). All layer-block structures in various scales, whether large as the global lithosphere plate or small as a dislocation structure, have a common slip mechanism, and the “4-dimensional