APPROACH OF GEOLOGICAL TECTONIC MAPPING OF OCEANIC PLATE IN SUBDUCTION ACCRETIONARY COMPLEX ZONE

The quality of geological mapping lies in reasonable determination of mapping units of different levels. The compositions of subduction accretionary complex zone are mainly derived from the structure-formation of oceanic lithosphere in ocean basin under various tectonic environments, including oceanic ridge formation (ophiolite), abyssal plain formation, oceanic island-seamount formation, intra-oceanic arc formation, trench formation and high-ultrahigh pressure rock formation. Besides, there are also rifted block formation, high-ultrahigh pressure rock formation, continental margin magmatic arc formation and wedge-top basin formation derived from continental lithosphere which are mixed into the subduction accretionary complex zone. Therefore, it is basic to identify and determine the geological formations of different sources for mapping unit division and compilation. Based on the scientific objective of distinguishing different material sources in subduction accretionary complex zone, the mapping units are divided into three levels: subduction accretionary complex zone(first-level unit), slice(second-level unit) and rock block and matrix (third-level unit) which are divided and named with the requirements for code, coloring and lithologic pattern. The paper briefly describes the requirements of graphic expression of structural deformation in subduction accretionary complex zone, and emphasizes that the structural deformations during subduction and collision are the two major deformation periods, thus the mapping must be reasonable and accurate.