The practice of thematic geological mapping in medium-large scale for intermediate-basic intrusive rocks:A case study of the Wu'an iron ore concentration area, Hebei Province

Mapping methods of igneous rocks have been upgraded and improved with the classification of igneous rocks, mapping practice and the development of the technology. The research on magmatic rocks has made a great progress in the past 20 years with the application of new technologies and new methods. The new research shows that there is multiple magmatic sources in a magmatic system; there isn't magmatic chamber and crystallization in a whole magmatic chamber in the natural magmatic system. The "unit-superunit" mapping method based on the theory of homogeneous magma evolution should be corrected and upgraded. Therefore, it is important to explore a set of mapping methods that are compatible with the understanding of the magmatic system. In this study, a mapping method for neutral basement intrusive rocks-magmatic "system-subsystem" mapping method is summarized as an example. Using this method, the authors identified six magmatic systems in the Wu'an area. Subsystems were divided for each magmatic system based on the characteristics of magma resource and metallogeny after the detailed research. The authors have clarified the processes of intrusive rock assembly and metallogeny in each system.