Lithology identification with gravity and magnetic anomalies for mine exploration in the China–Mongolia border

Abstract:

China-Mongolia border is an important metallogenic province, its structural is complex and the study of it is of great significance for future detecting. In the last three years, we have conducted gravity and magnetic survey in the eastern segment of the China–Mongolia border along the profile, hoping to get a detailed characterization of the subsurface of this area. In this study, we conducted lithology identification in this area with measured gravity and magnetic data.

In our work, topological calculations were performed on inversion data and physical property data for lithology identification. Our work can be summarized into the following steps: Firstly, the rock density and magnetic susceptibility near the survey profiles were summarized by field reconnaissance, and the lithology was divided into several types. Thus, a correspondence between lithology and physical properties was defined to some extent. Secondly, different mapping equations were established according to the physical properties for each lithology.Then, inversion of the gravity and magnetic data have been performed to get the physical properties (density and susceptibility) below the profile. Lastly, the lithology was identified through gravity and magnetic inversion result and the mapping equations mentioned above.

In our study, the magmatic rocks within 50 km of the lower half space can be divided into four major types based on the identification result. The lithology varies significantly from north to south below this profile. Moreover, the lithology distribution trend and the formation age of the lower half space is summarized based on characteristics of the gravity and magnetic fields and the tectonic setting.

For lithology identification with different types of data, we think that identify lithology information by one of the data can be conducted firstly, such as magnetic susceptibility, and then bring the results to lithology identification among the inversion of other data , which greatly improves the accuracy of identification of lithology. In addition, for the physical properties, we must fully consider the relationship between the location of rock outcrops and the study area, if outcrop with the measured area is too far away, there is no use value, and we must fully consider the impact of weathering for outcrops.