Rock magnetic fabric, structural deformation and mineralization of the Damoqujia gold deposit, Shandong Province

In order to study the Damoqujia gold deposit located in the Zhaoyuan - Pingdu fault zone in eastern Shandong Province, the authors selected an area with typical structural characteristics to conduct magnetic fabric investigation. 112 core samples with direction signals were collected at 36 sampling points in different structural parts of the fault zone, and all samples were arranged along the exploration lines. Magnetic fabric studies show that the study area is dominated generally by weakly magnetic rocks. Magnetic susceptibility has a higher value in metamorphic rocks of the Jiaodong Group; nevertheless, the magnetic susceptibility seems to be lower in biotite granite, especially in strongly altered rocks subjected to high extent of fragmentation. Magnetic anisotropy shows that the rocks extruded in NE direction, and the regional compressive stress direction of the tectonic stress field indicated by the magnetic fabrics is similar to that of the Damoqujia ore deposit. A comparison between the magnetic fabric anisotropy (P value) along No. 80-81 lines and the Au content of rocks subjected to different degrees of mineralization reveals that the P value is negatively correlated to gold grades. Gold mineralization of weakly mineralized mylonite is comparatively hosted in magnetic-foliation-developed rocks. At the late stage of mineralization, gold content changed negatively with the values of rock magnetism; especially the relative tension quartz vein, which had the highest gold content due to the filling of ore fluids during the relaxation phase of the strong strain area.