胶东大磨曲家金矿床岩石磁组构、构造变形与金矿化

在胶东地区招远-平度断裂带上的大磨曲家金矿区选取了典型的构造区域进行岩石磁组构研究。沿着断裂带在不同构造部位的36个采样点钻取了112个定向岩心样品,所有样品均沿勘探线布置。磁组构研究显示,研究区以弱磁性岩石为主,总体上,胶东群变质岩的磁化率值较高,而玲珑黑云母花岗岩的磁化率值较低,尤以碎裂程度高的强蚀变岩的磁化率值最低;磁化率各向异性方位主要为NE向挤压,磁组构所指示的构造应力场与大磨曲家矿区的区域挤压应力方向是相同的;对具不同程度矿化的81线的Au含量与80线磁组构各向异性度(P值)进行对比研究发现,P值与金品位呈负相关关系;弱矿化糜棱岩中的金矿化在磁面理发育的岩石中较为发育,成矿晚期,Au元素含量随着岩石磁性的减弱而增加,特别是在强应变后弛豫阶段矿液充填于相对张性的石英脉中Au含量最高。

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.