Structure Of Ore-controlling And Element Geochemistry Characteristics Of Shangzhuang Gold Deposit, Shandong Province, China

The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of the Wangershan fault zone in the northwestern part in the Jiaodong gold province, China. Different from other tectonic metallogenic belts in Jiaodong Northwest gold deposit, Shangzhuang gold deposit has its own characteristics in structure; for example, the geological body in the mining area has double-layer structures in the vertical. Linglong granite in the upper is intrusive contacted with the Guojialing granite in the lower, developing ductile deformation.The wedge Wangershan fault trending NW is the controlling fracture, the orebody is mainly loacated on the hanging wall of the fault belt with strongly hydrothermal alternation and high degree of crushing near the main fault. Geochemical data shows that the formation environment of the original rock of ore-forming fluid is similar to that of Guojialing granite. By the analyses of structural features and mechanics in Shangzhuang mining area, It is revealed that the deformation evolution has mainly undergone four phases: the early ductile deformation, the second NE-striking horizontal simple shear, the third NE-striking compression-shear shear and the final NW-striking compression; and the mineralization happened during the third stage in which the maximum principal stress gradually transited from NE to NW. The compression-shear strain field during the mineralization is characterized by theλ-type structure, the positive flower structure, etc. Orebodies are mostly equidistantly located in the dilatational space, which is distributed in the integral compressional circumstances. And the dilatational spaces are developed where the fault attitude changes or shear joint systems develop.The calculation of the elemental mass balance interprets by elemental calculation to explains the elementary activity law: the composition of alteration rock in the central of alteration belt has the largest degree of variation, a large number of permeability fluid carry active components into the dilation space, which has significance to the further enrichment of the ore-forming element(Au) and the remobilization of correlative elements (Ag, Cu, Zn, Hg, Pb). The original rock Guojialing granite is altered to sericite-quartz and change into siliconization alteration rock in the end, the average volume expansion ratio of them are 33.87% and 28.47%. From the original rock far away from the alteration zone to the central of the alteration zone, siliconization and potash feldspathization increase, manifesting as the generation of siliconization and potash feldspathization tension veinlet zone. The extensive exist of veinlet zone indicate the general development of fracture during the ore-forming period. Tectonic fracture zone is not only the transportation channel and precipitated space of ore-forming fluid carrying minerals, but also the favorable position of the mineralization.