Alteration-Mineralization Network Structure Of Luoshan Gold Deposit In Northwest Jiaodong

Luoshan gold deposit is a typical altered deposit which located in the junction of Potouqing fault and Jiuqu-Jiangjia fanlt in southern of the Linglong gold field in the northwest of Jiaodong Peninsula. With the shallow-middle ore bodies have been mined, the deposit reserves fell sharply in recent years. Mineralization network is an important key of metallogenic system applied to prediction of prospecting. Basing on systemic geological field observations and exploring-mining documentation, the paper analysed characteristics of ore-controlling structures, alteration belt as well as the mineralization network of Luoshan gold deposit.Luoshan gold deposit is mainly controlled by faults, Potouqing fault and secondary ore-controlling fractures or joints respectively control the ore body morphology and attitude of altered rock type and multimetal sulfide vein-type. The ore-controlling faults experienced four stages structure-activity: ductile shearing activity before the ore-forming stage, ductile-brittle shearing activity before the ore-forming stage, compression-shearing and stretching-shearing activity of ore-forming stage, compression-shearing activity after ore-forming stage.Wall rock alteration has a clear belt as a whole which controlled by Potouqing fault, from the footwall of major fracture planes to the external, altered rocks present a gradual change trend in the mass: from fault gouge, through beresitization belt, sericite-quartz alteration belt, potassic granitic belt, to fresh granite.however, while it occurs superposition of other altered rock controlled by the secondary fracture and joint fissure. The alteration timing: from K-feldspar alteration, sericitization, pyritization to carbonation.By the method of mass balance calculation, the migration of the elements in a series of alteration process from original rock to beresitization was studied. The result of study shows that the immigration elements are mainly Si, K, Fe and Al, the moving out elements are mainly Na; trace elements of Ba, Sr, Cu and Ag are active, and secondly are Ag, Pb, Rb and Zn, of which, Ba and Sr always move out, Cu, Pb, Rb, Zn, Ag and Au mostly move in which indicate multimetal sulfide and mineralization are in the same stage.Mineralization types present as domimated horizontal belt, the structure belt changed from the compressional schistosity belt near the fault plane to the fissuring belt far from fault plane with the fractured altered rock type to multimetal sulfide vein-type mineralization. Altered rock type mineralization mainly occurred in pressure torsion fractured zone of the potouqing fault, and multimetal sulfide vein-type mineralization developed in the tensile, transtensional tectonic space of the secondary fault far from the main faults footwall. It is long-term evolution of fault-fracture system with difference of tectonic position and the change of the ore-forming fluid’s transportion-reaction-precipitation that led to the formation diversity of alteration-mineralization and its network structure.