Features of Ore-Controlling Structure and Prediction of Mineralization at Depth in the Sanjia Gold Deposit,Shandong Province

The Sanjia gold deposit,of the quartz vein gold type,lies at the southern end of the Chahe-Sanjia fault in the Mouping-Rushan gold ore belt in eastern Shandong,Its country rock is mainly composed of ancient metamorphic rocks and Kunyushan granite. This work has studied the spatial form,activity periods,dynamic characteristics and wall rock alteration of the Sanjia gold deposit. It was pointed out that this gold deposit was controlled by the major fault (Chahe-Sanjia) and its secondary faults which determine distribution of ore bodies. The ore-controlling fault zone had undergone three periods of deformation by stress:dextral compressive shear with tensile component in early time,dominating tensile deformation in middle and later periods when polymetallic sulfide quartz vein formed,and compressive shear of fractures filled with quartz,carbonate and polymetallic sulfide in later. Furthermore,this study summed up the distribution regularities of the ore bodies in the fault belt. The result of deep geochemistry shows that ore types and ore mineral assemblage are characterized by zone subdivision in vertical direction. Reverse zone subdivision of mineral assemblages is consistent with deep mineralization superposition indicated by geochemical primary halos. It is inferred that the potential ore bodies exist below -506m in the deposit based on the distribution law of ore bodies in the faults and the primary halo characteristics. This study provides a line of important evidence for exploration of deep-seated ores.