Study On Tectono-alteration Net Of Gold In Northwest Jiaodong

The northwest of Jiaodong is the important area where gold mines concentrated. NNE-striking, NE-striking and NEE-striking faults are the dominantly control structure. The three gold belts, Sanshandao, Huangshanguan-yexan and Zhaoyuan, which disunite from west to east in the north-west area of Jiaodong, control the most gold mines and consist the structure-alteration net in this region.The tectono- alteration net, which connects the metallogenic system with exploration, is the unite of structures, fluids, alteration, mineralization and other information of geologe. The trellis of the net are the structures, the content of the net compose of alteration, mineralization and other information of geologe, and fluids is the media between the two parts. The faults that control gold veins have acted several times for the regional stresses evolution during Yanshan period. In the early period of Yanshan, the regional stresses system pressed along NW-SE direction, and the stones that occur in the structure belts appear ductile deformation dominantly. Therefore ,In the middle and last period of Yanshan, the regional stress system transformed from NW-SE direction pressure to NW-SE direction tension, and the stones in the structure belt expressed brittle deformation. The transformation of regional stresses provided the conditions that activated and transited gold element and then made it precipitate. The characters of faults and the types of structure spaces dominate the distribution, bearing and level belting of alteration and mineralization. Pressure faults control alteration gold veins and tensile faults control quartz aurous veins.The almost gold deposits of north-west of Jiaodong are the results of corresponding period mineralization. The attenuation of lithosphere, transformation of stresses system and the activity of faults and volcano, provided not only lots of dynamical source but also some material and other resources for gold mineralization in northwest of Jiaodong in Mesozoic. Geological fluids are the most active factor during the gold mineralization, and their temperature, salt degrade, pressure and component influence the development of gold precipitation and country rock alteration. The fluids evolvement is divided three stages, which are high temperature stage, middle-high temperature stage and middle-low temperature stage. The salt degrade of ore fluid is middle or low, and the pressure of mineralization is from 20Mpa to 60Mpa. The gold of aurous veins come from the stratum of Jiaodong group dominantly, and some of the gold originate from upper mantle. The ore fluids consist of volcano water or the mixture of volcano water and rainwater.The faults that formed after the gold mineralization destroyed or reformed the prior gold ore bodies. Mapping the alteration belts is one of good methods that are used to decide the degree of destruction or reform caused by later faults. The method was successfully used to forecast metallogeny and explore gold ore body in Pingdu Dazhuangzi gold mine and enlarge the gold resource of this area.