Study On The Ore Controlling Factors And Mineragenetic Type Of The Gold Deposit In Wujiawan Area Of Northen Hanyin

The northern region of Hanyin is located in the southern of Indo-fold orogenic belt in South Qinling. The area exposed to the Lower Silurian Meiziya group metamorphosed pelitic clastic containing carbon. It has been the discovery of gold belt from Yangpingwan in Shiquan County, passed Huanglong in Hanyin County, extended to the liufang in Hanbin district. The gold ore belt from east to west about 100 km long, north-south width of 10~20km, is a major focus area of gold mineralization. By studying on the metallogenic characteristics and the fluid inclusions in quartz veins of Wujiawan gold deposit in northern Hanyin, the author mainly carried out the homogenization temperature measurement, laser Raman component analysis and so on, and explored the nature of ore-forming fluid in Wujiawan gold deposit. The author combined with the study of ore controlling factors in the northern Hanyin regional, and then summed up the ore controlling tectonic model and prospecting of the region, and preliminary discussed the genesis of Wujiawan gold deposit. The paper has achieved the following results and progress:(1) Researching the metamorphic minerals of sericite quartz schist(biotite garnet geological thermometer) in Meiziya formation shows that, the main mineral assemblage of rocks in Northern Hanyin are: biotite + quartz + Muscovite + chlorite ± garnet. The metamorphic degree of rocks in this area may be low greenschist facies, locally up to high greenschist facies.(2) Gold ore bodies of Wujiawan gold deposit are mainly distributed in the vicinity of schist and siliceous rock zone at the lithologic interface. The ore bodies are obviously controlled by fracture structure. Themainly prospecting criteria include pyritization, silicification and so on.(3) The homogeneous temperature of the inclusion in Wujiawan gold deposit are mainly concentrated 230~280℃, indicating the deposit is a epithermal deposit. The corresponding salinity and density are 2~10wt%(NaCleq)and 0.62~0.93g/cm3 respectively, which shows the ore-forming fluid belongs to low-salinity and density fluid system. The capture pressure of fluid inclusions is 38.04~95.38 MPa, and the ore-forming depths are about 1.38~3.47 km, so it is a middle-shallow deposit. The fluid inclusions of Wujiawan gold deposit mainly developed CO2-H2 O system inclusions. Generally speaking, the ore-forming fluid is low-salinity, rich-CO2 fluid.(4) Through the study of the regional tectonic background and the metallogenic characteristics of the ore deposit and the fluid inclusion geochemistry in quartz veins, it is suggested that Wujiawan gold deposit should belong to orogenic type gold deposit, and shown as the interlayer fracture zone ore controlling.