Study On Geological Characterisitics And Genesis Of Boka Gold Deposit, Dongchuan District, Yunnan Province

Boka gold desposit is located in the north ent of Cu-Au-Pb-Zn-Fe metallogenicarea in Dongchuan，Yunnan province， which is characterized by a complex andprotracted depositional and deformation history. Its outlying areas in recent years havefound a number of gold and copper-gold deposit, showing in this area have a greaterpotential for gold prospecting. So studing Boka gold desposit’s mine type andmetallogenic genesis has a very important and necessary means.Through the geological survey and sampling andanalysis of indoor test,combined with metallogenic geological background and geological characteristics aswell as deposit geochemistry of Boka gold deposit to discussion on the desposit type,to summed up the metallogenic genesis. Mainly made with understanding:(1) the Boka gold desposit is to cut by nearly North-South fracture zone strictlycontrolled, linearly lenticular orebodies distribution. Shear fracture zone formatedbefore jinningian and later suffered a period of stress to make it more broken.(2) The surrounding rocks of Boka gold desposit mainly for the early-middleproterozoic volcano-sedimentary epimetamorphic rocks building. The intrusive rocksof Kunyang-rift period, Jinningian,Chengjiang period, hercynian extensively developein mining areas which include bright green gabbro, diorite, acidic and alkaline syenite,albitite. Previous information suggests that these golden background of the rock witha very high value, especially intrusive body glow green gabbro, and albitite rock. Thefield outcrop and microscopic showed that shear zone, wild and crushing of rock havedifferent degrees of breaking and cracking.(3) the mineralized wall rock alteration, contour cut within the fracture zone,type of hydrothermal alteration: greisenization, chloritization(propylition),carbonateization，albitization，tourmalinization,quartz-sericitiztion, siliconization, andso on. The types of wall rock alteration show that m etallogenic hydrothermal heat athigh-low temperature. The hydrothermal alteration mainly along in rock extensionalfracture development.(4) the studing of metallogenic fluid inclusions indicate that Boka gold depositmetallogenic fluid has undergone high-temperature, high-salinity, with crystals to low temperature, low salinity reduction in rock. The studing of Oxygen and hydrogenisotopes from the predecessor shows fluid from magmatic hydrothermal, the studingsulfur isotopes from author indicate that the fluid from the mantle.(5) therefore, the author first raised the mineralization type of Boka gold depositis controlled by the shear fracture zone of magmatic hydrothermal altered-rock typegold deposit.(6) the predecessors did Boka gold quartz veins in different rock40Ar-39Ar dating,show that Boka gold desposit formate at the time for the late Paleocene to earlyEocene.(7) seismic data from predecessors shows that the XiaoJiang Fault was deepinginto the mantle，which is a super shell fracture. Through the geological survey, theauthor believes XiaoJiang Fault in the hercynian provides a channel for large basalteruptions. So presumably also as Boka gold desposit of magmatic hydrothermal offersa channel.Above and results regional of magma event indicates that, author think themetallogenic genesis of Boka gold desposit is--late Paleocene to early Eocene, whichis in the late of India-Asia main collision, this district is in stress relaxation, regionalis in strike-slip pull geological background, While fluids and magma derived frommantle along XiaoJiang Fault upward migration, continuous extraction of surroundingrock during the migration process of metallogenic elements such as gold, and finallyprecipitated in the shear fracture zone mineralization.