下吉宝沟金矿的发现及其地质特征

THE GEOLOGICAL CHARACTERISTICS OF XIAJIBAOGOU GOLD DEPOSIT

下吉宝沟金矿产在二长岩中 ,它的形成与二长岩关系密切 ,二长岩既是容矿岩又是含矿岩 .下吉宝沟二长岩是高碱度的偏碱性同熔型岩体 ,其硫同位素和稀土元素表明有一定的壳源物质混入 ,是岩浆演化晚期的产物 .二长岩岩体中北西向和北东向两组裂隙控制了矿体的产状 .下吉宝沟金矿形成于晚侏罗世 ,主要与黄铁矿化和毒砂化有关 ,硅化微弱 ,金矿化产生于二长岩成岩后期 ,成矿物质可能来自深部 .

The Xiajibaogou gold deposit is located in the central section of the Ergun block.Its geography location is about 15 km to the southeast of Jilalin town,Ergun city,Inner Mongolia Autonomous Region.The Ergun River (the boundary river between China and Russia)is located in its west about 10 km.There is the Jilalin large placer gold deposit nearby.Xiajibaogou gold deposit occurs in monzonite and is closely related to it.The monzonite is both host rock and mineralized rock.Hercynian granites are broadly distributed around the monzonite.NW striking and NE striking tensional fractures occur in the monzonite.The orebodies are controlled by the tensional fractures.Xiajibaogou gold deposit was formed in late Jurassic.Its Au mineralization is mainly related to pyritization and arsenopyritization,other than silication.Au mineralization occurred following the monzonite.The ore forming matter probably came from depth.The ore is altered type.There are metallic minerals (pyrite,arsenopyrite etc.)and nonmetallic minerals(feldspar,sericite,muscovite,pyrophyllite,etc.)in the ore.A/NKC of the Xiajibaogou monzonite range from 1 43 to 1 85, σ from 3 13 to 7 28,Na 2O+K 2O from 8 78 to 10 9,ΣREE from 70 024×10 -6 to 228 97×10 -6 , δ Eu from 0 480 to 0 683 and ΣCe/ΣY from 4 70 to 7 51.The δ Eu presents negative anomaly.The ΣCe/ΣY is larger,so the Xiajibaogou monzonite fractionation is better.The Xiajibaogou monzonite is high alkalinity and alkali lime syntectite.Its sulfur isotope and rare earth element show some crustal mass mixed into it,suggesting that the Xiajibaogou monzonite be hysterogenetic substance.The application results of magnetic measurement and phytogeochemical method are obvious in the Xiajibaogou gold deposit.They have indicating significance on prospecting in Ergun region.