内蒙古西口子-八道卡地区岩金成矿特征

西口子-八道卡地区大地构造位置处于额尔古纳地块北部.区内出露变质岩系为古元古界新华渡口群和新元古界震旦系加疙瘩群.侏罗纪中-酸性岩浆岩活动强烈.基底断裂构造呈近东西向,在侏罗纪形成一系列左行的压扭性北东向断裂构造及伴随的北西向、近南北向张性断裂.金矿化体呈脉状、透镜体状发育在变质岩系、黑云二长花岗岩体的破碎蚀变带内或变质岩系与石英闪长岩的接触部位,受左行压扭性北东向断裂构造与北西向、近南北向张性断裂构造的联合控制.金矿化类型为蚀变岩型和石英脉型,金矿化与硅化、黄铁矿化、绢英岩化关系密切.地球化学研究表明金矿化与黑云二长花岗岩、石英闪长岩关系密切,成矿物质主要来源于地壳深部或地幔,成矿热液属富碱质的、具有弱还原性质的岩浆热液.依据区内金矿成矿作用特点,总结了金矿找矿标志.

MINEROGENIC CHARACTERISTICS OF GOLD MINERALIZATIONIN IN XIKOUZI-BADAOKA AREA,INNER MONGOLIA

Xikouzi Badaoka area is rectonically located in the north of Ergun massif,where the Proterozoic metamorphic rocks are outcropped, with intense Jurassic magmatic activities.The E W trending basement structures are superposed by a series of Jurassic left handed compresso shearing NE trending faults and tensile N S trending faults.The Au mineralization bodies occur as veins and lenses in altered fracture zones within metamorphic rocks and biotite admellite,or in the contacts between the metamorphic rocks and quartz diorite.The gold ores are altered rocks and quartz veins.The associated wall rock alterations include silicification,pyritization and beresitization.The REE patterns of porphyroid biotite admellite and quartz diorite are similar to those of gold orebodies.The S isotopic values of pyrites in ores are between- 1.4 and- 8.5.The vapor phase compositions of minerogenic fluid are mainly H2O,CO2 and N2 ,with minor CH4,C2H6 and O2;while the liquid phase,mainly Cl- ,F- ,SO42- ,Na+ and K+ with minor Ca2+ and Mg2+ .Geochemistry studies indicate that the Au mineralization is closely related to biotite admellite and quartz diorite.The minerogenic materials are mainly derived from lower crust and/or mantle.The minerogenic fluid is alkali riched weakly reducible magmatic hydrothermal solution.