古利库金(银)矿床地质特征和成因

古利库金(银)矿床为冰长石-绢云母型,产出与燕山中期"减压-剪切"环境下中心式火山喷发活动有关;矿床(体)受火山穹隆和爆破角砾岩筒及北西向、北东向断裂构造控制;容矿岩石为早白垩世龙江组、光华组安山岩、英安岩和新元古界-下寒武统落马湖群糜棱岩化的长英质片岩、片麻岩;矿床划分出矿化早期、主期和晚期3个矿化期,6个成矿阶段,3类组分矿体(Au型、Au-Ag型和Ag型)和脉状、网脉状两种形态矿体;围岩蚀变主要有硅化、冰长石化、绢云母化、白云石化、黄铁矿化等,硅化和冰长石化与矿化关系最密切;成矿温度185~255℃;成矿压力13.5 MPa (平均);成矿溶液盐度0.564% NaCl (平均);成矿深度500~600m.文中对成矿作用、矿床成因和成矿模式亦进行了探索和阐述.

GEOLOGY AND GENESIS OF GULIKU GOLD (-SILVER) DEPOSIT

Guliku gold( silver) deposit,located at the connection of Mesozoic Dayangshu volcanic fault basin and Neoproterozoic Early Cambrian Luomahu intermediate uplift on the east margin of Daxinganling volcanic belt,is of a adular sericite type.The deposit is genetically related to the eruption of central type in depressurization shearing environment during middle Yanshanian period.The ore bodies are controlled by volcanic domes,explosion breccia pipes and faults striking northwest and northeast.The wallrocks are Cretaceous andesite,dacite and rhyolitic breccia lava,and Neoproterozoic lower Cambrian mylonitized felsic schist and gneiss.The mineralization is in three periods,including six stages,i.e.,disseminated pyrite chalcedonized quartz stage,early adular quartz stage,foliated dolomite quartz stage,late adular quartz stage,sulfide oolitic quartz stage and comby stockwork quartz stage.The ore bodies occuring as quartz veins or stockworks can be classified into Au type,Au Ag type and Ag type.The mineral assemblage is dominated by pyrite,chalcopyrite,galena,argentite,tetrahedrite,stephanite,electrum,molybdenite,quartz,chalcedony,ankerite,calcite,adular,sericite and pyrophyllite.The texture of ore is mainly brecciform,banded,comby or disseminated network.The wallrock alterations are presented as silicification,adularization,sericitization,dolomitization,pyritization,kaolinization and propylitization,of which silicification and adularization are the most closely related to Au( Ag) mineralization.In the ore forming fluid,cations are mainly K + and Na +,with less Mg 2+ and Ca 2+ ;anions are dominantly SO 2- 4 and Cl -,followed by F -.The gas in the ore fluid is composed of majorly H 2O and CO 2,with minor CO and CH 4.The mineralization is achieved in 185～255℃,13 5 MPa,0 564% NaCl and 500～600 meters depth.The pH values of ore bodies in main and late mineralizing stages are respectively 5 47,5 11 and 4 77.The E h value in main mineralizing stage is -0 80～-12 5V,belonging to reduction environment.The S and Pb isotopic study shows that the ore materials of Guliku Au( Ag) deposit are derived from volcanic basement and associated granitoid.The isotopic composition ( δ D -76‰～-94‰, δ 18 O -6.58‰ ～-14.11‰)suggests that the mineralizing solution is from mainly meteoric water.Based on the metallogenetic study,a mineralization model for Guliku Au( Ag) deposit is proposed,i.e.,an adular sericite type of epithermal gold ( silver) deposit with horizontally zoned Au Ag ore bodies occuring in the limb of a paleo volcanic dome on the margin of a Mesozoic continental volcanic basin.