内蒙古安乐锡铜矿床地质特征及成因

GEOLOGICAL CHARACTERISTICS AND GENESIS OF THE ANLE TIN COPPER DEPOSIT,INNER MONGOLIA

论述了安乐锡铜矿床的矿体、矿化分带、稀土元素、稳定同位素等地质特征，探讨了矿床成因，确定锡的物质来源具有双重性：重稀土富集型锡石与花岗斑岩同源；轻稀土富集型锡石与次火山岩脉同源。

The Anle tin copper deposit is one of the important deposits in the southwestern part of the Huanggang Ganzhuermiao tin polymetallic ore belt in Inner Mongolia.Being all distributed along the margin of the volcanic basin,tin copper orebodies,subvolcanic dikes,granite porphyry bodies and fault structures are close in time and interdependent in space.K Ar isotopic ages of volcanic and subvolcanic rocks are 122 8×10 6 a～137 05×10 6 a,and Rb Sr isotopic age of granite porphyry is 134 2×10 6 a.The ore forming process took place a bit later than the formation of subvolcanic rocks and granite porphyry,both belonging to the late stage of Early Yanshanian.Mineralization is spatially conditioned by semiconcealed granite porphyry body,assuming ringed horizontal zoning and reverse zoning of Sn—Sn,Cu—Cu,Ag in outward and downward directions. REE characteristics of rocks and cassiterite show duality of tin sources:HREE enrichment type cassiterite possesses the same source as granite porphyry,whereas LREE enrichment type cassiterite is of the same source as subvolcanic rocks.Nevertheless,the two types of cassiterite underwent the same ore forming processes. δ 34 S values of ores vary in the range of -5 50‰～2 50‰,suggesting the derivation of sulfur from the mantle.REE components indicate that the ore forming and rock forming processes of the ore deposit have characteristics of mantle source.Hydrogen and oxygen isotopic compositions of cassiterite are δ 18 O=-2 64‰～-3 06‰ and δ D=-45‰～-225‰,implying that ore forming fluids came mainly from meteoric water. Controlled by “S” type fault structure,the orebody thickens and becomes richer at the hinge part,which resulted from the continued action of structural dynamic force.Mineralization underwent the whole process from high temperature through intermediate temperature to low temperature,dominated however by intermediate high temperature and exhibiting multi stage metallogenic characteristics of the identical phase. It is concluded from the above discussion that the Anle tin copper deposit is a mesothermal hypothermal deposit formed by structural dynamic force,subvolcanic magma and granitic magma at the same location in the late stage of early Yanshanian period.