辽宁本溪大台沟铁矿床地球化学特征及成因探讨

为探讨辽宁大台沟铁矿床的成矿物质来源及形成环境,选取典型铁矿石5块进行主量元素、微量元素和稀土元素分析测试。结果显示:大台沟铁矿床保存有明显的化学沉积特征,化学成分主要由Fe_2O_3,FeO和SiO_2组成(Fe_2O_3+FeO+SiO_2=87.33%～96%),其他组分(MnO,MgO,CaO,Na_2O,K_2O,TiO_2,P_2O_5,Al_2O_3)含量较低;页岩标准化后的稀土元素配分曲线显示为稀土总量低(ΣREE平均为19.65×10^-6),轻稀土元素相对亏损,重稀土元素相对富集;且具有一定的Eu(Eu/Eu~*=1.52～2.72),Y(Y/Y~*=1.18～1.52),La(La/La~*=1.17～2.26)的正异常,弱的Ce(Ce/Ce~*=0.79～0.92)异常;Y/Ho值平均34.19接近于海水的分布范围;Sr/Ba值平均1.79,属于火山岩和海相沉积物;Ti/V值平均38.84,属于火山建造。这些特征表明:该矿床的形成可能与海相火山沉积物有关,属于火山沉积变质型铁矿范围;成矿物质来源于热水和海水的混合作用;矿床形成于相对于缺氧的环境。

GEOCHEMICAL CHARACTERISTICS AND GENESIS OF THE DATAIGOU IRON DEPOSIT IN BENXI,LIAONING PROVINCE

Major and trace elements of five typical iron ores and host rocks from banded iron formation(BIF) in the Benxi area of Liaoning Province are analyzed in order to study the origin of ore-forming material and metallogenic environment.The results show that the BIF has obvious chemical deposition characteristics.The average bulk compositions of ores are characterized by enrichment of Fe2O3,FeO and SiO2(Fe2O3+FeO+SiO2=87.33%~96%),while MnO,MgO,CaO,Na2O,K2O,TiO2,P2O5,Al2O3 have low contents.In addition,the shale-normalized REE distribution patterns of the ores display very low(ΣREE=19.65×10^-6) REE concentrations,depletion of LREE and enrichment of HREE.The patterns also show positive anomalies of Eu(Eu/Eu^*=1.52~2.72),Y(Y/Y^*=1.18~1.52) and La(La/La^*=1.17~2.26) and weak Ce(Ce/Ce^*=0.79~0.92) anomalies.Moreover,the average Y/Ho ratio of ores is 34.19,close to the range of seawater,the average ratio of Sr/Ba is 1.79,characteristic of volcanic and marine sediments and the average ration of Ti/V is 38.84,belonging to volcanic formation.These chemical features indicate that the formation of the BIF is related to marine volcanic sediments and belongs to volcanic sedimentary metamorphic iron deposit,formed in the hypoxic environment with the ore-forming material originated from the mixing of thermal fluid and seawater.