山东单县覆盖区铁矿成矿规律及矿床成因

Metallogenic regularity and genesis of iron deposit of coverage area in Shanxian County,Shandong Province

山东单县地区铁矿为赋存于华北克拉通内的深覆盖区BIF型铁矿,近年来,该区铁矿找矿勘查和预测研究工作取得了较大的进展。为了更好地指导区域铁矿勘查工作,在系统研究相关地区以往矿产勘查和研究成果的基础上,对区内大刘庄铁矿床的地质特征、地球物理特征、矿床特征和矿石特征等进行了详细的剖析。研究区铁矿主要受变质地层控制,属受构造活动和侵入岩影响的BIF型铁矿,铁矿体呈层状和似层状(少量为透镜状)多层平行相间产出,成矿地质体为山草峪组含矿变质建造,成矿时代为新太古代晚期。铁矿带与重磁异常关系密切,其形态与磁异常形态基本吻合,显示"磁高矿厚、磁低矿薄、磁宽矿层多、磁窄矿层少"的特征;铁矿带与重力异常梯度带旁侧的高值区及剩余重力异常带分布基本一致。上述重磁异常部位是铁矿勘查的重点位置。矿石成分和稀土元素特征表明,SiO_2、Fe_2O_3和FeO总量相当高,具有明显的Eu正异常、无明显Ce异常、Y略呈正异常、Y/Ho比值较高等特征,相关研究成果显示,研究区成矿物质来源于海底热液,成矿过程中加入了较多的碎屑物质;研究区BIF含矿建造经受了长期的区域变质作用,并受到了区域构造运动和岩浆侵入活动的影响。单县地区铁矿含矿建造是典型的BIF型铁矿,其成矿过程是鲁西地区大地构造演化的重要组成部分。

The iron ore deposit of BIF type in the study area of Shanxian County in Shandong province is located in deep coverage area of North China Craton. In recent years,great progress has been made in prospecting and prediction of iron deposits in this area. In order to provide guidance for regional iron ore exploration,the authors analyze the geological,geophysical,deposit and orebody characteristics of the Daliuzhuang iron deposit after systematically studying mineral exploration and achievements in scientific research of these areas. Based on the study of metallogeny of iron deposits in this area,it is concluded that its iron ore is identified as BIF type which is controlled by metamorphic strata,and is affected by tectonic and intrusive activities. The iron ore body occurs as layered and layer-liked（ with a few lenticular） in a multilayer parallel phase. The ore-forming geological body is ore-bearing metamorphic formation of the Shancaoyu Formation; its metallogenic epoch is late Neoarchean. Iron ore belt is closely related to gravity and magnetic anomalies,whose morphology is basically consistent with the shape of magnetic anomalies,which shows ″high magnetic value with thick ore body,low magnetic value with thin ore body,wide magnetic anomalies with many seams,and narrow magnetic anomalies with few seams″.Iron ore belt is consistent with the high value in the lateral of gravity anomaly gradient zone,and the residual gravity anomaly zone. The gravity and magnetic anomalies are the focus of iron ore exploration. The mineral composition and REE analysis show the extremely high total amount of SiO2,Fe2O3 and FeO in the study area,obviously positive Eu anomaly,none obvious Ce anomaly,slightly positive Y anomaly,and a higher ratio of Y/Ho. Considering related research,it is found out that ore-forming source of the study area originated from seafloor hydrothermal fluid,added by more detrital materials in the ore-forming process. The BIF in study area has undergone long-term regional metamorphism and been affected by regional tectonic movement and magmatic intrusion. In conclusion,the ore-bearing formation of iron ore in Shanxian County area is a typical BIF type,and its formation is an important part of tectonic evolution in western Shandong province.