广西乐业县岩旦-岩堂金矿床找矿模型及成矿预测

Prospecting Model and Metallogenic Prediction of Yandan-Yantang GoldDeposit in Leye County,Guangxi

广西乐业县岩旦-岩堂金矿是滇黔桂"金三角"新发现的一处大型卡林型金矿,为探究该矿床深部及外围找矿潜力,明确下一步找矿方向,开展了详细的矿床地质特征研究,并结合土壤地球化学和地球物理勘探异常,建立了该矿床的找矿模型,从而对深部成矿进行预测。研究表明:矿床中分布的矿体主要为受断层破碎带控制的脉状矿体,其次为受地层控制的层状和似层状矿体;背斜核部的NEE向断层F1是主要的控矿构造,矿体有沿断层向东侧伏的趋势;土壤地球化学异常以Au-As为主,沿断层分布,且断层东部地表以As异常为主,具矿体前缘晕特征;地球物理激电测深表明金矿体具有低阻高极化的特点,在断层东部的高极化异常明显增强,暗示存在隐伏金矿体。综合地质与物化探研究成果认为,沿NEE向F1断层及其与近SN向断层的交会处具有较好的找矿潜力,为优先找矿靶区。

Yandan-Yantang gold deposit is located in Leye County,Guangxi,which is a large-scale carlin-type gold deposit,with a gold resource of more than 20 tons,newly discovered in Yunnan-Guizhou-Guangxi“Golden Triangle”area,China.The deposit is located in the northwest of Lingyun-Leye isolated carbonate platform,Guangxi.The host rock is calcareous sandstone with mudstone of Baifeng Formation of Middle Triassic.The orebodies are mainly controlled by anticlines and faults.The orebodies mainly occurs as vein type one in fault fracture zone,and a small amount are stratabound orebodies.The largest orebody is located in the core of the anticline and controlled by F1 fault,inclining northward,with a dip angle of 30°~60°,a width of 1.0~38.8 m,a length of nearly 2.5 km,a depth of 50~400 m,and Au grade of 0.50×10^-6~7.00×10^-6 in general,and the average grade is 2.0×10^-6.The main mineralization and alteration are silicification,kaolinization,pyritization,arsenopyrite mineralization and stibium mineralization.The gold bearing minerals are arsenian pyrites and arsenopyrites.It has a typical combination of low temperature elements such as Au-As-Sb-Hg.Generally,it has typical carlin-type gold deposit characteristics.The results of soil and rock geochemical survey show that the Au and As elements in the ore-bearing fracture zone have good coincidence,they are all located in the core of anticline and distributed along the striking of F1 fault.However,only As anomaly appears in the east of the fault,which is consistent with the feature that As is the front halo of orebody in carlin-type gold deposit,suggesting that the orebody may lie to the east.The geophysical data of TDIP and CSAMT show that the gold orebody has the characteristics of low resistivity and high intensification rate.The high intensification anomaly of TDIP lies to the east,which also shows that the gold orebody tends to extend to the east.Based on the geological characteristics and geophysical and geochemical anomalies,it is considered that the F1 reverse fault in the core of anticline is the main ore-controlling fault,and the orebody has the trend of lying to the east,suggesting that the deep part of the mining area has good ore prospecting potential.