相山云际矿床电性特征及找铀意义

The conductivity characteristics of Xiangshan Yunji deposit and significance of further uranium prospecting

采用音频大地电磁测量方法,获得了相山云际矿床1000 m深度范围的电阻率。云际矿床及外围地区在浅部表现为西部高阻东部低阻的特征,在深部表现为东、西高阻,中间低阻的形态。分析了云际矿床及外围火山岩地层、控矿断裂及铀矿体的电性特征。风化层和下白垩统打鼓顶组分布于近地表和浅部,电阻率小于1000Ω·m,表现为低阻特征;下白垩统鹅湖岭组从浅部至深部均有分布,其电阻率介于1000~2000Ω·m,表现为高阻特征;次斑状花岗岩主要位于深部,电阻率大于2000Ω·m,为岩株、岩墙状的高阻体;控矿断裂F1、F2表现为条带状低阻,虽然向深部电阻率逐渐增高,但在相同深度其电阻率明显低于两侧围岩,断裂延伸超过1000 m,断裂在0 m标高以上电阻率相对较低,反映了此深度范围断裂附近岩石相对破碎富水,在0 m标高以下电阻率相对较高,反映了断裂深部岩石破碎程度较小,含水性相对较低;云际矿床目前的勘探深度大约400 m,已探明的多个铀矿体处于0~300 m深度,铀矿体产出部位电阻率明显低于围岩。云际矿床铀矿体严格受断裂F1、F2控制,断裂切割深度大,陡倾,断裂深部仍具备热液活动及矿化的有利条件,该地区进一步的铀矿找矿工作应沿断裂F1、F2深部低阻带进行。

The resistivity data of Yunji deposit within a depth of 1000 meters was obtained by audio magnetotelluric method.Resistivity of the shallow part is high in the west and low in the east in Yunji deposit and peripheral area,while in the deep,it shows high resistivity in both of the east and west,but low resistivity between east and west.Based on the analysis of conductivity characteristics of volcano rock,ore controlling fracture and ore body,The shallow layer refers to the weathering and Daguding group,and its resistivity is lower than 1000Ω.m.The resistivity of Ehuling group is from 1000Ω.m to 2000Ω.m.The resistivity of porphyrogranit in the form of stock or dike is higher than 2000Ω.m,mainly distributed in the deep.The faults F1 and F2 are cutting more than 1000 meters deeply,appearing as a low resistivity belt.The resistivity of F1 and F2 become higher in the deep,but it is lower than surrounding rock at the same elevation.Above the elevation of 0 meters,the resistivity of the ore-controlling faults are lower than it is below 0 meters because of racture zoon and water content.The prospecting depth of Yunji deposit is about 400 meters.The uranium ore body,controlled by F1 and F2,lie from ground to the depth of 300 meters,and they have a lower resistivity than surrounding rock.Dipping steedly and cutting deeply,F1 and F2 can support the hydrothermal activity and mineralization.So,it is supposed to prospect uranium along the low resistivity belt of F1 and F2 deeply.