安徽铜陵舒家店铜矿的电磁法试验研究

Experiment Research of Electromagnetic Exploration Method in Shujiadian Copper Deposit,Tongling,Anhui Province

安徽铜陵地区是长江中下游铜-金-铁-硫成矿带内的一个重要成矿区,成矿类型主要为矽卡岩和热液型,成矿作用与岩浆岩活动密切相关,而舒家店斑岩型铜矿是近年来在该地区新发现的矿床类型,矿体主体主要赋存在靠北西接触带的岩体中,铜矿化与舒家店辉石闪长岩密切相关。针对该类型矿床开展的电磁法找矿有效性试验对本地区寻找同类型的矿床具有重要意义。本文首先在该矿区开展了可控源音频大地电磁测深和复电阻率两种电磁法野外测量工作,接着对两种试验的数据进行反演,并结合该区地质与钻孔资料对剖面进行了地质解释。CSAMT反演结果基本反映了该矿区的地电结构,电阻率从高到低依次为:花岗闪长斑岩、闪长岩、辉石闪长岩、石英闪长斑岩和志留系下统坟头组砂岩及粉砂岩地层。铜矿体位于高阻(闪长岩)和低阻(辉石闪长岩)的过渡带上,处于高阻闪长岩的右侧。虽然CSAMT的结果不能直接反映铜矿体,但可以通过追踪CSAMT各线中高阻体的位置来大致推测矿体的存在位置与走向。复电阻率法获得了零频电阻率,极化率,时间常数和频率相关系数4个反演断面图。在零频电阻率反演断面图中,辉石闪长岩电阻率表现中等,花岗闪长斑岩和闪长岩的电阻率比较高,这与CSAMT反演的结果相同。在矿体处,电阻率表现较小,极化率中等,时间常数和频率相关系数较大。本文最后得出如下结论:可控源音频大地电磁测深能够获得深部电阻率结构,对找矿提供间接信息,而复电阻率法通过反演的零频电阻率、极化率、频率相关系数和时间常数可以为斑岩型铜矿提供直接找矿信息。

TheTongling area in Anhui province is one of the important deposits for Copper-Gold-Iron-Sulfur metallogenic belt in the middle and lower reaches of the Yangtze river.In this area,there are two main metallogenic types,the porphyry type and the hydrothermal type,and the mineralization is closely related with magmatic activities.Shujiadian porphyry copper deposit is a new type of copper deposit discovered in Tongling in recent years.The ore body is mainly aboudant in the rock mass which is adjacent to the north-west-contact-zone, and is closely related with the pyroxene diorite. The effective experiment of electromagnetic exploration method for this type of ore deposit is of great significance for searching the same type of deposit in this area.In this paper,Controlled Source Audio Magnetotelluric （CSAMT）and Complex Resistivity（CR）were firstly carried out,and then the measured data were inverted.Combined with geological and drilling data,we interpreted the inversion results.The CSAMT result basically reflects the geoelectric structure in this area. the corresponding resistivity, from high to low, is granodiorite-porphyry,diorite,pyroxene- diorite,quartz-diorite-porphyry,and sandstone and siltstone strata in the Silurian Fentou formation.The copper ore body is in the transitional zone from high resistivity （diorite）to low resistivity（pyroxene diorite）and is located on the right side of the diorite.Although the CSAMT result cannot directly give response to the copper ore body,it can roughly predict the position and trend of ore body according to the high resistivity（diorite）position in each line of the CSAMT result.It can obtainρ0 ,m,c,τparameters from complex resistivity method.In the results of zero frequency resistivity,the resistivity of pyroxene-diorite is medium,and the resistivity of granodiorite-porphyry and diorite are high,which have the same result with CSMAT,but in the ore body,zero frequency resistivity is relatively low,polarization coefficient is medium,frequency correlation coefficient and time constant are high.Finally, the following conclusions in this paper are that CSAMT can obtain deep resistivity structure,but it can not find porphyry copper deposit directly,Whereas,it can directly find the porphyry copper deposit usingρ0 ,m,c,τparameters obtained from complex resistivity method.