内蒙古高尔旗半隐伏银铅锌多金属矿中大比例尺重力测量应用效果

The application of large and medium scale gravity measurement to the Gaoer Banner half-concealed Ag-Pb-Zn polymetallic deposit,Inner Mongoli

在内蒙古高尔旗银铅锌多金属矿玄武岩覆盖区开展了重力测量工作。矿体处在1∶5万剩余重力正负异常交替带之负异常一侧等值线同向扭曲处。1∶1万重力、激电、土壤测量成果显示,矿体与近EW向条带状视极化率异常、土壤铜铅锌银等多金属异常带相对应,处在重力、视电阻率高低异常的变化带上。矿体北侧对应剩余重力负异常、低阻,南侧对应剩余重力正异常、高阻。北侧剩余重力负异常为较低密度的隐伏岩体(石炭系正长花岗岩)引起,低阻主要与近EW向构造破碎带及赋存其中的大脉网脉状矿(化)体有关;剩余重力正异常与较高密度泥鳅河组有关,高阻是泥鳅河组细粒长石石英砂岩、粉砂岩引起,也许正是这套细粒长石石英砂岩及粉砂岩的致密性对矿液的运移起到了阻隔作用,才得以在其北侧的构造破碎带中富集成矿。可见中大比例尺重力、激电、土壤测量工作不仅为研究成矿环境提拱了重要的地球物理依据,同时也为矿体定位提供了重要信息。

Gravity survey has been carried out in the basalt overburden area of the Gaoer Banner half-concealed Ag-Pb-Zn polymetallic deposit,Inner Mongolia.In residual gravity anomaly map of 1:50000,the Gaoer Banner ore deposit is located at the distortions of the negative gravity anomaly contour line in the contact zone of alternate positive and negative anomalies.Results of 1:10000 gravity survey,IP and geochemical soil measurement show that orebodies correspond to nearly east-west banded apparent chargeability anomalies,and Ag-Pb-Zn polymetallic anomalies correspond to the variable area of high and low resistivity anomalies.The north of the orebody is characterized by negative residual gravity and low-resistance,while the south of the orebody shows positive residual gravity and high resistance.Negative residual gravity in the north results from the concealed rock mass(Carboniferous granite)with low density,low-resistance related to east-west tectonic fracture zone and the stockwork vein in it.Positive residual gravity is associated with Niqiuhe Formation.Sandstone with high density and high resistance results from fine-grained feldspar quartz sandstone and siltstone of Niqiuhe Formation.The fine-grained feldspar quartz sandstone and siltstone block and ore fluid migration probably resulted in deposit formation in the structural fracture zone on the northern side.Large scale gravity sun,ey,electrical measurements and geochemical soil survey are not only important geophysical basis for the study of metallogenic environment,but also provide important information for orebody location.