西藏朗县秀沟铬铁矿高精度重磁勘探效果  

THE EFFECTS OF USING HIGH-PRECISION GRAVITY AND MAGNETIC METHODS TO EXPLORE CHROMITE IN THE XIUGOU IRON DEPOSIT,LANGXIAN COUNTY,TIBET

作　　者：刘天佑[1] 杨宇山[1] 刘建雄[2] 苟金昌 苏保华 

机构地区：[1]中国地质大学地球物理与空间信息学院,湖北武汉430074 [2]中国冶金地质总局西北地质勘查院,陕西西安710061 [3]西藏林芝腾荣矿业有限公司,西藏林芝860400

出　　处：《物探与化探》2012年第3期325-331,共7页Geophysical and Geochemical Exploration

基　　金：全国危机矿山接替资源找矿项目(200799084);国土资源部公益性行业科研专项(200911017-03)

摘　　要：2010年笔者完成了西藏朗县秀沟工区1∶5 000高精度重磁勘探,重力测量总精度达0.069 4 mGal。根据岩矿石物性特征建立了铬铁矿地球物理模型与找矿标志。局部重力高异常0.1～0.6 mGal、宽度几十米至一二百米,并且磁异常中等强度、反向磁化的重磁异常组合特征是识别铬铁矿的标志;局部重力高异常带与环状镶边的正磁异常带的组合特征是识别超基性岩带的标志。运用小波分析提取铬铁矿与超基性岩体局部重磁异常,倾斜角(tilt-angle)法识别岩体边界,Paker法密度填图及2.5D交互反演推断了蛇纹石化橄榄岩的范围及14个铬铁矿与矿化体的重磁远景异常,其中6个远景异常已经得到证实。指出在西藏进行铬铁矿勘探,不仅要求野外施工精度高,而且要求室内处理解释工作精细,应充分运用各种数据处理的新方法技术,才能够获得良好的地质效果。The authors completed the assignment of 1∶5 000 gravity and magnetic high-precision measurement in the Xiugou chromite deposit of Nangxian,Tibet,in 2010 and the total accuracy of gravity measurement was over 0.069 4 mGal.According to physical characteristics of rocks and minerals,both the geophysical models and the exploration indicators in search for chromite were established.The composite characteristics of gravity and magnetic anomalies seem to be indicators identifying chromite.The characteristics include the criteria that the amplitudes of local gravity anomalies range from 0.1 to 0.6 mGal,their widths range from tens of meters to 100 or 200 meters,the amplitudes of magnetic anomalies are moderate,and the magnetization direction is reversed.Moreover,the composite characteristics of local high gravity anomaly zones and braided rings with positive magnetic anomalies constitute indicators identifying ultrabasic rock zones.In addition,the authors utilized the approaches including the wavelet analysis method to extract the local gravity and magnetic anomalies generated by chromite and ultramafic rocks,employed the tilt-angle method to identify rock boundaries,applied Paker method to density mapping,and also used interactive 2.5D inversion method.The areas of serpentinized peridotite and 14 gravity and magnetic perspective anomalies of chromite and mineralized bodies were delineated,six of which were proved to be related to mineralization.It is also pointed out that the chromite exploration in Tibet requires not only high-precision field measurement but also careful indoor data processing and interpretation.Furthermore,making full use of new data processing techniques is essential for obtaining good geological effects.

关 键 词：重磁勘探 铬铁矿 西藏 小波分析 倾斜角(tilt-angle)法 密度填图 2.5D反演 

分 类 号：P631[天文地球—地质矿产勘探] P632[天文地球—地质学]