During transient electromagnetic method （TEM） exploration of a copper mine, we detected the late-channel TEM signal reversal phenomenon （a voltage change from positive to negative） caused by the influence of the i...During transient electromagnetic method （TEM） exploration of a copper mine, we detected the late-channel TEM signal reversal phenomenon （a voltage change from positive to negative） caused by the influence of the induced polarization （IP） effect, which affects the depth and precision of the TEM detection. The conventional inversion method is inefficient because it is difficult to process the data. In this paper, the Cole-Cole model is adopted to analyze the effect of Dc resistivity, chargeability, time constant, and frequency exponent on the TEM response in an homogeneous half space model. Singular Value Decomposition （SVD） is used to invert the measured TEM data, and the Dc resistivity, chargeability, time constant and frequency exponent were extracted from the measured TEM data in the mine area. The extracted parameters are used for interpreting the detection result as a supplement. This reveals why the TEM data acquired in the area has a low resolution. It was found that the DC resistivity and time constant do not significantly change the results, however, the chargeability and frequency exponent have a significant effect. Because of these influences, the SVD method is more accurate than the conventional method in the apparent resistivity profile. The area of the copper mine is confined accurately based on the SVD inverted data. The conclusion has been verified by drill and is identical to the practical geological situation.展开更多
The transient electromagnetic(TEM)responses measured in areas with highly pola-rizable media commonly show induced polarization(IP)effects,which poses difficulties to the TEM data interpretation and inversion with con...The transient electromagnetic(TEM)responses measured in areas with highly pola-rizable media commonly show induced polarization(IP)effects,which poses difficulties to the TEM data interpretation and inversion with conventional methods.When present,the IP effects break the monotony in TEM decay curves and can even cause sign reversals,and lead to the singularity and non-monotony of inversion method.It is therefore important to take the IP effects into account when processing those TEM data.In this paper,a new inversion method is developed to invert TEM data with IP effects.The Cole-Cole model was introduced to the forward modeling solver so that the IP effects can be accurately calculated.The regularization terms were adapted to the objective function and a global optimization method,the particle swarm optimization algorithm,was used to solve the optimization problem,which weakened the singularity and non-monotony of the inversion greatly.Field data were collected in Wulong gold mine where IP effects were detected.The data were in-verted using the method developed in this paper,and the inversion results were able to identify the depth extension of NO.163 ore-bearing quartz veins and their associated fine-grained diorite veins.The global inversion method in this paper primarily solved the inversion problem of IP-affected TEM responses,and recovered the polarization parameters,which can be used as an aid to the geo-logical interpretation.展开更多
In this paper the authors propose the natural field induced polarization (IP) method and present the way to pick up IP effect. The relations between the object and anomaly are studied by taking field experiments as ex...In this paper the authors propose the natural field induced polarization (IP) method and present the way to pick up IP effect. The relations between the object and anomaly are studied by taking field experiments as examples. The effectiveness and usability of the method are testified.展开更多
基金supported by the National Technology R&D Program in the 11th Five year Plan of China(No.2007BAQ00168-1-1)the National Natural Science Foundation of China(No. 41103052/D0309)the Shanxi Province Excellent Graduate Innovation Program(No. 20113038)
文摘During transient electromagnetic method （TEM） exploration of a copper mine, we detected the late-channel TEM signal reversal phenomenon （a voltage change from positive to negative） caused by the influence of the induced polarization （IP） effect, which affects the depth and precision of the TEM detection. The conventional inversion method is inefficient because it is difficult to process the data. In this paper, the Cole-Cole model is adopted to analyze the effect of Dc resistivity, chargeability, time constant, and frequency exponent on the TEM response in an homogeneous half space model. Singular Value Decomposition （SVD） is used to invert the measured TEM data, and the Dc resistivity, chargeability, time constant and frequency exponent were extracted from the measured TEM data in the mine area. The extracted parameters are used for interpreting the detection result as a supplement. This reveals why the TEM data acquired in the area has a low resolution. It was found that the DC resistivity and time constant do not significantly change the results, however, the chargeability and frequency exponent have a significant effect. Because of these influences, the SVD method is more accurate than the conventional method in the apparent resistivity profile. The area of the copper mine is confined accurately based on the SVD inverted data. The conclusion has been verified by drill and is identical to the practical geological situation.
基金This study was supported by the National Key Research and Development Project of China(No.2018YFC0603803)the Fundamental Research Funds of CAGS(No.AS2020J01).
文摘The transient electromagnetic(TEM)responses measured in areas with highly pola-rizable media commonly show induced polarization(IP)effects,which poses difficulties to the TEM data interpretation and inversion with conventional methods.When present,the IP effects break the monotony in TEM decay curves and can even cause sign reversals,and lead to the singularity and non-monotony of inversion method.It is therefore important to take the IP effects into account when processing those TEM data.In this paper,a new inversion method is developed to invert TEM data with IP effects.The Cole-Cole model was introduced to the forward modeling solver so that the IP effects can be accurately calculated.The regularization terms were adapted to the objective function and a global optimization method,the particle swarm optimization algorithm,was used to solve the optimization problem,which weakened the singularity and non-monotony of the inversion greatly.Field data were collected in Wulong gold mine where IP effects were detected.The data were in-verted using the method developed in this paper,and the inversion results were able to identify the depth extension of NO.163 ore-bearing quartz veins and their associated fine-grained diorite veins.The global inversion method in this paper primarily solved the inversion problem of IP-affected TEM responses,and recovered the polarization parameters,which can be used as an aid to the geo-logical interpretation.
基金The study is supported by the National Natural Science Foundation of China
文摘In this paper the authors propose the natural field induced polarization (IP) method and present the way to pick up IP effect. The relations between the object and anomaly are studied by taking field experiments as examples. The effectiveness and usability of the method are testified.
