Influence of induced polarization effects on AMT forward modeling and its numerical simulations for sandstone uranium deposits
The extensively applied audio magnetotellurics(AMT)has become a primary method for deep geophysical exploration of sol-id mineral resources.However,its data processing and interpretation often only consider electromagnetic effects but ignore induced po-larization(IP)effects,which is inconsistent with actual geological conditions.Based on the two-dimensional AMT finite-element for-ward modeling with IP effects,this study simulated the magnitude and regularity of the influence of various parameters of IP effects on the two-dimensional forward response.Moreover,this study conducted a numerical simulation on the geoelectric model of sandstone u-ranium deposits in the Erlian Basin.The results show that:(1)With an increase in the values of polarizability,frequency correlation coefficient,and time constant,the two-dimensional AMT forward modeling with IP effects based on the Cole-Cole model primarily re-duced the abnormal response value of two-dimensional forward modeling apparent resistivity and increased the abnormal response value of impedance phase.This is beneficial for detecting low-resistivity targets rather than high-resistivity targets;(2)The zero-frequency resistivity and polarizability in IP effects exhibit a significant influence on the two-dimensional forward response.The influence of both frequency correlation coefficient and time constant on the forward response primarily depends on the polarizability.High polarizability suggests their significant influence on the forward response;(3)In the case of disseminated and sulfide-bearing lithologies in the sand bodies of sandstone uranium deposits,greater IP effects will significantly influence the detection of target sand bodies using frequency-domain AMT.Therefore,forward modeling is necessary before detection to determine the magnitude of IP effects.
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