激电效应对AMT正演的影响及其在砂岩型铀矿中的数值模拟

doi:10.11720/wtyht.2024.1218

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Abstract

The extensively applied audio magnetotellurics (AMT) has become a primary method for deep geophysical exploration of solid mineral resources. However, its data processing and interpretation often only consider electromagnetic effects but ignore induced polarization (IP) effects, which is inconsistent with actual geological conditions. Based on the two-dimensional AMT finite-element forward 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 uranium 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 reduced 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.

Key words： audio magnetotellurics induced polarization effect two-dimensional forward modeling sandstone uranium deposit

Received: 22 May 2023 Published: 19 September 2024

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	Ying-Cai HU
	Rui-Ting WANG
	Xiu LI

Cite this article:

Ying-Cai HU,Rui-Ting WANG,Xiu LI. Influence of induced polarization effects on AMT forward modeling and its numerical simulations for sandstone uranium deposits[J]. Geophysical and Geochemical Exploration, 2024, 48(4): 1006-1017.

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https://www.wutanyuhuatan.com/EN/10.11720/wtyht.2024.1218 OR https://www.wutanyuhuatan.com/EN/Y2024/V48/I4/1006

Schematic diagram of 2D audio magnetotelluric forward modeling

Equivalent circuit diagram of Cole-Cole model

Parameters of layered model

Comparison of one-dimensional and two-dimensional forward calculation results in layered model

Parameter of two-dimensional forward modeling with different polarizabilities

Forward response results of different polarizabilities in TM mode

Forward response results of different polarizabilities in TE mode

Two dimensional forward modeling parameters with different frequency correlation coefficients

2D TM mode forward response results of different frequency correlation coefficients in low polarizability

2D TE mode forward response results of different frequency correlation coefficients in low polarizability

2D TM mode forward response results of different frequency correlation coefficients in high polarizability

2D TE mode forward response results of different frequency correlation coefficients in high polarizability

2D forward modeling parameters with different time constants

2D TM mode forward response results of different time constants in low polarizability

2D TE mode forward response results of different time constants in low polarizability

2D TM mode forward response results of different time constants in high polarizability

2D TE mode forward response results of different time constants in high polarizability

Schematic diagram of geoelectric model in sandstone type uranium deposits

2D TM mode apparent resistivity result map of geoelectric model in sandstone type uranium deposit

2D TM mode impedance phase result map of geoelectric model in sandstone type uranium deposit

Forward response results of AMT 2D TM mode in high time constant and high frequency correlation coefficient

2D inversion results of geoelectric models for sandstone type uranium deposits with different IP parameters

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