深海多金属硫化物瞬变电磁激电效应初探

瞬变电磁法是深海多金属硫化物勘探的有效手段。海底多金属硫化物中高品位的金属组分会引起极强的激电效应，且对瞬变电磁响应产生显著影响。本文通过实验室测量和数值模拟对深海多金属硫化物的激电效应进行了探讨和分析。首先对西南印度洋中脊热液区的岩矿石样品进行了较为系统的电性测试，典型硫化物的复电阻率在频率域有最大达160 mrad相位移动，时间域与频率域的测量结果表明，极化率参数可以很好地区分硫化矿物与围岩。利用Cole-Cole模型对实测复电阻率进行解释，得到复电阻率的特征参数，分析各参数与块状硫化物组分和结构的关系，并根据极化率参数对典型硫化物进行了分类。将典型硫化物的激电参数用于计算层状介质的瞬变电磁响应，计算结果表明，在海底多金属硫化物矿床瞬变电磁法响应的最佳观测时窗内可同时观测到激电效应的影响。虽然在采集时窗晚期瞬变响应发生畸变，但在信号接收早期，激电效应能有效增强瞬变电磁法对深海多金属硫化物的探测能力，为瞬变电磁实测数据提供解释依据。

Primary study on transient electromagnetic induced polarization effects of deep-sea polymetallic sulfides

Transient electromagnetic method (TEM) is an effective method for deep-sea polymetallic sulfide exploration. High-grade metal components in seafloor polymetallic sulfides cause extremely strong induced polarization effects and have a significant impact on transient electromagnetic response. In this paper, the inductive effects of deep-sea polymetallic sulfides were analyzed through laboratory measurement and numerical simulation. First, systematic electrical tests were carried out on rock ore samples from the hydrothermal vent fields on the southwest Indian Ocean Ridge. The complex resistivity of typical sulfides has a phase shift of up to 160 mrad in the frequency domain. The time domain and frequency domain measurements show that the polarizability parameter is a good indicator to distinguish sulfide minerals and surrounding rocks. Using the Cole-Cole model to interpret the complex resistivity to obtain the characteristic parameters of complex resistivity, the relationship between parameters and the composition and structure of the massive sulfide was analyzed, and the typical sulfides were classified based on the polarizability parameter. The induced polarization parameters of the typical sulfides were used to calculate the transient electromagnetic response of the layered medium, which show that the influence of induced polarization effect can be observed simultaneously in the best observation window of the TEM response of the deep-sea polymetallic sulfide deposit. Although the transient response is distorted in the late stage of the acquisition window, in the early stage of signal reception, the induced polarization effect effectively enhances the detection capability of the TEM for deep-sea polymetallic sulfides, which provides an explanation basis for the transient electromagnetic measurement data.