深海拖曳式瞬变电磁的响应规律

通过分析深海堆积型热液硫化矿的电性特征,建立探测深海热液金属硫化物矿床地电模型:运用瞬变电磁全空间理论计算方法,模拟计算深海热液金属硫化物矿床瞬变电磁响应,为设计深海拖曳式瞬变电磁系统提供依据.计算结果表明:深海与无海水情况下的瞬变电磁相比,响应曲线形态变化不大,响应幅值显著增加；拖曳高度严重降低了低阻矿化层的瞬变电磁响应幅值:随着拖曳高度的增加,低阻矿化层的异常响应向后延迟并迅速衰减,当拖曳高度超过50 m时异常响应将难以分辨；在一般情况下,在1～100 ms时窗内可以探测到海底金属硫化矿层引起的异常.

Responses of the towed transient electromagnetic sounding on deep seafloor

By analyzing the electrical characteristics of the deep-sea hydrothermal sulfide ores,an electrical model was established.The transient electromagnetic(TEM) response to the model was computed according to the theory of the TEM response in full-space,which provided a basis for the deep-sea towed TEM system.The results show that the TEM responses to models in deep-sea are similar in the curve shape to that on the earthground,while the amplitude increases significantly.The towing height seriously reduces the TEM response to the mineralized low-resistivity layer.The abnormal response delays and decreases rapidly when the towing height increases.It is difficult to distinguish the response when the height is more than 50 m.Generally,it is possible to distinguish the response to the mineralized low-resistivity layer within 1?100 m window.