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Zhou S.,Central South University | Zhou S.,Changsha 5D Geo survey and Technical Co. | Xi Z.-Z.,Central South University | Song G.,Changsha 5D Geo survey and Technical Co. | And 3 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012

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.

Lai L.-B.,Central South University | Xi Z.-Z.,Central South University | Wang H.,Central South University | Hou H.-T.,Central South University | And 4 more authors.
Wutan Huatan Jisuan Jishu | Year: 2014

The integral equation method for solving large sparse matrix controls 3D transient electromagnetic forward modeling for near region of a line source in speed. It is not only saving memory and computing time, but also reducing the discrete matrix condition number for improving the calculation speed and accuracy by the method of system iterative that we take the anomaly structure as a whole system, the substructure from subsystems within themselves and solve the various abnormal body alone to establish the relationship between the subsystem, thus get the whole system. This method is correct by comparison with the analytical solution. The secondary horizontal electric field and vertical magnetic field transient response calculation results of the simple and complex three-dimensional body show that: the secondary horizontal electric field value reflects the electrical characteristics of three-dimensional abnormal body, its extremun corresponding to left and right boundary of the abnormal body; vertical magnetic field response reflects the longitudinal resolution of abnormal body, curves increasing with offset slowly.

Tan S.-C.,Central South University | Wang H.,Central South University | Xi Z.-Z.,Central South University | Zhou S.,Changsha 5D Geo survey and Technical Co.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2012

The transient electromagnetic method was only used to interpret vertical component for a long time. And for this reason, there exist some problems, such as information deficiency, low exploration precision and inadequate explaining ability in productive activities and exploration. Therefore, this work calculates the transient electromagnetic field by using eigencurrent model and Galerkin method, and defines a function to get the ratio of the vertical component and horizontal component and gives explanations based on the ratio. In the mean time, the relevant physical simulation experiments were carried out. The results show that the deficiency of single-component explanation can be avoided by fully using three components in explanations through this method, and the position and tendency of the low-resistance plane can be simply judged.

Xi Z.-Z.,Central South University | Xu P.-Y.,Central South University | Long X.,Changsha 5D Geo survey and Technical Co. | Wang H.,Central South University | And 2 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2011

The orthogonal horizontal magnetic dipole source simulates the natural electromagnetic field well, it conveniently realizes the tensor survey of controlled electromagnetic source in a high frequency band. The field distribution of orthogonal horizontal magnetic dipole source in homogeneous isotropic medium is computed. The result indicates that the horizontal components of the electromagnetic field show a belt of relatively low value in each quadrant, the scalar apparent resistivity shows a distortion belt in the same position, while the tensor apparent resistivity doesn't show distortion belt; The tensor apparent resistivity is low in the near zone and high in the transition region, and tends to the true value in the far zone. Field experiment was carried out to confirm the numerical result. As the true resistivity of test location is unknown, the test result of orthogonal horizontal magnetic dipole source is contrasted to that of the natural electromagnetic field. The result shows that, similar to the electric dipole source, the field of orthogonal horizontal magnetic dipole source also has a near zone, a transition zone, and a far zone. In the far zone, the relative distance of the source and survey station has no effect on the measurement result, namely, in the far zone measurement can be done in any azimuth. So the influence of separation should be considered to ensure that the measuring is in the far zone.

Xi Z.-Z.,Central South University | Zhu W.-G.,Central South University | Zhang D.-J.,Changsha 5D Geo survey and Technical Co. | Zhang L.-L.,Bureau of Mineral Resources | And 2 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2012

When the enrichment iron ore is buried more than 500 m, it is difficult to achieve the longitudinal resolution of iron ore abnormalities by using audio-frequency magnetotelluric (AMT) method directly. For this reason, based on the geological factors of the ore genesis, metallogenic environment, ore controlling space, and so on, the geological model was made and then the electrical model was set up, which was used to achieve the aim of indirect ore prospection by AMT method. The prospecting tests results in Qijiang-type iron deposit and Ningxiang-type iron deposit prove that the AMT method can deterimine prespecting mark, ore-bearing strata, ore-bearing structure and so on. So, indirectly detect deep-buried rich iron ore.

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