Analysis On The Response Characteristic Of The Transient Electromagnetic Method To Detect The Sparse Disseminated Iron Ore

Recently, transient electromagnetic method is widely used in more fields with its probing depth, strong ability of penetration and the small effect on the terrain, which becomes an indispensable means in searching for the mineral resources, environmental protection, safe production and hydrogeological services. However, the application of transient electromagnetic method in iron exploration is limited; study of the response characteristics of transient electromagnetic method in iron ore is fewer.Magnetic method is the main geophysical exploration method in the exploration of iron ore zones for a long time; however the effect of sparse disseminated magnetic iron ore is not obvious, thus this kind of magnetic method can’t explore the iron ore with weak magnet. Electrical probing includes conducted electrical method and inducted electrical method. The result of exploration of conducted electrical method shows that values of apparent resistivity of sparse disseminated iron ore are high, which are called high resistivity that has little difference with the apparent resistivity of surrounding rock material. Transient electromagnetic method is considered as represent of inducted electrical method, which has clear distinction with the conducted electrical method. The resistivity rate of transient electromagnetic is intends apparent resistivity rate which is different from the apparent resistivity of inducted electrical method.This paper analyzes transient electromagnetic response characteristics of sparse disseminated iron ore from three perspectives. Firstly, Through analysis of using the theory of "smoke ring" from the microscopic point of view, in the process of "smoke ring" penetrating through the iron ore,81%of the time spreads in the iron minerals so that81%transient electromagnetic response of the overall iron ore comes from the iron materials. Therefore, transient electromagnetic response of iron is higher than that of the response of the other materials. Secondly, through the analysis of transient electromagnetic relaxation effects from the macro point of view, sparse disseminated iron ore belongs to superparamagnetic body. Because of the relaxation effects, secondary field of superparamagnetic body is slower than the average magnetic body, thus the response of superparamagnetic secondary field is higher than that of the average magnetic body. Finally, through the construction and modeling of one-dimensional model of water in the sparse disseminated iron ore, iron rock ore and mined-out area, according to the different time, the values of the corresponding induced electromotive force are figured out and the decay curve are showed. Through the analysis of the decay curve, values the intended apparent resistivity are in order of the surrounding rock iron ore, mined-out area and sparse disseminated iron ore. The above conclusions are proved to be scientific through the engineering instances.In conclusion, as to exploration of the iron ore and the mined-out area of the iron ore by using transient electromagnetic method, transient electromagnetic response characteristics should be analyzed comprehensively combined with the corresponding geological information. The correct basis to determine the differences should be get, which could get the correct conclusion to solve the practical problems.