Method for determining electromagnetically the locations of underground ore deposits

Method for electromagnetically determining the position of an underground conductive body in an area, such as in a mountainous or undulating area, where the transmission of radio waves is prone to be disturbed, said method comprising the steps of:

• providing a loop for generating a primary electromagnetic field and means for generating a current in the loop, the primary electromagnetic field for being propagated underground to interact with an underground conductive body to provide a secondary electromagnetic field;
• positioning the loop in an area in which the position of an underground conductive body is to be determined, to define a propagation area of the primary field;
• positioning the means for generating a current in the loop adjacent to the loop;
• providing a borehole within the propagation area;
• providing probe means for being disposed in the borehole and for receiving at least a portion of a total electromagnetic field, the total electromagnetic field comprising at least a portion of the primary electromagnetic field and at least a portion of the secondary electromagnetic field;
• providing receiver means for receiving signals from the probe means;
• providing means for transmitting measurement information from the probe means to the receiver means;
• providing reference coil means, separate from the receiver means, for receiving at least a portion of the primary electromagnetic field;
• providing means for transmitting measurement information from the reference coil means to the receiver means;
• said receiver means comprising means for determining the secondary electromagnetic field from the measurement information from the probe means and from the measurement information from the reference coil means;
• positioning both the reference coil means and the receiver means remotely from the loop and in an area wherein there is mountainous or undulating terrain between the loop and the combination of the reference coil means and the receiver means;
• disposing the probe means in the borehole;
• generating a current in the loop to create the primary electromagnetic field;
• propagating the primary electromagnetic field underground, in the propagation area, to interact with an underground conductive body to provide the secondary electromagnetic field;
• measuring the total electromagnetic field comprising the primary electromagnetic field and the secondary electromagnetic field;
• measuring the primary electromagnetic field;
• transmitting measurement information of the total electromagnetic field from the probe means to the receiver means;
• transmitting measurement information of the primary electromagnetic field from the reference coil means to the receiver means;
• and
• determining the secondary electromagnetic field to generate information about the location of the conductive body.

Apparatus for electromagnetically determining the position of an underground conductive body, said apparatus comprising:

• a loop for generating a primary electromagnetic field and means for generating a current in said loop, the primary electromagnetic field for being propagated underground to interact with an underground conductive body to provide a secondary electromagnetic field;
• said loop being configured for being positioned at a surface of terrain, generally above an area in which the position of an underground conductive body is to be determined, to define a propagation area of the primary field;
• said means for generating a current in said loop, for being positioned adjacent said loop;
• probe means for being disposed in a borehole being provided within the propagation area;
• said probe means for receiving at least a portion of a total electromagnetic field which total electromagnetic field comprises at least a portion of the primary electromagnetic field and at least a portion of the secondary electromagnetic field;
• receiver means for receiving signals from said probe means;
• means for transmitting measurement information of the total electromagnetic field from said probe means to said receiver means;
• reference coil means, separate from said receiver means, for receiving at least a portion of the primary electromagnetic field;
• means for transmitting measurement information of the primary magnetic field from said reference coil means to said receiver means;
• said receiver means comprising means for determining the secondary electromagnetic field from the measurement information from said probe means and from the measurement information from said reference coil means;
• and
• both said reference coil means and said receiver means being configured for being positioned underground and remotely from said loop.