Generally speaking, the explorationist in the mineral industry is keenly aware of
the capabilities of the reflection seismic method in providing accurate and comprehensive
images of the subsurface geology to those charged with finding oil and gas.
Why then does he not apply this method to finding ore deposits? The purpose of this
paper is to introduce and in some cases reacquaint those involved in mineral exploration,
gold in particular, to the capabilities and advantages of seismic exploration.
Of the several methods employed in exploration geophysics, the reflection seismic
method provides the most geologically descriptive imagery, and to depths well in
excess of those possible with other geophysical methods. The imagery depicts both
stratigraphy and structure on sections in which distance is displayed horizontally and
travel-time of the seismic waves is measured vertically. The travel-time is readily converted
In addition to providing detailed stratigraphic and structural information, certain
aspects related to alteration and metamorphism can also be interpreted. For
example, higher seismic velocities are associated with silicification, silication and metamorphic
processes. Lower velocities are associated with sericitization and argillization.
Other properties of seismic waves, e.g., frequency, amplitude, coherency and
resonance, can be useful in defining, alteration, fracturing and/or brecciation.
In applying seismic exploration methods to mineral exploration, one may consider
several frames of reference from which to view the seismic effort. The first might
be whether the refraction or reflection method should be used. Another might be
whether a high degree or a low degree of resolution is required. This will affect the
data acquisition parameters needed to execute a successful survey. An important consideration
is the size and orientation of the target or potential target, its physical
properties and the geologic structure and stratigraphy. Of course most of these and
other factors will be “unknowns” until after the seismic survey is completed, but the
explorationist is well served if aware of these factors during the planning and design
of the program.
Seismic methods use acoustic (sound) waves to penetrate the various soil and rock
units in the subsurface. By using the physical laws that govern the refraction and
reflection of acoustic waves, and by observing the travel times of the waves from the
wave source to sensors deployed along lines or in patterns away from the source, certain
valuable information can be derived. For instance, sedimentary strata and
unconformities, geologic structure, and anomalous features such as rock alteration,
tectonic breccia, massive sulfide, and skarn can be discerned.