The resolving power of gravity and magnetic gradients in the search for mineral deposits
Evan Morris and Sandra Vidakovic
Abstract of a paper presented at the Geological Association of Canada annual meeting, 2002
ABSTRACT
Our research was prompted by the developments in gravity gradiometry over the last two decades. We were interested in determining which components of the gravity field are best suited to exploring for mineral deposits. This led us to examine the power of various gravity gradients to resolve anomalies. This knowledge would allow equipment development to be concentrated on the most useful gradients, and it would allow geophysicists to use the most useful gravity gradients when interpreting data from multi-gradient sensors.
The ability to resolve gravity and magnetic bodies increases as the level of the derivative of the gravity or magnetic field increases. However, there are cases where the resolution of a derivative is no better than that of the gravity or magnetic component it is derived from. The vertical component of gravity has a much higher resolution than the horizontal component. The actual resolving power depends on the geometry of the body creating the anomalous gravity or magnetic field. For example, it is easier to resolve spheres than horizontal cylinders. The resolving power of magnetic gradients is equal to or greater than that of gravity gradients. For magnetic bodies, the resolving power varies considerably depending on the strike of the body in relation to magnetic north. The analytic signal often has a higher resolving power than any single gravity or magnetic component, though in some cases a single field component has a better resolving power than the analytic signal.