Although overburden cover in the flat valleys of Dos Santos has hindered exploration and left this area unexplored or underexplored, Galore’s modern geophysical survey has reduced exploration risk substantially by identifying 12 primary targets. These targets are now defined and are available for a systematic follow-up program.
Galore's geophysical exploration program was designed to detect breccia pipes and associated mineralization. These are caused by explosive events related to ascending granitic magma. Breccia pipes are sub-vertical pipes filled with angular rock fragments, which generally come to surface and are detected by their lower rock density and therefore create gravity lows. The underlying intrusions evolve over time to include a fluid phase, which is capable of creating the pipe and may contain high concentrations of metals which are transported in a fluid phase to fragment filled pipes, which create pathways for mineralizing fluids to travel up the pipe and fill the open spaces with mineralization.
Reactive rocks, like limestone, can react with these fluids to produce smaller, higher density, ore bodies like “mantos” (blankets of dense mineralization). Mantos may be detected in a gravity survey as gravity highs because of their much higher rock density.
Intrusive rocks generally are magnetic to some degree. When these are intruded in low magnetic sedimentary rocks, as is the case at Dos Santos, they can be reliably identified by the magnetometer that is part of the airborne system. In both mineralization types that we are searching for, magnetic highs are an important feature to define an exploration target. In deciding on a gravity survey both styles of mineralization were considered. Both high and low gravity anomalies associated with magnetic highs are important targets and both types were identified in this survey.