For mineral exploration (or prospecting/economic geology) you need a thorough grasp of minerals, alteration, geochemistry, geophysics and rock systems (i.e. you need to understand what you are looking at). You'll get these studying geology.
Geoengineering will cover resource (reserve) calculations, mine design, geostatistics and rock properties. A combination will certainly increase your hire-ability.
In the mining industry, engineers and geologists alike make fun of each others professions, so take whatever advice you get with a grain of salt. Feel free to message me if you have more specific questions.