The volcanic activity is the process that creates the new minerals on the planet. In this process, the magma from the mantle rises toward the surface. Some magma solidifies inside the crust, while some on the surface, though then its called lava. Be it inside the crust, or on the surface, it is always a large amount of magma or lava that comes to a certain area, causing the formation of certain minerals, and they are in high concentration. The magma and the lava manage to cover large areas, either pushing aside old rocks, or covering them with thick layers, thus resulting in monotonous high concentrated certain types of minerals in some areas.
