Intrusive Deposits
Another important class of mineral deposits is associated with large intrusive bodies of igneous rocks (Chapter 3). Recall that magma forms when the combination of temperature and pressure within the Earth are such that the minerals within a particular rock body begin to reach their melting points-presence of water is also a factor in the melting process. As the minerals melt, the chemical bonds between atoms break, releasing charged atoms called ions (e.g., K+, Ca2+, Cl-, SiO44-) that make up the magma. When the magma eventually begins to cool, the ions will be incorporated into new minerals in a sequential manner according to the specific crystallization temperatures of different minerals. Because minerals crystallize at different temperatures, this means that during the early phases of the cooling process the magma chamber will contain both molten material and solid mineral grains.