The various theories of ore genesis
explain how the various types of mineral deposits form within the Earth's crust
. Ore genesis theories are very dependent on the mineral
Ore genesis theories generally involve three components: source, transport or conduit, and trap. This also applies to the petroleum
industry, which was first to use this methodology.
- Source is required because metal must come from somewhere, and be liberated by some process
- Transport is required first to move the metal bearing fluids or solid minerals into the right position, and refers to the act of physically moving the metal, as well as chemical or physical phenomenon which encourage movement
- Trapping is required to concentrate the metal via some physical, chemical or geological mechanism into a concentration which forms mineable ore
The biggest deposits are formed when the source is large, the transport mechanism is efficient, and the trap is active and ready at the right time.
Ore genesis processes
Evans (1993) divides ore genesis into the following main categories based on physical process. These are internal processes, hydrothermal processes, metamorphic processes and surficial processes.
These processes are integral physical phenomena and chemical reactions internal to magmas, generally in plutonic
rocks. These include;