Minerals deposits are found in the deep earth crust. Ages ago people could find the minerals in the upper layers of earth. But the minerals so found were less in quantity. That is when the ancient humans came to know that minerals are found underground. So when there was more and more requirement for the minerals, people started digging the ground to find it.
The ore genesis theory explains the process of formation of minerals underground. Source, transport and trap are the three main components of ore genesis. These three factors determine the amount of deposition. The large source, efficient transport and the trap at the right time improves the deposit of minerals. In these conditions large deposits are formed.
There are different processes that leads to concentration of minerals.
- Hydrothermal deposit process
In this the minerals are formed in association with magma and water. It is a physicochemical phenomenon cause by water movement. At high temperature the magma matter moves the minerals through the conventional sea water cells. Mineralisation occurs deep underground. This metal gets precipitated when temperature and pressure is favourable. Most metals are hydrothermally liberated. As the hydrothermal water moves upwards, it causes dissolved minerals to precipitate from the solution.
- Magmatic deposit process
These deposits are formed on igneous rocks. Crystallization takes places at high temperature. These crystals settle down at the bottom of the rocks. Sulphide ores containing nickel, platinum and copper form from this process. The magma separates this ore from the deposits.
- Metamorphic process
Metamorphic reaction causes the ore deposits to form by lateral secretion. This metamorphic reaction occurs during shearing. In this process there is liberation of minerals such as quartz, carbonates and sulphides. In this reaction there is no hydrothermal flow. These minerals are extracted from deforming rocks and then it is focused into zones of reduced pressure.
- Exogenous process [surficial process]
In this process the concentration of minerals is generally caused by the action of environment. It is combination of both physical and chemical phenomena. In this process first erosion takes place followed by deposition. These deposits are separated by winnowing and magnetic separation.