Sketch, label, and describe how a placer deposit accumulates and explain how these placer deposits are related to the vein deposits.
Sketch, label, and describe how a placer deposit accumulates and explain how these placer deposits are related to the vein deposits.
The natural separation of heavy minerals from light ones by moving water, air, or gravity is called mechanical concentration. The mineral deposits formed by this process are called placers. The minerals which commonly occur as placer deposits are diamond, gold, platinum, magnetite, monazite.
The process of formation of placer deposits are:
- The ore minerals are released from the rock by weathering and disintegration.
- The disintegrated materials are carried downslope by water and air. Ultimately this material reaches the stream or seashore.
- The heavier placer minerals sink to the bottom in the moving water or air while the lighter material is carried further. Thus the heavier minerals are separated from, the lighter ones.
- In this way, the heavy minerals get accumulated in particular localities to form placer deposits.
These placer deposits require a primary source, such as an ore deposit in the form of veins. This source must be exposed to weathering on a slope from where the disintegrated material may be carried away by water or air. The ore mineral in the vein deposit must be of such chemical composition that is it can resist weathering. For a mineral to be concentrated as a placer deposit, it must have a higher density than the worthless material with which it occurs.
Different types of placers are stream placers, beach placers, and Aeolian placers.
- The deposits occurring along the seashores where mineral concentration is done by wave action are called beach placers.
- The action of wind forms aeolian placers.
- The water action causes stream placers.
The diagram below shows the different ways by which stream placer deposits can be formed.
Step by step
Solved in 3 steps with 1 images
