Why are plateaus called a 'storehouse of minerals'?

Plateaus are known as a 'storehouse of minerals' because they are rich in minerals. Due to this, mining areas are usually located in plateau areas.

For example, we get gold from the Plateau of Western Australia; copper, diamonds and gold from the Plateaus of Africa; and coal, iron, manganese and mica from the Chhota Nagpur Plateau in India.