What are the ore minerals form?

Answer 1

After the oceans formed; you could imagine that the water was full of all sorts of materials, which were dissolved from the rocks as the waters slowly filled up the oceans, when the earth cooled sufficiently for large volumes of water to accumulate.

The dissolved materials included a lot of iron salts (probably iron chloride and iron sulphate); as well as the soduim chloride still present today.

The first forms of life that developed are thought to be bacteria (similar to today's blue-green algae). They didn't require oxygen, but converted carbon dioxide and water to sugars using sunlight; much like todays plants. Oxygen was actually a waste product, so they excreted it (blue green algae still do this today). Conditions were ideal for them, so they multiplied rapidly, and had the oceans mostly to themselves for hundreds of millions of years.

The oxygen they gave off reacted with the dissolved iron salts in the water to form iron hydroxides and iron oxides. These materials are insoluble; so they settled to the bottom. It took millions of years for the oxygen to react with all the dissolved iron, and very thick deposits formed. These can still be seen today, and are called

'banded iron formation'.

Finally, when most of the iron had been precipitated out of the water, there was an excess of oxygen, which was partly dissolved in the water, and then also passed into the atmosphere, enabling marine and terrestrial oxygen requiring life forms to develop. This where the oxygen in the atmosphere came from; and if it weren't for the early cyanobacteria, life on earth would not exist.

Over time, the large deposits of iron rich sediments were moved and changed because of the movements of the crustal plates, and they eventually formed large deposits of magnetite and haematite, which make up most of the world's iron ore deposits.

That is why most iron ore deposits are found in ancient rock formations.

Answer 2

Name the 3 ways ores are formed?