Shipwrecks and Salvage > 1. Oceans and Electrolytes >
Identify the origins of the minerals in oceans as:
- leaching by rainwater from terrestrial environments
- hydrothermal vents in mid-ocean ridges
- Seawater has a typical salinity of 3.5% by mass, with this high concentration of free ions making it a strong electrolyte solution.
- Thus, seawater is highly conducting of electricity, which strongly affects the reactions that can take place in it.
- Sodium chloride is the most common salt present, with seawater being a 0.47 mol/L sodium chloride solution.
- There are considerable concentrations of other ions also.
- The two major sources of minerals in oceans are:
- Leaching by rainwater.
- When rainwater falls, it penetrates rocks and soils and leaches out minerals through weathering.
- Minerals that dissolve in this process flow through waterways into oceans, with the main ions involved being sodium, calcium, magnesium, chloride, sulfate, and hydrogen carbonate.
- Dissolution of salts by water passing through hydrothermal vents.
- Mid-ocean ridges exist near tectonic plate boundaries and often have cracks, or fissures, in the rock.
- Water percolates down fissures, comes close to up-welling magma, is heated to high temperatures at high pressures, and then is forced back into the ocean through other fissures.
- As hot water passes through these fissures, it dissolves ionic substances from the rocks.
- The variety of ions released in this process include sodium, magnesium, potassium, chloride, bromide and sulfate.
- Some heavy minerals crystallise due to the change in temperature and deposit on the ocean floor, while others remain soluble.
- Leaching by rainwater.