The Origins of the Minerals in Oceans

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.


EasyChem - Hydrothermal Vents


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