Evaporites are non-clastic, or chemical sediments, created through the precipitation of dissolved salts from water. They most frequently occur at the site of a former large water body such as a lake or landlocked sea, on coastal plains (sabkha zones), or where rivers feed very arid desert areas. As the water involved slowly evaporates the salts become more concentrated and at well-defined concentrations they begin to recrystallise. They are different to the more conventional clastic sedimentary rocks which include mudstone, siltstone and sandstone.
Sometimes referred to as salines, these rocks form an economically important group of minerals. Sylvite (potassium sulphate) and minor amounts of halite (rock salt) are extracted by Cleveland Potash Ltd. from their mine at Boulby, near Staithes. This is Europe’s deepest shaft mine as the sylvite lies within Permian strata over a kilometer below the surface. They are some 290 million years old and were laid down when a shallow ancient sea, dubbed the Zechstein and which occupied much of northern England, underwent several cycles of evaporation and transgression. Sea water comprises ~3.5% dissolved salts of which the bulk is sodium chloride or common salt. Evaporation yields successively limestone, anhydrite (calcium sulphate), halite and finally potassium and magnesium salts. Anhydrite was formerly mined and processed at Billingham on Teesside.
Evaporite deposits can flow under pressure producing salt-domes which disturb the strata through which the pass and internally exhibit complex folding. They also retain heat and may be a target for future geothermal energy projects.
Images above show:
Sylvite – as mined at Cleveland Potash Mine, Boulby, Cleveland.
Halite – also found within Boulby Mine.
Cleveland Potash Mine, Boulby, East Cleveland. UK.
Anhydrite – once mined at Billingham on Teesside.
February 2010 – Evaporites
Evaporites are non-clastic, or chemical sediments, created through the precipitation of dissolved salts from water. They most frequently occur at the site of a former large water body such as a lake or landlocked sea, on coastal plains (sabkha zones), or where rivers feed very arid desert areas. As the water involved slowly evaporates the salts become more concentrated and at well-defined concentrations they begin to recrystallise. They are different to the more conventional clastic sedimentary rocks which include mudstone, siltstone and sandstone.
Sometimes referred to as salines, these rocks form an economically important group of minerals. Sylvite (potassium sulphate) and minor amounts of halite (rock salt) are extracted by Cleveland Potash Ltd. from their mine at Boulby, near Staithes. This is Europe’s deepest shaft mine as the sylvite lies within Permian strata over a kilometer below the surface. They are some 290 million years old and were laid down when a shallow ancient sea, dubbed the Zechstein and which occupied much of northern England, underwent several cycles of evaporation and transgression. Sea water comprises ~3.5% dissolved salts of which the bulk is sodium chloride or common salt. Evaporation yields successively limestone, anhydrite (calcium sulphate), halite and finally potassium and magnesium salts. Anhydrite was formerly mined and processed at Billingham on Teesside.
Evaporite deposits can flow under pressure producing salt-domes which disturb the strata through which the pass and internally exhibit complex folding. They also retain heat and may be a target for future geothermal energy projects.
Images above show:
Sylvite – as mined at Cleveland Potash Mine, Boulby, Cleveland.
Halite – also found within Boulby Mine.
Cleveland Potash Mine, Boulby, East Cleveland. UK.
Anhydrite – once mined at Billingham on Teesside.