64
elements such as thallium can be present at concentrations of several hundred ppm.
Nodules can also be considered as strategic reserves for base metals and certain
rare metals. Several countries, including the United States and Germany, have undertaken to resume analyses of their collections of nodules using modern analytical
methods in order to determine the variability in the composition of minor elements
and in particular rare earths.
The chemical elements concentrated in crusts are rather similar to those of nodules. There are however variations for rare earths, platinum and cobalt which tend to
be significantly more concentrated in crusts. Rare earth concentrations can reach a
few thousand ppm in certain hydrogenated crusts, compared to a few hundred ppm
in nodules.
Rare earths are extracted from seawater and the higher concentration in crusts is
related to their lower growth rate.
Hydrothermal sulphides are characterised by very high base metal contents in
relation to crusts and nodules. The sum total of copper and zinc frequently exceeds
15 %. As these are sulphide deposits, the sulphur content is very high and the iron
content varies between 1 and 43 %.
Several minor elements are found alongside the main metals. Copper ore deposits, characterised by their formation at temperatures of over 300 °C, may also be
rich in selenium, cobalt, nickel, molybdenum, tellurium, bismuth and gold. Zinc
ore deposits, formed at between 100 and 250 °C, are often rich in cadmium, lead,
arsenic, antimony, germanium, indium and barium.
Notes
1. The minimum and maximum values presented represent average values for the
sites. Certain specific mineral associations can have far higher concentrations.
2. Data in brackets (2–43)? Only calculated for a few sites.
3. Many concentrations are calculated based on old analytical methods and would
be worth reviewing using quicker, more sensitive methods (ICP-MS).
4. For minor and trace elements, the concentrations exploited and types of landbased deposits need to be checked.
Y. Fouquet and B. Martel-Jantin
elements such as thallium can be present at concentrations of several hundred ppm.
Nodules can also be considered as strategic reserves for base metals and certain
rare metals. Several countries, including the United States and Germany, have undertaken to resume analyses of their collections of nodules using modern analytical
methods in order to determine the variability in the composition of minor elements
and in particular rare earths.
The chemical elements concentrated in crusts are rather similar to those of nodules. There are however variations for rare earths, platinum and cobalt which tend to
be significantly more concentrated in crusts. Rare earth concentrations can reach a
few thousand ppm in certain hydrogenated crusts, compared to a few hundred ppm
in nodules.
Rare earths are extracted from seawater and the higher concentration in crusts is
related to their lower growth rate.
Hydrothermal sulphides are characterised by very high base metal contents in
relation to crusts and nodules. The sum total of copper and zinc frequently exceeds
15 %. As these are sulphide deposits, the sulphur content is very high and the iron
content varies between 1 and 43 %.
Several minor elements are found alongside the main metals. Copper ore deposits, characterised by their formation at temperatures of over 300 °C, may also be
rich in selenium, cobalt, nickel, molybdenum, tellurium, bismuth and gold. Zinc
ore deposits, formed at between 100 and 250 °C, are often rich in cadmium, lead,
arsenic, antimony, germanium, indium and barium.
Notes
1. The minimum and maximum values presented represent average values for the
sites. Certain specific mineral associations can have far higher concentrations.
2. Data in brackets (2–43)? Only calculated for a few sites.
3. Many concentrations are calculated based on old analytical methods and would
be worth reviewing using quicker, more sensitive methods (ICP-MS).
4. For minor and trace elements, the concentrations exploited and types of landbased deposits need to be checked.
Y. Fouquet and B. Martel-Jantin