Resource consideration
A wide array of trace metals (Co, Ni, Ti, Cu), rare metals
(Te, Pt, Zr, Nb, W, Bi, Mo, Tl, Th, V), and REEs are
sorbed in large quantities onto the Mn and Fe oxides making crusts a potential resource for many metals used in
emerging high-tech, green-tech, and energy applications.
Such high concentrations of metals are sorbed because
of the very slow growth rates, extreme specific surface
area (average 325 m
2
/cm
3 of crust), and high porosity
(average 60 %) of crusts (Hein et al., 2000). The tonnage
of Fe–Mn crusts in most areas of the global ocean is
poorly known. However, a rough estimate for the PCZ
area is about 7,533 million dry tonnes (Hein and
Koschinsky, 2014). Using this tonnage estimate, Fe–Mn
crusts in the PCZ are calculated to contain about four times
more Co, three and a half times more Y, and an incredible
nine times more Te than the entire land-based reserve base
for those metals; these crusts also contain half the Bi and
a third of the Mn that make up the entire land-based
reserve base (Hein et al., 2013). The reserve base is
defined as land-based deposits that are currently economically viable (reserves), marginally economic, and
subeconomic.
There are two technological challenges to overcome
before Fe–Mn crust mining can become viable. A deeptowed or autonomous underwater vehicle-mounted
instrument must be developed that can measure Fe–Mn
crust thicknesses in situ in real time. This measurement
gives the tonnage of crusts per square meter of
seabed. This is a difficult challenge because there are
a great variety of rocks on which crusts grow that have
variable physical properties, many of which overlap with
those of the crusts. The second technological challenge
is developing a mining tool that can remove the Fe–Mn
crust from the substrate rock without collecting any substrate rock, to which crusts can be attached tightly to
weakly. That separation of crust from substrate will have
to be done on an uneven and commonly rough seabed.
These challenges will require significant engineering
innovations.
Summary
Fe–Mn crusts grow on nearly all rocks exposed at the
seabed throughout the global ocean where sediment
does not accumulate. Crusts are composed predominantly
of Fe and Mn oxide minerals that precipitate from
cold seawater and acquire abundant metals and other
elements by sorption from seawater. Metals essential to
many emerging technologies are enriched in crusts to the
extent that they are considered a potential resource for
mining in the near future. Four contracts for exploration
for crusts have been taken out with the International Seabed Authority, one each by Japan, China, Russia, and Brazil. Fe–Mn crusts also have a unique potential as recorders
of oceanographic events that have occurred over the past
70 Ma.
Bibliography
Frank, M., O'Nions, R. K., Hein, J. R., and Banakar, V. K., 1999.
60 Myr records of major elements and Pb-Nd isotopes from
hydrogenous ferromanganese crusts: reconstruction of seawater
paleochemistry. Geochimica et Cosmochimica Acta, 63,
1689–1708.
Halbach, P., Manhein, F. T., and Otten, P., 1982. Co-rich ferromanganese deposits in the marginal seamount regions of the Central
Pacific Basin—results of the Midpac’81. Erzmetall, 35,
447–453.
Hein, J. R., and Koschinsky, A., 2014. Deep-ocean ferromanganese
crusts and nodules, Chapter 11. In Holland, H. D., and Turekian,
K. K. (eds.), Treatise on Geochemistry. Elsevier: Oxford, Vol.
13, pp. 273–291.
Hein, J. R., Koschinsky, A., Bau, M., Manheim, F. T., Kang, J.-K.,
and Roberts, L., 2000. Cobalt-rich ferromanganese crusts in the
Pacific. In Cronan, D. S. (ed.), Handbook of Marine Mineral
Deposits. Boca Raton: CRC Press, pp. 239–279.
Hein, J. R., Conrad, T. A., and Dunham, R. E., 2009. Seamount
characteristics and mine-site model applied to exploration- and
mining-lease-block selection for cobalt-rich ferromanganese
crusts. Marine Georesources and Geotechnology, 27, 160–176.
Hein, J. R., Mizell, K., Koschinsky, A., and Conrad, T. A., 2013.
Deep-ocean mineral deposits as a source of critical metals for
high- and green-technology applications: comparison with
land-based deposits. Ore Geology Reviews, 51, 1–14.
Klemm, V., Levasseur, S., Frank, M., Hein, J. R., and Halliday,
A. N., 2005. Osmium isotope stratigraphy of a marine ferromanganese crust. Earth and Planetary Science Letters, 238, 42–48.
Koschinsky, A., and Hein, J. R., 2003. Uptake of elements from seawater by ferromanganese crusts: solid phase association and seawater speciation. Marine Geology, 198, 331–351.
Cross-references
Deep-sea Sediments
Dust in the Ocean
Energy Resources
Geochronology: Uranium-Series Dating of Ocean Formations
Guyot, Atoll
Manganese Nodules
Marine Mineral Resources
Paleoceanographic Proxies
Paleoceanography
Phosphorites
Radiogenic Tracers
Seamounts
Technology in Marine Geosciences
COLD SEEPS
Marta E. Torres
1 and Gerhard Bohrmann
2
1
College of Earth, Ocean, and Atmospheric Sciences,
Oregon State University, Corvalis, OR, USA
2
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
Synonyms
Cold vents; Methane seeps
COLD SEEPS
117
A wide array of trace metals (Co, Ni, Ti, Cu), rare metals
(Te, Pt, Zr, Nb, W, Bi, Mo, Tl, Th, V), and REEs are
sorbed in large quantities onto the Mn and Fe oxides making crusts a potential resource for many metals used in
emerging high-tech, green-tech, and energy applications.
Such high concentrations of metals are sorbed because
of the very slow growth rates, extreme specific surface
area (average 325 m
2
/cm
3 of crust), and high porosity
(average 60 %) of crusts (Hein et al., 2000). The tonnage
of Fe–Mn crusts in most areas of the global ocean is
poorly known. However, a rough estimate for the PCZ
area is about 7,533 million dry tonnes (Hein and
Koschinsky, 2014). Using this tonnage estimate, Fe–Mn
crusts in the PCZ are calculated to contain about four times
more Co, three and a half times more Y, and an incredible
nine times more Te than the entire land-based reserve base
for those metals; these crusts also contain half the Bi and
a third of the Mn that make up the entire land-based
reserve base (Hein et al., 2013). The reserve base is
defined as land-based deposits that are currently economically viable (reserves), marginally economic, and
subeconomic.
There are two technological challenges to overcome
before Fe–Mn crust mining can become viable. A deeptowed or autonomous underwater vehicle-mounted
instrument must be developed that can measure Fe–Mn
crust thicknesses in situ in real time. This measurement
gives the tonnage of crusts per square meter of
seabed. This is a difficult challenge because there are
a great variety of rocks on which crusts grow that have
variable physical properties, many of which overlap with
those of the crusts. The second technological challenge
is developing a mining tool that can remove the Fe–Mn
crust from the substrate rock without collecting any substrate rock, to which crusts can be attached tightly to
weakly. That separation of crust from substrate will have
to be done on an uneven and commonly rough seabed.
These challenges will require significant engineering
innovations.
Summary
Fe–Mn crusts grow on nearly all rocks exposed at the
seabed throughout the global ocean where sediment
does not accumulate. Crusts are composed predominantly
of Fe and Mn oxide minerals that precipitate from
cold seawater and acquire abundant metals and other
elements by sorption from seawater. Metals essential to
many emerging technologies are enriched in crusts to the
extent that they are considered a potential resource for
mining in the near future. Four contracts for exploration
for crusts have been taken out with the International Seabed Authority, one each by Japan, China, Russia, and Brazil. Fe–Mn crusts also have a unique potential as recorders
of oceanographic events that have occurred over the past
70 Ma.
Bibliography
Frank, M., O'Nions, R. K., Hein, J. R., and Banakar, V. K., 1999.
60 Myr records of major elements and Pb-Nd isotopes from
hydrogenous ferromanganese crusts: reconstruction of seawater
paleochemistry. Geochimica et Cosmochimica Acta, 63,
1689–1708.
Halbach, P., Manhein, F. T., and Otten, P., 1982. Co-rich ferromanganese deposits in the marginal seamount regions of the Central
Pacific Basin—results of the Midpac’81. Erzmetall, 35,
447–453.
Hein, J. R., and Koschinsky, A., 2014. Deep-ocean ferromanganese
crusts and nodules, Chapter 11. In Holland, H. D., and Turekian,
K. K. (eds.), Treatise on Geochemistry. Elsevier: Oxford, Vol.
13, pp. 273–291.
Hein, J. R., Koschinsky, A., Bau, M., Manheim, F. T., Kang, J.-K.,
and Roberts, L., 2000. Cobalt-rich ferromanganese crusts in the
Pacific. In Cronan, D. S. (ed.), Handbook of Marine Mineral
Deposits. Boca Raton: CRC Press, pp. 239–279.
Hein, J. R., Conrad, T. A., and Dunham, R. E., 2009. Seamount
characteristics and mine-site model applied to exploration- and
mining-lease-block selection for cobalt-rich ferromanganese
crusts. Marine Georesources and Geotechnology, 27, 160–176.
Hein, J. R., Mizell, K., Koschinsky, A., and Conrad, T. A., 2013.
Deep-ocean mineral deposits as a source of critical metals for
high- and green-technology applications: comparison with
land-based deposits. Ore Geology Reviews, 51, 1–14.
Klemm, V., Levasseur, S., Frank, M., Hein, J. R., and Halliday,
A. N., 2005. Osmium isotope stratigraphy of a marine ferromanganese crust. Earth and Planetary Science Letters, 238, 42–48.
Koschinsky, A., and Hein, J. R., 2003. Uptake of elements from seawater by ferromanganese crusts: solid phase association and seawater speciation. Marine Geology, 198, 331–351.
Cross-references
Deep-sea Sediments
Dust in the Ocean
Energy Resources
Geochronology: Uranium-Series Dating of Ocean Formations
Guyot, Atoll
Manganese Nodules
Marine Mineral Resources
Paleoceanographic Proxies
Paleoceanography
Phosphorites
Radiogenic Tracers
Seamounts
Technology in Marine Geosciences
COLD SEEPS
Marta E. Torres
1 and Gerhard Bohrmann
2
1
College of Earth, Ocean, and Atmospheric Sciences,
Oregon State University, Corvalis, OR, USA
2
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
Synonyms
Cold vents; Methane seeps
COLD SEEPS
117