vapor to brine. Earth and Planetary Science Letters, 149,
101–112.
Yang, K., and Scott, S. D., 2006. Magmatic fluids as a source of
metals in seafloor hydrothermal systems. In Christie, D. M.,
Fisher, C. R., Lee, S.-M., and Givens, S. (eds.), Back-Arc
Spreading Systems: Geological, Biological, Chemical, and
Physical Interactions. Washington, DC: American Geophysical
Union. Geophysical Monograph Series, Vol. 166, pp. 163–184.
Cross-references
Black and White Smokers
Hydrothermal Plumes
Hydrothermalism
Marine Mineral Resources
Oceanic Spreading Centers
Serpentinization
Volcanogenic Massive Sulfides
HYDROTHERMALISM
John W. Jamieson
1
, Sven Petersen
1 and Wolfgang Bach
2,3
1
GEOMAR Helmholtz Centre for Ocean Research, Kiel,
Germany
2
Department of Geosciences, University of Bremen,
Bremen, Germany
3
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
Definition
Hydrothermalism refers to the convective circulation of
seawater through oceanic lithosphere with possible contributions of volatiles and metals from underlying magma
chambers.
Introduction
The circulation of seawater through oceanic lithosphere is
the principal mechanism for the transfer of heat and
chemicals between the ocean and underlying crust and
has a direct effect on the composition and heat budget of
oceanic lithosphere and the composition of seawater
(e.g., German and Seyfried, 2014). Along submarine tectonic plate boundaries (see “Mid-ocean Ridge Magmatism
and Volcanism,” “Magmatism at Convergent Plate
Boundaries,” “Intraoceanic Subduction Zone,” “Hydrothermal Plumes”) and hot-spot chains, the heat associated
with crystallization in shallow magma reservoirs and
cooling of hot rock drives the circulation of seawater
through the permeable crust. As the fluid circulates, it is
heated, reacts chemically with the surrounding rock, and
ultimately discharges back at the seafloor (see “Hydrothermal Vent Fluids (Seafloor)”). To date, over 500 hydrothermal discharge sites have been discovered along
submarine tectonic boundaries, at an average spacing of
about one major discharge site per 100 km of ridge axis
(http://www.interridge.org/IRvents). Cooling of the crust
by hydrothermal circulation accounts for about 30 % of
the heat lost from newly formed (<1 million year old) oceanic lithosphere (Wolery and Sleep, 1976; German and
Seyfried, 2014).
The circulation of seawater and the fluid-rock interactions (both chemical and thermal) that occur are a direct
result of magmatic heat input into the system and cooling
of the newly accreted lithosphere. Our understanding of
these processes derives mainly from observations of alteration minerals within oceanic crust exposed on large-scale
oceanic faults and from Ocean Drilling Program drill cores
(Alt and Teagle, 2003; Teagle et al., 2003). Additional
information has been gained from slices of oceanic crust
that have been thrust onto land by plate tectonic processes
(i.e., ophiolites; (Gillis, 2002). As seawater flows downward into the crust and reacts with the surrounding rock,
progressive chemical alteration of both the rock and fluid
takes place. As a consequence of this process, some
dissolved components within the original seawater are
transferred to the rock, whereas chemical constituents
within the host rock may be leached by the fluid
(Figure 1). Evidence from seismic studies indicates that
the depths within the crust to which fluids circulate can
vary from less than 1 km to greater than 4 km, depending
on factors such as the depth of the axial magma chamber
and the depth of the brittle-ductile transition zone. Temperatures of the circulating seawater-derived fluids can
reach more than 500
C in the reaction zone at the base
of the circulating cell. Here, the intensity of fluid-rock
interactions reaches a maximum, and the high temperatures cause the fluid, which is now rich in dissolved metals
and reduced sulfur leached from the surrounding rock, to
become positively buoyant. Seawater is converted to variable salinity fluids in the course of supercritical phase
separation, and these fluids rapidly ascend back to the surface along focused, deep-seated permeable pathways such
as fault planes (Figure 1). Where hot, mineral-laden fluid
reaches the seafloor, it mixes with cold ambient seawater,
causing a sudden change in temperature, redox conditions,
and the precipitation of sulfide minerals from the hydrothermal fluid. The precipitated minerals both accumulate
at the vent site, forming massive sulfide spires and
mounds, and are vented into the overlying water column
as “smoke,” which has led to such vents being referred
to as “black or white smokers” or “chimneys.” Several
(tens to hundreds) individual vents often occur in a cluster,
or vent field, that can be spread over hundreds of m above
a hydrothermal upflow zone. As the chimneys grow, they
often collapse, and a new chimney begins to grow on the
talus of the collapsed chimney. Over time, the sulfide
material from neighboring vents coalesces to form massive sulfide mounds (Figure 1). Most of the dissolved
material, however, is ejected into the water column,
forming a hydrothermal plume that can rise to several hundred meters above the seafloor (Figure 1). The thermal and
chemical anomalies associated with these plumes can be
traced over several kilometers from the vent site, and the
344
HYDROTHERMALISM
101–112.
Yang, K., and Scott, S. D., 2006. Magmatic fluids as a source of
metals in seafloor hydrothermal systems. In Christie, D. M.,
Fisher, C. R., Lee, S.-M., and Givens, S. (eds.), Back-Arc
Spreading Systems: Geological, Biological, Chemical, and
Physical Interactions. Washington, DC: American Geophysical
Union. Geophysical Monograph Series, Vol. 166, pp. 163–184.
Cross-references
Black and White Smokers
Hydrothermal Plumes
Hydrothermalism
Marine Mineral Resources
Oceanic Spreading Centers
Serpentinization
Volcanogenic Massive Sulfides
HYDROTHERMALISM
John W. Jamieson
1
, Sven Petersen
1 and Wolfgang Bach
2,3
1
GEOMAR Helmholtz Centre for Ocean Research, Kiel,
Germany
2
Department of Geosciences, University of Bremen,
Bremen, Germany
3
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
Definition
Hydrothermalism refers to the convective circulation of
seawater through oceanic lithosphere with possible contributions of volatiles and metals from underlying magma
chambers.
Introduction
The circulation of seawater through oceanic lithosphere is
the principal mechanism for the transfer of heat and
chemicals between the ocean and underlying crust and
has a direct effect on the composition and heat budget of
oceanic lithosphere and the composition of seawater
(e.g., German and Seyfried, 2014). Along submarine tectonic plate boundaries (see “Mid-ocean Ridge Magmatism
and Volcanism,” “Magmatism at Convergent Plate
Boundaries,” “Intraoceanic Subduction Zone,” “Hydrothermal Plumes”) and hot-spot chains, the heat associated
with crystallization in shallow magma reservoirs and
cooling of hot rock drives the circulation of seawater
through the permeable crust. As the fluid circulates, it is
heated, reacts chemically with the surrounding rock, and
ultimately discharges back at the seafloor (see “Hydrothermal Vent Fluids (Seafloor)”). To date, over 500 hydrothermal discharge sites have been discovered along
submarine tectonic boundaries, at an average spacing of
about one major discharge site per 100 km of ridge axis
(http://www.interridge.org/IRvents). Cooling of the crust
by hydrothermal circulation accounts for about 30 % of
the heat lost from newly formed (<1 million year old) oceanic lithosphere (Wolery and Sleep, 1976; German and
Seyfried, 2014).
The circulation of seawater and the fluid-rock interactions (both chemical and thermal) that occur are a direct
result of magmatic heat input into the system and cooling
of the newly accreted lithosphere. Our understanding of
these processes derives mainly from observations of alteration minerals within oceanic crust exposed on large-scale
oceanic faults and from Ocean Drilling Program drill cores
(Alt and Teagle, 2003; Teagle et al., 2003). Additional
information has been gained from slices of oceanic crust
that have been thrust onto land by plate tectonic processes
(i.e., ophiolites; (Gillis, 2002). As seawater flows downward into the crust and reacts with the surrounding rock,
progressive chemical alteration of both the rock and fluid
takes place. As a consequence of this process, some
dissolved components within the original seawater are
transferred to the rock, whereas chemical constituents
within the host rock may be leached by the fluid
(Figure 1). Evidence from seismic studies indicates that
the depths within the crust to which fluids circulate can
vary from less than 1 km to greater than 4 km, depending
on factors such as the depth of the axial magma chamber
and the depth of the brittle-ductile transition zone. Temperatures of the circulating seawater-derived fluids can
reach more than 500
C in the reaction zone at the base
of the circulating cell. Here, the intensity of fluid-rock
interactions reaches a maximum, and the high temperatures cause the fluid, which is now rich in dissolved metals
and reduced sulfur leached from the surrounding rock, to
become positively buoyant. Seawater is converted to variable salinity fluids in the course of supercritical phase
separation, and these fluids rapidly ascend back to the surface along focused, deep-seated permeable pathways such
as fault planes (Figure 1). Where hot, mineral-laden fluid
reaches the seafloor, it mixes with cold ambient seawater,
causing a sudden change in temperature, redox conditions,
and the precipitation of sulfide minerals from the hydrothermal fluid. The precipitated minerals both accumulate
at the vent site, forming massive sulfide spires and
mounds, and are vented into the overlying water column
as “smoke,” which has led to such vents being referred
to as “black or white smokers” or “chimneys.” Several
(tens to hundreds) individual vents often occur in a cluster,
or vent field, that can be spread over hundreds of m above
a hydrothermal upflow zone. As the chimneys grow, they
often collapse, and a new chimney begins to grow on the
talus of the collapsed chimney. Over time, the sulfide
material from neighboring vents coalesces to form massive sulfide mounds (Figure 1). Most of the dissolved
material, however, is ejected into the water column,
forming a hydrothermal plume that can rise to several hundred meters above the seafloor (Figure 1). The thermal and
chemical anomalies associated with these plumes can be
traced over several kilometers from the vent site, and the
344
HYDROTHERMALISM