296 Resources from the Ocean Roor
e
Fig. 10.13. "La Dame Blanche" , a chimney made of anhydrite at an active hydrothermal site with fluids of 285 °C
and active animal colonies. North Fiji
Basin axis, 1900 m watrer depth. [J. M.
Auzende et aI. , 1989, C. R. Acad. Sci .
Paris, 309, II, 1787]
As the ores and other minerals precipitate within cracks in the basalt, they tend to
clog the hydrothermal system, eventually turning it off. Ores near the surface may be
brecciated by hydrofracturing and may be covered by new lava in several cycles.
Fossile massive sulfide ore deposits as in Southeast Japan (Kuroko) or Cyprus
(Troodos) permit the study of these complicated relationships on land.
Metalliferous hydrothermal systems were recently also discovered in back arc
basins: Manus basin north of Papua New Guinea, Lau basin west of the Tonga Plate
boundary (Fig. Appendix AS.l) and others with oceanic crust. Vents in the Okinawa
Through issue from continental crust.
Of course, hydrothermal processes are everywhere associated with volcanic activity - Santorini off Greece, Ebeko in the Kurile Islands, Loihi seamount off Hawaii
(the latest creation of the fire goddess Pele) are examples.
Hydrothermal activity is of fundamental importance for plate tectonics (heat budget of the lithosphere) and for geochemistry (origin of seawater, fractionation of
metals from basalts, sil ica cycle). The heat transfer by this process is of the order of
one fourth of the total global heat loss. Every 8 to IO million years the volume of the
entire ocean passes through hydrothermal systems - conditioning the seawater and
resetting its chemistry. Ultimately, this process also stabilizes the chemistry of the
atmosphere and climate. It should be kept in mind, that seawater/basalt interaction is
not restricted to volcanically active regions - the entire seafloor is young and cools
continuously, and can drive weak hydrothermal flow almost everywhere.
Economically, the Ridge Crest deposits and other deep-sea hydrothermal ores are
as yet not important, despite their presumed large volume throughout the oceanic
e
Fig. 10.13. "La Dame Blanche" , a chimney made of anhydrite at an active hydrothermal site with fluids of 285 °C
and active animal colonies. North Fiji
Basin axis, 1900 m watrer depth. [J. M.
Auzende et aI. , 1989, C. R. Acad. Sci .
Paris, 309, II, 1787]
As the ores and other minerals precipitate within cracks in the basalt, they tend to
clog the hydrothermal system, eventually turning it off. Ores near the surface may be
brecciated by hydrofracturing and may be covered by new lava in several cycles.
Fossile massive sulfide ore deposits as in Southeast Japan (Kuroko) or Cyprus
(Troodos) permit the study of these complicated relationships on land.
Metalliferous hydrothermal systems were recently also discovered in back arc
basins: Manus basin north of Papua New Guinea, Lau basin west of the Tonga Plate
boundary (Fig. Appendix AS.l) and others with oceanic crust. Vents in the Okinawa
Through issue from continental crust.
Of course, hydrothermal processes are everywhere associated with volcanic activity - Santorini off Greece, Ebeko in the Kurile Islands, Loihi seamount off Hawaii
(the latest creation of the fire goddess Pele) are examples.
Hydrothermal activity is of fundamental importance for plate tectonics (heat budget of the lithosphere) and for geochemistry (origin of seawater, fractionation of
metals from basalts, sil ica cycle). The heat transfer by this process is of the order of
one fourth of the total global heat loss. Every 8 to IO million years the volume of the
entire ocean passes through hydrothermal systems - conditioning the seawater and
resetting its chemistry. Ultimately, this process also stabilizes the chemistry of the
atmosphere and climate. It should be kept in mind, that seawater/basalt interaction is
not restricted to volcanically active regions - the entire seafloor is young and cools
continuously, and can drive weak hydrothermal flow almost everywhere.
Economically, the Ridge Crest deposits and other deep-sea hydrothermal ores are
as yet not important, despite their presumed large volume throughout the oceanic