Minerals Report - International Seabed Authority

low temperature vents emitting around 10-30 o C of water, are considerably
warmer than typical ocean water, which is normally around 2-3 ο C. The
significance is that in the vicinity of this warm water, a majority of vents
specific biota are present.
Dr. German observed that although the mid-ocean ridge extends as a
near continuous volcanic chain, it does not exhibit the same activity
everywhere. He stated that one of the important features associated with the
range is plate spreading, which is fastest across much of the equatorial and
southern East Pacific Rise (10-20 cm per year), with intermediate spreading
rates in the eastern and central Indian Ocean and extreme NE Pacific (5-7 cm
per year), and much slower spreading rates throughout the Atlantic ocean (2-3
cm per year), and along the SW Indian and Arctic Ridges (less than 2 cm per
year) after. Dr. German remarked that it almost took a decade of further
research to locate the first “black smoker” on the slow-spreading mid-Atlantic
ridge. The first seafloor hydrothermal vent was discovered along the fast
spreading east Pacific Rise. He pointed out that the discovery of vents in the
slow spreading ridge was initially dispensed with based on the theory that
hydrothermal activity could not occur at ridges that exhibited less than certain
threshold-spreading rates. At the time, he continued, hydrothermal vents
have been discovered even along the SW Indian Ocean which is one of the
world’s slowest spreading ridges. However, he pointed out that the
abundance of hydrothermal venting correlates with the spreading rate, thus
hydrothermal activity is most abundant along the south eastern Pacific Rise
followed by the north eastern Pacific Rise, the Juan de Fuca Ridge in the NE
Pacific Ocean, and the central mid-Atlantic Ridge.
Dr. German explained that the majority of currently active
hydrothermal fields are in the fast spreading ridges. He noted that it may
well be that the most economically interesting concentrations of polymetallic
sulphides are actually produced in fault-controlled systems along slowspreading
ridges. He theorized that as faulting can play an important role in
controlling the distribution of hydrothermal venting, ridge crests, as well as
fresh volcanism, there is scope for important hydrothermal circulation
throughout all the world’s ocean ridge systems. With respect to international
ventures, he stated that the French and US research programmes would
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