Unknown
International Seabed Authority
In:
In: Polymetallic Massive Sulphides and Cobalt-Rich Ferromanganese Crusts: Status and Prospects. ISA Technical Study, 2 . International Seabed Authority, Kingston, Jamaica, pp. 7-35. ISBN 976-610-467-0
Publication Date:
2016-06-22
Description:
Since 1979, polymetallic massive sulphide deposits have been found at
water depths up to 3,700 m in a variety of tectonic settings at the modern seafloor
including mid-ocean ridges, back-arc rifts, and seamounts. Many of the sulphide
deposits consist of a black smoker complex on top of a sulphide mound which
commonly is underlain by a stockwork zone. It has been widely established that
circulating seawater which is modified in a reaction zone close to a subaxial
magma chamber is the principal carrier of metals and sulphur which are leached
out of the oceanic basement. Precipitation of massive and stockwork sulphides at
and beneath the seafloor takes place in response to mixing of the hightemperature
(up to 400°C) metal-rich hydrothermal seawater fluid with ambient
seawater. Polymetallic seafloor sulphide deposits can reach a considerable size
(up to 100 million tonnes) and often carry high concentrations of copper
(chalcopyrite), zinc (sphalerite), and lead (galena) in addition to gold and silver.
Extremely high concentrations of gold have recently been found in a new type of
seafloor mineral deposit previously only known as epithermal (magmatic) gold
deposits on the continents. Due to the high concentration of base and precious
metals, seafloor polymetallic sulphide deposits have recently attracted the
interest of the international mining industry. The recovery of those deposits
appears to be both economically and environmentally feasible due to certain
advantages over land-based deposits and will likely become reality within this
decade. For logistical and technical reasons, future mining operations will largely
focus on deposits in national rather than international waters.
Type:
Book chapter
,
NonPeerReviewed
Format:
text
Permalink
|
Location |
Call Number |
Limitation |
Availability |
