Minerals Report - International Seabed Authority
Minerals Report - International Seabed Authority Minerals Report - International Seabed Authority
3. Marine Minerals Related to Deep Ocean Sources 3.1 Massive Sulphides and Manganese Deposits As described, divergent plate boundaries expressed as a submerged volcanic mountain range that extends through all the major ocean basins of the world (Figure 2) are part of a global exchange system of heat and materials from the Earth's interior to the lithospheric plates. However, seafloor hot springs and associated hydrothermal mineral deposits do not occur continuously along the axis of this submerged volcanic mountain range. They are highly localized at specific sites along that axis where the right conditions are present. These conditions comprise hot rocks kilometres beneath the seafloor connected to faults and fractures that create permeable pathways for the circulation of seawater to produce hot springs. The fields of hot springs and mineral deposits are generally small, with diameters up to several hundred meters. Polymetallic massive sulphides containing iron, copper, zinc, silver and gold in variable concentrations (also known as massive sulphides meaning that the deposits contain at least 60 percent metallic sulphides minerals) are precipitated where high-temperature hot springs discharge through mineralised chimneys ( 1/ ). Deposits of relatively pure manganese oxide (c. 50 percent manganese by weight) may accumulate at low-temperature hot springs (to tens of degrees Celsius or Fahrenheit) at some distance (kilometres) from the high-temperature hot springs (6). Once formed at the axis of a submerged volcanic mountain range, massive sulphide and manganese deposits may be carried to either side of the divergent plate boundary on conveyor belts of spreading lithosphere where the deposits may be buried beneath lava flows and sediment. INTERNATIONAL SEABED AUTHORITY 76
Figure 2. World map showing plate boundaries, the 200 nautical mile zone extending from coastal states, and sites at plate boundaries where some of the larger massive sulphide deposits have been found (27). Only a small percentage of prospective areas of the deep seafloor have been explored in sufficient details to find such deposits. Numbers indicate locations where the submerged volcanic mountain range at divergent plate boundaries lies within the 200-mile zone of a coastal state, as listed in table 2. INTERNATIONAL SEABED AUTHORITY 77
- Page 34 and 35: While noting that the continuity of
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3. Marine <strong>Minerals</strong> Related to Deep Ocean Sources<br />
3.1 Massive Sulphides and Manganese Deposits<br />
As described, divergent plate boundaries expressed as a submerged<br />
volcanic mountain range that extends through all the major ocean basins of<br />
the world (Figure 2) are part of a global exchange system of heat and<br />
materials from the Earth's interior to the lithospheric plates. However,<br />
seafloor hot springs and associated hydrothermal mineral deposits do not<br />
occur continuously along the axis of this submerged volcanic mountain range.<br />
They are highly localized at specific sites along that axis where the right<br />
conditions are present. These conditions comprise hot rocks kilometres<br />
beneath the seafloor connected to faults and fractures that create permeable<br />
pathways for the circulation of seawater to produce hot springs.<br />
The fields of hot springs and mineral deposits are generally small,<br />
with diameters up to several hundred meters. Polymetallic massive sulphides<br />
containing iron, copper, zinc, silver and gold in variable concentrations (also<br />
known as massive sulphides meaning that the deposits contain at least 60<br />
percent metallic sulphides minerals) are precipitated where high-temperature<br />
hot springs discharge through mineralised chimneys ( 1/ ). Deposits of<br />
relatively pure manganese oxide (c. 50 percent manganese by weight) may<br />
accumulate at low-temperature hot springs (to tens of degrees Celsius or<br />
Fahrenheit) at some distance (kilometres) from the high-temperature hot<br />
springs (6).<br />
Once formed at the axis of a submerged volcanic mountain range,<br />
massive sulphide and manganese deposits may be carried to either side of the<br />
divergent plate boundary on conveyor belts of spreading lithosphere where<br />
the deposits may be buried beneath lava flows and sediment.<br />
INTERNATIONAL SEABED AUTHORITY 76
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