Minerals Report - International Seabed Authority

Focussing on sites of sea floor mineralisation that have been
discovered, Dr. Rona informed participants that the first discovery came by
chance in the 1960s in the Red Sea at the same time of the development of the
theory of plate tectonics. Professor Rona described an international Indian
Ocean expedition, during which various ships that were transiting through
the Red Sea coming to and from the Indian Ocean, ran the echo sounders on
their ships in the course of transits, and got reflections from layers within the
water column that were totally anomalous. He pointed out that usually the
reflections from the echo sounders come back from the sea floor. When
samples were taken in the area, it was found that the reflect surfaces were
layers of highly salty metal and rich water at certain places along the axis of
the Red Sea. Dr. Rona explained that the Red Sea is a part of a plate boundary
where sea floor spreading is occurring, i.e. carrying Saudi Arabia and Africa
apart at a slow rate of centimetres per year. Professor Rona further explained
that Saudi Arabia and Africa are about 200 kilometres apart at this time.
Along the axis of the Red Sea where the hot rocks are welling up from the
earth's interior in this submerged plate boundary, there are several deep
basins from which hot springs are welling up from the sea floor. The largest of
these basins is the Atlantis II Deep he pointed out, just west of the sacred city
of Mecca.
Professor Rona remarked that the thick layers of rock salt, formed at a
time when the Red Sea’s circulation was restricted by surrounding
landmasses, represented a special phenomenon. He noted that at that time
there was more inflow and evaporation than inflow. He briefly reviewed the
history of the formation of these deposits; namely the penetration of cold,
heavy seawater into the lithosphere, the subsequent dissolution of metals and
salts into this heavy seawater as it passes through volcanic rocks, the heating
of this body of water by the hot rocks and the up welling of it beneath the axis
of the Red Sea, and its final discharge as a metal rich brine that is heavier than
surrounding seawater. Dr. Rona described this process of concentration of
metals as a most efficient one. He noted that the Red Sea brines deposit is the
largest seafloor hot spring deposit known on earth at this time. With regard
to the resource evaluation of the metals to be found in the Atlantis II Deep,
Professor Rona informed participants that the volume of brines had been
estimated at 94 million tonnes dry weight containing 2 percent zinc and 0.5
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