Minerals Report - International Seabed Authority

SUMMARY OF THE PRESENTATION AND DISCUSSIONS ON HYDROTHERMAL
SULPHIDES MINERALIZATION OF THE ATLANTIC – RESULTS OF
INVESTIGATIONS 1985-2000
In the absence of Dr. Cherkashev, or any of the authors of the paper,
Dr Geoffrey Glasby of the Department of Economic Geology and
Geochemistry at the University of Athens read his paper. Apologising for his
delivery since he was not familiar with its contents, Dr Glasby’s presentation
resulted in a discussion of the paper. Unfortunately, these discussions did not
have the benefit of responses from Dr Cherkashev.
The discussions focussed on three issues. The fact that gold and silver
had been found in massive sulphides deposits at the Mid- Atlantic Ridge
whose origins are ultra-mafic rocks rather than ordinary seafloor rocks, the
abnormally high values of gold that were reported, and nomenclature
problems with the TAG mound.
A number of participants expressed difficulties with the presence of
gold and silver in the deposits as reported in the paper. One participant
expressed the view that the information that had been provided during the
workshop seemed to suggest that the Mid-Atlantic Ridge massive sulphides
did not reveal the presence of either gold or silver, let alone the high values
reported. Other participants were of the view that at latitude 24˚30’ N, the
contents of copper and gold found in the deposit, reported as averaging
16.25% and 10.4% were too high. In particular, with regard to the unit for
measuring gold, this participant suggested that maybe the correct unit is parts
of gold per million (ppm). Yet other participants suggested a unit of parts per
billion (ppb).
INTERNATIONAL SEABED AUTHORITY 185