Minerals Report - International Seabed Authority

It should be noted that other massive sulphides were also dredged in
the immediate vicinity of the Logachev-1 and 2 hydrothermal fields,
approximately 30 km to the east of the Mid-Atlantic Ridge (Sharapov and
Akimcev, 1993). Currently this is the only find in the Atlantic.
Prediction of a hydrothermal field at 24°30' N?
Massive sulphides in this area of the Mid-Atlantic Ridge were dredged
in the course of regional investigations at a scale of 1:1 000 000 - 1: 200 000 in
1987. Five sulphides samples were obtained from a terrace on the eastern
slope of a rift valley located between 4000 - 4200 metres depth that is
composed of blocks of serpentites and gabbro-peridotites. The massive
sulphides debris collected represents the fragments of chimneys and consists
mostly of chalcopyrite, bornite, pyrites and marcasite. Very high contents of
copper and gold averaging 16.25% and 10.4%, respectively, were found here.
The hydrothermal mounds were photographed this year by the deep-towed
system of the R/V Professor Logachev.
MIR Sulphide mound of the TAG hydrothermal field
The MIR (Figure 5) mound was discovered by photo profiling in 1985
(Rona et al., 1986) and was first visited by the Mir submersible during the 15 th
cruise of the R/V Akademik Mstislav Keldysh in 1988 (Lisitsyn et al., 1989).
Samples collection along latitudinal and longitudinal profiles was carried out
during the dives of the Alvin and the Mir submersibles in 1990 and 1991
respectively (Rona et al., 1993). Detailed photo profiling of the MIR mound
and sampling by heavy TV-equipped grabs were performed in 1992-1993
during the 6 th cruise of the R/V Professor Logachev. Based on these studies the
zonality of the MIR mound was established, large volumes of the deposit
were recovered (up to 1.2 tonnes) and the resources of this, the largest
sulphide deposit were estimated (Stepanova et al., 1996).
INTERNATIONAL SEABED AUTHORITY 182