Minerals Report - International Seabed Authority

Based on the potential resources contained in these deposits, they are
considered to be medium – large, with tonnage estimates between 5 to 50
million tonnes, and with the highest potential in the eastern flanges of the
slope of the valley.
The ages of the sulphides samples from the Logachev- 1 site range
from about 10-60,000 years (Lalou et al., 1996).
Logachev - hydrothermal field (Figure 4)
The Logachev - 2 hydrothermal field was discovered in 1993-94 at the
same time as the Logachev-1 field. The Logachev – 2 field is 5,500 kilometres
southwest of it, and was studied in detail during 1996 and 1997 on the 16 th
cruise of the R/V Professor Logachev.
The field is located between 2660metres and 2700 metres depth in the
same geologic setting as Logachev - 1. The host rocks at this deposit are also
gabbro-peridotites. Modern volcanic activity is not observed, but 6 sulphides
mounds with diameters of up to 120 metres, and surrounded by a field of
metalliferous sediments are revealed within its limits. The sulphides contain
7.5 - 22.5% copper, 0.19 - 1.58% zinc and 0.23 - 10.1 g/t gold. Unique for
massive sulphides were the contents of valuable components that were
recovered in a large bulk sample collected by T/V equipped grab. These
included 20.5% copper, 21.2% zinc and 424-ppm gold; in this case the content
of gold in particular large-volume samples varies from about 101.1 to 875.1
ppm.
It has been suggested that the mineralisation that has been determined
in the Logachev hydrothermal field represents a new type of sulphides
mineralisation that differs from the earlier types that have been studied. This
mineralisation is characterized by a peculiar composition and genesis that is
related to the deep recycling and serpentinisation processes (Bogdanov, 1997).
INTERNATIONAL SEABED AUTHORITY 180