The samples studied through this research were collected from
active black smokers located in the mid-oceanic ridge from a depth of
2276m by a sea-born ship “Academician Mstislav Keldysh”(2002), in its 47th
research mission. The collected samples were studied by microscopic,
microprobe and X-ray analysis (Debye-sherer). These samples were in the
form of narrow pipes with zoned structure, which included the following
zones from the core to the margin: isocobanite, Chalcopyrite, Bornite and
cupper sulfide zones. For the first time, it has been observed that tetragonal
phase within the cupper-sulfide zone in recent sulfide, deposits. Tetragonal
phase of Cu2S, which is an unstable form of chalcocite, is stable only at high
pressures (more than 0.8 Kb) and temperatures higher than 102 oC. The
tetragonal form of Cu2S in one of the studied samples was associated with
Chalcocite-Djurleite mixture and in another studied sample was associated
with chalcocite-Bornite mixture. Its average chemical composition was also
determined as Cu2.02S. It is likely that the emergence of this unstable phase
in young hydrothermal deposits, which are formed at 250-350 oC, is not odd
but after hydrothermal activity and temperature reduction it is changed to
more stable phases. Evaluation of older black smokers showed no trace of
tetragonal phase.