FORMATION AND DECAY OF A MODERN MASSIVE SULFIDE DEPOSIT IN THE INDIAN-OCEAN

In December 1993, the first massive sulfides were recovered from the I ndian Ocean floor. north of the Rodrigues Triple Junction. The polymet allic deposit is situated in the fourth Central Indian Ridge segment, close to the rift axis: it is hydrothermally no longer active. The dep osit appears to be typical of mid-ocean ridge massive sulfide occurren ces bur is in a phase of disintegration and about to be buried by sedi ment. The chimney structures were formed by multiple hydrothermal even ts and are now degraded by mass wasting showing various stages of weat hering. Later-stage, low-temperature hydrothermal mineralization proce sses led to copper and gold enrichment. Ht re we report on the geologi cal setting, mineral zonation, different sulfide types and stages of f ormation of the ''Sonne Sulfide Field'', which is part of a larger min eralized zone.