Mineralogical and geochemical investigation of massive sulfide deposits from the Central Indian Ridge

The submarine MESO mineral zone was discovered at the eastern wall of a neovolcanic ridge, which subdivides the central graben of the Central Indian Ridge. Hydrothermal deposits comprising stumps and fragments of chimney relicts are dominated by pyrite, marcasite and chalcopyrite. Chalcopyrite as well as bornite are commonly replaced by digenite and rarely by covellite along cracks and edges of mineral grains, and include indications for waning hydrothermalism, weathering and increasing oxidation. Sphalerite is present as an accessory mineral only in a few sulfidic chimney samples. However, a silica-sulfate mound-like material (lasper-type) is enriched in sphalerite. The sulfide samples show relatively high metal contents (up to 50 wt. %) due to the almost complete absence of non-sulfide minerals.