Do marine moulds influence Hg and Si precipitation in the hydrothermal JADE field (Okinawa Trough)?

Several massive sulfide smoker fragments from the JADE field (Okinawa Trough, Japan) yielded filamentous aggregates of both cinnabar (HgS) and amorphous silica (Si02), resembling fungal hyphens. For this similarity, polished and thin sections of filaments were compared with recent moulds that had formed on sulfide samples. Since the influence of marine moulds on mineral precipitation is poorly known, studies on bacterial and algal mineralization mechanisms were reviewed to generally identify microbial metabolism processes that could lead to the formation of the observed filaments. The development of HgS pseudomorphs is likely to have occurred through methylation reactions, while the filament replacement by silica probably happened via an intermediate formation of silica-carbon compounds, followed by a successive breakdown of these phases under changing geochemical conditions.