The mantle sequence serpentinized peridotites of north of Nain have been converted to carbonate- silica assemblage known as listwaenite at various temperature and pH in response to CO₂ and SiO₂ bearing fluids. On the basis of carbonate and silica minerals content, three types of listwaenite have been recognized: carbonate, carbonate- silica and silica listwaenites. Generaly carbonate minerals are magnesite, dolomite, ferrite-dolomite and ankerite. Calcite and other carbonate minerals are rare. Silica minerals (including quartz, chalcedony and chert) accompanied by accessory Cr-spinel, chlorite, sulfide minerals also occur in listwaenites. Silica matrix in silica listwaenite containing high amounts of Hg, Ag and As elements and shows that these elements have transported by SiO₂ bearing hydrothermal fluids as arsenide complexes.