Geochemistry of the Tenryu Canyon deep-sea fan biological community (Kaiko)

The Tenryu Canyon deep-sea fan biological community is characterized by both reduced and oxidized sediments in the immediate vicinity of the pore water vents. The upper sediments in contact with the clams are reduced, the organic matter is enriched in sulfur, and inorganic sulfides (Fe, Cu, Zn) are forming. Towards the outer fringes of the communities the sediment is oxidized and metals generally associated with ferro-manganese oxides are concentrated. Several metals, Cd, Pb, Mo show distributions which are strongly influenced by the metabolism of the clam colony. Comparison of water and sediment geochemistry leads to the conclusion that there should be a downward flux of oxygenated seawater on the boundaries of the colony and an upward flux of chemically more reduced deep pore water at the location of the colony. Trace metals anomalies as well asδ¹⁵N anomalies of organic matter may be useful to prospect for extinct venting areas in ancient subduction zones.