MARINE-SEDIMENTS IN A REGION OF RECENT VOLCANIC ACTIVITY IN THE BAY OF PLENTY, NEW-ZEALAND

The chemical composition of recent marine sediments and pore waters in areas of shallow underwater volcanic vents in the Bay of Plenty, New Zealand, was studied. Values of pH in the sediments in active sites we re higher than in control sites, and concentrations of Fe, Cu, and Ni were elevated; however, the general chemical composition of the sedime nts and pore waters was rather similar to that of common shelf sedimen ts. The chemical composition of pore waters agrees well with the usual diagenesis of these sediments; the increase in temperature might infl uence the rates of diagenetic processes. No signs of uniform seeping o f volcanic waters through the sediments were detected. Hydrothermal wa ters and gases are preferentially transported through sulfur tubes. Th ese tubes and sulfide concretions replacing magnetite were collected a t and near the hydrothermal vents.