Chrolonological study of drilled cores from active hydrothermal fields in the Okinawa Trough

Abstract

Among sediment cores collected from Ieyama hydrothermal field in the Okinawa Trough, mineralization layers with occurrence of barite and sphalerite were identified between 53-65 mbsf. We have conducted chronological study of barite in the sediment using ²²⁶Ra‐²¹⁰Pb dating and ESR dating. The results yielded 20-90 yrs. and 350-1050 yrs. as formation ages. On the other hand, radiocarbon dating of planktic foraminifera in the surface sediment at 0.15-0.20 mbsf collected from three places in the study field yielded 900‐1500 yrs.There results provide constraint on mineralization process that occurred beneath the seafloor.