FLUXES OF HYDROTHERMAL MATTER IN SEDIMENT S OF THE EASTERN PACIFIC RISE (20-DEGREES-S) AT LATE QUARTERNARY

A study of the ancient hydrothermal activity was carried out based on the determination of bottom sediments adjacent to the rift zone locate d at 21-degrees-S within the Eastern Pacific rise. Geochronological me asurements were performed by the radiocarbon method and by nonequilibr ium Th.-230 644 samples of bottom sediments were anslysed on 24 elemen ts. About 40% of variability factors should be assigned to the hydroth ermal activity influence. The detailed distribution of main ore elemen t fluxes was investigated within the surficial sediment layer. The ele ments include Fe, Mn, Cu of hydrogenic-hydrothermal origin and Ti as a product of primary rock ewathering. The maximal fluxes of the element s of hydrothermal origin were fixed at the substantial distance from t he ridge axis as these ''hydrothermal'' elements arrive to the sedimen ts only after the plum destruction. The enhanced contents of edaphogen ic elements in contrast are confined to the ridge axis. Samples of 7 c olumns of bottom sediments aging in the range of 24 up to 340 thousand years were analysed for the estimates of temporal variations of the f ollowing parameters: hydrothermal maller content and hydrothermal flux , Fe/Mn ratio, Ni-content. It was shown that the content of the hydrot hermal matter and Fe/Mn ratio should be considered as the most effecti ve indicators of the hydrothermal activity evolution at the mobile oce anic bottom in contrast to corresponding hydrothermal flux. The cyclic character of the hydrothermal process is reliably fixed by the ore ma tter content variations only in columns located near the ore matter so urce.