Hydrothermal Plumes At EPR 13° N And MAR Logatchev Sites

Hydrothermal plumes present us a magnifying glass to understand hydrothermal activity. They provide natural laboratories for measuring the chemical reactions that control the ultimate dispersal of various hydrothermal species. They are potent tools for realizing the environment effect of hydrothermal activity, finding hydrothermal polymetallic sulfide, locating, characterizing, and quantifying seafloor hydrothermal discharge. This paper summarized the types, movement and geochemistry of hydrothermal plume and the influence on its spreading based on the understanding of the general situation on the research of marine hydrothermal plumes. From the CTD data obtained during the DY105-12,14 cruise (November 2003) at East Pacific Rise (EPR) 12°39′N～12°54′N and the DY105-17A cruise (October 2005) at Logatchev site (MAR 14°45'N),the temperature anomalies were discussed. Through the geochemical data of the water samples obtained at EPR12°39′N～12°54′N, the geochemical characteristics of hydrothermal plume and its influencing factors were discussed. We discovered that the depletion of magnesium in the plume may be caused by a fluid lacking of magnesium which rises after the hydrothermal fluid reaches equilibrium with ambient seawater. The decrease of calcium may be caused by many factors in which the formation of carbonate particles during carbon dioxide-rich fluid entraining ambient seawater rises upward is the main factor. The enrichment of chlorine and bromine might be the result of inputting later brine which is generated by phase separation due to hydrothermal activity.