ENRICHING MECHANISM OF MINERALIZING ELEMENTS IN CO-RICH CRUST ON ALLISON SEAMOUNT, CENTRAL PACIFIC OCEAN

Based on its structure, growth age and growth generations, the crust A1-1 from the Allison seamount of the Central Pacific Ocean was sub-sampled at an average interval of 1.3 mm in order to measure the concentrations of major and trace elements for each layers and subsequently to calculate the enrichment coefficient and distribution coefficient of the mineralizing elements of the crust. According to the coefficients and special element ratios, the constraint of paleo-environment on the enrichment of mineralizing elements in the crust was discussed. The study shows that the elements enriched in the crust are just those that have shorter resistant time in seawater. The crust is an important "sink" for the elements that are easily scavenged. The element behaviors in seawater are the intrinsic causation for their enrichment in crust. The release of iron and barium resulted from the dissolution of carbonate is favorable for crust growth, but dilutes the accumulation of manganese, cobalt and nickel. The development of Minimum Oxygen Zone and the strengthening of Antarctic Bottom Water are favorable for the oxidation and scavenging of manganese and cobalt. The growth hiatus occurring in crust is resulted from weakening and ultimate change of Antarctic Bottom Water. Volcanic ash restrains crust growth. It was at 6.8 Ma when the crust grew from rqpid to slow rake.