Geochemistry and sedimentary environments of the Quaternary sediments in the mid-Pacific Ocean

The geochemistry, sediment sources and sedimentary environments are examined on the basis of analyses of the major and trace element contents in the sediments from the PC5356, PC5362 and PC5417 drill holes in the mid-Pacific Ocean, in integration of the multivariable statistical analysis. Vertically, there are three phases of marked changes in element contents in different burial depths of sediments. The contents of Al₂O₃, Fe₂O₃, TiO₂, MnO and P₂O₅ remain unchangeable in the early sediments, and show a marked increase in the middle sediments and a decrease in the late sediments in which CaCO₃, CaO and Sr contents are relatively higher and there is a negative correlation with the trace element contents. The element correlation analysis and R-mode factor analysis show that there is a positive correlation between SiO₂ contents and Al₂O₃, Fe₂O₃, K₂O, MnO, TiO₂, Cu, Ni and Zr contents indicating the same terrigenous origin, while a negative correlation between SiO₂ contents and CaCO₃, CaO and Sr contents indicating a distinct biogenetic origin. The Quaternary sediments in the mid-Pacific Ocean consist mainly of calcareous-siliceous clay and calcareous ooze. They may owe their origin to the volcanism in the early stages, and biological action in the late stages.