The Geochemistry Of REEs And Nd Isotope In Deep-sea Sediments From The Eastern Pacific And Their Geological Implications

The samples of deep-sea surface sediments, core sediments, nodules associated withsurface sediments and micro-nodules in surface sediments studied in this thesis werecollected from China Investigation Area in the eastern Pacific. The contents of REEs,major and minor elements, the compositions of minerals, and the values of εNd wereobtained. Based on these data, the REEs enrichment mechanism of sediments and nodules,and the paleoceanography from early Miocene to present in eastern Pacific are studied.The results are listed as follow. (1) The sediments in eastern Pacific show the commonfeatures of higher contents of LREE than HREE, and of negative Ce anomalies. TheREEs patterns are similar to that of seawater, but different with those of China Loess andthe Yellow Sea sediments. The fractions of Fe-Mn granules, clay minerals and phosphatedebries are major contributors of REEs to bulk sediments, and the calcareous fossils arethe diluent of REEs in bulk sediments. (2) The clay fractions of sediments in the easternPacific are most terrigenous, some are authigenous. The terrigenous clay minerals couldcome from fluvial deposits from North America, the materials of volcanic islands in theeastern Pacific and eolians from east Asian. (3) The cycles of REEs, CaCO3, and εNd inthe calcareous core sediments record the evolution of history ocean water. From earlyMiocene, the history water experienced cyclic changes of temperature, redox, andvolcanic activity. The distributions of REEs, minerals and other elements alone the coreof zeolite clay could reveal the origins and history of volcanic debries or ashes insediments. From early Miocene, the volcanic materials were changed from alkline tobasic.