Clay Mineral Distribution In The Sediments Of The Northwest Parece Vela Basin

The thesis expatiate on the distribution of the surface sediments in the researcharea via the XRD analyses clay minerals which are carried out after the extraction offractions smaller than 2μm in size from the surface sediment samples.The verticalchanges of content and assemblage types are researched in the thesis.Illitecrystallinity,Illite chemical index and semctite abundance were analyzed.Thesources of the sediments,sediment types and environmental evolvement werediscussed.Analysis results indicate:illite is the most abundant in the research area with anaverage percentage content;smectite content is less than illite with an averagecontent;kaolinite and chlorite are much lower in content with an averagecontent.According to calculation and comparison,two mineral assemblages andprovinces can be compartmentalize in the study area:ProvinceⅠ has Illite-richedassemblage,which primarily locate the flat seafloor between the Palau Ridge and theParece Vela Rift;ProvinceⅡ has Smectite-riched assemblage,which is right aroundParece Vela Rift,eastern region of the study area.With these results and based on thedistribution patterns of each clay mineral, several primary conclusions wereachieved with their source and sink:1)Illite derived from the East Asian continentand circumjacent islands.Based on illite chemical index and illite crystllinity,it wasindicated the illite form in the physical weathering environment and be likely to theloess in the Chinese mainland;2)A majority of smectite with Fe-rich characteristicoriginate from the basic volcanic material's alteration.The eolian blow is maintransport mode,furthermore the river's material import is not neglectable.The oceancurrent have certainly influence to the clay minerals' distribution,especially thesmectite's distribution.The result show that four clay mineral make up in the fractions smaller than2μm in eight piston core samples collected from the Parece Vela Basin.Smectite andillite make up of the primary component,kaolinite and chlorite make up of secondarycomponent.The average value of illite crystllinite was intervenient into the range ofloess′ and paleosol′. The average value of illite chemical index are all less than 0.5.The average value of smectite abundance are mostly less than 1.