Study On The Chatacteristics Of Minerals Of Surface Sediment In The Qiantang River And Analysis Of Provenance

River sediments are mostly derived from the influx of weathered rocks and soils in river basins.Their material composition are affected by the types of rocks and the degree of weathering in source region,and have the characteristics of source areas'material.They can preserve the whole process from weathering and denudation to transport and deposit,as well as the climatic information of source region.Through the provenance study of river sediments can determine the regional location of source area,the characteristics of parent rocks and their assemblages,as well as the transport path and distance information of river sediments.Qiantang River is located in Zhejiang province,China,and it's north is close to the Yangtze River estuary.The Qiantang River Estuary is a typical tidal estuary.Under the action of strong tidal bore,a lot of sediments from the Yangtze River Estuary and offshore sediments will enter the Qiantang River Estuary area,affecting the characteristics of sediments of the Qiantang River Estuary profoundly.In this paper,the surface sediments of Qiantang River are studied.we collected river sediments systematically in Qiantang River Basin,at the same time,potential source areas such as surface soil of Qiantang River Basin,sediments of Yangtze River Estuary and Yongjiang River were collected.We collected 120 samples altogether.The XRD analysis of magnetic minerals and detrital minerals was the key point,in addition,the active iron test were also carried out to identify the source of river sediments to established the source of topsoil-tributary sediments-stream sediments,and study on the relationship between sediments in Qiantang River Basin and Yangtze River sediments.Concludes as follows:?1?The results show that the main kinds of magnetic minerals in river sediments of Qiantang River Basin are magnetite,magnethematite,hematite,goethite,pyrrhotite,ilmenite and siderite.Magnetite content ranging from 0.25%to 4.50%,with an average of 0.66%;Magnethematite content ranging from 0.50%to 5.37%,with an average of 1.63%;Hematite content ranging from 0.79%to 5.89%,with an average of 2.26%;Pyrrhotite content ranging from 0.50%to 5.89%,the average value is 0.15%;Goethite content is 0.16%².37%,average value is 1.20%;Ilmenite content is 0.13%⁰.73%,average value is 0.36%;Siderite content is 0.08%⁰.99%,average value is 0.41%.The high-value areas of hematite,magnethematite and ilmenite are mainly distributed in the upper reaches of Qiantang River Basin,while the low-value areas are mainly distributed in the lower reaches;the high-value areas of magnetite,pyrrhotite,goethite and siderite are mainly distributed in the lower reaches of Qiantang River Basin,and the low-value areas are mainly distributed in the upper reaches.?2?The results show that the main kinds of detrital minerals in river sediments of Qiantang River Basin are quartz,plagioclase,potassium feldspar,calcite,dolomite and pyroxene.Quartz content ranged from 35.09%to 76.01%,average value is 54.01%;Plagioclase content ranged from 6.08%to 30.53%,average value is16.17%;Potassium feldspar content ranged from 3.59%to 26.46%,average value is9.62%;Calcite content ranged from 0.01%to 8.91%,average value is 1.78%;Dolomite content ranged from 0.53%to 9.28%,average value is 3.22%;Pyroxene content ranges from 5.49%to 29.47%,the average value is 15.20%.The high value areas of quartz,potassium feldspar and Muscovite content mainly distribute in the upper reaches of Qiantang River Basin,while the low value areas mainly distribute in the lower reaches.The high value areas of plagioclase,calcite and pyroxene content mainly distribute in the lower reaches of Qiantang River Basin,and the low value areas are the main ones.It should be distributed upstream.?3?It is found that there are also significant spatial differences in the content of active iron in river sediments of Qiantang River Basin.The test results of active iron show that the total active iron content and Fe²⁺content of the sediments in the upper reaches of Wenyan are lower,while the Fe³⁺content and Fe³⁺/Fe²⁺value are higher,while the lower reaches of Wenyan are just the opposite.The sediments in Qiantang River and Hangzhou Bay are of weak oxidation type,while the sediments of other rivers and topsoil are of oxidation type.Source analysis shows that the sediment characteristics of different rivers in Qiantang River Basin show obvious differences in space,indicating that the sediment sources of different rivers have different source region.The characteristics of active iron,magnetic minerals and detrital minerals in the upper reaches of Wenyan River are in good agreement with those in the topsoil of the drainage basin,means that the material comes from the weathered rocks and topsoil of the drainage basin.The sediments in Fuchun River are mainly come from Xin'an River,Fenshui River and Lanjiang River,while the sediments of other tributaries have little influence.The sediments in Qiantang River and Hangzhou Bay of the lower reaches of Wenyan mainly come from the sediments of the Yangtze Estuary.sediments in Cao'e River and Puyang River have little effect on sediments in Qiantang River,sediments in Youngjiang River have little effect on sediments in Hangzhou Bay.Research shows,the difference of sediment characteristics of different rivers in Qiantang River Basin is due to their different provenance areas.The difference of chemical weathering and lithology of parent rocks makes the soil have different characteristics in the process of formation.The transport trends of sediments in different source areas are different under hydrodynamic action,which affects the spatial distribution of sediment characteristics.