The Element Characteristics Of Aggradation Red Earth In Mid-subtropics And Its Source Material

Variousquaternary sediments was widely distributed in southern China, and the aeolian material, such as XiaShu loess located in the middle and lower reaches of Yangtze River region, Quaternary clay accretion and the old red sand deposition distributed in the southeast coastal, river and other places of attracted wide attention, while the material sources on aeolian deposits remains controversial. In this paper, clay accretion Quaternary is the researchingsubject, and through the; analysis of different sediment samples’ constitution of strontium isotope and the characteristic of REE and major elements in subtropical regions, the following was concluded:(1) The constitution of major geochemical elements in the subtropical aggradation red earth are center on SiO2, Al2O3, TFe2O3 (TFe2O3= Fe2O3+FeO). The three oxides changes in the content from 53.15% to 88.88%, and the average value is 83.31%, lower than the average content of the upper crust 86.2%. While the content of TIO2 varied from 0.55% to 1.37%, with an average of 0.99%, higher than average levels of the upper crust 0.5%.The content of SIO2 in soilhave a slight loss, while TiO2 showing cumulative status. K2O, CaO, MgO and Na2O are soluble active substances, and theyare very easily lost in the warm and humid environment, the different types of aggradation red earth with the different distribution of content. The content of these constants elements in aggradation red earth in descending order as:SiO2, Al2O3, Fe2O3, K2O, TiO2, CaO, MgO, Na2O, MnO. At the profile ofGuQuan, San Yuan, FuJiaWan in subtropical regions, the content of the alkali metal element oxide of K2O, Na2O, CaO and MgO showed a increasing trend upwarda content from the profile of low-end, and weathering erosion appears to increase the number of CIA trend; Changes of SiO2, Al2O3, Fe2O3 have a good comparability about their opposite trends, and changes in trends of an alkali metal element oxide K2O, Na2O and CaOare almost exactly the same, showing synchronization. It indicates that, in the four profiles, weathering intensity gradually weakenedfrom the bottom upwards. Different depth of profiles, different material sources may have changed, and the material sources of homogeneous clay may be influenced by many factors.(2) In different subtropical regions, for the aggradation red clay, such as homogeneous and yellow-brown clay soil and other terms, the content of rare earth are different. The averagecontent of reticulate clay’ ∑REE are similar with homogeneous clay, while the reticulate’s scope of REE pattern is much larger than homogeneous clay. The content of Yellow-brown soil and XiaShu loess clay’ ∑REE have a close value,while the scope of REE’content in Yellow-brown soil is greater than the XiaShe loess. The homogeneous and yellow-brown clay have a small value of (La/Yb)N, (Gd/Yb)N, (Eu/Sm)N, (Nd/Yb)N, (Nd/Lu)N, and (La/Lu)N, and they are close to the close and different toreticulate clay. The characteristic values of yellow-brown soil are similar to XiaShu loess to some extent, are relatively close to the Yangtze River floodplain deposition, especially XiaShu loess, which eigenvalues Sm/Nd, Nd/La, (La/Yb)N, (Gd/Yb)N, (Eu/Sm)N, (Nd/Yb)N, (Nd/Lu)N, (La/Lu)N is almost equal to the Yangtze River floodplain, maintaining the overall similarity. The value of 8Ce inreticulate clay is significantly less than the homogeneous, while closer to the floodplain sediments; similarly, the value of δCe,δEu, (Eu/Sm)Nin yellow-brown soildeviates from the Yangtze River floodplain, and is closer to the northern loess. On the other hand, some characteristics of the rare earth are close to crust and the deposition of lake.;there are certain similarities, such as textured clay and clay in a the value of Nd/La, (Gd/Yb)Nin closer to the homogeneous and reticulate clay;the value of (Gd/Yb)N, (Eu/Sm)Nin yellow-brown soils deposition are close to weathering crust. REE’characteristics described above indicate that different clay deposits accretion has exactly the different source material.(3)By analyzing strontium isotope data, and compared to the northwest Gobi Desert, the northern loess and paleosol, aggradation red earth in the subtropical have higher strontium isotope ratios. XiaShu Loess strontium isotope ratios was obviously no correlation with CIA, with strontium ratio decreases in yellow-brown soil with increasing CIA, textured clay, and laterite homogeneous strontium isotope ratio was obviously no correlation with CIA.In the subtropical aggradation, weathering intensity is not the main cause of its strontium isotope ratios’change, but may be related to the relevant source material(4) The PI and DI provenance function through aggradation red earth REE determination, characteristics of major elements and the contrast of Sr isotope ratio characteristics, all of which indicated that:the material source of aggradation laterite is more complex; different types of deposits in same regions and the same typesin the different areas, there exist differences in the sediment provenance. All kinds of aggradation red earth comes aeolian origin, and theyare the mixtures of far-source and the near-sourcematerial. As winter winds increased, the fine fraction of northern loess enter the south with high air flow; floodplain sediments of the river dried up or diversion outcropping loose, lake deposits, and weathering crust formed in the late Neogene to Quaternary Granite have become the source area south of clay. The aggradation red earth are greatly influenced by the Yangtze river floodplain sediment, with the increase of distance of the Yangtze river, this effect decreases, such as reticulate red clay near the Yangtze River.The aggradation red earth are greatly influenced by the Yangtze river floodplain sediment, with the increase of distance of the Yangtze river, this effect decreases, such as reticulate red clay near the Yangtze River.The source material of XiaShu loess dominated by the influence of the Yangtze River floodplain, showing more consistent with the characteristic elements of the Yangtze River floodplain; yellow-brown soil material sources, homogeneous textured clay and clay exhibit multi-source, namely by near source of the combined effect of lake and river sediments, weathering crust and far source of north dust deposition;the mixing ratio is different in different regions, due to the interference with local wind and East Asian monsoon system. Among them, the provenance of yellow-brown soil is center on river and lake sediments, having a good provenance similarity with XiaShu loess.