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This research has been done with the aim of comparing the result of Chandab flood spreading sediments source identification by using rare earth element (REE) and the other geochemichal elements (OGE) as tracers. In addition, the contribution of sediment source in 2002 and 2021 have calculated and compared. Discriminat analysies indicate that,Cs, Ba, Fe, Sc, Cr, Ta, Sb, As, Zn, Ce and Na can discriminate Alluvialls (Tehran alluvials, Old alluvials and River), Hezrdarreh Conglomerate, Lower red formation conglomerate, Upper red formation, middle tuff member of Karaj formation, tuffs of pyroclastics and andsite member of karaj Formation and Andsites of pyroclastics and andsite member of karaj Formation as sediment sources.The solution of linear multivariate equations showed that the mention sources respectively produces 0.4, 5.56, 0.62, 70.82, 16.53, 4.90 and 1.18 percent of the flood spreading area sediments in 2002 year. Stududy on the gadared samples from the surface part of Chandab watershed soils (Surface and rill erosions) and active part of chanel and gully erosions indicate that, Zn and Th can discriminate mention erosions and contribution of Chandab flood spreading area by them were 42 and 58 percent respectively. The comparsion of sediment sources contribution by REE and OEG methods indicated that REE and OEG methods can discriminate sediments sources by 5 and 11 elements respectively. On the other hand, OEG method unlike REE method can discriminate Hezrdarreh Conglomerate Formation from Lower red conglomerate sediments and Tuff sedmintes from Andesite sediments of Pyroclstic and Andesite member of Karaj Formation.
Rare earth elements are able to estimate the contribution of sediment source with the largest contribution, but unable to estimate contribution of sediment source with low contributions. However, unlike REE method, OGE merthod has been able to determine the contribution of all 7 sediment sources.
Changes of sediment sources contribution from 2002 untill 2014,were investigated by gathering 6 representative composite samples from the sediments of the Chandab flood spreading area in 2021. The concentration of elements was determined by the neutron activation method.The results indicate that, contributions of Upper red Formation 2% has decreased and Hezrdarreh Conglomerate Formation 3% has increased. The construction of a dam on the Upper red formation in 2004 was the reason for the decrease of this contribution,s. The reason for the increase in the contribution of Hezrdarreh formation is the implementation of the gas transmission pipe operation from the east of the country to Tehran on this formation in 2004.
Key words: Other geochemical elemens , Rare earth elements , Discriminant analysis , Earth dam , Flood spreading area, Gas Pipelines Operations
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