ASSINATURA ISOTÓPICA Sm-Nd DE SEDIMENTOS EM SUSPENSÃO: IMPLICAÇÕES NA CARACTERIZAÇÃO DA PROVENIÊNCIA DOS SEDIMENTOS DO RIO PARAÍBA DO SUL - SP

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In order to identify the soure area for the sediments in suspension that contribute to the Funil RJ reservoir, Sm-Nd isotopic Sm-Nd signatures indicates the homogenization of the sediments. Despite this homogeneity, a variation in the space distribution of the Sm-Nd isotopic characteristics is noticed among the sub-basins. This is due to differences in the isotopic signatures of the source rocks and to the variation in the occurence area of each lithology in each sub-basin. The Guaratingueta and Piquete sub-basin show the highest T DM (2.11 e 2.13,Ga respectively) due to the erosion of the Mantiqueira Complex( average T DM 2.9 Ga) and of the Andrelândia Group ( T DM 2,1 Ga) lithologies. The sub-basin Buquira ( T DM 1.76 Ga) and Matos ( T DM 1.78 Ga) are influenced by Complexo Embu.s biotite gneiss (1.56 . 1.67 Ga). Embu.s Complex paragnaiss ( T DM 1.94 Ga) cover 77% of the area of the Uma sub-basin, whose T DM 1.96 Ga. The Paratei ( T DM 1.85 Ga) and divisa ( T DM 1.859 Ga) sub-basin have as their principal source, the sedimentary rocks of the Thaubate Basin ( T DM 1.9 Ga). The mass balance obtained from _ Nd(0) and T DM shows a good correlation between the discharge on the suspended sediments and the estimated average of the existent rocks in each sub-basin. The average values of R sed-rock are 1.08 ( _ Nd(0) ) and 1.02 ( T DM ) suggesting, for the analyzed period, the existence of a steady-state dynamic balance between the weathering and erosion;transportation processes in region of the Paraiba do Sul river basin.