Anomalias de elementos terras raras, urânio e tório em rochas e solos de diferentes litologias no Agreste de Pernambuco

Abstract

The Southern Agreste region of PE is an area with anomalous occurrence of ETRs, U and Th. Thus, the objective of this work was to evaluate the distribution of total and environmentally available levels of REEs in soil related to rocks and mineralogy. For the development of the work, 45 soil samples were collected at depths of 0.0-0.20 and 0.20-0.40 m and fresh rock in the Agreste region of Pernambuco representing the lithological diversity and the contents of U and Th. The following analyzes were carried out: a) petrographic analysis, identification and composition of minerals in rock, b) chemical and physical analysis of soil characterization; c) total and environmentally available levels of ETRs, U and Th in rocks and soils. Data were submitted to descriptive statistics, with the determination of mean, maximum, minimum and standard deviation. Pearson correlations and factorial analysis between ETRs and soil chemical and physical attributes were performed. Analysis of soil grouping was also performed. From the results it was possible to identify the relationships between the accessory minerals of the original materials, with the composition of the soil. The orthognaisse (point 8) presented allanite and monazite in its composition, the other mother rocks presented REEs, U and Th enriched in accessory minerals. The rocks presented different levels of REEs, U and Th between and within the same rock type. The soil presented the same tendency of distribution of elements verified in the rocks, but with enrichment. The following order of rock was verified considering the abundance of REEs in the rocks: gneiss > tonalite > granite > granodiorite > pegmatite> diorite > amphibolite > quartz vein > sandstone. The mean (maximum and minimum) REEs, U and Th levels were 165 mg kg-1 (628.23 and 13.95 mg kg-1), 0.40 mg kg-1 (1.95 and 0.00 mg kg -1) and 18 mg kg-1 (92.23 and 3.48 mg kg-1) respectively. Anomalous values of REEs, U and Th were observed in the rock and soil of the Southern Agreste of Pernambuco.