Stratigraphic analysis and distribution of arsenic in quaternary sedimentary deposits of the southeastern portion of the Quadril?tero Ferr?fero, basin of the Ribeir?o Carmo, MG.

A regi?o do QF, em Minas Gerais, tornou-se internacionalmente conhecida pela explora??o de ouro no s?culo XVIII. Nesse artigo, ser?o apresentados valores de refer?ncia (background) para o ars?nio em sedimentos aluviais provenientes de ?reas que foram intensamente afetadas pela explora??o de ouro no passado, contidas na bacia do ribeir?o do Carmo. A an?lise da sucess?o faciol?gica dos perfis aluviais foi realizada em dep?sitos sedimentares de plan?cies de inunda??o, barrancos de rios (cutbank) e terra?os aluviais e foi o alicerce para a obten??o do valor de refer?ncia do ars?nio em dep?sitos de f?cies de canal e de plan?cies de inunda??o. A partir do conhecimento do valor de refer?ncia obtido pelo m?todo estat?stico, com base na confec??o de curvas de freq??ncia acumulada em escala linear, foram gerados mapas geoqu?micos no sistema SIG. A obten??o do valor de refer?ncia e do mapa geoqu?mico do ars?nio, na bacia do ribeir?o do Carmo, com representa??o das ?reas com concentra??es an?malas desse elemento, ? fundamental para o diagn?stico e planejamento ambiental de um distrito mineiro potencialmente contaminado por ars?nio.The Quadril?tero Ferr?fero region, in the State of Minas Gerais, became internationally known due to the exploitation of gold in the eighteenth century. In this paper, we will present background values for arsenic in alluvial sediments from areas that were heavily affected by the exploitation of gold in the past, in the Carmo River Basin. The analyses of the facies succession of the alluvial profiles were carried out in the sedimentary deposits of flood plains, cutbank and alluvial terraces; this being the foundation for obtaining the arsenic background in the facies of the channel and flood plains. From the knowledge of the background obtained by the statistical method, and based on the construction of cumulative frequency curves on a linear scale, geochemical maps were generated in the SIG system. The acquisition of the background values and the geochemical map for arsenic in the Carmo River Basin, representing areas with anomalous concentrations of this element, are essential for the diagnosis and environmental planning of a mining district potentially contaminated by arsenic