Geochemical denudation in a scarp zone, upper das Velhas river, Quadrilátero Ferrífero, Minas Gerais, Brazil

Abstract

This study evaluates geochemical denudation in the upper course of das Velhas river, southern Quadrilátero Ferrífero, Minas Gerais - Brazil, within the Cachoeira das Andorinhas Environmental Protection Area. The local geology consists of metamorphic rocks from the Minas (Proterozoic) and the Rio das Velhas (Archean) Supergroups. A total of 23 surface-water samples were collected across different stream orders during both dry a wet season. Analyses included Atomic Spectrometry for major and trace elements, along with measurements of rain fall, pH, Eh and stream discharge. Elemental concentrations in solution follow the order: Na > Mg > Si > Ca > K > Al > Fe > As > Zn > Mn > Mo > Ba > Sr. The presence of gibbsite, combined with low concentrations of Al and F in solution, indicates a transitional stage between monosialitization to alitization. Lithology is the main control on denudation, with an average rate of 7.27 t/km²/year and vertical lowering of relief of 2.58 m/Ma. The results highlight the strong geological control over the relief denudation in the region and provide essential parameters for unstinting landscape evolution