Possible use of Si-Phytoliths in metal anomaly prospection. Example from Riacho dos Machado region, Cerrado, Minas Gerais, Brazil.

International audienceThis work investigates the distribution of selected heavy elements in soil samples and Si-Phytoliths from plants. The aim is to verify if metal contents are indicative for metal anomalies in the soil. Samples were collected in profiles near the Riacho dos Machados Goldmine. Granitic-gneissic rocks, in tectonized contact with the overlaying rocks, form the basis of the investigated region, which belongs to the Rio dos Machados Group of the Espinhaço Super Group. The whole rock substrate is covered by lateritic to arenitic soils with different exposure depths. Metal-rich fluid invaded this unit, forming metal anomalies, forming Zn-Pb-Au deposits, like that of Salobre-Porteirinha. After appropriate preparation, the samples were analyzed by ICP-OES (Si-Phytoliths) and XRF (soil). Anomalies in the investigated profile are indicated by high metal contents in the Si-Phytoliths of the selected species. Using different species, the metal concentration at different depths can be determined