Enrichment in Heavy Metal (HM) and Rare Earth Element (REE) in Fluvial Placer Deposits: Case Study of Zambesi River (Mozambique)

Abstract

Mozambique has a huge mineral potential that is largely untapped. Tantalum-niobium, other rare metals, gold and semiprecious stones are abundant. Deposits of heavy mineral sands and a wide range of industrial minerals comprise a few of the mineral wealth in Mozambique that are under development. One of the most interesting zones of Mozambique is definitely the Zambezi River, where the placers deposits are rich in HM and REE. For this reason, ENEA in 2013 has performed an extensive multidisciplinary research along the Lower Zambezi, in cooperation with the Minas Rio Bravo Company (Mozambique). The aim of the research is to verify the REE and heavy metal abundances by measuring geochemical and mineralogical characteristics of the sediments from the bottom of the Zambezi, in the area between Tete and Tambara cities. The analyses were carried out at the Department of Physics and Earth Science of Ferrara University by X-ray fluorescence analysis, X-ray diffraction analysis and pycnometer method. The result of XRD shows that the main minerals are quartz and feldspar. Unfortunately, the XRD peak of the main mineral phases covers up the others. However, chemical analyses reveal high presence of Iron and Titanium oxides and trace elements, as Cesium, Chromium and Lanthanum, suitable for industrial mining purposes. Furthermore, the data of density are comparable to the detecting phases found with XRD. The goal of the survey is to determinate the economic value of the Zambezi sediments for industrial minerals sector. Secondly, the results are important to improve the geochemical and mineralogical knowledge of this zone.