Petrology of weathering materials developed on granites in Biou area, North-Cameroon: implication for rare-earth elements (REE) exploration in semi-arid regions

Abstract

Due to the increasing demand resulting from the use of REE in many fields of human life, a weathering profile developed on granites in the semi-arid region of Biou area (North-Cameroon) has been characterized for rare-earth elements (REE) exploration. The mineralogical compositions of weathered materials were revealed by X-ray diffraction (XRD). X-ray Fluorescence (XRF) and Inductively Coupled Plasmas-Mass Spectrometry (ICP-MS) have been used to determine the geochemical composition of granites and the overlying weathered materials. The S-type and peraluminous granites are constituted by quartz, orthoclase, microcline, plagioclase, biotite, muscovite, pyroxene and opaque minerals. Accessory minerals are probably responsible for the interesting contents in REE + Y and some trace elements (e.g., Zr, Zn, Ba, Rb). The weathering profile show from the bottom to the top: (i) saprolitic horizons; (ii) lower loose clayey horizon; (iii) iron duricrust horizon; (iv) upper loose clayey horizon; (v) and organo-mineral horizon. Some weathered rock fragments remain in the loose clayey and organo-mineral horizons. The mineralogical composition of the weathering materials is dominated by illite, muscovite and feldspar. The low weathering degree of the materials is justified by the climatic and reducing conditions. The large ion lithophiles and ferromagnesian elements (Mg, Fe, V, Cu, Co, Cs Cr, Ni, Sc and Li) which are supposed to be mobile are so much accumulated in the weathering materials. REE show very low degree of fractionation in weathering profile due probably to the lack of good drainage. The whole weathering materials shows high REE + Y contents as its parent rock. Geochemical mass balance and enrichment factor reveal that REE, especially light REE, are so much enriched in the iron duricrust horizon (ion-adsorption REE deposit type). Some heavy REE are also enriched in the lower loose clayey horizon. This first survey has revealed that the weathering materials developed on granites in Biou area are favorable for further REE exploration.

Heavy Metal Contamination and Ecological Risk Assessment in Soils of the Pawara Gold Mining Area, Eastern Cameroon

“…Moreover, Hg absorption into the soil is also enhanced by the presence of these clay minerals [89]. Studies from [90] indicated that trace elements such as Cr, Co, Cu, Fe, Mg, V and Ni turn to be trapped within the duricrust layer along the soil profile even though they are normally mobile in the weathering environment. This accumulation is caused by hot humid climatic conditions as is the case within the Pawara area that favors the oxidation of Fe-and Albearing minerals.…”

Mineralogical, geochemical, and geotechnical features of lateritic soils from termite mounds in two contrasting savannah areas (central Cameroon) as raw materials for brick making

“…According to Nyassa Ohandja et al [ 21 ], the reddish color of the fired bricks is due to the high proportion of Fe 2 O 3 in the raw materials. These higher iron proportions in HS materials can be explained by a relative accumulation of this oxide in the lower parts of the relief, which confirms the presence of goethite in these materials [ 37 , 38 ]. For both microclimates, the proportions of Fe 2 O 3 remain higher in the internal parts compared to the external parts.…”