RESUMO
To identify potential heavy minerals in the Mbiame floodplain in the Northwestern region of Cameroon, geochemical and petrographical data from alluvial deposits were utilized. The grains are mixed with inclusions of zircon and ilmenite, and the megacrysts come from felsic to intermediate igneous rocks like old basalt-andesite and magmatic gneiss. The Mbiame region lies between latitudes 6° 8' and 6° 24' N and longitudes 10° 39' and 10° 57' E, East of Mount Oku. One of the principal volcanic massifs on the Cameroon Volcanic Line (CVL), Mt. Oku is situated over a basement composed of migmatites, biotite diorites, and Pan-African granite-gneisses that date back to 600 Ma. The Mbiame Floodplain is located in the Pan African Fold Belt, which is made up of the Benin-Nigeria belt, which is a component of the Central African Fold Belt, and the Trans-Saharan belt. Between the Congo and West African cratons is a heavily eroded and deformed combination of Neoproterozoic plutonic and volcanic arcs and Paleoproterozoic micro-continents. The Central Cameroon Shear Zone serves as the primary lineament for the Pan African Orogeny, which is structurally separated into the Northwestern Cameroon Domain (NWC), the Adamawa-Yade Domain (AYD), and the Yaounde Domain (YD) in Cameroon. The field work was carried out during the dry season. During the field campaign, numerous bulk sediments were sampled from three (03) pits of vertical lithological succession along the left terrace of the Mbiame plain and twelve (12) were selected for laboratory analyses. The criteria for sample collection were based on texture (grain size) and color parameters. To identify the heavy minerals in the sediments and to understand the source of the sediments, the selected 12 bulk samples from the different layer of the pits were dried and sieved for heavy mineral determination. Heavy mineral separation was performed on about 2 g of the concentrate using bromoform liquid and the retained heavy minerals were mounted and observed under a petrographic microscope for optical properties identification. Twelve (12) bulk sediment samples weighing 100 g each were ground up in a mild steel pulverizer before being examined for major and trace elements. At Acme Analytical Laboratories Ltd., Vancouver, Canada, the geochemical study was carried out utilizing a combination of mass spectrometry (ICP-MS) for trace elements and inductively coupled plasma emission spectrometry (ICP-ES) for significant oxides. Lithium metaborate/tetraborate (LiBO2/Li2B4O7) flux was combined with 0.2 g of sample in crucibles, and the mixture was fused in a furnace. After the beads cooled, they were digested in ACS-grade nitric acid and then subjected to ICP-MS analysis. To calculate loss on ignition (LOI), a sample split at 1000 °C was ignited, and the weight loss was then measured. Data of this paper are further presented and discussed in Etutu et al. [1].
RESUMO
Sediment quality and trace metal accumulation are two of the most pressing issues facing the aquatic ecosystem around the world. Twenty-four (24) samples of stream sediments were collected along the Dibamba River, in the economic and industrial capital of Cameroon, to judge the trace metal levels in this river flowing near the city of Douala. Trace metal concentrations were disclosed with an ICP-MS on two different grain size fractions (very fine-grained sand and clay). The sediments indicate possible adverse effects of trace metals on surrounding biota as elements like Cr, Cu, Ni, Zn, Pb, and Hg show positive enrichment of greater than 1 when compared to background values from the upper continental crust (UCC) and sediment quality factors such as TEL (threshold effects level), PEL (probable effects level), ERL (effects range low), and ERM (effects range medium) values. The sediments show values of Degree of contamination (DC = 2-4), Pollution load index (PI = 1-2), and individual potential risk (EI = 92-219) indicating moderate pollution and ecological risk. Statistical and multivariate analyses point to both anthropogenic and geogenic sources for the heavy metals in the Dibamba stream sediments. The geogenic origin of the heavy metals is linked to the weathering of gneiss and migmatite found in the river banks. This study found low to mild levels of metal pollution and toxicity in the sediment, but it also warned that the continued development of nearby industries and businesses, the provision of transportation services, and waste disposal activities could result in a gradual outflow and accumulation of metals in the sediment, endangering the aquatic ecosystem.
RESUMO
Black shales are highly enriched in essential elements containing critical information on metallic richness and paleoclimatic imprints during deposition. The Cretaceous period marks the age of Basin formation from which the Mamfe Basin was formed from the Albian to Cenomanian. The purpose of this study is to investigate the geochemical behaviour of the shales in the Mamfe Basin and their paleoclimatic and metallogenic significance. Twenty-five representative shale samples were collected from seven sites outcrops in the Mamfe Basin. The major and trace elements composition in the shale samples were analysed using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In comparison with standard values for metalliferous shales, the shales from the Mamfe Basin are enriched in Boron (B), with only few samples enriched in Li, Rb, Cu, Pb and Zn. The Aluminium module (Alm) and ternary diagram plotted from Al-Fe-Mn shows that all the shales are considered as terrigenous sediments with only 02 samples (08%) falling within the zone of metalliferous sediments. The paleoclimatic characteristics that were inferred from the C-values (0.3-3.1), Sr/Cu (0.6-8.9), Sr/Ba (0.1-2.8), Rb/Sr (0.3-0.9), Fe/Mn (1.8-180), Al/Mg (0.31-31) and Mg/Ca (0.05-16.4) data of the shales in the Mamfe Basin indicate that the climate that existed during source area weathering ranged from a sub humid to a more humid climate with few samples ≤5% displaying arid climate.
