Use of Landsat 8 OLI Images to Assess Groundwater Potential Areas in the Bamun Plateau: Cameroon Volcanic Line (CVL)

The problem of groundwater supply in the Bamun plateau situated in the Cameroon Volcanic Line exists and no proper solution has been found so far. This investigation intends to find the suitable groundwater potential zones by overlaying the geomorphologic map, lineament map, lineament density map and lithological map, using visual interpretation of Landsat imagery. The results reveal that about 1921 structural elements, ranging in size, from 30 m to 5.845 km with an average length of 671 m in the field. The total length of the mapped lineaments is approximately 1289 km. The most important lineament (5.845 km length) diagonally crosses the study area in the direction NNE-SSW. In addition to this trend, all others are smaller than 14 km. More than 92% of lineaments are less than 5 km in size and only 1.3% of them are larger than 10 km. Small lineaments are thus the most numerous. According to their directions, the lineaments listed are grouped into 18 directional classes of 10-degree intervals. The rosette of their directions highlights the preferred directions NE-SW, N-S, E-W, NNE-SSW and ENE-WSW. Most of the lineaments clusters in the central part of the area are N20° - 30°E and N60° - 70°E trending lineaments. In this study, the NE-SW trend dominates the structural trend followed by NW-SE and N-S. This can be an indication of the directions of groundwater movement in the area. Alluvial plain and valley have moderate to very good groundwater potential that occurs all over the study area. Porosity of the volcanic rocks varies greatly, but it is everywhere more porous than the underlying, unweathered bedrock. There are essentially three classes (low, average and high) of groundwater potential zones. Hight potential zones are observed around the localities of the Khogham, Mbatpit and Mbam massifs on the one hand and Manswen, Njikwop, Mfelap, Foumban, Njindaré, Nkoundem and Ngwen jigoumbé localities on the other hand. About 13% of the area has good groundwater potential around the mountains while 58% is moderately good which corresponds to high to moderate lineament densities situated at average altitude 1200 m and about 31% of the area has poor groundwater potential corresponding to low lineament density areas. Moreover, this work has helped develop a detailed lineament map that can be used for mining and hydrological prospecting campaigns.

Geochemical Characterization of Novokrivoyrog Metavolcanics: Tectonic Implications and Relationship with the Early Proterozoic Banded Iron Formation (BIF) of Krivoy Rog in Ukraine

The geochemical characterization of Novokrivoyrog metavolcanics (2.2 Ga) and Krivoy Rog iron ores (1.8 Ga) in Ukraine represent an important tool for the understanding of their genesis and tectono-magmatic evolution. The petrological classification of the metavolcanics on SiO2/(Zr-TiO2) and (Zr-TiO2)/(Nb/Y) Harker-type diagrams shows similarities to subalkaline andesitic basalts. An additional classification of the basalts on TAS (Na2O + K2O/SiO2) and AFM (FeO-MgO-Na2O + K2O) diagrams exhibits a variable magmatic character from calc-alkaline to tholeiitic. The distribution of High Field Strength Elements, (HSFE: Ti, Zr, Y, Hf, Nb), V, Cr, and Rare Earth Elements (REE) in most of the rocks is close to calc-alkaline basalts (CAB) and can be compared to Precambrian mid-ocean ridge basalts (MORB) where high thermal (>250°C) basaltic alteration is intensive under pH conditions between 2 and 4. These contributed to the deposition of the Krivoy Rog BIFs. Indeed REE distribution patterns of the BIFs suggest that they can be subdivided into shales and shaly BIFs (rich in LREEs since their detrital and clastic inputs are much higher) with (La/Yb)N > 1 as indication of clastic inputs;chert and cherty BIFs showing positive Eu anomaly with (La/Yb)N 1 emphasizes post-depositional effects related to the enrichment of light REEs over heavy REEs with a positive Eu anomaly. The distribution of REE patterns of Krivoy Rog BIFs can finally be compared to Precambrian iron formations of mixed submarine hydrothermal fluids and seawater origin which correspond to the MORB signature of the Novokrivoyrog metavolcanics.

Temporal Evolution of the Barombi Mbo Maar, a Polygenetic Maar-Diatreme Volcano of the Cameroon Volcanic Line

The Barombi Mbo Maar (BMM), which is the largest maar in Cameroon, possesses about 126 m-thick well-preserved pyroclastic deposits sequence in which two successive paleosoil beds have been identified. The maar was thought to have been active a million years ago. However, layers stratigraphically separated by the identified paleosoils have been dated to shed lights on its age and to reconstruct the chronology of its past activity. The results showed that the BMM formed through three eruptive cycles: the first ~0.51 Ma ago, the second at ~0.2 Ma and the third ~0.08 Ma B.P. The ages indicate that the BMM maar-forming eruptions were younger than a million years. The findings also suggested that the maar is polygenetic. At a regional scale, the eruptive events would have occurred during some volcanic manifestations at Mt Manengouba and Mt Cameroon. Therefore, with the decrease in the recurrence time of eruptions from ~0.3 Ma to 0.1 Ma, and given the possible relation between its eruptive events and those of its neighboring polygenetic volcanoes, the BMM is expected to erupt within the next 20 ka.

High-Precision Structural Map of Southeast Cameroon Using Phase Filters on Potential Gravimetric Data

The south-east of Cameroon encompasses a wide variety of geological structures among which we can cite the Congo Craton (CC), the Sanaga Fault (SF), the Yaoundé Domain, the Panafrican belt, the Protozoic series and the Dja complex. The presence of all these structures justifies the great tectonic activity to which this area was subject from the rupture of Pangea to the creation of the different plates that exist today. In this work, we will bring out a high-resolution structural map of the study area by applying the qualitative analysis of the phase filters on 200,900 points of gravimetric data obtained from the combination of the XGM2016 and ETOPO1 models. Then, with these same data, we will bring out another structural map with the maxima method called Multi-Scale Horizontal Derivative of Vertical Derivative (MSHDVD) which will be compared to the first in order to show the limits of the MSHDVD method. To do this, we will first use the extension method to highlight the map of residual anomalies, then a combination of derivative, gradient and phase filters to highlight the geological structures responsible for fracturing in this area. Phase filters have the advantage that they make it possible to highlight all the geological edges responsible for the fracturing without taking into account the depth, while the MSHDVD method highlights the existing geological contacts (edges) at depths well defined by the examiner. The structural map obtained with the MSHDVD method shows that the major structural direction in this zone is W-E while that obtained from the interpretation of the phase filters is more precise and shows that the major structural direction in this area would be N-S and this result would be in perfect agreement with the tectonics of East Cameroon.