Mapping Hydrothermal Alteration Targets from Landsat 8 OLI/TIRS and Magnetic Data Using Digital Image Processing Techniques in Garoua, North Cameroon

Abstract

A geological based remote sensing study was carried out over the Poli group in Garoua (northern Cameroon), renowned for its hydrothermally occurring mineralizations (Gold and Uranium). In this study, Landsat 8 OLI/TIRS coupled with magnetic data were used in order to realize a regional litho-structural mapping of hydrothermal alteration targets, required for mineral exploration. Hence, the enhancement of both Landsat 8 and magnetic data was achieved via digital image processing (DIP) techniques notably Band rationing (BR), Principal Component Analysis (PCA), Horizontal gradient (HG), and lineament extraction algorithms. Based on reference band ratio combinations (Sultan's and Kaufmann's) and Crosta Technique (PCA analysis), hydrothermally altered minerals such as hydroxyl-bearing minerals and iron oxides were identified. The PCA map was shown to better illustrate hydrothermally altered areas than Band ratios. Thus, a classification map emphasizing on mineral targets was obtained from the PCA map. Besides, the CET grid analysis tool (horizontal gradient) from Geosoft software 8.4 and the line algorithm (pan band 8) from Geomatica 2013 allowed the extraction of subsurface and surface lineaments respectively. The resulting lineaments showed a predominant E-W trending direction, which suggests a major tectonic event having prevailed within the area. Other directions include NE-SW/ENE-WSW, and N-S. The generation of a target exploration map, via ArcGIS 10.4.1, was performed by the overlay of hydrothermal alteration mapping and structural mapping. New regional maps, providing a useful insight for further mining exploration, were obtained.

+-Evidence of Porphyry Deposits in the Ntem Complex: A Case Study from Structural and Hydrothermal Alteration Zones Mapping through Landsat-8 OLI, Aeromagnetic and Geological Data Integration in the Yaounde-Sangmelima Region (Southern Cameroon)

“…The remote sensing results are consistent with magnetic results (Figure 9). These structures and directions are consistent with previous studies [25] [85] in the area and at the vicinities. Indeed, these works have highlighted many faults or fractures interpreted as tectonic accidents affecting the CC, the basement of the CAFB domain without providing a real explanation on the faulting history or kinematics to help understanding geodynamics at the northern margin of the CC.…”

“…RS has become a standard tool in geological studies by highlighting faults/fractures in structural studies [10] [11] [12] [13] [14] and in mapping lithology and/or hydrothermal alteration zones related to mineral ore deposits [15]- [20] in different geological contexts across continents. Some recent pioneer studies involving Landsat suites data have been done in Cameroon to address structural [21] hydrological [22] or lithology and mineral exploration [23] [24] [25] issues.…”

Integration of Landsat 8, gravity, and field data for exploration of gold mineralization in Gamba District, Northern Cameroon

“…In this study, the PCA was applied to bands 1, 3, 6, and 7 to enhance the effect of hydroxyl-bearing minerals (e.g., epidote, chlorite, muscovite, and biotite). Bands 4 and 5 were not selected to avoid vegetations that share the same spectral signature with hydroxyl-bearing minerals (Anaba Fotze et al, 2019). Likewise, PCA was applied to bands 2, 4, 5, and 6 to map iron-bearing minerals.…”

“…The visible and near‐infrared (VNIR) and short‐wave infrared (SWIR) spectra can be used to identify the assimilation characteristics of hydrothermally altered minerals (e.g., Al‐OH, Mg‐OH, Si‐OH, and CO 3 2− ) associated with ore deposits (Neh‐Fru, Andongma, Yongue, & Anaba Fotze, 2020). Concerning the Northern Cameroon, in a regional exploration survey, Anaba Fotze, Djieto Lordon, Penaye, Sep, and Neh‐Fru (2019) used Landsat 8 imagery to identify hydrothermal alteration minerals, which were assumed to be connected with uranium and gold deposits. The determination of northern Cameroon fault has shown altered hydrothermal areas responsible for uranium mineralization (Kouske, Suh, Ghogomu, & Ngako, 2012).…”

“…The visible and nearinfrared (VNIR) and short-wave infrared (SWIR) spectra can be used to identify the assimilation characteristics of hydrothermally altered minerals (e.g., Al-OH, Mg-OH, Si-OH, and CO 3 2À ) associated with ore deposits (Neh-Fru, Andongma, Yongue, & Anaba Fotze, 2020). Concerning the Northern Cameroon, in a regional exploration survey, Anaba Fotze, Djieto Lordon, Penaye, Sep, and Neh-Fru (2019) used…”