Remote Sensing And Gis Investigations For Geological And Alteration Zones Related To Hydrothermal Mineralization Mapping, Maman Area, Eastern Sudan

Abstract

ABSTRACT The optical multispectral of Landsat 7 Enhanced ETM+ is used for geological mapping and detection of the alteration zones related to hydrothermal mineralization in the area around Maman town, Eastern Sudan. The area represents a basement complex terrain dominated by low - grade ophiolitic - decorated metavolcanosedimentary sequences, intruded by orogenic grantoids and anorogenic granites, overlain by Recent alluvial and aeolian sediments. Digital image processing techniques involve pan sharpening fusion of simple linear stretching; and decorrelation stretching of triple sets (7, 4 and 1); and (7, 5 and 3) were used to discriminate various lithological units and structural manifestations for geological mapping. Additionally, the digital image processing is used to demarcate the alteration zones related to hydrothermal mineralization by their spectral signatures of the related iron oxides/ hydroxides and clay minerals. Spectral ratioing colour composite image (5/7, 4/5, 3/1) coupled with the Feature Oriented Principal Selection technique (FPCS) as Crosta’s image were applied to identify the spectral signatures of the alteration zones. Supervised classification of the produced images were vectorized and spatially analyzed in the GIS framework to demarcate the most probable alteration zones. The remote sensing applications with field geological and geochemical data disclose the existence of many potential promising prospective zones. These results show the strengthening of using the spectral and spatial analysis of the optical multispectral data in geological mapping and mineral exploration investigations. Geologic remote sensing has been widely applied in Sudan since the last century. It has been used for geological mapping, mineral exploration, geotechnical and hydrogeological investigations (El Khidir, et al. 2014; El Sheikh, et al. 2014 a & b; El Khidir and Babikir, 2013; Ali, et al. 2012; Kenea, 1997; and Abdelsalam, et al. 1995). Exploitation of remote sensing in mineral exploration is well understood by geological mapping, delineation the regional and local structural features such as fracture and faults. Ore deposits were identified through the detection of the hydrothermally altered rocks by their spectral signatures (Gupta, 2003; Sabins, 1999, 1997). 2. STUDY AREA The study area lies around Maman town, Kassala State, East Sudan, near the Eritrean borders. It is bounded by longitudes 36⁰ 28` and 37⁰ 00` E and latitudes 16⁰ 04` and 16⁰ 45` N (Fig. 1). The Maman area belongs to the Red Sea arid to semi –arid climate. Generally the rainfall in the Red Sea Hills is negligible in the north and slightly rainy in the south, the annual average is about 137 mm with occasional freak storms. Summer (March – October) is usually hot (up to 46° C) whereas a mild winter revealing between November – February. Due to the lack of rain water, the vegetation is scarce where bushes of thorn trees mainly acacia, are confined to khors and wadies. Geomorphologically, the area characterized by a rugged mountainous terrain. To the east the mountainous terrain extended in NS direction in the Eritrean borders, but grades gently westward to the flat plains of the River Gash watershed. The topography is generally controlled by structural and lithological factors. The flat plains are covered with aeolian sands and alluvial silts and marked by series interconnected hills. The drainage in the study area is well developed represented by many intermittent stream and khors. The drainage pattern is structurally controlled, and most wadies and khors follow fault plains and major joints. Hand dug wells along khors and wadies are the main water supply in the investigation area. bands and panchromatic of spatial resolution 30 m and 15 m, respectively. ii. Landsat 7, ETM+ data, path 171, row 49, acquisition date 2000‐10‐23, with 6 multispectral bands and panchromatic of spatial resolution 30 m and 15 m, respectively. 2. Previous georeferenced digital map of Robertson Research Map - Portsudan Sheet (GRAS, 1988)..