Hydrogeophysical and structural investigation using VES and TDEM data: A case study at El-Nubariya–Wadi El-Natrun area, west Nile Delta, Egypt

AbstractThe geoelectric survey includes 93 Vertical Electric Soundings (VES) and 26 TEM stations were conducted to delineate the subsurface structures and hydrogeological regime of El-Nubariya–Wadi El-Natrun area. The VESes AB/2 was varying from 1 up to 700m in successive steps, while TEM stations were measured using coincident loop of 50m side length.The interpretation of the geoelectrical data shows that the depth to the main aquifer ranges from 6m at the northern part near the Nubariya city to about 90m at the southern parts where it increases to the south and southeast directions. Generally the aquifer system in the area can be divided into Pleistocene and Pliocene aquifers. The Pleistocene aquifer is the shallower aquifer in the area and it consists almost of gravelly to clayey sand deposits. The Pliocene aquifer is the main aquifer where it is composed of sand to gravelly sand deposits.Depending on the results of the geoelectric prospecting represented by the true resistivity map, we can infer the quality of the groundwater. A brackish groundwater can be found at the northern and northeastern parts of the study area at shallow depths whereas relatively fresh water can be detected at the southern and southeastern parts around Wadi El Natrun city at deep depths.The area under consideration is affected by a group of normal faults that divided the investigated area into five main divisions, northern, eastern, western, southern and central divisions. The inferred faults from the geoelectric sections are traced and collected to construct a structure map. It is worth to mention that Wadi El Natrun and its lakes are structurally controlled by faulting systems trending NW direction

Mapping the groundwater potentiality of West Qena area, Egypt, using integrated remote sensing and hydro-geophysical techniques

The integrated use of remote sensing imagery and hydro-geophysical field surveys is a well-established approach to map the hydrogeological framework, and thus explore and evaluate the groundwater potentiality of desert lands, where groundwater is considered as the main source of freshwater. This study uses such integrated approach to map the groundwater potentiality of the desert alluvial floodplain of the Nile Valley west of Qena, Egypt, as alternative water source to the River Nile. Typically ground gradient, faults and their stress field, lateral variation of rock permeability, drainage patterns, watersheds, rainfall, lithology, and soil types are the main factors believed to affect the groundwater recharge and storage from the infiltration of present-time and paleo-runoff. Following this generally accepted approach, different remote sensing data sets (SRTM DEM, Landsat-8, ALOS/PALSAR-1, Sentinel-1, and TRMM) as well as auxiliary maps (geological and soil maps) were used to identify and map these factors and prepare thematic maps portraying the different influences they exert on the groundwater recharge. These thematic maps were overlaid and integrated using weights in a GIS framework to generate the groundwater potentiality map which categorizes the different recharge capabilities into five zones. Moreover, the aeromagnetic data were processed to map the deep-seated structures and estimate the depth to basement rocks that may control the groundwater occurrence. In addition, the vertical electrical sounding (VES) measurements were applied and calibrated with the available borehole data to delineate the subsurface geological and hydrogeological setting as well as the groundwater aquifers. Different geoelectric cross-sections and hydro-geophysical maps were constructed using the borehole information and VES interpretation results to show the lateral extension of the different lithological units, groundwater-bearing zones, water table, and the saturated thickness of the aquifer. The GIS model and geophysical results show that the southwest part of Nag’a Hammadi-El-Ghoneimia stretch has very high recharge and storage potentiality and is characterized by the presence of two groundwater-bearing zones. The shallow groundwater aquifer is located at a depth of 30 m with a saturation thickness of more than 43 m. However, there are NW–SE faults crossing the study area and most likely serve as recharge conduits by connecting the shallow aquifer with the deeper ones. Such aquifers connection has been confirmed by investigating the chemical and isotopic composition of their groundwater.Published versio

Integrated geophysical, remote sensing and geochemical investigation to explore gold-mineralizations and mapping listvenites at Wadi Haimur, Eastern Desert, Egypt

Although the continuity of gold mining work since Pharaonic times till today, Wadi Haimur is still promised source for gold. Wadi Haimur is located in west Allaqi-Heinai-Suture (AHS), south Eastern Desert of Egypt. Gold mineralization is mainly confined within quartz-carbonate and sulphide-bearing quartz veins within sheared, altered rocks, while listvenitization plays a significant role in gold concentration along the Haimur area. Therefore, critical analyses of remote sensing data were applied to map alteration zones and delineate listvenites. Spatially enhanced images were processed to trace lineaments and weakness zones which may represent pathways of mineralized, ascended hydrothermal fluids. Ground geophysical, magnetic and geoelectric surveys were performed to study the depth-extension of mineralized bodies in the vicinity of the historical mines within Wadi Haimur. Interpretation of land-magnetic data indicates the presence of mineralized veins associated with narrow shear zones. Derivatives and high-pass filters were utilized to map shallow mineralized sources and deduce their trends. Upward continuation and low-pass filters were used to detect the deep sources. Depths to magnetic bodies were estimated using Power-Spectrum, Euler and inversion of single anomalies. Geochemical sampling was performed to test the results. According to the remarkable variation in resistivity and chargeability values of resistivity and induced-polarization tomography profiles, the subsurface lithology was classified and probable mineralized zones within the subsurface were detected. Encouraging results from regolith, trenching, rock-chip sampling and Reverse-Circulation (RC) drilling indicated the extension of auriferous anomalies within the bedrock. Good correlation of RC-holes auriferous anomalies depths and deduced depths from magnetic interpretation was revealed.HIGHLIGHTS Integrated geophysical, geochemistry and remote sensing data are used to delineate mineralized ore deposits. The estimated average depths of mineralized sources are 12.5, 48 and 463 m for shallow, intermediate and deep magnetic bodies, respectively. Massive sulphide-bearing zones ± gold concentrations were suggested for zones with low-resistivity and high-chargeability signatures