The use of Geoelectrical Methods for Delineation of Lead-Zinc Mineralization: A Case Study of Eziama Village, Abia State, South- East, Nigeria

2D Electrical Resistivity (ER) and Instantaneous Potential (IP) geophysical techniques were used at Eziama village in Abia state of Nigeria to investigate possible Pb-Zn mineralization. The dipole-dipole electrode configuration was employed for data acquisition and Earth Imager software was used for inversion of the acquired data. The analysis of the result of the study showed the presence of the Pb-Zn ore along traverses 1, 2 and 3 while traverses 4 and 5 appear barren. Along traverse 1, the mineralized zone falls within the fractured basement and is characterized by low resistivity (about 316 – 5623 ohm-m) and high chargeability (33.2 – 128 ns) at lateral distance of 73 – 103 m. On traverse two, the ore body was identified at lateral distance of about -18 to 53 m as delineated on the IP structure with resistivity and chargeability of the anomalous zone ranging from 4.6 – 677 ohm-m and 41.8 – 142 ns respectively at depth of about 21.4 m while on traverse three, two ore bodies labeled a, a’ and b, b’ on the ER and IP cross-sections were delineated at lateral distance of about -130 to -93 m and 78 to 98 m respectively with depth to the top of the suspected ore bodies ranging from about 7.1 m for body ‘a’ and about 14.3 m for ‘a’. Traverses four and five however showed no prospect for Pb-Zn mineralization. The result of this investigation has once again demonstrated the usefulness of combined electrical resistivity and induced polarization techniques in solid mineral exploration.

Empirical Correlations between the Hydraulic Properties Obtained from the Geoelectrical Methods and Water Well Data of Arak Aquifer

A number of empirical correlations have been achieved between the hydraulic properties measured through geoelectrical methods and water well data of Arak Aquifer located in Markazi province, Iran. The geoelectrical method of Vertical Electrical Sounding (VES) technique was used to calculate the hydraulic properties of the aquifer. Through the VES technique, the pivotal hydraulic properties such as porosity, hydraulic conductivity, and specific yield of the layers were calculated. The results of VES technique were compared with the data obtained from seven observation water wells that were already drilled as exploratory coring boreholes in the region. The results demonstrate that as the porosity and hydraulic conductivity of the water-bearing layer increase, the results of VES technique appear much identical to the water well records. Furthermore, the specific yield was calculated as 4.6% that was very close to the value of 3.5% measured through the previous pumping tests. Moreover, VES technique predicted the water table of the aquifer very close to the water level monitored in the observation water wells. The obtained correlations can be used as an alternative for drilling of new observation wells that are inefficient in time and expense, and may encounter environmental limitations of drilling and site construction.

Textural and mineralogical controls on temperature dependent SIP behavior during freezing and thawing

<p>Geoelectrical methods are increasingly being used for non-invasive characterization and monitoring of permafrost sites, since the electrical properties are sensitive to the phase change of liquid to frozen water. Here, electrical resistivity tomography (ERT) is most commonly applied, using resistivity as a proxy for various quantities, such as temperature or ice content. However, it is still challenging to distinguish between air and ice in the pore space of the rock based on resistivity alone due to their similarly low electrical conductivity. Meanwhile, geoelectrical methods that utilize electrical polarization effects to characterize permafrost are also being explored. For example, the usage of the spectral induced polarization (SIP) method, in which the complex, frequency-dependent impedance is measured, can reduce ambiguities in the subsurface conduction properties, considering the SIP signature of ice. These measurements seem to be suitable for the quantification of ice content (and thus the differentiation of ice and air), and for the improved thermal characterization of alpine permafrost sites. However, to improve the interpretation of SIP measurements, it is necessary to understand in more detail the electrical conduction and polarization properties as a function of temperature, ice content, texture, and mineralogy under frozen and partially frozen conditions.</p><p>In the study presented here, electrical impedance was measured continuously using SIP in the frequency range of 10 mHz to 45 kHz on various water-saturated solid rock and loose sediment samples during controlled freeze-thaw cycles (+20°C to -40°C). These measurements were performed on rock samples from different alpine permafrost sites with different mineralogical compositions and textures. For all samples, the resistance (impedance magnitude) shows a similar temperature dependence, with increasing resistance for decreasing temperature. Also, hysteresis between freezing and thawing behavior is observed for all measurements. During freezing, a jump within the temperature-dependent resistance is observed, suggesting a lowering of the freezing point to a critical temperature where an abrupt transition from liquid water to ice occurs. During thawing, on the other hand, there is a continuous decrease in the measured resistance, suggesting a continuous thawing of the sample. The spectra of impedance phase, which is a measure for the polarization, exhibit the same qualitative, well-known temperature-dependent relaxation behaviour of ice at higher frequencies (1 kHz - 45 kHz), with variations in shape and strength for different rock texture and mineralogy. At lower frequencies (1 Hz - 1 kHz), a polarization with a weak frequency dependence is observed in the unfrozen state of the samples. We interpret this response as membrane polarization, which likewise depends on the texture as well as on the mineralogy of the respective sample. This polarization response partially vanishes during freezing. Overall, the investigated SIP spectra do not only show a dependence on texture and mineralogy, but mainly a dependence on the presence of ice in the sample as well as temperature. This indicates the possibility of a thermal characterization, as well as a determination of the ice content, of permafrost rocks using SIP.</p>

Analisa Persebaran Wetland Berdasarkan Metode Geolistrik di Kecamatan Pandak, Kab. Bantul, DIY

ABSTRAKWetland merupakan tanah lunak tersaturasi air yang berada di dekat permukaan yang menjadi permasalahan dalam pembangunan di sekitar daerah penelitian di Desa Gilangharjo, Kab. Bantul, DIY. Oleh karena itu dilakukan pengukuran metode geolistrik untuk mengetahui persebaran kedalaman wetland di sekitar daerah penelitian sebagai bahan kajian pendukung dalam program pembangunan desa. Dalam penelitian ini dilakukan pengukuran metode geolistrik sounding sebanyak lima titik sounding, kemudian data lapangan diproses menggunakan pemodelan inversi 1 Dimensi (1D) untuk mendapatkan kurva model 1D resistivitas batuan. Berdasarkan kurva model 1D resistivitas batuan didapatkan nilai resistivitas wetland berkisar antara 5.66 - 29.6 ohm.m dan kedalaman wetland berkisar antara 0.592 - 2.25 meter yang meningkat ke arah tenggara. kata kunci : Wet soils, resistivitas, geolistrik sounding ABSTRACTWetlands is a soft water saturated rocks in near surface which becomes a problems of developement in surrounding area of Gilangharjo Village, Bantul District, DIY. Therefore, the research with using geoelectrical methods has been conducted to delineating spreading of wetlands depth in surrounding research areas as a supporting data for village developing programs. In this research is conducted sounding geoelectrical methods measurements as much five sounding points, then the field data is processes with using 1D inversion modelling to get 1D resistivity models curve of rocks. Based on 1D resistivity models curve of rocks is obtained wetlands resistivity value is between 5.66 - 29.6 ohm.m and the depth of wetlands is between 0.592 - 2.25 meters which increase to southwest. keywords : Wet soils, resistivity, sounding geoelectric.

Application of geoelectrical methods for identification of soil layer

Landslide is a geological event caused by the movement of rock or land mass that can be defined as the displacement of slope-forming material, which is the original rock as well as the other material that is moving with the gravity. The factors that influence landslides are soil layer, slip surface and saturated soil. Mapping or determining the landslide area is done by identifying several parameters that can trigger landslide. The geophysical method that can be used to analyse soil layer is resistance type of geoelectrical. Variations of each rock or soil layer resistance below the measuring point can be obtained from the measurements of current and potential differences. The research site is located East Aceh district, Indonesia. Geoelectrical measurements using Wenner-Schlumberger electrode configuration. Based on geological information, field observation and geophysical measuring results, the area is dominated by clay, sand and gravel material. Lithology of clay dominates the underside of the surface (until the depth of ± 30 meters. water that is held in sand lithology causes saturation of the sand. this is because there is a layer of clay under the sand which has low permeability or even impermeable properties. Saturated sand lithology can lead to contact between particles and has the potential to weaken it, causing soil movement.