Electrical and Seismic Tomography Used to Image the Structure of a Tailings Pond at the Abandoned Kettara Mine, Morocco

Abstract

International audienceThe Kettara site (Morocco) is an abandoned pyrrhotite ore mine in a semi-arid environment. The site contains more than 3 million tons of mine waste that were deposited on the surface without concern for environmental consequences. Tailings were stockpiled in a pond, in a dyke, and in piles over an area of approximately 16 ha and have generated acid mine drainage (AMD) for more than 29 years. Geophysical methods have been used at the Kettara mine site to determine the nature of the geological substrate of the tailings pond, the internal structure of the mine wastes, and to investigate the pollution zones associated with sulphide waste dumps. Electrical resistivity tomography (ERT) and seismic refraction data were acquired, processed, and interpreted; the results from ERT and seismic refraction were complementary. A topographical survey of the tailings disposal area was also undertaken to estimate the volume of wastes and quantify the AMD process. Two-dimensional inverse models were used to investigate the geophysical data and indicated alteration zones at depth. It was determined that the material could be classified into three categories: tailings, with low resistivity (5-15 Omega m) and low velocity (500-1,800 m/s); altered, black shales, with intermediate resistivity (20-60 Omega m) and velocity (2,000-3,500 m/s), and; materials with high resistivity and velocity (> 60 Omega m and > 4,000 m/s, respectively), including unaltered shales associated with quartzite seams. The low-resistivity zone generates AMD, which migrates downward through fractures and micro-fractures. The substrate is composed of broken and altered shale, which facilitates AMD infiltration

Abandoned Mine Tailings Affecting Riverbed Sediments in the Cartagena–La Union District, Mediterranean Coastal Area (Spain)

“…It is therefore necessary to gain deeper knowledge of the current condition of these deposits with high potential risk. There are examples of studies on tailings ponds using (i) magnetometry, enabling us to deduce the variations of the tailings structures [3,4]; (ii) electromagnetics, used to investigate the structural and hydrogeological settings of oil sands tailings dykes [5]; (iii) seismic, to derive the internal pond boundaries by means of refraction and reflection waves [6,7]; and direct-current geoelectrical imaging surveys [8], where the electrical resistivity tomography (ERI) method is strongly affected by the variation of some important properties of tailings such as moisture, soil salinization, particle size distribution, acid mine drainage, etc. [9,10].…”

Multidimensional Investigation of Bedrock Heterogeneity/Unconformities at a DNAPL‐Impacted Site

“…Lithologic and hydrogeologic properties can be evaluated geophysically by measuring their electrical and seismic properties from core, within coreholes or from surface (Slater ; Knight et al ). These complementary physical characteristics of the geologic units can provide more rigorous assessments of hydrogeologic unit geometries and media properties, and can even be jointly interpreted by using one model result or measurement set to constrain or inform the other (e.g., Cardarelli et al ; Lghoul et al ; Kotyrba and Schmidt ; Reiser et al ; Juhojuntti and Kamm ). Specifically, two‐dimensional (2D) and 3D inverse methods adapted to electrical resistivity and seismic refraction measurements can provide valuable insights into the lateral continuity and dimensional relationships of distinct lithostratigraphic units defined along coreholes under ideal conditions.…”

Estimation of the Pb Content in a Tailings Dam Using a Linear Regression Model Based on the Chargeability and Resistivity Values of the Wastes (La Carolina Mining District, Spain)

“…The combination of these two techniques has been used in different areas of earth sciences, such as mining [31][32][33], hydrogeology [34,35], and environmental sciences [8,36,37].…”

“…Although all have common characteristics in their physical properties, each presents differences in their chemical properties, depending on the type of host rock, the type of mineralization, and the efficiency of the concentration process. Therefore, to evaluate the contaminating potential of these wastes, it is necessary to conduct an internal study of these large structures, considered environmental liabilities [8].…”