Near Surface Geophysics for the Structural Analysis of a Mine Rock Pile, Northern New Mexico

Dam, Remke L. Van; Tech, Socorro New Mexico; Gutierrez, Luiza A. F.; McLemore, Virginia T.; Wilson, Gordon; Hendrickx, Jan M. H.; Walker, Bruce M.

doi:10.21000/jasmr0501178

Cited by 4 publications

(2 citation statements)

References 10 publications

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“…Location of prior drill holes in the rock pile 3. Geophysical surveys (van Dam et al, 2005) 4. Molycorp mitigation plans (Norwest Corporation, 2003).…”

Section: Mapping Proceduresmentioning

confidence: 99%

Characterization of Goathill North Mine Rock Pile, Questa Molybdenum Mine, Questa, New Mexico

McLemore¹,

Donahue²,

Phillips³

et al. 2006

JASMR

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Abstract. Rarely do rock pile characterization methods allow for examination and sampling of the interior of large rock piles in-situ. The regrading of the Goathill North (GHN) rock pile at the Questa mine provided a unique opportunity to examine and sample the interior of a large rock pile through the construction of trenches cut into the rock pile as earth-moving progressed. Maps of each bench were created to document the different stratigraphic units, including the thickness, dip, and extent of the units. Units were defined based on grain size, color, and other physical properties. Units were correlated between benches and downward through the series of successively excavated trenches. Typically, paste pH increased with distance from the outer, oxidized zone (west) towards the interior units (east) of the GHN rock pile. The outer zone was oxidized (weathered) based upon the white and yellow coloring, low paste pH, presence of jarosite and gypsum, and absence of calcite. However, the oxidation/reduction (weathering) state in the interior zone is not yet determined. The base of the rock pile closest to the bedrock/colluvium surface represents the oldest part of the rock pile since it was laid down first. Portions of the base appeared to be nearly or as oxidized (weathered) as the outer, oxidized zone, suggesting that air and water flow along the basal interface occurred and possibly was an active weathering zone. Analyses of samples from unweathered, unoxidized drill core samples and from the GHN rock pile are similar in clay mineralogy as determined by XRD and electron microprobe analyses, which suggests that the majority of clay minerals in the GHN samples were derived from the original, pre-mined hydrothermal alteration and not post-mining weathering. Additional

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“…Location of prior drill holes in the rock pile 3. Geophysical surveys (van Dam et al, 2005) 4. Molycorp mitigation plans (Norwest Corporation, 2003).…”

Section: Mapping Proceduresmentioning

confidence: 99%

Characterization of Goathill North Mine Rock Pile, Questa Molybdenum Mine, Questa, New Mexico

McLemore¹,

Donahue²,

Phillips³

et al. 2006

JASMR

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“…Electrical resistivity imaging, ground penetrating radar and induced polarisation methods have been widely employed in studies of leachate transport from landfills (Nobes et al 2000;Abu-Zeid et al 2004;Porsani et al 2004;Dahlin et al 2010). They have also been used in mining environmental studies, in order to image AMD plumes (Buselli and Lu 2001;Rucker et al 2009), tailings ponds (PlacienciaGómez et al 2010; or waste rock piles (Van Dam et al 2005;Poisson et al 2009;Anterrieu et al 2010;Mele et al 2013). This study uses ground penetrating radar (GPR) and geoelectrical multiplegradient array surveying to examine the effectiveness of the backfilling and sealing of mine waste at a small openpit copper mine in northern Sweden.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the effectiveness of backfilling and sealing at an open-pit mine using ground penetrating radar and geoelectrical surveys, Kimheden, northern Sweden

et al. 2014

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At Kimheden, a small copper mine in northern Sweden, reclamation of the two open pits was investigated using ground penetrating radar and geoelectrical multiplegradient array measurements. The pits had been backfilled with waste rock, with a dry cover being applied on top in 1996 in order to reduce the influx of oxygen to the sulphidic mine waste and the subsequent production of acid mine drainage. The dry cover consists of a sealing layer of clayey till and a protective layer of unsorted till. As geochemical sampling in the drainage from the pits had previously revealed the continued release of contaminating oxidation products, the purpose of the geophysical survey undertaken in 2010 was to identify deficiencies in the cover or other pathways for oxygen to reach the waste rock. The radar images did not reveal any damage in the sealing layer but risks of deterioration of the cover in the long term were identified with both the radar and geoelectrical data. The radar localised regions of thinner protective layer where the sealing layer could be exposed to frost action. The geoelectrical measurements indicated the existence of seepage through the dry cover that presented a risk of erosion of the sealing layer. 2-D inversion of geoelectrical data also imaged some pathways of groundwater around the main pit. The results from the geophysical investigations were used together with other site data in order to show that both deficiencies in the cover and superficial fractures in the pit walls may explain an ongoing influx of oxygen to the mine waste.

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Preliminary Status Report on Molycorp Goathill North Trenches, Questa, New Mexico

McLemore¹,

Walsh²,

Donahue³

et al. 2005

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Rarely do rock pile characterization methods allow for examination and sampling of the undisturbed interior of large rock piles in-situ. The regrading of the Goathill North (GHN) rock pile at the Molycorp Questa mine, New Mexico provided a unique opportunity to examine and sample the undisturbed, interior of a large rock pile through the construction of trenches cut into the rock pile as earth-moving progressed. Weekly during the regrading of the GHN rock pile, contractors excavated a trench to allow for sampling of rock pile material. Trenches typically had four benches, which were 1.5 m wide and did not exceed 1.2 m in height, to give an overall slope of 1.4 horizontal to 1.0 vertical within the trench. Each trench extended for a length sufficient to explore site conditions, maintain the regraded 2:1 slope, and ensure personnel safety. Once excavated, trench walls and benches were surveyed using a differential global positioning system. For every trench, maps and logs of each bench were created to describe the different "mine soil" units, including the thickness, dip and extent of the units. Units were defined based on color, grain size, stratigraphic position, and other physical properties that could be determined in the field. Units were correlated between benches and to both sides of each trench, and several units were correlated downward through the series of successively excavated trenches. The field sampling crew began sampling within each of the identified units after the unit boundaries were identified and mapped. The following in situ measurements were taken along either the horizontal or vertical surfaces of each exposed bench and along the base of the trench: sand cone (density), tensiometer (matric suction), gravimetric moisture content, grain size, infiltration, and nuclear gauge measurements (density, moisture content). Gravimetric water content samples were collected at the locations selected for the measurement of matric suction and infiltration tests. Samples were collected from each defined unit for geochemical, geotechnical (including shear box tests, slake durability tests), biological, and electron microprobe analyses. Channel sampling for pyrite reserve modeling was performed in short 1.5-m long horizontal slots using a rock hammer to chip material to be placed into a sample bag. Additional material from selected layers was collected for potential weathering-cell tests in the future. Typically, paste pH increases with distance from the outer, oxidized zone (west) towards the interior, unoxidized zone (east) of the GHN rock pile.

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Near Surface Geophysics for the Structural Analysis of a Mine Rock Pile, Northern New Mexico

Cited by 4 publications

References 10 publications

Characterization of Goathill North Mine Rock Pile, Questa Molybdenum Mine, Questa, New Mexico

Characterization of Goathill North Mine Rock Pile, Questa Molybdenum Mine, Questa, New Mexico

Evaluation of the effectiveness of backfilling and sealing at an open-pit mine using ground penetrating radar and geoelectrical surveys, Kimheden, northern Sweden

Preliminary Status Report on Molycorp Goathill North Trenches, Questa, New Mexico

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