Using stochastic crosshole seismic velocity tomography and Bayesian simulation to estimate Ni grades: Case study from Voisey's Bay, Canada

Perozzi, Lorenzo; Gloaguen, Erwan; Rondenay, S.; McDowell, Glenn

doi:10.1016/j.jappgeo.2011.06.036

Cited by 12 publications

(7 citation statements)

References 40 publications

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“…Several examples of the successful use of traveltime tomography in the EDZ substantiate the conclusions drawn from the velocity analysis (Enescu et al, 2002;Perozzi et al, 2012). Figure 5 shows the results of straight-ray, minimum-structure traveltime tomography in two boreholes in the EDZ that are approximately 25 m apart.…”

Section: Statistical Distribution Of Physical Propertiessupporting

confidence: 54%

“…Along with tools for processing of reflections from steep dips and small bodies, specialized recording geometries incorporating boreholes may be critical in some circumstances. There is also the possibility of tomographic imaging that uses traveltime transmission in addition to, or instead of, seismic reflection imaging (for example, at Voisey's Bay: Enescu et al, 2002;Perozzi et al, 2012). The choice of a technique based on impedance contrasts as opposed to a technique sensitive to velocity variation (traveltime delay) depends ultimately on the range of seismic velocities and densities associated with the mineralized zones and the country rock.…”

Section: Introductionmentioning

confidence: 99%

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Seismic properties of the Voisey’s Bay massive sulfide deposit: Insights into approaches to seismic imaging

Duff¹,

Hurich

Deemer

2012

GEOPHYSICS

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Seismic methods offer significant potential advantages for minerals exploration over more traditional geophysical techniques because of the comparatively high resolution of seismic imaging. This is particularly true as minerals exploration is required to explore deeper to find resources. However, adaptation of seismic imaging techniques to the complex crystalline targets common in the mining environment requires a thorough understanding of the physical properties of the specific combination of ore and host rocks under consideration to choose an appropriate imaging technique. Analysis of the sulfide ores and associated host rocks from the Voisey's Bay nickel-copper-cobalt deposit indicates that in the pyrrohotite-pentlandite-rich but pyrite-poor assemblage at Voisey's Bay, seismic velocities are significantly lower (mean ∼ 4500 m∕s) than either the felsic or mafic host rocks (mean ∼ 5900 m∕s and ∼6400 m∕s). This observation is in contrast with pyrite-rich massive sulfide ores that have velocities that are significantly higher than typical host rocks. The large velocity contrast between the Voisey's Bay ores and their host rocks makes them good targets for tomographic imaging. However, due to the trade-off between the low velocities and high densities of the Voisey's Bay sulfides, acoustic impedance contrasts can be quite modest making them less attractive for seismic reflection imaging. Detailed analysis of two different mineralized zones at Voisey's Bay further demonstrated that, depending on the limiting signal-to-noise ratio, the choice of an effective seismic imaging technique is not universal across a mineral deposit and may be affected by subtle variations in sulfide mineralogy and by the structural/magmatic setting. Our analysis clearly indicated that knowledge of physical properties and geologic setting is critical to the choice of which seismic technique to apply in a given exploration setting.

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Section: Statistical Distribution Of Physical Propertiessupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Seismic properties of the Voisey’s Bay massive sulfide deposit: Insights into approaches to seismic imaging

Duff¹,

Hurich

Deemer

2012

GEOPHYSICS

View full text Add to dashboard Cite

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“…This technique has been developed and applied in the last 30 years in a number of settings worldwide [14]. Cross -hole seismic travel time tomography is based on the assumption that the energy travels from a source (lowered into a borehole) to a receiver (lowered into another neighboring borehole) along a well constrained ray path [15]. The technique is computationally intensive, and is costly because of the need for boreholes.…”

Section: Introductionmentioning

confidence: 99%

Soil and Subsurface Sediment Microzonation Using with Seismic Refraction Tomography for Site Assessment (Case Study: IKIA Airport, Iran)

Rezaei

2016

OJG

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The site effects relating to the amplification of ground motion under earthquake loading are strongly influenced by both the subsurface soil condition and the geologic structure. In this study, for site characterization at the Imam Khomeini International Airport (IKIA) area in south of Tehran, insitu seismic refraction tomography were carried out as a part of site investigations project, in addition geologic setting, borehole drilling, ground waters information and measurements. Based on seismic refraction studies, three layers are separable which with increasing in depth the S and P wave velocity is increased and this indicates increasing in compaction of soil and geologic materials. In the second and third separated layers, the zones with low and high seismic shear wave velocity is approximately equal, and northeast and southwest of the airport site has the low velocities, in addition to containing loose soils, highly weathered stones, and low depth to groundwater. In terms of Poisson's ratio, the most important and key installations of airport site are located in suitable positions. According to Iranian Seismic Code, most of the lands around the airport are in class 2 and 3. It seems that a fault or a discontinuity is passed from northwest to the southeast of the study area. This site, according to geological, subsurface geophysical, and geotechnical boreholes studies, is high risk-earthquake prone.

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“…Crosshole seismic tomography has been used by Vale Technology Development (Canada) Ltd. (referred to as Vale hereafter) to provide geophysical images of massive sulphides in the Eastern Deeps deposit at Voisey's Bay, Labrador, Canada (Enescu et al 2002;Perozzi et al 2012). The purpose of these surveys is to obtain information on ore-body geometries, and to use this information, along with any relevant geological information, to place spatial constraints on the location and extent of economic ores.…”

Section: Introductionmentioning

confidence: 99%

“…The goal of this particular study is to provide Vale with a high resolution seismic velocity map of the target region via waveform tomography, and to investigate the feasibility of waveform tomography in similar hardrock environments. The geological setting is highly heterogeneous, with strong velocity contrasts and variable levels of seismic anisotropy (Enescu et al 2002;Cosma & Enescu 2003); Perozzi et al (2012) performed traveltime tomography on the same data set presented in this paper, however they did not consider anisotropy to be a factor.…”

Section: Introductionmentioning

confidence: 99%

Waveform-based simulated annealing of crosshole transmission data: a semi-global method for estimating seismic anisotropy

Afanasiev¹,

Pratt²,

Kamei³

et al. 2014

Geophysical Journal International

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S U M M A R YWe successfully apply the semi-global inverse method of simulated annealing to determine the best-fitting 1-D anisotropy model for use in acoustic frequency domain waveform tomography. Our forward problem is based on a numerical solution of the frequency domain acoustic wave equation, and we minimize wavefield phase residuals through random perturbations to a 1-D vertically varying anisotropy profile. Both real and synthetic examples are presented in order to demonstrate and validate the approach.For the real data example, we processed and inverted a cross-borehole data set acquired by Vale Technology Development (Canada) Ltd. in the Eastern Deeps deposit, located in Voisey's Bay, Labrador, Canada. The inversion workflow comprises the full suite of acquisition, data processing, starting model building through traveltime tomography, simulated annealing and finally waveform tomography.Waveform tomography is a high resolution method that requires an accurate starting model. A cycle-skipping issue observed in our initial starting model was hypothesized to be due to an erroneous anisotropy model from traveltime tomography. This motivated the use of simulated annealing as a semi-global method for anisotropy estimation. We initially tested the simulated annealing approach on a synthetic data set based on the Voisey's Bay environment; these tests were successful and led to the application of the simulated annealing approach to the real data set. Similar behaviour was observed in the anisotropy models obtained through traveltime tomography in both the real and synthetic data sets, where simulated annealing produced an anisotropy model which solved the cycle-skipping issue. In the real data example, simulated annealing led to a final model that compares well with the velocities independently estimated from borehole logs. By comparing the calculated ray paths and wave paths, we attributed the failure of anisotropic traveltime tomography to the breakdown of the raytheoretical approximation in the vicinity of strong velocity discontinuities.

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Using stochastic crosshole seismic velocity tomography and Bayesian simulation to estimate Ni grades: Case study from Voisey's Bay, Canada

Cited by 12 publications

References 40 publications

Seismic properties of the Voisey’s Bay massive sulfide deposit: Insights into approaches to seismic imaging

Seismic properties of the Voisey’s Bay massive sulfide deposit: Insights into approaches to seismic imaging

Soil and Subsurface Sediment Microzonation Using with Seismic Refraction Tomography for Site Assessment (Case Study: IKIA Airport, Iran)

Waveform-based simulated annealing of crosshole transmission data: a semi-global method for estimating seismic anisotropy

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