Hunting for Ni-Cu-PGE ore bodies is no easy task, especially in the harsh conditions at the Nunavik Nickel Project in Nunavik, northern Quebec. As the near-surface deposits are found, better tools and sound geological understanding are needed to find deeper deposits. As part of Canadian Royalties’ exploration routine, multiple physical rock properties are measured and analysed to augment magnetic, electromagnetic and reflection seismic survey results and improve discrimination between volcano-sedimentary host rocks, Ni-Cu-PGE bearing mafic / ultramafic intrusions and mineralised lenses. Globally, the geophysical signatures of these three vary significantly throughout the property and survey configuration and parameters have been optimized accordingly. High-resolution magnetics allows detection of mineralised peridotite intrusions, while non-magnetic ones, pyroxenitic and/or gabbroic, can be mapped as local breaks through the volcano-sedimentary large-scale magnetic folded pattern. At depth, an intrusion’s footwall can be inferred from unconstrained 3D magnetic susceptibility inversion isocontours. Ground and downhole electromagnetics (EM) are key surveys for direct detection of semi-massive to massive Ni-Cu-PGE lenses. Delineation between ore-lenses and graphiticand/or pyrrhotite-rich sediments is challenging but can be achieved by optimizing the moving loop’s size and the borehole EM loop’s location, and combining this with B-Field measurements at low repetition rates. Conductivity models calculated for each area of interest, combined with known geology and magnetic inversion, provide an efficient geoscientific 3D model for pinpointing potential embayment, structural traps and ultimately, Ni-Cu-PGE lenses. Recently, reflection seismic was added to Canadian Royalties’ exploration program to support and speed up the mapping process at both the deposits and district scale. Seismic sections provide complementary information from the first 100 meters to greater depths, and are extremely useful to better understand the global geological setting. The Nunavik Nickel case study is a good example of how the integration of geology and geophysics can lead to exploration success.

The benefits of working with legacy seismic data are broad and valued in a wide range of geoscience applications and result from the comprehensive volume of industry and public seismic data acquired over several decades. Legacy seismic data exist in many parts of the world including areas that, due to stricter regulatory processes, environmental restrictions, demographic changes, or other factors would be challenging or even impossible to survey today. Examples are numerous but one includes 2D marine seismic data acquired in the 1980s with a large airgun array to provide a deep cross-section through the Appalachians beneath the now sensitive Gulf of St Lawrence, eastern Canada (Marillier et al., 1989). Sometimes benefits arise through the use of newly developed techniques to extract additional information from legacy seismic data. This idea is obviously not new and many examples can be found in the literature. One example is the use of extended Vibroseis correlation developed in 1980s (Okaya and Jarchow, 1989) applied to increase the depth range of marine Vibroseis seismic data acquired in 1971 in two of the Great Lakes of North America (Milkereit et al., 1992). Marine seismic data in the Great Lakes are sparse, but contain information about deep Grenvillian terranes that, in this case, could only be revealed using a technology developed more than a decade after data acquisition.

Two seismic reflection profiles acquired by Xstrata Canada in the Noranda mining camp were reprocessed and interpreted with the objective of providing key information on the geologic contacts and structures associated with vokanogenic massive sulfide (VMS) deposits at depth. The Amulet and Ribago seismic profiles run approximately from east to west and cross the volcanic rocks of the Noranda formation, which host most of the ore deposits in this camp. The seismic data interpretation relies strongly on a detailed three-dimensional geologic model built from an extensive number of exploration boreholes available in this area and is further supported by physical rock property measurements from in situ borehole logging data. Some reflections observed on the Amulet and Ribago seismic profiles correlate with rhyolite/andesite or silicified-andesite/andesite contacts that host the prospective exhalites of the Noranda formation. In particular, the silicified-andesite/andesite contact hosting the C-contact exhalite is imaged clearly down to a vertical depth of 1,100 in along the Ribago profile. The processing sequence included dip moveout (DMO) corrections and poststack migration. The seismic data reprocessing allowed the identification of two diffractions that correlate with known sulfide bodies intersected in boreholes located close to the Ribago profile. One of these diffractions, at approximately 1,200-m depth, coincides with the main massive sulfide intersection of the subeconomical Ribago orebody. Diorites cause several reflections observed within the Flavrian pluton. Some diorite units also have sufficient acoustic impedance contrast to produce strong reflections when juxtaposed against volcanic rocks. However, such reflections do not predominate in the Amulet and Ribago profiles, possibly because reflective diorite units are not so significant or have limited lateral continuity in this part of the Noranda formation. The reconciliation of the detailed three-dimensional geologic model and two-dimensional seismic data was not necessarily a straightforward task. A significant complication results from the inherent limitations of two-dimensional seismic imaging techniques in a complex three-dimensional geologic environment. Nevertheless, results presented in this paper indicate that seismic methods can image prospective contacts and deep-seated massive sulfide mineralization and can be a valuable exploration tool in the Noranda mining camp.

The Downhole Seismic Imaging consortium conducted two consecutive vertical seismic profiling surveys in the Norman West mining camp (Sudbury, Canada) in 1998 and 1999. These were aimed toward imaging a massive sulfide ore deposit situated within the footwall of the Sudbury Igneous Complex (SIC). Three-component seismic data were acquired in four boreholes with variable signal-to-noise ratio and poor polarization quality. Consequently, the images suffered from strong azimuthal ambiguity. A strike filter, passing only reflections originating from within the SIC, was applied during migration to enhance interpretability of the images obtained. Migrated images showed structures correlating with the known position of an ore deposit located 1800 m away from one borehole (N40). Diffraction coherency migration enhanced the image of the deposit, and suggested strong seismic scattering from within the footwall of the SIC.

We investigate the effect of petrophysical scale parameters and structural dips on wave propagation and imaging in heterogeneous media. Seismic wave propagation effects within the heterogeneous media are studied for different velocity models with scale lengths determined via stochastic analysis of petrophysical logs from the Matagami mine, Quebec, Canada. The elastic modeling study reveals that provided certain conditions of the velocity fluctuations are met, strong local distortions of amplitude and arrival times of propagating waves are observed as the degree of scale length anisotropy in the P-wave velocity increases. The location of these local amplitude anomalies is related to the dips characterizing the fabric of the host rocks. This result is different from the elliptical shape of direct waves often defined by effective anisotropic parameters used for layered media. Although estimates of anisotropic parameters suggest weak anisotropy in the investigated models, these effective anisotropic parameters often used in VTI/TTI do not sufficiently describe the effects of scale length anisotropy in heterogeneous media that show such local amplitude, travel time, and phase distortions in the wavefields.Numerical investigations on the implications for reverse time migration (RTM) routines corroborate that mean P-wave velocity of the host rocks produces reliable imaging results. Based on the RTM results, we postulate the following: weak anisotropy in hardrock environments is a sufficient assumption for processing seismic data; and seismic scattering effects due to velocity heterogeneity with a dip component is not sufficient to cause mislocation errors of target structures as observed in the discrepancy between the location of the strong seismic reflections associated to the Matagami sulfide orebody and its true location. Future work will investigate other factors that may provide plausible explanations for these mislocation problems, with the objective of providing a mitigation strategy for incorporation into the seismic data processing sequence when imaging in hardrock settings. (c) 2012 Elsevier B.V. All rights reserved.

Commencing in 1988 and continuing for 5 years, Lithoprobe acquired a series of high-resolution seismic experiments within and near base-metal mining camps in Canada, including the Abitibi subprovince of Quebec and Ontario, the world-class Sudbury Ni–Cu mining district, the Buchans mine in Newfoundland, and the Thompson Ni belt in Manitoba. This work, undertaken in close cooperation with the Geological Survey of Canada and major Canadian mining companies, stimulated an intensive and broadened series of followup studies with the common objective of assessing potential applications of multichannel seismic (MCS) imaging for deep mineral exploration and mine development. This research was motivated by a widely recognized disparity between the depths from which ores can be profitably mined (up to 2 km or more) and the resolving depths (typically <500 m) of commonly used geophysical methods for mineral exploration. Initial rock-property studies established that the expected contrast in acoustic impedance between ores and host rocks should be sufficient to generate observable reflections and (or) scattered waves. For an ore deposit to be directly detectable with MCS, however, it is also necessary for it to meet geometrical criteria including a minimum thickness of 1/8 wavelenth (typically ∼5 m) and a lateral extent similar to the Fresnel radius (typically ∼100 m). Both Lithoprobe and followup seismic studies, calibrated with borehole data, reveal that lithologic contacts that are characterized by large impedance contrast and significant lateral continuity, such as igneous intrusive contacts between mafic and felsic rocks, are the most likely features to be imaged with the MCS techniques. In some camps such as Buchans, however, faults and shear zones are better imaged than lithologic contacts. In either case, these studies show that well-designed and carefully processed seismic profiles can provide a valuable geophysical tool for interpreting the stratigraphic and structural framework of mineral systems and, more rarely, direct-detection capabilities for deep ore deposits.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 20083D Seismic imaging of Massive Sulfides: seismic modeling, data acquisition and processing issuesAuthors: Erick AdamElizabeth L'HeureuxEmmanuel BongajumBernd MilkereitErick AdamSEISServ, Quebec CitySearch for more papers by this author, Elizabeth L'HeureuxUniversity of TorontoSearch for more papers by this author, Emmanuel BongajumUniversity of TorontoSearch for more papers by this author, and Bernd MilkereitUniversity of TorontoSearch for more papers by this authorhttps://doi.org/10.1190/1.3064083 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract We present results showing recent trends in the value of modeling studies, acquisition geometry, and processing techniques in seismic imaging of massive sulfides. Forward modeling is valuable in assessing the impact on seismic wave scattering by host rock heterogeneity in delineating exploration targets. Favourable settings for seismic imaging and resolving power for mineral exploration targets are identified. With borehole access, we can take advantage of an acquisition geometry that combines surface and downhole recording for quality control on the velocity field and statics. Improved processing of seismic data demonstrated the usefulness of finding optimal azimuths to characterize the strike, dip and amplitude variations of seismic anomalies. The data used in this paper includes borehole logs and 3D seismic data that were acquired in the Trill area of the Sudbury basin in Ontarion, Canada (Milkereit et al., 2000).Permalink: https://doi.org/10.1190/1.3064083FiguresReferencesRelatedDetailsCited byEnhancing 3D post-stack seismic data acquired in hardrock environment using 2D curvelet transform13 March 2015 | Geophysical Prospecting, Vol. 63, No. 43D imaging challenges in steeply dipping mining structures: New lights on acquisition geometry and processing from the Brunswick no. 6 seismic data, CanadaSaeid Cheraghi, Alireza Malehmir, and Gilles Bellefleur6 September 2012 | GEOPHYSICS, Vol. 77, No. 5 SEG Technical Program Expanded Abstracts 2008ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2008 Pages: 3713 publication data© 2008 Copyright © 2008 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 15 Dec 2008 CITATION INFORMATION Erick Adam, Elizabeth L'Heureux, Emmanuel Bongajum, and Bernd Milkereit, (2008), "3D Seismic imaging of Massive Sulfides: seismic modeling, data acquisition and processing issues," SEG Technical Program Expanded Abstracts : 3621-3624. https://doi.org/10.1190/1.3064083 Plain-Language Summary PDF DownloadLoading ...

PreviousNext No AccessSEG Technical Program Expanded Abstracts 20043‐D seismic exploration in the Val d'Or mining camp, QuebecAuthors: Erick AdamBernd MilkereitBernard SalmonErick AdamHydro‐Québec, Division Pétrole et gazSearch for more papers by this author, Bernd MilkereitDept. of Physics, University of TorontoSearch for more papers by this author, and Bernard SalmonAur Resources Inc.Search for more papers by this authorhttps://doi.org/10.1190/1.1839656 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InReddit Abstract A 3‐D seismic survey was acquired to explore for deep massive sulphide ore deposits in the vicinity of the Louvicourt mine near Val d'Or, Québec. The seimsic data was processed and the optimum imaging offsets and azimuth have been determined. The seismic stacked volume shows a detailed image of the existing mine as well as a deep and steeply dipping reflection. Uncertainty in the 3‐D velocity distribution, caused by the absence of marker horizons, results in a location uncertainty of the imaged reflection. The location error has been estimated and alternate methods to derived the velocity field have been proposed.Permalink: https://doi.org/10.1190/1.1839656FiguresReferencesRelatedDetails SEG Technical Program Expanded Abstracts 2004 ISSN (print):1052-3812 ISSN (online):1949-4645 Copyright: 2004 Pages: 2586 publication data© 2004 Copyright © 2004 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 03 Jan 2005 CITATION INFORMATION Erick Adam, Bernd Milkereit, and Bernard Salmon, (2004), "3‐D seismic exploration in the Val d'Or mining camp, Quebec," SEG Technical Program Expanded Abstracts : 1167-1170. https://doi.org/10.1190/1.1839656 Plain-Language Summary PDF DownloadLoading ...

1. University of Toronto, Dept. of Physics, Toronto, Canada M5S 2J8, bm@physics.utoronto.ca 2. University of Western Ontario, Dept. of Earth Sciences, London, Ontario, Canada, N6A 5B7 3. Geological Survey of Canada, Bedford Institute of Oceanography, P.O. Box 1006 Dartmouth, Nova Scotia, Canada, B2Y 4A2 4. Now at: Hydro-Quebec, Oil and Gas Division, Quebec, Quebec, Canada G1V 4P1 5. Kiel University, Geosciences, 24118 Kiel, Germany

PreviousNext No AccessHardrock Seismic Exploration15. 3D Seismic Imaging for VMS Deposit Exploration, Matagami, QuebecAuthors: Erick AdamGervais PerronGrant ArnoldLarry MatthewsBernd MilkereitErick Adam, Gervais Perron, Grant Arnold, Larry Matthews, and Bernd Milkereithttps://doi.org/10.1190/1.9781560802396.ch15 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract Detecting deep mineral resources in the vicinity of existing mining camps is expensive and time consuming. The 3D seismic method is used routinely in oil and gas exploration to map deep stratigraphic contacts and structural features. Its ability to map volcanic contacts and the 1-km deep Bell Allard volcanogenic massive sulfide (VMS) deposit was tested recently in the Matagami mining camp. The survey objectives were to identify the seismic response of a VMS ore deposit and to map the main lithological contacts. The Bell Allard VMS deposit appears as a 100 m wide zone of high seismic amplitudes. The deposit is underlain by a larger amplitude anomaly that we attribute to a gabbro sill, or possibly to the alteration zone of the deposit. We show that the depth of the main exploration target (the Key Tuffite) can be identified on a large portion of the seismic survey area and that its southwest limit defines the location of a regional fault (the Daniel fault). The azimuth and dip of a synvolcanic fault was determined from amplitude analysis of a large gabbro sill. The Matagami 3D seismic experiment shows that seismic methods can image a deep VMS deposit and map important lithological contacts at a regional scale at a cost comparable to two 800-m deep boreholes per square kilometer. When applied in the appropriate geological context, a 3D seismic survey has the potential to assist deep mineral exploration and increase the chances of making cost-effective discoveries. Permalink: https://doi.org/10.1190/1.9781560802396.ch15FiguresReferencesRelatedDetailsCited bySeismic imaging across fault systems in the Abitibi greenstone belt – an analysis of pre- and post-stack migration approaches in the Chibougamau area, Quebec, Canada19 May 2021 | Solid Earth, Vol. 12, No. 5Sparse 3D reflection seismic survey for deep-targeting iron oxide deposits and their host rocks, Ludvika Mines, Sweden24 February 2021 | Solid Earth, Vol. 12, No. 2High‐resolution seismic imaging of crooked two‐dimensional profiles in greenstone belts of the Canadian shield: results from the Swayze area, Ontario, Canada9 August 2019 | Geophysical Prospecting, Vol. 68, No. 1Diffractivity — Another attribute for the interpretation of seismic data in hard rock environment, a case studyMohammad Javad Khoshnavaz, Andrej Bóna, Muhammad Shahadat Hossain, Milovan Urosevic, and Kit Chambers5 August 2016 | Interpretation, Vol. 4, No. 4Using supervirtual first arrivals in controlled-source hardrock seismic imaging—well worth the effort29 April 2016 | Geophysical Journal International, Vol. 206, No. 1Enhancing 3D post-stack seismic data acquired in hardrock environment using 2D curvelet transform13 March 2015 | Geophysical Prospecting, Vol. 63, No. 4Delineating structures controlling sandstone-hosted base-metal deposits using high-resolution multicomponent seismic and radio-magnetotelluric methods: a case study from Northern Sweden6 April 2015 | Geophysical Prospecting, Vol. 63, No. 43D seismic survey for geothermal exploration in crystalline rocks in Saxony, Germany23 April 2015 | Geophysical Prospecting, Vol. 63, No. 4High-resolution 2D seismic imaging and forward modeling of a polymetallic sulfide deposit at Garpenberg, central SwedenOmid Ahmadi, Christopher Juhlin, Alireza Malehmir, and Mie Munck8 October 2013 | GEOPHYSICS, Vol. 78, No. 63D stochastic gravity inversion using nonstationary covariancesPejman Shamsipour, Denis Marcotte, Michel Chouteau, Martine Rivest, and Abderrezak Bouchedda1 February 2013 | GEOPHYSICS, Vol. 78, No. 2Multidisciplinary study of the hanging wall of the Kiirunavaara iron ore deposit, northern SwedenMai-Britt Jensen, Artem Kashubin, Christopher Juhlin, and Sten-Åke Elming12 October 2012 | GEOPHYSICS, Vol. 77, No. 63D constraints and finite-difference modeling of massive sulfide deposits: The Kristineberg seismic lines revisited, northern SwedenMahdieh Dehghannejad, Alireza Malehmir, Christopher Juhlin, and Pietari Skyttä6 September 2012 | GEOPHYSICS, Vol. 77, No. 53D reflection seismic imaging for open-pit mine planning and deep exploration in the Kevitsa Ni-Cu-PGE deposit, northern FinlandAlireza Malehmir, Christopher Juhlin, Chris Wijns, Milovan Urosevic, Petri Valasti, and Emilia Koivisto7 September 2012 | GEOPHYSICS, Vol. 77, No. 53D imaging challenges in steeply dipping mining structures: New lights on acquisition geometry and processing from the Brunswick no. 6 seismic data, CanadaSaeid Cheraghi, Alireza Malehmir, and Gilles Bellefleur6 September 2012 | GEOPHYSICS, Vol. 77, No. 53D seismic imaging of volcanogenic massive sulfide deposits in the Flin Flon mining camp, Canada: Part 1 — Seismic resultsD. J. White, D. Secord, and M. Malinowski6 September 2012 | GEOPHYSICS, Vol. 77, No. 52D reflection seismic investigations at the Kevitsa Ni-Cu-PGE deposit, northern FinlandEmilia Koivisto, Alireza Malehmir, Pekka Heikkinen, Suvi Heinonen, and Ilmo Kukkonen7 September 2012 | GEOPHYSICS, Vol. 77, No. 5Seismic methods in mineral exploration and mine planning: A general overview of past and present case histories and a look into the futureAlireza Malehmir, Raymond Durrheim, Gilles Bellefleur, Milovan Urosevic, Christopher Juhlin, Donald John White, Bernd Milkereit, and Geoff Campbell7 September 2012 | GEOPHYSICS, Vol. 77, No. 5Reflection seismic investigations in the Dannemora area, central Sweden: Insights into the geometry of polyphase deformation zones and magnetite-skarn deposits30 November 2011 | Journal of Geophysical Research: Solid Earth, Vol. 116, No. B113D reflection seismic investigation for mine planning and exploration in the Kevitsa Ni‐Cu‐PGE deposit, northern FinlandAlireza Malehmir, Christopher Juhlin, Chris Wijns, Milovan Urosevic, Petri Valasti, Emilia koivisto, Ilmo Kukkonen, Pekka Heikkinen, and Markku Paananen25 May 2012Enhancing base-metal exploration with seismic imagingThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent .Canadian Journal of Earth Sciences, Vol. 47, No. 5Elastic seismic wave scattering and imaging of massive sulfides: rock physics and implications for seismic data acquisition and processingE. L. Bongajum, I. White, and B. Milkereit21 October 20103D seismic reflection imaging of volcanic-hosted massive sulfide deposits: Insights from reprocessing Halfmile Lake data, New Brunswick, CanadaAlireza Malehmir and Gilles Bellefleur4 December 2009 | GEOPHYSICS, Vol. 74, No. 6Shallow 3D seismic-reflection imaging of fracture zones in crystalline rockCedric Schmelzbach, Heinrich Horstmeyer, and Christopher Juhlin31 October 2007 | GEOPHYSICS, Vol. 72, No. 6Physical property analysis, numerical and scale modeling for planning of seismic surveys: Voisey's Bay, LabradorDeanne Duff and C. A. Hurich6 October 2006 Hardrock Seismic ExplorationISBN (print):978-1-56080-114-6ISBN (online):978-1-56080-239-6Copyright: 2003 Pages: 277 publication data© 2003 All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means without written permission of the publisherPublisher:Society of Exploration Geophysicists HistoryPublished in print: 01 Jan 2003 CITATION INFORMATION Erick Adam, Gervais Perron, Grant Arnold, Larry Matthews, and Bernd Milkereit, (2003), "15. 3D Seismic Imaging for VMS Deposit Exploration, Matagami, Quebec," Geophysical Developments Series : 229-246. https://doi.org/10.1190/1.9781560802396.ch15 Plain-Language Summary PDF DownloadLoading ...

Following extensive petrophysical studies and presite surveys, the Trill area of the Sudbury basin was selected for conducting the first 3-D seismic survey for mineral exploration in North America. The 3-D seismic experiment confirms that in a geological setting such as the Sudbury Igneous Complex, massive sulfide bodies cause a characteristic seismic scattering response. This provides an excellent basis for the direct detection of massive sulfides by seismic methods. The feasibility study suggests that high‐resolution seismic methods offer a large detection radius in the order of hundreds to thousands of meters, together with accurate depth estimates.

Lithoprobe high-resolution seismic surveys have provided the first systematic images of the deep stratigraphy in four major Canadian mining camps (Noranda, Matagami, Sudbury, and Selbaie). Systematic compressional wave velocity and density measurements in deep boreholes have established that lithological contacts were the main impedance contrast imaged, although reflections from faults and deformation zones have also been observed. The strongest reflections are attributed to mafic intrusions and some sulphides and oxides. Integrating seismic, physical rock property measurements, and geological data has resulted in the revision of several geological models with direct impact on local strategies for deep mineral exploration. Mining companies have shown an interest in seismic reflection methods and this has led to several follow-up studies. The application of seismic methods to the direct detection of massive sulphides, based on physical rock property measurements, has been studied through two-dimensional and three-dimensional (3D) seismic imaging and vertical seismic profiling technologies. The challenge will now be to optimize 3D seismic imaging for mineral exploration and to improve seismic data processing by enhancing the seismic response from deep, lenticular orebodies.

A high-frequency vibroseis seismic survey was conducted by Lithoprobe across a well-known section of the Matagami mining camp to assess the usefulness of seismic methods in lithological mapping. The data have been reprocessed to enhance shallow reflections. Critical processing steps for the preservation of the shallow features include refraction static corrections, cross-dip corrections, and first break mutes. The seismic data were calibrated using geophysical logs from two boreholes adjacent to the profile. Physical rock property measurements suggest that strong reflectivity within the volcanic sequence occurs at rhyolite-gabbro contacts. The Lower Wabassee Group, a sequence of gabbros and basalts with interlayered rhyolite horizons, has been identified as a seismic marker. This reflective package overlays the horizon where most sulphide deposits are known to be located. In the Matagami mining camp, seismic reflection methods can be used to map the deep volcanic stratigraphy and structures.