Mar 1, 2014 - Airborne multi-sensor geophysical mapping of 3D geology ..... Hard Rock: A Tutorial. Hardrock Seismic ...... The illustration is for the programs ...
KEGS Geophysical Symposium 2014
Integrating Geophysics and Geology Saturday, March 1st, 2014 Intercontinental Hotel, Toronto Delegate program generously sponsored by:
We thank the symposium sponsors
Continental Breakfast
Reception
Morning Coffee Break
KEGS PDAC Symposium 2014 - Program
Integrating Geophysics and Geology Saturday, March 1st, 2014, Intercontinental Hotel, Ballroom A, 225 Front Street West, Toronto
Schedule Oral Program Time 8:00 8:40
Presenters
Title
Continental Breakfast and Poster setup Edna Mueller-Markham, Opening remarks President of KEGS
8:45 9:10 9:35 10:00 10:25
10:45 11:10 11:35 12:00 12:25 12:30 1:15 1:40
Physical Properties Chairs: David Hatch, Gedex, and Edna Mueller-Markham, PGW Greg Hodges, CGG, and Laurie A user’s guide to integrating geophysics and Reed, Reed Geophysical Consultant geology Bernd Milkereit, University of Toronto Petrophysical and seismic Data - the perfect combination for the integration of geology and geophysics Mark Shore, Magma Geosciences The unifying links between geophysics and other earth sciences Vince Gerrie, DGI Geoscience Physical properties - The quantitative link between geophysics and geology Coffee Break and Poster Viewing Business Perspective Chairs: Alan King, Geoscience North, and Rob Harris, Geonics Ken Witherly, Condor Consulting The importance of bringing geology and geophysics together to build mineral system models Hernan Ugalde, Paterson, Grant & Case studies in integrated geological and Watson geophysical 3D modelling: Value added to exploration and mining projects Richard Osmond, Globetrotters Exploration success – A business model and Resources case study Nasreddine Bournas, Geotech An integrated approach for assessing the mineral potential of the Liptako Metallogenic Province (East side of the Fleuve Niger) Katherine McKenna, GPX Surveys Introduction to the Ground Geophysical Survey Safety Association (GGSSA) Lunch and Poster Viewing Mining Case Histories Chairs: Luise Sander, SGL, and Claire Samson, Carleton University Taronish Pithawala, Geosoft Geologically-constrained magnetic inversion at the Great Whale Iron Property Mathieu Landry, Glencore Geophysics & geology; an inevitable match for success – Examples from Raglan Mine
2:55 3:15 3:40 4:05 4:30
Coffee Break and Poster Viewing Integration Tools Chairs: Michel Chouteau, École Polytechnique de Montréal, Elizabeth Baranyi, Geosoft Desmond Fitzgerald, Intrepid Reducing ambiguity in 2 & 3 D geology objects Geophysics derived from potential field observations James McNae, RMIT University Using implicit geological constrains in 3D EM modelling Peter Lelievre, Memorial University Choices for effectively incorporating geological Newfounland constraints into geophysical inversion John McGaughey, Mira Geoscience A framework for the quantitative integration of geological and geophysical data
Posters •
Discussion of the Terraquest fixed-wing XDS VLF system – Implications for uranium exploration in sandstone basins Jeremy Brett, MPH Consulting, and Peter Walker, GeoAlgorithms
•
Airborne multi-sensor geophysical mapping of 3D geology Brenda Sharp, Jurriann Feijth, Jean Lemieux, and Asbjorn Christensen, CGG
•
Helicopter AFMAG (ZTEM) survey results over epithermal gold and gold-skarn deposits in the Guerrero Gold Belt, Mexico Jean Legault, G. Plastow, C. Izarra, S. Zhao, Geotech, and G. Kearvell, Newstrike Capital
•
Integration of geology and deep DCIP/MT technology on the Junior Lake property, Northwestern Ontario Darcy McGill, Michele Tuomi, and Mehran Gharibi, Quantec
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Optimization of ground electroprospecting survey techniques for mining exploration Igor Ingerov, AGCOS, and E. Ermolin, National Mineral Resource University
•
The use of reduction to the pole versus total gradient for the interpretation of aeromagnetic data: pros and cons Martin Bates and Marianne McLeish, Sander Geophysics
•
VPMA methodology: dating a rock from its magnetic anomaly only Renato Cordani, Reconsult
ORAL PROGRAM
A User’s Guide to Integrating Geophysics and Geology Abstract for KEGS 2014 By Greg Hodges, Laurie Reed There always has been, and still is, a problem integrating geophysics into geology: getting geologists to use geophysics and getting geophysicists to use geology in their interpretation, and express their results in terms that geologists can use. Not enough geologists have a good understanding of what geophysics measures, how to understand the geological meaning of the measurements, and how to use them in an effective exploration project. But it’s not enough to say that geologists need to learn geophysics: many geophysicists often do not think (or communicate) in geological terms. The two groups must learn enough of each other’s fields to ensure overlapping expertise, exchange of information, and full integration. But as the minority, geophysicists need to facilitate the communication by understanding geology and the needs of the geologists. Rock properties are the indispensable link between geophysics and geology. To use geophysics explorers must be able to make the connection between geology and the changes in rock properties. Geophysicists must know the rock property measurements inherent in their data, and all explorers should know the rock types and changes that affect the properties, so they can see the geology that is apparent in the geophysical data. Every explorer should know what can (and cannot) be distinguished by magnetic susceptibility, electrical resistivity, density, velocity, and radioelement concentration. It’s about the rock property measured, much more than the method of measurement. Going into the exploration project, explorers need to predict how the targeted changes to lithology and structure will change the rock properties in a way that might be measurable. The “Four Cs” of geophysical detection need to be considered: is there enough Concentration and suitable rock property Contrast; what is the effect of Cover; and what else might Confuse the interpretation? Geophysicists need to understand the target and host geology, and all the factors that will affect these detection factors: property contrast, concentration relative to the method footprint, the amount and effect of cover, and both geological and ambient noise. Interpretation of the geophysical results should be a process of interpreting the data to determine the rock property changes that exist, and from that predicting the geological changes that caused them. The best interpretations are focused on geology and include the known geology: “What geology caused this change to the geophysical data?” The results should be expressed - and presented - in a style as close to geological as possible. The geophysicist has to ask whether the results will be comprehensible to the geologist, and, if not, provide the proper interpretation. Most of us know of many times when IP pseudo-section “pant-leg” anomalies were targeted, wasting money and credibility.
Geophysicists also have to consider the planned use of the data – will the model provide the information that is needed to follow up? The most useful model is not the fanciest, but the one that best fits the geology and provides the required geological information most cost-effectively. Often, the model still needs interpretation to be understood in geological perspective. The geophysical work is not done when rock property model is developed, even if the ambiguous model-to-data correlations are resolved. The real integration of geology comes when converting the rock property model to geology – lithology and location and alteration state. This stage of interpretation requires a solid understanding of influences on rock properties, the relevance of structure to the target, and economic geology; and most of all, knowledge of the local rocks. Multiple rock property measurements from multiple geophysical surveys provide more than one look at the geology. However, these measurements need to be integrated into a single interpretation. There is only one “geology” at any location, so differing or conflicting geophysical interpretations from different data sets only show that the process is incomplete. A solid understanding of the interaction between the geophysical measurement and geology is needed to understand the different pictures each method map paint of the geology, and how to rationalize or overlap these. Where different methods present different pictures of the geology, it suggests that they are sensitive to different parts of the geology – obviously different rock property changes, but also different depths or layers in the geological column. A rock layer may be transparent to one method, and control the signal on another. Different rock properties may change at different places across a transitional alteration zone. The final Interpretation should integrate all the geophysical results and the geological knowledge into a single, cohesive, interpretation of the geology. It is critical to understand the limitations of each geophysical method and the geological data. Geophysics maps rock properties well over an area, but doesn’t identify the rock. Geology identifies the rock at the sample point (hopefully!), but not between the outcrops. The two characteristics are complementary, if used well. Rock properties are the link between them. Not until both stages are complete - geophysics to rock property, rock property to geology - is the interpretation complete. Effective use of geophysics is a matter of understanding the effect of geological processes on rock properties, and hence the effect on the geophysical data. It requires combined interpretation of multiple geophysical data sets into multiple rock property models, into a single geological description, integrating the available geological information. Geologists need to understand the effect of geological changes on the rock properties, and geophysicists need to think in terms of rock when interpreting their data. No geophysicist should graduate into exploration without a good education in geology, and no geologist should graduate without exposure to applied geophysics.
Petrophysical and Seismic Data - the Perfect Combination for the Integration of Geology and Geophysics
Bernd Milkereit*, Ramin Saleh University of Toronto, Toronto, ON, CANADA
the surface. The modeling of elastic seismic waves requires detailed 3D petrophysical data. Petrophysical information is obtained through lab core samples and in situ borehole logging measurements. Note that, compiling boreholelogging data into a 2D/3D petrophysical model mostly involves intense statistical analysis. Upon the availability of such petrophysical models there are many possible applications. For example, forward seismic modeling can be used to study resolvability of different geology settings, or seismic imaging techniques can help to design more efficient seismic surveys. Also inverse methods can be implemented to reverse time migration problems or AVO studies can be used for reservoirs characterization.
Summary Densities and compressional (Vp) and shear (Vs) wave velocities provide a robust framework for the lithological identification and interpretation of most common sedimentary, igneous and metamorphic rocks. The wellknown Nafe-Drake curves for silicate rocks show many ores have adequate impedances contrast compare to their common hosts, suggesting the feasibility of detecting ores using high-resolution reflection techniques. Generally to solve a scattering problem, modeling approach is the key and this is only possible if a geological model can be translated into a petrophysical model. Examples of comprehensive petrophysical databases for seismic imaging will include permafrost settings, gas hydrate reservoirs and massive sulfide deposits. More recently a 3D petrophysical model of deep mines become available, that can be used for geotechnical and monitoring purposes.
S−waves
Depth [m]
T=0.070 s
P−wave model
P−waves
100
100
200
200
300
300
400
100
100
200
200
200
300
300
400
400
200 400 Distance [m] −4000
300 400
400 200
Introduction
Density model
S−wave model
100
−2000
Although the seismic reflection method showed a great success in oil and gas industry, it was not conventionally in use for mining purposes. The main reason was the success of electromagnetic and potential field methods as a cheap and an easy method for exploration purposes. In the past decades the demands for deep resources increased and that required a use of seismic methods for deep mine exploration (Debicki, 1996). 2-D and 3-D surveys have successfully detected and imaged large massive sulphide deposits such as the magmatic and volcanic massive sulphide (VMS) deposits. In addition, other types of deposits have a better chance to be imaged indirectly. Examples are exploration of lode gold and porphyry deposits by reflections from alteration haloes, unconformity Uranium deposits by haloes and basement offsets, and Mississippi Valley-type (MVT) deposits by white spots in otherwise reflective carbonates (Salisbury&Snyder, 2007). Most ore deposits are often fairly small (
