Erick Adam

Development of 3-D seismic exploration technology for deep nickel‐copper deposits—A case history from the Sudbury basin, Canada

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.

Integrated seismic and borehole geophysical study of the Sudbury Igneous Complex

Reflection seismic and borehole geophysical data place important constraints on the subsurface geometry of the Sudbury Structure, which is the site of the worlds largest Ni-Cu camp. Seismic reflections can be traced from outcrop within the Sudbury North Range to about 4.5 km depth beneath the center of the Sudbury Basin, where the layer thickens abruptly from 1 to 3 km. Further south the North Range norite can be followed to about 10 km depth beneath the South Range. Borehole studies show systematic variations of p- and s-wave velocity, Poissons ratio and density within the Igneous Complex. Quartz-rich granophyre is distinguished from the norite and footwall rocks by relatively low Poissons ratios (0.20–0.23 versus 0.23–0.25). These changes in physical rock properties define an important subdivision of the Igneous Complex, compatible with a simple model involving differentiation of melted crustal rock into dominantly felsic and mafic components. This study documents the importance of interlayering to the seismic reflection response of the crystalline crust.

3‐D seismic exploration in the Val d'Or mining camp, Quebec

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, Quebec. 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 3D 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.

3D Seismic imaging of Massive Sulfides: seismic modeling, data acquisition and processing issues

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).

Integrated borehole geophysical and 3‐D seismic study of a deep massive sulfide deposit, Sudbury Basin, Canada

The Sudbury Basin in Canada was selected for conducting one the world’s first 3-D seismic survey for deep base-metal exploration. The 3-D seismic experiment confirms that in a geological setting such as the Sudbury North Range, massive sulphide bodies cause a characteristic seismic scattering response. This provides an excellent basis for the direct detection of deep massive sulphides in the crystalline crust by seismic methods.