The physical properties of the Lac de Gras kimberlites and host rocks with correlations to geophysical signatures at Diavik Diamond Mines, NWT

Abstract

The geophysical response of any target is dependent upon the physical properties of the body and the surrounding host rock. The objective of this study is to develop an understanding of the physical properties of the kimberlites and host rocks at the Diavik Diamond Mine. Physical property data were collected at the Diavik Diamond Mine during a Mathematics of Information Technology and Complex Systems (MITACS) internship with Diavik. Data was collected using equipment supplied by Aurora Geosciences Ltd. The physical properties measured include density, resistivity, magnetic susceptibility and remanent magnetization. Samples were collected from drill core from previous drill programs that took place on Diavik property. In total, 400 kimberlite and surrounding host rock samples were collected from 16 kimberlite pipes. Pipes were selected based on core quality and pipe location. -- The physical property data was statistically analyzed. Then, magnetic and gravity forward models of pipe A154N were made using GRAV3D (UBC-GIF 2002) and MAG3D (UBC-GIF 2002) software packages. These models were based on the data collected, along with a constrained geometric model of kimberlite pipe A154N given by Diavik. These forward models were compared to collected total magnetic field and gravity ground data which underwent a regional/residual separation using Li and Oldenburg's Method (1998). MAG 3D and GRAV3D inversion software was then used to invert the residual data. The resulting subsurface models created by the inversion were then compared to the known model of pipe A154N. -- After studying the physical properties and modeled geophysical signatures of pipe A154N, airborne total magnetic field data over the pipe was reviewed. Directional filters and edge detection techniques were tested to see how successful these methods were in helping to define the pipe A154N anomaly both on a large-scale map and in profiles over the pipe.