In‐mine seismic delineation of mineralization and rock structure

Abstract

Significant progress has been made towards the goal of generating detailed seismic images as an aid to mine planning and exploration at the Kambalda nickel mines of Western Australia. Crosshole and vertical‐seismic‐profiling instrumentation, including a slimline multi‐element hydrophone array, three‐component geophone sensors, and a multishot detonator sound source, have been developed along with special seismic imaging software to map rock structure. Seismic trials at the Hunt underground mine established that high frequency (> 1 kHz) signals can be propagated over distances of tens of meters. Tomographic as well as novel 3-D multicomponent reflection imaging procedures have been applied to the data to produce useful pictures of the ore‐stope geometry and host rock. Tomogram interpretation remains problematic because velocity changes not only relate to differing rock types and/or the presence of mineralisation, but can also be caused by alteration/weathering and other rock condition variations. Ultrasonic measurements on rock core samples help in assigning velocity values to lithology, but geological assessment of tomograms remains ambiguous. Reflection imaging is complicated by the presence of strong tube‐wave to body‐wave mode conversion events present in the records, which obscure the weak reflection signatures. Three‐dimensional reflection data processing, especially three‐component analysis, is time consuming and difficult to perform. Notwithstanding the difficulties, the seismic migrations at the Hunt mine show a striking correlation with the known geology. Combined seismic and radar surveying from available underground boreholes and mine drivages is probably needed in the future to more confidently delineate mineralisation.

Seismic methods in mineral exploration and mine planning: A general overview of past and present case histories and a look into the future

“…Downhole seismic surveys such as side scan, VSP and mine seismic profiling (MSP), and in-mine seismic surveys are best suited for imaging steeply dipping to subvertical structures (e.g., Price, 1974;Cosma, 1983;Wong et al, 1983Wong et al, , 1984Gustavsson et al, 1984;Galperin, 1985;Peterson et al, 1985;Spathis et al, 1985;Harman et al, 1987;Mutyorata et al, 1987;Duncan et al, 1989;Juhlin et al, 1991;Sinadinovski et al, 1995;Frappa and Moinier, 1993;Cao and Greenhalgh, 1997;Greenhalgh and Bierbaum, 1998;Urosevic and Evans, 2000;Greenhalgh et al, 2000Greenhalgh et al, , 2003Wong, 2000;Adam et al, 2003;Cosma et al, , 2007Perron et al, 2003;Bellefleur et al, 2004aBellefleur et al, , 2004bXu and Greenhalgh, 2010). They have typically higher resolution than surface seismic data, which make them attractive for delineating fracture and fault zones for mine planning or as a complement to surface seismic surveys.…”

Underground Vertical Seismic Profiling with Conventional and Fiber-Optic Systems for Exploration in the Kylylahti Polymetallic Mine, Eastern Finland

“…2D surveys can be carried out for exploration at a regional-scale, followed a combination of a smaller-scale 3D survey and borehole seismic measurements for more focused exploration and precise resource delineation [6,16,28]. For resource delineation, borehole seismic surveys have been proven to be particularly useful, implementing either crosshole tomography approaches [29][30][31] or reflectivity imaging [32][33][34][35][36][37] using Vertical Seismic Profiling (VSP) methods. Additionally, the application of new technologies, such as passive seismic imaging methods [38] or the use of fiber-optic technologies [39], provides new possibilities for seismic surveying.…”

Tube wave to shear wave conversion at borehole plugs

“…; Hardage ; Greenhalgh et al . , ; Xu and Greenhalgh ). In particular, tube‐to‐body‐wave conversions have been exploited as secondary sources for borehole seismic experiments (Norris and Aronstam ; Aronstam ).…”