Seismic methods for the detection of kimberlite pipes
Milovan Urosevic & Brian J. Evans
Pages 632-635 | Published online: 06 Dec 2018
The results of a seismic experiment conducted in Northern Territory over known kimberlite pipes are shown. A very low reflectivity sedimentary sequence and unfavourable near surface conditions resulted in a poor quality surface seismic data. The delineation of the external kimberlite pipe shape at depth, based on the principle of using the P-wave reflections that terminate against the pipe flanks, is not simple. However, by a combined analysis of P and S-reflected waves the pipe shape and its structure may be recoverable from seismic data.
In this experiment, most of the seismic energy produced by an explosive charge at a shallow depth generated shear and guided waves rather than P-waves. Totally refracted P, S and guided waves generated additional wave modes in a kimberlite pipe that are used to precisely determine pipe location and its diameter. We also show that single borehole imaging has a potential for the delineation of the external pipe form and structure. The use of such unconventional seismic methods may be the solution for assisting an economic assessment of individual kimberlite pipes in the Northern Territory.
Russian Scientist to test this new diamond tech
A team of Russian scientists, led by Alrosa’s head of the company’s geophysical exploration program, will test new technology based on seismic waves to help detect kimberlite fields.
Quoted in Rough & Polished, Alrosa’s senior geophysicist Evgeniy Goncharov explained how the new tech works: “Seismic waves when passing through different kinds of rock change their property, which will help us determine kimberlite pipes. To create a 3D map of the underground area it is important to do the measurements at different depths, thus the detectors will move down the holes in 2-4 meter steps”.
The new tech demands the drilling of two holes, each 130 meters deep, spaced at 250 meters from each other. Then, an emitter is put in one hole, producing seismic waves; a detector that registers the activity of the waves is put in the other hole. The waves, which move with varying speeds through different types of rock, can cover a distance up to 250 meters. The data received can then be used to determine which kind of rock is more likely a kimberlite. According to the report, the new tech will be tested in March 2019.