CONFIDENTIAL – LEVEL 1
Distribution: DG, IC, RH, CB, GT, RM, MM, SS, SV.
The DRC-RTC™ Kimberlite Detector
Preliminary Field Tests - WA
Stewart A. Humphreys Phd.
Consultant Research Geologist – DRC (Division 5) – Field Operations
IntroductionAs consultant to the DRC Research and Technical Services, (RATS), one of my tasks is to bring new technologies and/or ideas to the attention of the other DRC section members so that we can decide if DRC should support research into new exploration ideas. One of the latest which may seem a bit strange is to use rats to detect kimberlites and lamproites. However this is not as bizarre as it seems as rats have proved their worth in detecting landmines in various parts of Africa as shown by the follow news story:
Maryann Mott for National Geographic News - February 10, 2004. In Mozambique, an African country littered with land mines from decades of civil war, 20 rats were recently used to search for explosives. So far, they've been successful. In November, the animals found nine mines in one day along the Limpopo Railway, says Bart Weetjens, director of APOPO, the Belgian research company that trains the animals. The Mozambique National Demining Institute accredited the technology in late September, allowing for the work to take place. Weetjens notes this is the first time the African giant pouch rats have been deployed in real mine fields. The rats combed three minefields along a rail line that connects the port city of Maputo with neighboring Zimbabwe. Despite the railway's economic importance, few trains travel this dangerous stretch. People fear vibrations caused by trains will trigger the instable explosives. APOPO came up with the idea of using rats while searching for a cheap and efficient way to detect mines. A trained rat costs about U.S. $2,000—about $10,000 less than a mine-sniffing dog. Other advantages include the rats' relatively small size (15 inches/40 centimeters), which make them easy to maintain and transport; their resistance to most tropical diseases; and their highly developed sense of smell.
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Rats are able to detect most types of mines," said Weetjens
. "In principle they could detect all mines because of the explosive content, if it weren't that some devices have been manufactured with accurate sealing, which leaves no escape for explosive trace vapors. But these can easily be found with a metal detector." Rats conditioned to TNT odors are trained to walk on a leash, which is attached to a bar that moves forward into a suspected field. When the animals smell explosive material they scratch or bite at the location. The rat's light weight—one-and-a-half to three pounds (0.7 to 1.5 kilograms)—does not trigger the mine. A rat and handler can search 180 square yards (150 square meters) in about half an hour. "After that, reliability of concentration for rats as well as trainers goes down," Weetjens said.
This isn't a problem, he notes, since well-rested, replacement rats are available. Currently the company has more than 100 rats in different stages of training at its facility in Tanzania, north of Mozambique.
Rats begin training at the age of five weeks when juveniles are weaned from their mothers. A positive reinforcement method known as clicker training is used. When the animal does something right, the trainer clicks a small, handheld noisemaker before giving the rat a piece of banana or peanut as a reward. (The same method is often used in America to train dogs in obedience schools.) The company says the rats learn the desired task relatively quickly—between six to ten months. "We now have some fourth-generation domestic animals. And generation after generation, the animals learn faster," said Weetjens. "It is too early, though, to conclude if this is due to selective breeding or to a more established training method and [increased] skills of the trainers." After an animal has been fully trained, a series of blind tests are conducted during a six-week period. If the rat passes, it is then licensed for de-mining operations. APOPO plans to use its trained rats elsewhere, including Angola, Cambodia, and Bosnia.
Following the success of this land mine detection program, in mid-2004 DRC approached APOPO which agreed to sell DRC 10 rats in return for a substantial donation to their training program. The rats were imported into Australia and underwent the usual quarantine processes; two had to be euthanized leaving eight for field testing.
We have approached the LIME division of CSIRO, as they have had significant success in quantifying the minute bacterial residues within the regolith profiles over much of mineralized areas of West Australia, and which has subsequently been proven a successful technique in base metals and gold exploration in WA. LIME have also agreed to participate in the proposed JV.
However our targets, kimberlites, are far less chemically reactive, but as some contain significant quantities of diamond (vis. Carbon), and sometimes sulphides, it was thought that regolith processes could have modified this primary carbon into chemically detectable forms, hence the interest in the rats which, as shown in the NG article, have heightened sensitivity to low level chemical residues. There is some suggestion from the nickel division that bacterial action in the regolith might affect diamond. We have learnt from WMC experience that kimberlites also produce a somewhat expansive mineral haloe if the right regolith material is sampled and correctly analysed. These are proprietary techniques which DRC is not willing to divulge at this point in time.
This project is of crucial importance to us as the diamond majors have decided to focus their exploration out of Australia, the main reason being the difficulty in dealing with the extensive highly weathered surficial regolith mantle covering most of West Australia. As our exploration section does not have the financial backing that the diamond majors have, urgent research is being directed to discovering alternative methods of detecting subtle bacteriological produced chemical haloes around the kimberlites. We have the means of detecting the kimberlite clusters down to a few hundred square kilometres, but this technique is not suitable for detailed follow up.
Progress to date
The project’s first phase required verification of the identification of existing metaliferous deposits, and this was done by testing the rats on known deposits not yet mined. (This was done within the auspices of the LIME section of the CSIRO and involved training the rats to recognize the low level chemical signatures; LIME will publish the results in due course. Conclusion – as expected, locating ordnance chemically was little different to locating metaliferous deposits – both had low-level, but significant, chemical signatures at ground level and the rats were successful in detecting both signals.
The second phase was to test the animals over the known kimberlites and lamproites. We consider this to be a more difficult phase of the research project as these rock types, while occasionally hosting diamond which, as far as we know, is chemically un-reactive in the regolith.
Two type areas were chosen – a typical Kimberley location and the north-west Yilgarn where we have quite a few kimberlites that are not generally known, allowing us some security that our field work would not attract undue attention.
Kimberley area
DRC employed local community people during the 2005 field testing over some small lamproites discovered on Liveringa Station in the West Kimberley by a junior company. Those tests were reasonably successful but we are not sure whether the rats reacted in response to the focussed magnetic field, or to subtle bio-chemical signals. LIME are analysing the soil samples and results are expected during the end of 2005 financial to clarify this. Further testing of magnetic field sensitivity is underway during the first half of 2006. (See Figure 1 below).
Figure 1: Patrick Williams (Nookanbah community), running the “DRC_RTC™” trial at the Marsink Lamproite, Liveringa Station, WA, during Dry Season 2004.
Yilgarn Testing
Quite a few kimberlites have been discovered on the Leonora 250,000 topographic sheet by the diamond majors and juniors, though none were economically viable. All occurrences were in bedrock or saprock, and considered useful as calibration examples. One buried pipe was discovered under Lake Ballard near Menzies, under 40 metres of lacustrine sediment but it is considered that this occurrence is not of the type-regolith target DRC have been commissioned to research. Hence, the Lake Ballard occurrence will not be field tested with the RTC method.
Problems
Weetjen’s comments above in the use of “clicker” training has proven correct, though we have discovered that span of attention time of both handler and rat is increased during colder weather. Rate of coverage was similar to that for mine detection, vis 150 square metres per half hour.
We did find that attrition rate was slightly higher than APOPO’s experience, and this needs to be factored into proposed breeding programs to ensure a commercially viable support population.
Conclusion
Clearly we have had some success in using this somewhat innovative exploration technique, with qualified success over the Kimberley lamproites. Positive responses have been obtained from the Yilgarn kimberlites, but LIME has yet to locate a suitable target under colluvial material. It was noticed that the rats were sensitive to magnetic fields, (if associated with small intrusives) and that led to the need of redesigning the restraining wires to cope with the extra length required for diamond exploration. This was due to the fact we used the existing harnesses used for mine-detection in Africa, which are of a shorter length.
Competitors – we note that SAM (sub audio magnetics) is a competitive technology in this area, but to date their data acquisition costs are greater than a factor of 5, and in addition need post acquisition data processing with the usual industry standard cost escalations.
We feel it prudent to involve local communities as much as possible, as the technique will allow them to develop low technology business stratagems to improve their incomes.
We feel this project could make a significant contribution to empowering indigenous communities and at the same time introduce them, in a positive way, to meaningful cooperation with the mining industry.
Recommendations
Continue existing program until Dec 2006.
Establish viability of breeding and training the rats in conjunction with WA Agriculture Department.
Negotiate with diamond majors for any data pertaining to source rocks hidden under regolith.
Investigate suitability of marsupial rats/animals for purpose in conjunction with CALM.
Project review in December 2006.