Oceanic Mineral Projects personnel have been involved in the diamond exploration of the Joseph Bonaparte Gulf, Australia since the early 1990's, with the initial high resolution geophysical and sampling surveys (Cambridge Gulf Exploration; Australian Kimberley Diamonds; Grosvenor). Marine exploration in the Gulf, which straddles the state boundary off the northwest coast of the Kimberley region of Western Australia and the Northern Territory, is challenging with extreme tidal currents, poor visibility and highly variable sediment types. In 1993 Cambridge Gulf Exploration proved there were alluvial diamonds in the Joseph Bonaparte Gulf, although not in their lease area, recovering 23 rough-cut diamonds of gem quality with a combined weight of 5.87 carats.
In 2005 Bonaparte Diamond Mines NL listed on the ASX and were awarded an aggregate area of about 515 kilometers squared, extending northwards from Lacrosse Island in the Cambridge Gulf out to the state territorial limit 3nm offshore Western Australia. The immediate challenges facing Bonaparte was designing and operating a sampling tool robust enough to work in the high tidal currents and recover large quantities of prospective gravels. Prior to listing, Bonaparte commissioned the design and fabrication of their Bonaparte Seabed Sampler (BoSS) and mineral processing plant. The system comprised tried and tested methodologies that had been proven in Southern Africa, re-engineered to be standalone, modular and easily transported for mobilisation on a vessel of opportunity. The BoSS has a 5m overall length with a sample footprint of 1.1m square and capable of an effective depth of 4m. The system operates by using compressed air to create a strong suction at the business end, where seabed sediments are agitated by high pressure water nozzles and are sucked into the sampler and up to the sampling vessel through a slurry hose. The sediments are then fed into the primary processing unit. A heave compensating tower was used to keep the hoist wire under constant tension to compensate for the vessel movement and keep the BoSS upright on the seabed. The primary processing unit was designed to screen up to 600m cubed of slurry by de-aeration, dewatering and screening to separate out the 1.5-12mm fractions for the secondary processing. Once at the secondary processing unit, the screened material were treated through an x-ray sorting machine.
The system was mobilised on the M.V. Pacific Challenger and through July/August 2005 a total of 327 individual samples successfully recovered, with the BoSS operational through the entire tidal cycle. Fluvial gravels were identified but no diamonds recovered. Wherein this was a disappointing result, the presence of agates, jasper and other kimberlite indicator minerals was encouraging. In 2006 the BoSS and modular processing plant was shipped to Cape Town, South Africa for a marine sampling programme off Namibia in ML 111, operated jointly by Bonaparte and Diamond Fields International.
Read more about operations in ML111.