Keyhole mining

A prototype of the world’s first remotely operated “keyhole” underground mining and dredging system will be built later this year in an attempt to exploit precious metals deposits in water-logged, sandy environments such as river beds and underground water systems.

The prototype was developed over the previous 10 years in Australia by Perth-based SORD Technologies, SORD being the acronym for Subterranean Operated Remote Dredge. It will be about a third the size of a full-size version and capable of mining at the rate of 100 tonnes per hour, or roughly 10% of the capacity envisaged for the full-size unit.

The 5-metre-long, wedge-shaped dredge will weigh 4.5 tonnes and stand 1 metre high, or roughly the same size as a station wagon.

Conventional dredging in mineral sands and waterbeds has accounted for significant global production of gold, diamonds, tin, tantalum, and heavy minerals. However, in the latter half of the 20th century, production from conventional dredging of these alluvial sources dramatically declined as the shallow, economically viable deposits were exhausted. SORD is designed to reach deposits beneath the depths of conventional dredging.

The Deep Lead gold system of Victoria, Australia, known for its water-logged, free-flowing sandy setting and gravels, produced more than 7 million oz. gold between 1860 and 1910. SORD Technologies owns the mining rights to the area thought to contain somewhere between 30 million and 50 million oz. gold — about the same amount taken from the prolific Kalgoorlie region Down Under.

The SORD system, which was developed with funding and expertise from Australia’s Federal Scientific Research & Development Agency and the Commonwealth Scientific and Industrial Research Organization (CSIRO), has two key elements. The first is a remote-controlled and powered wedge-shaped dredge that can travel underground, following and extracting a layer of valuable minerals. Similar to a self-propelled head from a cutter suction dredge used by diamond trawlers of the coast of Africa, SORD sucks the materials through a self-cleaning grizzly screen and pumps the valuable minerals back to the surface. The other part, known as the “shield,” forms a water-filled inflatable tunnel that attaches to the rear of the SORD head. The shield protects the water pipes, slurry lines and power cables connecting the SORD head to the surface. The shield is made of a light, flexible, and durable fabric that is drawn down from surface, zipped together and inflated to provide a hermetically sealed environment that enables the SORD umbilical “cords” to float and move freely through the tunnel from the surface to the SORD head.

The patented technology will enable SORD to move backwards and forwards to mine deposits up to 200 metres below the surface of the sea or land and up to one kilometre from the “keyhole” entry point.

Testing of the prototype will mark the first time all the components will be used together.

— The preceding is from an information bulletin published by the Commonwealth Scientific and Industrial Research Organization, based in Melbourne, Australia.