In situ leach

In-situ leach (ISL) or solution mining is a process of extracting metals and salts from an ore body without the need for conventional mining involving drill-and-blast, open-cut or underground mining.

Process

In-situ leach mining involves pumping of a leachate solution into the ore body via a borehole, which circulates through the porous rock, and is extracted via a second borehole.

The leachate solution varies according to the ore deposit - for salt deposits the leachate can be fresh water into which salts can readily dissolve. For metallic ores such as uranium and copper acids are generally needed to enhance solubility of the ore minerals within the groundwater.

Applications

In-situ leach is used to extract deposits of potash, potassium chloride, sodium chloride, sodium sulphate and uranium oxide. It has been proposed as an economic method of extracting supergene ores of copper carbonate in the United States and elsewhere.

The world's first ISL uranium mine began operating in the Unted States in 1974. Few projects are licensed to operate via ISL in the United States, although some significant ISL mines are operating in Kazakhstan and Australia. ISL mining produces around 21% of the world's uranium production.

Controversies

In-situ leach techniques are considered to be one of the more controversial methods of mining. This is based upon the fact that in most proposed cases of mining of metallic ores rather than salts, the leachate solution is invariably acid.

The concerns of environmental groups and landholders centre around;

• Acidification of groundwaters
• Mobilisation of potentially hazardous heavy metals and, in the case of uranium oxide, radioactive heavy metals .
• Disturbance of the groundwater table, mixing of groundwater aquifers and general disturbance of the land atop the ore body
• Destruction of habitat for stygofauna and other rock-inhabiting organisms, bacteria, etcetera.
• Potential spillages of acidic and metal-bearing or salt-bearing leachates upon the surface

Examples

• The Beverley Uranium Mine, South Australia, is an operating ISL uranium mine and Australia's first such mine.
• The Honeymoon Uranium Mine, South Australia, due 2008, will be Australia's second ISL uranium mine.

See also

• Mining
• Mineral exploration
• Uranium ore deposits

External links

Heathgate Resources Acid Leach Infopage