New Detection Method for Copper Mining

By Benedette Cuffari, M.Sc.Apr 11 2017

As one of the first metals to ever be extracted by human beings, copper is an easily stretchable, moldable and shaping material that is simultaneously resistant to corrosion. Copper is often employed as a supplemental material used in building construction, however its conducible nature also allows for this material to be useful in power generation and transmission processes, as well as during the production and manufacturing and various electronics, industrial machinery and motor vehicles¹.

Copper is typically found deep within the crust of the earth, and both underground mining and open pit mining techniques are used in order to properly extract copper from these location.

There are two different types of ore deposits that are estimated to contain 80% of the world’s copper supplies. Sediment-hosted stratabound copper deposits contain copper that is concentrated within the layers of the sedimentary rocks, and this type of ore specifically contains an estimated 20% of the world’s copper resources¹.

In contrast to this type of copper supply, porphyry deposits, or porphyries, contain copper minerals that occur as a dispersion of fine particles². As one of the largest sources of copper available today, as it accounts for about 60% of the world’s copper supplies, understanding the factors that affect the mining of copper from porphyries is of significant interest to mining industries.

Porphyries are derived from magma chambers that are located at a depth of 10-15 km below the surface of the Earth. At this location, the magma is heated to approximately 900 °C, and as it rises and comes into the contact with the surrounding minerals, the release of hydrothermal fluids cools and crystallizes the magma.

At this point of release, water is pushed out of the magma in the form of bubbles that escape to the Earth’s surface³. At a depth of 2-3 km, these precipitated bubbles cool the surface of the rocks, while often containing a substantial amount of copper that is present in the form of sulphide.

The amount of magma that is present within these deposits is therefore a determining factor as to predicting how much copper can be extracted from a given porphyry location. The range of copper concentrations within porphyries may include anywhere from 1 million to 200 million tons of copper, therefore there is an urgent need to adequately assess the potential concentration of copper minerals available within a deposit before investing in the mining technologies to do so.

In their recent work published in Scientific Reports titled “Tempo of magma degassing and the genesis of porphyry copper deposits,” a group of researchers from the University of Geneva in Switzerland have developed a technique that is capable of determining such important information regarding copper concentrations present with porphyries³.

While certain porphyry properties are known to positively favor the size of the deposits, such as higher concentrations of the ore ingredients, such as copper and sulphur, that are present within the magma, the presence of an efficient method of partitioning between these elements into the precipitated magmatic fluid is also a determining factor³. Despite this knowledge, there remains a challenge in understanding further conditions that determine the magnitude of copper endowment present within these deposits.

In an effort to respond to this challenge, the researchers obtained over 100,000 simulations that resembled the exact emplacement, cooling and magmatic degassing that occurs within nature to further understand this process.

By assuming a uniform set of conditions that would allow for the ideal formation of a large copper deposit, the group of researchers utilized a Monte Carlo approach in order to quantify their results. In their statistical analysis, they measured the volume of cooled magma to determine the total mass flux of particles that were outgassed from the fluid over time⁴.

With further mathematical considerations, the researchers determined the precise ratio that measured the amount of other chemical components present within the magma, such as water, copper, strontium and yttrium.

By understanding this ratio, as well as the duration of time required for the formation of these chemical components to precipitate from the magma, the researchers believe that the employment of a set of probabilities illustrating these components could allow for the successful determination of the amounts of copper present within these types of deposits.

By accurately assessing the size of a copper deposit prior to engaging in any mining activities, the researchers believe that a large amount of money and time could be saved in avoiding the traditional and time-consuming mining explorations.

References

1. "Facts About Copper." Geology. Web. http://geology.com/usgs/uses-of-copper/.
2. Calcutt, Vin. "Introduction to Copper: Mining & Extraction." Copper Development Association Inc. August 2001. Web. https://www.copper.org/publications/newsletters/innovations/2001/08/intro_mae.html.
3. "Copper-bottomed Deposits." University of Geneva. 15 Mar. 2017. Web. http://www.unige.ch/sciences/Actualites/2017/News-150317-1_en.html.
4. Chelle-Michou, Cyril, Bertrand Rottier, Luca Caricchi, and Guy Simpson. "Tempo of Magma Degassing and the Genesis of Porphyry Copper Deposits." Scientific Reports 7 (2017): 40566. Web.
5. Image Credit: Shutterstock.com/FCG

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