A new, inexpensive method to potentially uncover copper deposits has been developed.
A University of Exeter geologist at the Camborne School of Mines, Dr. Ben Williamson, has – with the Natural History Museum’s Dr. Richard Herrington – proposed a new method to explore for porphyry type copper deposits.
These type of deposits account for around three quarters of the world’s copper and significant amounts of molybdenum and gold.
According to Williamson’s study, “the deposits, which originally form at several kilometres depth below the Earth’s surface, above large magma chambers, are relatively rare, particularly the largest deposits which are most economic to mine.”
“In addition, most near-surface deposits have already been discovered. Any new method to locate deeper deposits is therefore of great interest to the mining industry.”
His work, which has been funded by Anglo American, compared the chemical compositions of minerals from magmatic rocks that host porphyry deposits against those which hold none.
Field tests were carried out in Chile to test the theory.
“Minerals from magmatic rocks which host porphyry deposits have distinctive chemical characteristics which can be used as one of a suite of indicators to home-in on porphyry deposits,” the University of Exeter stated.
“Unravelling the causes of the distinctive chemical signatures has also brought new insights into the formation of porphyry copper deposits, and more generally the generation of the magmatic rocks from which they form, which are an important component of the Earth’s crust.”
The major outcomes of the field tests showed that the magma chamber below the porphyry undergoes discrete injections of water-rich melts or watery fluids which enhance the magma’s ability to transfer copper and other metals upwards to form a porphyry copper deposit.
“This new method will add to the range of tools available to exploration companies to discover new porphyry copper deposits,” Williamson said.
“Our findings also provide important insights into why some magmas are more likely to produce porphyry copper deposits than others, and add to our understanding of how their parent magmatic rocks evolve.”