The genesis of metal resources

The demand for metals continues to grow, driven by the development of new technologies and the need for infrastructure to sustain ever-increasing populations. With improved understanding of the processes that transport and accumulate metals into economically viable deposits, we can target new places for exploration. In this Web Focus, we bring together a collection of primary research articles and opinion pieces that advance our understanding of how and where metals become enriched in Earth's crust and discuss strategies for their extraction.



Mine and monitor impacts p161


Modern societies require more and more metals, not least for renewable energy generation. Scientists from a range of disciplines are needed to prospect for ore deposits and provide a basis for sustainable exploration.



The quest for sea-floor integrity pp163-164

Till Markus, Katrin Huhn & Kai Bischof


The status of sea floors is an important part of healthy marine ecosystems and intact coastlines. We need laws and a sea-floor management regime to make the exploitation of marine resources sustainable.

Biomining goes underground pp165-166

D. Barrie Johnson


Ore bodies buried deep in Earth's crust could meet increasing global demands for metals, but mining them would be costly and could damage the environment. Reinventing an ancient technology for bioleaching metals could provide a solution.


News and Views

Economic geology: Ore metals beneath volcanoes pp168-170

Olivier Nadeau


Metals often accumulate in the crust beneath volcanoes. Laboratory experiments and observations reveal important roles for magmatic vapours and brines in transporting and concentrating the metals into deposits worth targeting for extraction.

Economic geology: Gold buried by oxygen pp170-171

Fabrice Gaillard & Yoann Copard


The Witwatersrand Basin in South Africa contains extraordinary amounts of gold. Thermodynamic calculations suggest that the gold may have accumulated there in response to a perfect storm of conditions available only during the Archaean.



Witwatersrand gold deposits formed by volcanic rain, anoxic rivers and Archaean life pp206-209

Christoph A. Heinrich


The Witwatersrand gold deposit is the largest in the world. Thermodynamic calculations show that such rich accumulations of gold could be linked to abundant volcanism, primitive life and the oxygen-free atmosphere of the Archaean.

Porphyry copper deposit formation by sub-volcanic sulphur dioxide flux and chemisorption pp210-215

Richard W. Henley, Penelope L. King, Jeremy L.Wykes, Christian J. Renggli, Frank J. Brink, David A. Clark & Ulrike Troitzsch


The processes that create economic-grade accumulations of metals above magma chambers are unclear. High-temperature laboratory experiments show that rapid reactions between magmatic gases and Earth's crust can trigger efficient metal deposition.

Transport of metals and sulphur in magmas by flotation of sulphide melt on vapour bubbles pp216-219

J. E. Mungall, J. M. Brenan, B. Godel, S. J. Barnes & F. Gaillard


Copper ore deposits accumulate at relatively shallow depths in the crust, but it is unclear how the metal is transported. Laboratory experiments show that metals may hitch a ride on magma bubbles and float toward shallower depths.



Generation of porphyry copper deposits by gas-brine reaction in volcanic arcs pp235-240

J. Blundy, J. Mavrogenes, B. Tattitch, S. Sparks & A. Gilmer


Most of the world's copper comes from porphyry ore deposits. Laboratory experiments suggest that these deposits form in a two-stage process over thousands of years, from the interaction between sulphur-rich gases and metal-rich brines.


From the archives



Expanding boundaries of exploration


Mineral exploration is pushing new frontiers. Given a poor track record on land, mining practises should be honed on home soil before venturing into the oceans.



Metals for a low-carbon society

Olivier Vidal, Bruno Goffé & Nicholas Arndt


Renewable energy requires infrastructures built with metals whose extraction requires more and more energy. More mining is unavoidable, but increased recycling, substitution and careful design of new high-tech devices will help meet the growing demand.

Road map to mineral supply

Richard Herrington


Access to metals and minerals is restricted mostly by geopolitical constraints, and not by a shortage of mineable deposits. In the face of rising demand, a full inventory of these commodities — in the Earth's crust as well as in recyclable waste — is urgently required.


News & Views

Economic geology: Copper conundrums

Cin-Ty A. Lee


The metal content of magmas erupted at subduction zone arcs is thought to be derived from the mantle. A correlation between crustal thickness and copper content in arc magmas worldwide, however, reveals an important role for the crust in the upper plate.

Economic geology: Gilded by earthquakes

Dave Craw


Gold is often deposited in Earth's crust by fluids that percolate through rock fractures. Earthquakes cause rock fractures to expand rapidly and could cause the fluids to evaporate, triggering almost instantaneous gold deposition.



Continental-root control on the genesis of magmatic ore deposits

W. L. Griffin, G. C. Begg & Suzanne Y. O'Reilly


Some giant ore deposits are formed from magma, but the precise controls on their formation are unclear. A Perspective article analyses the distribution of some diamond, platinum-group element and gold deposits worldwide, and suggests that the structure and composition of sub-continental lithospheric mantle could play a role in ore genesis.


Progress Article

Giant ore deposits formed by optimal alignments and combinations of geological processes

Jeremy P. Richards


Giant ore deposits are priority targets for mining companies. A review of the characteristics of several giant porphyry and epithermal deposits worldwide suggests that they formed from ordinary processes that were fortuitously operating at maximum efficiency.



Triggers for the formation of porphyry ore deposits in magmatic arcs

Jamie J. Wilkinson


Porphyry ore deposits supply much of the copper, molybdenum, gold and silver used by humans. A review of the main processes that trigger porphyry ore formation suggests that sulphide saturation of the magmas that supply the metals could be the overriding mechanism that helps control the temporal and spatial distribution of the ore deposits.



High gold concentrations in sulphide-bearing magma under oxidizing conditions

Roman E. Botcharnikov, Robert L. Linnen, Max Wilke, Francois Holtz, Pedro J. Jugo & Jasper Berndt


Magma transports metals to the Earth's surface to form ore deposits, but only sulphide-undersaturated magmas were thought to be capable of generating large amounts of ore. Laboratory experiments indicate that large volumes of gold ore can also be generated by sulphide-saturated magma, if the redox conditions of the magma are suitable.



Magmatic—hydrothermal origin of Nevada's Carlin-type gold deposits

John L. Muntean, Jean S. Cline, Adam C. Simon & Anthony A. Longo


During the Eocene, profuse magmatism and hydrothermal activity in the Great Basin of western North America produced Earth's second largest concentration of gold in Nevada. An integration of mineral analyses, experimental data and age and isotope data suggests a magmatic source for these deposits.

Sulphide magma as a source of metals in arc-related magmatic hydrothermal ore fluids

Olivier Nadeau, Anthony E. Williams-Jones & John Stix


The metal content of ore deposits formed during subduction-zone volcanism was thought to be established when the ore fluid separates from the parent magma. Analyses of metal concentrations in erupted melts and the volcanic gases emitted after an eruption in Indonesia reveal that metals can be added to the ore fluid later, during mixing with separated melts.

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