Table of contents


Economic geology

(Image credited to Jacques Jangoux / Alamy)

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Editorial

Expanding boundaries of exploration p891

doi:10.1038/ngeo2006

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.


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Commentaries

Road map to mineral supply pp892 - 894

Richard Herrington

doi:10.1038/ngeo1947

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.


Metals for a low-carbon society pp894 - 896

Olivier Vidal, Bruno Goffé & Nicholas Arndt

doi:10.1038/ngeo1993

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.


The phosphorus trilemma pp897 - 898

Michael Obersteiner, Josep Peñuelas, Philippe Ciais, Marijn van der Velde & Ivan A. Janssens

doi:10.1038/ngeo1990

Mineable phosphorus reserves are confined to a handful of countries. Reductions in wastage could free up this resource for low-income, food-deficient countries.


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In the press

Tilting at Europa p899

Emily Lakdawalla

doi:10.1038/ngeo1998


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News and Views

Atmospheric science: Rainfall's oceanic underpinnings pp901 - 902

John Fasullo

doi:10.1038/ngeo1997

Understanding the processes that govern the complex spatial structure of rainfall is crucial. Idealized numerical simulations reveal the strong influence that ocean heat transport exerts on this structure.

See also: Letter by Frierson et al.


Volcanology: Magma giant pp902 - 903

Gabriele Uenzelmann-Neben

doi:10.1038/ngeo1958

Episodes of excessive magmatism have repeatedly formed large volcanic provinces on Earth. Seismic data from the Shatsky Rise in the northwestern Pacific Ocean reveal that such oceanic plateaux can be built from individual, giant volcanoes.

See also: Article by Sager et al.


Palaeoclimate: Biodiversity-dominated feedback pp903 - 904

Stefan C. Dekker

doi:10.1038/ngeo1989

About 5,500 years ago, there was a shift from savannah to desert vegetation in the Sahara. Conceptual modelling suggests that the transition was controlled by a climate–vegetation feedback that was also influenced by plant diversity.

See also: Letter by Claussen et al.


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Perspective

Continental-root control on the genesis of magmatic ore deposits pp905 - 910

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

doi:10.1038/ngeo1954

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.


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Progress Article

Giant ore deposits formed by optimal alignments and combinations of geological processes pp911 - 916

Jeremy P. Richards

doi:10.1038/ngeo1920

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.


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Review

Triggers for the formation of porphyry ore deposits in magmatic arcs pp917 - 925

Jamie J. Wilkinson

doi:10.1038/ngeo1940

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.


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Letters

Experimental evidence for a phase transition in magnesium oxide at exoplanet pressures pp926 - 929

F. Coppari, R. F. Smith, J. H. Eggert, J. Wang, J. R. Rygg, A. Lazicki, J. A. Hawreliak, G. W. Collins & T. S Duffy

doi:10.1038/ngeo1948

Little is known about the structure of possible mantle materials of extra-solar super-Earths with interior pressures of up to 1,000GPa. Dynamic X-ray diffraction measurements of ramp-compressed magnesium oxide, an important component of Earth’s mantle, show a solid–solid state transition at about 600GPa, with a high-pressure structure that is stable up to 900GPa.


Transport-driven formation of a polar ozone layer on Mars pp930 - 933

Franck Montmessin & Franck Lefèvre

doi:10.1038/ngeo1957

Spectral observations from the Mars Express spacecraft have revealed an ozone layer that forms at night in south polar Mars. Data analysis and climate models suggest that poleward transport of oxygen and seasonal changes in hydrogen radicals explain the ozone layer’s presence in the southern hemisphere, and its absence in the north.


Link between Antarctic ozone depletion and summer warming over southern Africa pp934 - 939

Desmond Manatsa, Yushi Morioka, Swadhin K. Behera, Toshi Yamagata & Caxton H. Matarira

doi:10.1038/ngeo1968

The recent rise in surface air temperatures over southern Africa is thought to largely result from the increase in atmospheric greenhouse gas concentrations. An analysis of climate data from the past four decades suggests that the warming may be linked to changes in Southern Hemisphere circulation induced by Antarctic ozone loss.


Contribution of ocean overturning circulation to tropical rainfall peak in the Northern Hemisphere pp940 - 944

Dargan M. W. Frierson, Yen-Ting Hwang, Neven S. Fučkar, Richard Seager, Sarah M. Kang, Aaron Donohoe, Elizabeth A. Maroon, Xiaojuan Liu & David S. Battisti

doi:10.1038/ngeo1987

In the tropics, substantially more rain falls just north of the Equator. An analysis of satellite observations, reanalysis data and model simulations suggests that the meridional ocean overturning circulation contributes significantly to the tropical rainfall peak north of the Equator.

See also: News and Views by Fasullo


Evidence from ice shelves for channelized meltwater flow beneath the Antarctic Ice Sheet pp945 - 948

Anne M. Le Brocq, Neil Ross, Jennifer A. Griggs, Robert G. Bingham, Hugh F. J. Corr, Fausto Ferraccioli, Adrian Jenkins, Tom A. Jordan, Antony J. Payne, David M. Rippin & Martin J. Siegert

doi:10.1038/ngeo1977

Subglacial meltwater channels beneath the Antarctic Ice Sheet have been reported, but the nature and distribution of these meltwater pathways are unclear. Remote sensing observations reveal persistent channelized features beneath the Filchner–Ronne Ice Shelf in West Antarctica, suggesting widespread channelized flow driven by melting.


A weak El Niño/Southern Oscillation with delayed seasonal growth around 4,300 years ago pp949 - 953

H. V. McGregor, M. J. Fischer, M. K. Gagan, D. Fink, S. J. Phipps, H. Wong & C. D. Woodroffe

doi:10.1038/ngeo1936

Palaeoclimate records indicate lower El Niño/Southern Oscillation (ENSO) variance during the middle Holocene compared with today, but the mechanisms leading to this muted variability are not clear. A 175-year oxygen isotope record from a Porites coral microatoll in the NINO3.4 region records persistently reduced ENSO variance about 4,300years ago, and season-specific analyses of the record suggest that insolation played an important role in this change.


Simulated climate–vegetation interaction in semi-arid regions affected by plant diversity pp954 - 958

M. Claussen, S. Bathiany, V. Brovkin & T. Kleinen

doi:10.1038/ngeo1962

The end of the African Humid Period about 6,000 years ago was associated with vegetation change and decreased precipitation. Conceptual modelling suggests that the nature of the feedback between climate and vegetation is dependent on vegetation type and diversity.

See also: News and Views by Dekker


Meridional shifts of the Atlantic intertropical convergence zone since the Last Glacial Maximum pp959 - 962

Jennifer A. Arbuszewski, Peter B. deMenocal, Caroline Cléroux, Louisa Bradtmiller & Alan Mix

doi:10.1038/ngeo1961

The position of the intertropical convergence zone is thought to be linked to changes in the Earth’s climate state. Analyses of marine sediment show that over the past 25,000 years, the intertropical convergence zone over the Atlantic Ocean migrated in response to climate changes.


Hidden hotspot track beneath the eastern United States pp963 - 966

Risheng Chu, Wei Leng, Don V. Helmberger & Michael Gurnis

doi:10.1038/ngeo1949

The surface expressions of mantle plumes—known as hotspot tracks—are rarely observed on continents because the lithosphere is so thick. Analysis of seismic data from the eastern United States, combined with geodynamical modelling, reveals a linear, east–west-trending seismic anomaly that may represent a hidden hotspot track extending from Missouri to Virginia.


Ephemeral isopycnicity of cratonic mantle keels pp967 - 970

David W. Eaton & H. K. Claire Perry

doi:10.1038/ngeo1950

The long-term stability of the continents has been attributed to a trade-off between thermal and compositional effects. Numerical simulations of the evolution of continents over 3 billion years, however, show that this state is ephemeral, and continents that are neutrally buoyant today were more (or less) buoyant in the geologic past.


Formation of an interconnected network of iron melt at Earth’s lower mantle conditions pp971 - 975

Crystal Y. Shi, Li Zhang, Wenge Yang, Yijin Liu, Junyue Wang, Yue Meng, Joy C. Andrews & Wendy L. Mao

doi:10.1038/ngeo1956

The differentiation of the Earth into mantle and core implies that there is a mechanism to separate iron from silicates. Three-dimensional imaging of samples experimentally subjected to high pressures reveals that liquid iron forms interconnected melt networks at lower mantle conditions, suggesting pathways through which iron can percolate towards the core.


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Articles

An immense shield volcano within the Shatsky Rise oceanic plateau, northwest Pacific Ocean pp976 - 981

William W. Sager, Jinchang Zhang, Jun Korenaga, Takashi Sano, Anthony A. P. Koppers, Mike Widdowson & John J. Mahoney

doi:10.1038/ngeo1934

The structure of oceanic plateaux is unclear, as they are remote and submerged beneath the seas. Seismic images of the Tamu Massif, part of the Shatsky Rise oceanic plateau in the northwestern Pacific Ocean, show that it is a single immense volcano, potentially the largest on Earth.

See also: News and Views by Uenzelmann-Neben


Helium in Earth’s early core pp982 - 986

M. A. Bouhifd, Andrew P. Jephcoat, Veronika S. Heber & Simon P. Kelley

doi:10.1038/ngeo1959

Some mantle plumes are enriched in 3He, but the source of this primordial isotope is unclear. The partitioning behaviour of helium between silicate and iron melts—as determined by experiments—suggests that sufficient helium may have been incorporated into the core when the Earth differentiated to explain the anomalous leakage at the Earth’s surface.


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