Ocean Islands

(Image credited to iStockphoto/© Josef Friedhuber)

Volcanic eruptions in the middle of tectonic plates, far from any volcanically-active plate boundaries, have created many of the thousands of ocean islands and seamounts that cover Earth's ocean floors. The geochemistry of their lavas may provide a window into processes occurring deep inside our planet. In this issue we collect research articles and opinion pieces that explore some possible mechanisms for the creation of ocean islands and seamounts, and highlight their connections to the deep and upper mantle.



Forty years of plume research p813


Mantle dynamics drive the formation of ocean islands and seamounts in the interior of oceanic plates. Yet the mechanisms for generating these volcanic edifices differ from chain to chain, and their material can be generated at a variety of depths.



Mantle plumes persevere pp816 - 817

Anthony A. P. Koppers


The ocean floor is littered with hundreds of thousands of mostly extinct volcanoes. The origin of at least some of these seamounts seems to rest with mantle plumes.


News and Views

Geodynamics: Christmas recycling pp823 - 824

Sally A. Gibson


The mechanisms for forming the abundant volcanic islands on ocean floors are debated. The geochemical signature of volcanic rocks from the northeast Indian Ocean suggests that seamounts there formed from melting recycled ancient continental rocks.


Review article

Role of the deep mantle in generating the compositional asymmetry of the Hawaiian mantle plume pp831 - 838

Dominique Weis, Michael O. Garcia, J. Michael Rhodes, Mark Jellinek & James S. Scoates


Volcanoes formed above the Hawaiian mantle plume exhibit a striking contrast in the geochemical characteristics of the lavas erupted at the northern Kea compared with the southern Loa volcanoes. Isotopic data show that these trends have persisted for more than 5 million years and may mirror compositional heterogeneities in the deep mantle.



Geochemical zoning of volcanic chains associated with Pacific hotspots pp874 - 878

Shichun Huang, Paul S. Hall & Matthew G. Jackson


Lavas erupted from volcanoes in the north of the Hawaiian volcanic island chain have a different geochemical signature from those in the south. Analysis of the geochemistry of lavas erupted in the Samoan and Marquesas volcanic chains reveals similar trends, implying that the lowermost mantle beneath the southern Pacific is isotopically enriched.

A deep mantle origin for the primitive signature of ocean island basalt pp879 - 882

Frédéric Deschamps, Edouard Kaminski & Paul J. Tackley


Seismic data have identified large-scale compositional heterogeneities in Earth's deep mantle, but their origin is debated. Numerical modelling demonstrates that seismological and geochemical constraints on the character of these heterogeneities can be satisfied if they are composed of primitive material formed early in Earth's history.

Origin of Indian Ocean seamount province by shallow recycling of continental lithosphere pp883 - 887

K. Hoernle, F. Hauff, R. Werner, P. van den Bogaard, A. D. Gibbons, S. Conrad & R. D. Müller


The origin of the Christmas Island Seamount Province in the northeast Indian Ocean is enigmatic. Radiometric dating and isotopic analysis of volcanic rocks from the seamounts imply that they were derived from the recycling of continental lithosphere and brought to the surface at a mid-ocean ridge.


From the archives


News and Views

Geodynamics: The ups and downs of sediments

Terry Plank & Peter E. van Keken


Neither recycled oceanic crust nor sediments alone can explain the composition of ocean-island basalts, but how about a mixture of the two? Recent modelling using the isotopes of hafnium and neodymium appears to support this contention.

Volcanism: Eruptions above mantle shear

Scott D. King


Why broad fields of volcanism are found in the interior of tectonic plates is hard to explain. Spatial correlations between sheared mantle flow and volcanism suggest that differential motion between surface plates and the mantle generates upwelling and melt.

Geodynamics: Surface impact of mantle processes

Philip A. Allen


Dynamic motions in Earth's mantle can be expressed at the surface. Rocks and landscapes beneath the North Atlantic Ocean record surface uplift driven by pulses of hot material upwelling in a mantle plume beneath Iceland.

Geodynamics: East Africa on the rise

Raphaël Pik


The growth of East Africa's high topography during the past 30 million years cannot be explained by typical mountain-building processes. Numerical modelling shows that much of this topography formed in response to upwelling in the underlying mantle.


Review article

The many surface expressions of mantle dynamics

Jean Braun


Earth's topography is attributed to the interactions of the tectonic plates, but flow within the mantle also contributes to surface uplift and subsidence. An overview of recent research indicates that mantle-induced dynamic topography can be reconstructed by integrating the geological record with models of mantle flow.



Role of recycled oceanic basalt and sediment in generating the Hf–Nd mantle array

Catherine Chauvel, Eric Lewin, Marion Carpentier, Nicholas T. Arndt & Jean-Christophe Marini


The isotopic composition of oceanic basalts suggests that they are composed of true recycled oceanic crust and sediments, which are mixed with the depleted mantle.

Recycled gabbro signature in hotspot magmas unveiled by plume—ridge interactions

N. A. Stroncik & C. W. Devey


The geochemistry of lavas erupted at locations where mantle plumes interact with mid-ocean ridges reflects the mixing between the two sources. Analysis of lavas erupted above the Foundation hotspot, near the Pacific–Antarctic Ridge, reveal a geochemical signature indicative of both a primitive mantle plume source and a recycled oceanic lithosphere source.

Patterns of intraplate volcanism controlled by asthenospheric shear

Clinton P. Conrad, Todd A. Bianco, Eugene I. Smith & Paul Wessel


Volcanism observed far from plate boundaries, in the interior of oceanic and continental plates, may result from flow in the underlying mantle. Comparison between a numerical model of mantle flow and the spatial distribution of intraplate volcanism indicates that rapid shear motion in the mantle may drive melting that causes intraplate eruptions.

Spatial and temporal variability in Hawaiian hotspot volcanism induced by small-scale convection

Maxim D. Ballmer, Garrett Ito, Jeroen van Hunen & Paul J. Tackley


Variations in the volume, geochemistry and location of volcanism in Hawaii cannot be explained as the simple consequence of an underlying mantle plume. A numerical model of the Hawaiian plume suggests that small-scale convection in the mantle erodes the base of the overlying tectonic plate and may help generate the anomalous volcanism.

Changes in African topography driven by mantle convection

Robert Moucha & Alessandro M. Forte


Africa's topography is characterized by large-scale uplifted domes and subsided basins. Numerical simulations of mantle flow suggest that high topography along Africa's eastern margin formed as a result of the northward migration of the tectonic plate over the African superplume during the past 30 million years.

Ocean circulation and mantle melting controlled by radial flow of hot pulses in the Iceland plume

Heather Poore, Nicky White & John Maclennan


V-shaped ridges of thickened oceanic crust above the Iceland plume are thought to record variations in the convection of the mantle below. Geochemical analyses of basalt samples taken from the ridges suggest the thickened crust formed as the result of blobs of hot mantle rising up in the underlying plume.

Transient convective uplift of an ancient buried landscape

Ross A. Hartley, Gareth G. Roberts, Nicky White & Chris Richardson


Hot mantle upwelling in the Icelandic plume has caused episodic uplift of sedimentary basins located off the northwest coast of Europe. Reconstruction of river profiles on an ancient buried landscape constrains the history of surface uplift and suggests that pulses of hot plume material spread out at velocities of 35 cm yr-1.

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