Jon Woodhead et al., School of Earth Sciences, University of Melbourne, Parkville VIC 3010, Australia. Posted online ahead of print 10 April 2012; doi: 10.1130/G32963.1.
Defining the magnitude and nature of the elemental mass transfers occurring during the subduction process is a key component in our aspiration to understand the geochemical evolution of the planet itself. In this study, Jon Woodhead and colleagues explore a potential new tool for such investigations. By analyzing the isotopic composition of the chemically immobile elements Hf and Nd in basalts from the Mariana Trough back-arc basin, they are able to define the "ambient mantle" composition. This baseline then forms a starting point from which to interpret the many and varied volcanic products of the Mariana Arc itself, ranging from depleted tholeiites to highly enriched shoshonites. While much research to date has concentrated on the influence of the subducting slab assemblage in controlling the composition of arc magmas, this study highlights the equally important role played by Earth's mantle in this process.
The invisible hand: Tectonic triggering and modulation of a rhyolitic supereruption
Aidan S.R. Allan et al., School of Geography, Environment and Earth Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand. Posted online ahead of print 10 April 2012; doi: 10.1130/G32969.1.
Sorting out what happens during prehistoric volcanic eruptions on timescales relevant to modern society is challenging due to the limits of what can be understood from the geological record. Discovery of minor volumes of "foreign" magma in early eruption deposits shows that the outbreak of the world's youngest super-eruption (the Oruanui eruption, Taupo volcano, New Zealand, 27 thousand years ago) was intimately controlled by tectonic stresses. Chemical fingerprintin
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Geological Society of America