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Durham University

Durham Geochemistry Centre

Volcanic processes and Climate

Magmas erupted at volcanoes serve as chemical (and to some extent physical) probes of the lithosphere and subjacent mantle. At Durham we use volcanic rocks to investigate the nature of the lithosphere and mantle, and the effects of such volcanism on climate.

Volcanic processes:

We are interested in how magma systems behave - how magma differentiates and on what timescales. Such processes will not only control the compositions of erupted magmas, but will also influence the hazards posed by a given volcano. In short, whether a volcano passively erupts basalt at frequent intervals in low volumes per eruption (such as Hawaii) or whether it violently erupts large volumes of rhyolite less frequently (such as in New Zealand) is largely controlled on what happens as the magma makes its way through the lithosphere. The objective of this research is to use the rock components, crystals, glasses, melt inclusions, volatiles) to monitor how magmas have evolved - including the roles of crystal fractionation, magma mixing and contamination - where they have evolved in terms of the architecture of storage systems in the crust, such as size and depth of magma chambers, and how fast they evolved.

Volcanism and Climate.

Basaltic fissure eruptions are sometimes characterised by the repeated eruption of huge batches of magma, over relatively brief intervals of time, and delivering large masses of volcanic gas to the atmosphere. The release of gases and aerosols may have a significant impact on the atmosphere, ocean chemistry and climate – and many have linked such eruptions with mass extinction events that punctuate the history of life on Earth. However, the precise impact of such volcanism on the atmosphere and biosphere remains highly debated because of uncertainties as to whether the atmospheric effects are sufficient to trigger an environmental response that results in climate change and/or a biotic crisis. Research in this area aims to use a combination of isotope and petrological techniques to constrain: (1) The source of the volatiles, using the exceptional sensitivity of key isotope systems to the presence of crustal material in the melt, linking that information with trace element and volatile measurements on coexisting phases (and melt inclusions). (2) The relative duration of volatile release during volcanism using the 187Re-187Os and Pb isotope systems to monitor variations in melt chemistry and volatile release. (3) The mechanism of volatile release, in particular, which gaseous species are present and the mechanism of S transport, either as gases or crystalline sulfide particles and/or sulfates, traced using highly siderophile element (HSE) abundances and Zn, Cu and S isotopes.