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Jane Chadwick, Vrije Universiteit Amsterdam (Netherlands)
Valentin Troll, Uppsala Universitet (Sweden)
Frances Deegan, Trinity College Dublin (Ireland)
Claus Siebe, Instituto de Geofisica UNAM (Mexico)
Carmela Freda, Instiuto Natzionale de Geofisic e Vulcanologia (Italy)
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The most explosive, highly active and most dangerous volcanoes on the planet are typically located at subduction zones, areas where one of the Earth's plates is forced beneath another. The explosive nature of subduction zone volcanoes is largely a consequence of their magma chemistry and volatile content, particularly CO2 and H2O. The CO2 systematics of arc volcanic systems has previously been considered to be largely a function of inputs from the Earth's mantle and carbon added during subduction. However, recycling of carbon within the Earth's crust may represent an important additional mechanism of CO2 production in volcanic systems via decarbonation of carbonate bearing rocks. CO2 and H2O have a fundamental control on magma dynamics including eruption, as well as being a long term control on the composition of the Earth's atmosphere.
Obtaining a better quantification of volatiles and particularly the CO2 cycle at subduction zones is therefore of direct importance to a wide range of issues, including volcanic hazard assessment and climate modelling. We present a multi-disciplinary approach integrating modern analytical and experimental petrology techniques combined with the interpretation of geophysical data to place constraints on the volatile cycles at two large CO2 producing arc volcanoes, Merapi, Indonesia and Popocatepetl, Mexico. Our results to date indicate that carbon recycling from long-term storage reservoirs, such as continental crust, is an important process at these large subduction zone volcanoes and potentially at other similar systems elsewhere.
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