Ansökan: Bildning och utveckling av andesite: atervinning av material fran jordskorpan i kontinental och oceanisk miljo

Tidsperiod:

1 januari 2009 – 31 december 2011

Projektledare:

Valentin Troll

Projektdeltagare:

John Gamble, Claus Siebe, George Morris, Chris Harris, Benjamin van Wyk de Vries, Jane Chadwick

Finansiär:

Vetenskapsrådet

Bidragstyp:

Projektbidrag

Budget:

390 000 SEK

Andesites are volcanic rocks typical of subduction zones, where oceanic lithosphere is recycled back into the Earth’s mantle. Close to 20% of the world’s population lives in close proximity to andesite volcanoes and in the 20th century these were responsible for over 130,000 human fatalities. It is therefore important to understand precisely how and when these volcanoes will erupt. Geophysical monitoring gives real-time clues about impending eruptions, but the rocks themselves retain evidence about a deeper history that permits us to reconstruct the complexities of their evolution and sub-volcanic plumbing systems. Andesites have been shown to involve complex phase equilibria including polystage mixing episodes that have complicated their liquid lines of descent. We have come to realise that these complexities derive from the manner in which “typical” andesite is manufactured deep in the Earth’s crust – andesites are not simple melts, rather they are mixtures of melts charged with cargoes of crystals that have multiple origins. Using recently developed micro-analytical methods (eg. micro-drilling and laser ablation) it is now possible, for the first time, to see inside an andesite, and to measure radiogenic and stable isotopes and trace elements with very high spacial resolution and to levels of precision and accuracy that were unprecedented until the last few years. Accordingly we can now begin to decipher a history of evolution in single crystals and their supernatant melts (including melt inclusions) and to begin to unravel the anatomy of “typical” andesite.