Fe-Mg DIFFUSION CHRONOMETRY IN PYROXENES FROM THE MINOAN ERUPTION OF SANTORINI, GREECE

Fe-Mg diffusion chronometry has been applied to orthopyroxene and clinopyroxene from the ~1628 BC ‘Minoan’ eruption of Santorini in order to investigate timescales of final magma chamber formation prior to the large, caldera-forming eruption. Fe-Mg interdiffusion was modelled across zone boundaries in pyroxene crystals in order to estimate their residence time in the 855°C Minoan magma chamber. Orthopyroxene yielded timescales between zero and ~30 years with a predominance of timescales under one year, suggesting very short timescales of final assembly of the Minoan magma chamber before eruption. These results are in agreement with melt inclusion barometry and previous diffusion modelling in plagioclase. Clinopyroxene gives longer timescales, ranging from tens to several thousands of years. Three approaches were implemented to estimate the timescales, each giving quite long timescales. The clinopyroxene crystals are hypothesized to have originated in a lower magmatic reservoir where they had a complex history.