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Increasing the spatial resolution of Laser Ablation Inductively Coupled Plasma MassSpectrometry (LA-ICP-MS) is a challenge in microanalysis of geological samples.Smaller sizes for the laser beam will allow for (1) high resolution determination of trace element compositions, (2) accurate estimation of crystal/melt partition coefficients, (3) detailed characterization of diffusion profiles, and (4) Our results are well consistent with the previously reported data obtained at lower spatial resolution, supporting the reliability of the method.

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We present new evidence that shows magma mingling can be a key process during highly explosive eruptions. Using fractal analysis of the size distribution of trachybasaltic fragments found on the inner walls of bubbles in trachytic pumices, we show that the more mafic component underwent fracturing during quenching against the trachyte. We propose a new mechanism for how this magmatic interaction at depth triggered rapid heterogeneous bubble nucleation and growth and could have enhanced eruption explosivity. We argue that the data support a further, and hitherto unreported contribution of magma mingling to highly explosive eruptions. This has implications for hazard assessment for those volcanoes in which evidence of magma mingling exists.