Fig. 7. Volatile abundances in Stromboli's melt inclusions and glass embayments contrasted against results of the saturation model. Data fromMétrich et al. (2001, 2005, 2009) and Bertagnini et al. (2003). (a) H2O vs. CO2; (b) H2O vs. S. The grey solid lines are model results from LP runs 1–4, whilst black dashed lines show model results from HP runs 5–6. Comparison of natural and modelled compositions confirms that the deep (PN100 MPa) LP magma contains a high (2–5 wt.%; model curves 2–3) fraction of gas bubbles at reservoir conditions. Glass embayment formed at P∼100 MPa are H2Opoorer than predicted by model curves 2–3, suggesting some extent of gas fluxing with CO2-rich gas bubbles. This triggers de-hydratation of the LP magma, and probably controls transition to HP magma. The same process likely occurs also in the upper conduit system (compare model trends 5–6 with volatile abundances in HP magmas). In a, isobars are traced under a fixed Fe2/Fetot ratio of 0.24 (Table 2), and are thus slightly different than those originally reported byMétrich et al. (2010) (who, yet using the same saturation model, used a constant ΔNNO value, thus yielding variable Fe2/Fe3 proportions depending on melt composition, and water particularly).
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