Noble gas variation during partial crustal melting and magma ascent processes

Noble gas isotopes, although present in trace amounts, are generally more reliable and less ambiguous recorders of their source than the major volatile species. In volcanic settings particular, this advantage derives from chemical inertness, as noble isotopic elemental fractionations strongly coupled to modified only by physical processes during magma ascent eruption. The Neogene volcano El Hoyazo (Betic Cordillera, SE Spain) is a highly favourable natural laboratory study links between partial crustal melting occurring at depth eruptive products surface, because partially melted xenoliths preserved silicic lavas. Comparing compositions lavas has potential yield new insights into behaviour inaccessible depths crust. At Hoyazo, gases trapped lava glasses, fluid/melt inclusions within xeno- phenocrysts, provide novel information on: (i) response process including mechanisms such mixing (and assimilation) two endmembers: i.e. extracted felsic melt country metapelitic crust, basic-intermediate underplating region. results reveal significant modification magmatic interaction with crust; (ii) variations degassing ascent, showing higher atmospheric influence samples shallower deeper minerals; (iii) crystals garnet both amphibole, xenoliths. addition, we find that also likely accumulating shrinkage bubbles, not remaining dissolved melt.