Origin of Subduction Zone Magmas Based on Experimental Petrology

Noble gas isotopic composition of deep underground water in Osaka plain, central Japan: Evidence for mantle He and model for new volcanism

“…Several models for the generation of magma in a subduction zone of an arc-trench system have been proposed already (e.g. Gill 1981;Tatsumi 1991). In Phanerozoic arc-trench systems, however, melting of the mantle wedge is enhanced by the addition of fluids derived from the subducting slab.…”

Solution mechanisms of silicate in aqueous fluid and H2O in coexisting silicate melts determined in-situ at high pressure and high temperature

“…Andesitic volcanism commonly is characterized by high water contents (e.g., Kushiro, 1972Kushiro, , 1990Tatsumi, 1986;Sisson and Grove, 1993;Grove et al, 2002) so it is appropriate to examine experimentally the structure of hydrous melts with similar degree of polymerization so as to further our understanding of magmatic processes under water-rich conditions. The composition of the starting material (Na 2 OÁ4SiO 2 -denoted NS4) was chosen in part because the degree of polymerization, NBO/Si, of NS4 composition melts is similar to that of typical andesitic melts (nominal NBO/Si = 0.5 of anhydrous melt -average NBO/T of andesitic melts is between 0.4 and 0.5; Mysen and Richet, 2005).…”

Structure of H2O-saturated peralkaline aluminosilicate melt and coexisting aluminosilicate-saturated aqueous fluid determined in-situ to 800°C and ∼800MPa

“…High activity of H 2 O during partial melting or crystallization typically results in silica-enriched melts that resemble andesitic composition (e.g., Kushiro, 1972;Tatsumi, 1986;Kushiro, 1990;Sisson and Grove, 1993;Grove et al, 2002). To this end compositions along the join tetrasilicate (Na 2 O4SiO 2 ) -tetra-aluminate [Na 2 O4(NaAl)O 2 ] were chosen.…”