Origin of alkali olivine basalts and hawaiites in the western Mexican arc: Evidence of rapid phenocryst growth and magma mixing during ascent along fractures

Abstract A detailed petrological study is presented to constrain the origin of a suite alkali olivine basalt and hawaiite (>5 wt% MgO) lavas that were erupted in rift zone within western Mexican arc (Trans-Mexican Volcanic Belt), adjacent Sangangüey andesitic stratovolcano, together with more evolved (mugearites benmoreites; <5 MgO). As previously documented literature, mafic are devoid any geochemical signature, despite their location an arc. In this study, new olivine-melt thermometer/hygrometer, based on partitioning behavior Ni2+ Mg2+, was applied basalts (SB). The results show high-MgO (>9 wt%) SB crystallized at higher temperatures lower melt-water contents (0–1.3 compared (≤5.7 H2O) west-central 5–8 MgO display evidence mixing between low-MgO mugearites. It proposed unique composition mugearites (i.e., low SiO2 elevated FeO TiO2 contents) result partial melting crust driven by influx intraplate under relatively hot, dry, reduced conditions. On basis crystal textures compositional zoning patterns, it shown both phenocryst growth magma occurred rapidly, most likely during ascent along fractures, not slowly prolonged storage crustal chamber.