Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone

Abstract Arc magmas typically contain phenocrysts with complex zoning and diverse growth histories. Microlites highlight the same level of intracrystalline variations but require nanoscale resolution which is globally less available. The southern Taupo Volcanic Zone (TVZ), New Zealand, has produced a wide range explosive eruptions yielding glassy microlite-bearing tephras. Major oxide analyses textural information reveal that microlite rims are commonly out equilibrium surrounding glass. We mapped microlites microcrysts at submicron for major trace element distributions observed three plagioclase patterns: (1) resorption overgrowth, (2) oscillatory zoning, (3) normal (sharp) zoning. Pyroxene textures diverse: calcium-rich bands, hollow textures, (4) (5) sector (6) (7) reverse Microlite chemistry inform processes operating during pre-eruptive magma ascent. They indicate plumbing system periodically intruded by short-lived sub-aphyric dykes entrain microantecrysts grown under physico-chemical conditions stored in rapidly cooled, previously dykes. Changes temperature gradients between intrusion host rock throughout ascent repeated injections lead to fluctuations cooling rates generate local heterogeneities illustrated rim compositions. Late-stage degassing occurs water saturation, forming thin calcic microcryst through partitioning effects. This detailed investigation cryptic conventional imaging shows significant proportion micrometre-sized crystal cargo TVZ antecrystic origin may not be attributed late-stage nucleation onset volcanic eruptions, as presumed.