Preeruptive Stratification of the Oruanui Rhyolitic Magma, Taupo Volcanic Center, New Zealand

University Of Chicago, Chicago IL

Investigators

Abstract

Anderson EAR-0106327 The proposed research focusses on the Orunaui rhyolitic ash-flow tuff, a geologically young and contrasting counterpart to the Bishop Tuff. We plan to test whether the preeruptive Oruanui magma was stably stratified. If the unsystematically erupted Oruanui pumice compositions nevertheless derive from a density stratified magma body, then the case will be strengthened that many big bodies of silicic magma probably achieve a stable density stratification by natural processes of magma formation, emplacement, crystallization and exsolution of gas. We will study the preeruptive state of the magma by studying inclusions and reentrants of glass in quartz and other phenocrysts, because these plausibly preserve a record of the preeruptive conditions, little modified by eruptive decompression, gas exsolution and crystallization. Our study will help understand the formation of silicic planetary crusts as well as the behavior of active bodies of silicic magma including their propensity for eruption and interactions with geothermal systems, which are sites of ore deposition and energy production.