High-Ti, bright-CL rims in volcanic quartz: a result of very rapid growth

Volcanic quartz commonly contains Ti-enriched zones and CO2-enriched melt inclusions, and crystallization temperatures and pressures derived from Ti-in-quartz geothermobarometry and H2O–CO2 glass geobarometry applied to these compositions are typically high. Consequently, these features are generally interpreted to represent high temperatures and/or pressures. Yet, growth rate estimates from some high-Ti/bright-CL quartz rims suggest they grew...