Estimating eruptive volatile emissions and fluxes in the Auckland Volcanic Field, Aotearoa New Zealand

Abstract Volcanic gas emissions and fluxes are crucial inputs to hazard assessments and global volatile budgets. However, for many volcanic areas (such as the Auckland Volcanic Field [AVF], a distributed basaltic system that underlies New Zealand’s largest population centre) neither directly measured nor analogue gas emissions data are readily available. In lieu of measured gas emissions data, we apply the petrologic method, using data from crystal-hosted melt inclusions and volcanic glass to calculate volatile emissions for a compositionally representative set of five AVF eruptions. Our results indicate that emissions from small-volume eruptions can rival those from polygenetic eruptions. Extrapolating this data for all 53 eruptive centres suggests that the AVF has emitted ~26,000 kt CO 2 , ~9,000 kt ~SO 2 , ~470 kt HCl, and ~2220 kt HF over its ~200 ky eruptive history. We extend our analysis to develop an estimate of volatile emissions during open- and closed-system degassing and model daily fluxes for eight previously developed AVF eruption scenarios. Scenario unrest timelines were coupled with a thermodynamic magma degassing model, EVo , to estimate open-system fluxes. For closed-system fluxes, we distributed scenario emissions over a simple log-normal magma discharge curve defined by the scenario eruption durations and data from the literature. We find that maximum, time-averaged daily SO 2 fluxes from distributed eruptions can be as high as those that have posed significant volcanic gas hazards to nearby populations, such as at La Palma in 2021. However, this is heavily dependent on scenario model inputs. Our results and the methodology may be used to estimate volcanic gas emissions and fluxes in other long dormant or unmonitored volcanic areas.