A Time Series of Hydrothermal Vent Fluid Geochemistry Preceding the Next Eruption at 9°50'N East Pacific Rise

Abstract During the past 30 years, the 9°50'N East Pacific Rise (EPR) hydrothermal field has been the focus of multidisciplinary studies spanning two periods of volcanic activity, in 1991-1992 and in 2005-2006. This research aimed to understand the hydrothermal response preceding the next magmatic event at this mid-ocean ridge. Hydrothermal vent fluids were collected in 2018, 2019, and 2021 from eleven discrete sites impacted by previous eruptions. Geochemical vent fluid analyses investigate fluid circulation depth, water-rock reactions, and gas concentrations. Results demonstrate that multiple sites experienced compositional stability between 2018 and 2019. In 2021 however, several vents were affected by a diking event that occurred in November 2020, as revealed by shifts in fluid circulation depth and gas contents. This study establishes a baseline to better understand volcanic and hydrothermal interaction, both at the scale of each individual vent field, and in a broader, regional scale across multiple well-studied vent complexes.