Dissolved Gas and Metal Composition of Hydrothermal Plumes From a 2008 Submarine Eruption on the Northeast Lau Spreading Center

Tamara Baumberger,Gretchen L Früh-Green,Nathaniel J Buck,John E Lupton,Edward T Baker,Sharon L Walker,Joseph A Resing,Marvin D Lilley

doi:10.3389/fmars.2020.00171

Abstract

Extrusion of lava onto the seafloor transports heat and mass from the lithosphere to the hydrosphere and the biosphere. During this process, large amounts of dissolved gases can be released into the ocean as hydrothermal plumes and serve as nutrients for microbial activity. Here we report the dissolved gas and metal composition of hydrothermal plumes associated with a submarine eruption at the Northeast Lau Spreading Center (NELSC) in the SW Pacific Ocean in November 2008. During this eruption, two different types of plumes were observed in the water column: a shallow event plume rich in H2 and poor in 3He and CH4, and a deep near-seafloor plume with high CH4, metals and 3He and intermediate H2 concentrations. Both were generated at the same time and at the same location. While the high abundance of H2 in the event plume points to ongoing reactions between hot rock and seawater, the distinct chemical characteristics of the near-seafloor plume likely result from the release of a mature fluid stored in the crust. The plume chemistry of the event plume favors a seawater-lava interaction event plume generation model. However, the heat budget asks for an additional process releasing enough heat to lift the plume within the time frame of this short event. The extremely high H2 concentrations suggest that the eruption was locally more explosive than assumed. A more explosive eruption style might enhance the heat flux from lava cooling.

Highlights

Observations of volcanic eruptions in the deep-sea are rare (Rubin et al, 2012)
The first indication of an on-going eruption at the Northeast Lau Spreading Center (NELSC) was observed on 20 November 2008 in tow-yo T08C-07 at 174.25◦W and 15.40◦S and at a water depth of 1170 m (Figure 2 and Table 1)
An extremely high dissolved H2 concentration of 6424 nM was measured, which is > 30000 times the concentration seen in local background seawater, while CH4 showed no enrichment above background and [3He] was not higher than 0.76 fM, indicating only a small magmatic component

Summary

Introduction

Observations of volcanic eruptions in the deep-sea are rare (Rubin et al, 2012). To date, only two submarine volcanoes have been visually observed during an eruption: NW Rota-1 in the Mariana arc (Chadwick et al, 2008) and West Mata in the NE Lau Basin (Resing et al, 2011). H2 and CH4 concentration data from young hydrothermal plumes associated with eruptions are very limited (Kelley et al, 1998; McLaughlin, 1998; McLaughlinWest et al, 1999; Resing et al, 2007; Baumberger et al, 2014). Two bottles were triggered in the event plumes, one at 900 m and one at 1350 m (Table 1) Both samples had similar plume chemistry to what was observed 18 h earlier: highly enriched H2, enhanced TDMn and TDFe and near background seawater CH4 and 3He concentrations, but with lower maximum concentrations

Methods

Results

Conclusion