Geochemistry, geology, education in a digital world

Volatile Signatures in Lō‘ihi Seamount Lavas: Primordial and/or Recycled Origins?

Date:

3He/4He, CO2, H2O, and the Presence of Primordial and Recycled Components in Lō‘ihi Seamount Lavas

I was invited to speak on the topic of the origin, evolution, and distribution of volatiles in planetary interiors for the Fall AGU meeting in 2021. Fellow session presenters shared work that tackled timescales of cycling, implications for large-scale planetary processes, and utilized a range of volatile species. I focused on the possible co-existence of primordial mantle source with recycled material by exploring variation recorded in Helium isotopes, major volatiles and trace elements. Not bad for a tiny volcano!

Thumbnail of YouTube Video showing Google Earth view of Lō‘ihi Seamount, an underwater Hawaiian volcano. Text inset states: Lō‘ihi Seamount: 975 meters below sea level, 150-200,000 years old (with reference to Guillou et al., 1997). Compass direction states that this view is nearly facing towards the North, perhaps 10 degrees to the East. An irregular volcano structure stands out from the rest of the seafloor. The shallowest, slightly flat area is annotated in grey and labeled 'summit'. There is a short, red line emanating from the summit, labeled, 'North Rift'. An even longer blue line emanates to the south from the summit, labeled 'South Rift'. The caption on this screen says, This is Loihi Seamount. It is a young volcano with two rift zones, which developed early in its history. Presenter Thi Truong is visible in corner.

Watch my presentation on YouTube

Before the session date, I produced a video that could be viewed by anyone before, during, and after the conference.

  • Tech: Sony NX5 HD Video Camera, Sony wireless Lav. Thanks to Jenn Wong-Ala for recording and checking audio.
  • Processing: Final Cut Pro, Windows Movie Maker (for green screen).
  • Pre-recorded presentation: Keynote.
  • Transcription: Self-typed and added timestamps manually to transcript file. See .SRT file

Accessibility and Setup

I presented virtually during the hybrid conference. I used automated captions during my 5-minute presentation segment while screen sharing on Zoom. My presentation was on Google Slides with automated captions enabled.

View of back of AGU presentation room during Thi's live remote presentation. About 2 dozen conference attendees are watching. The chairs appear to be spaced apart for social distancing.
Talk during AGU Session in New Orleans. Credit: McKayla Meier

Plain Language Summary

Studies of Hawaiian volcanoes contribute valuable insights about Earth processes and mantle evolution, and are fundamental for understanding the construction of the largest volcanoes on terrestrial planets. The pre-shield stage exists in every Hawaiian volcano, but is usually blanketed by high volume tholeiitic lava flows which erupt during the main shield stage.

Submarine Lō‘ihi Seamount represents the elusive pre-shield stage, and has transitioned to early shield-type tholeiitic eruptions. Previous studies suggest that Lō‘ihi basaltic glasses have trapped gases with a signature deriving from an ancient, primordial reservoir within the deep mantle. The persistence and distribution of this signature is unknown, and its rare signature is easily contaminated by Earth’s atmosphere, as well as subducted materials that have been recycled into the mantle.

We analyzed the chemical composition of deeply erupted glasses to understand the evolution and modification of rare gas signatures at young Lō‘ihi Seamount. Our results suggest that tholeiitic shield-type lavas continue to sample the primordial mantle reservoir. This signal does not appear to be diluted even though relative melt volume has increased.