Generation of mantle heterogeneity introduced by subduction: A phase equilibria and geochemical analysis of mantle mixing and its impact on ocean island magma genesis

About

Date: 

08/28/2017 (All day)

PI/Speaker: 

Jenna Adams

Original report written by Jenna Adams. Interview and editing by Bailee Abell.

Earth Science PhD. student Jenna Adams is helping to decipher the origin and evolution of magmas erupting on the Earth’s surface—one experiment at a time. With the results of her research, scientists will gain a better idea of how to accurately predict volcanic eruptions before they occur.

Adams became interested in Volcanology as an undergraduate student when she pursued a research thesis aimed at using thermodynamic modeling to document the relative size, frequency, and location of magma mixing events—the mixing of magmas beneath a volcano prior to eruption. The success of her undergraduate thesis led her to study volcanology and geochemistry in her graduate program at UCSB.

“The overarching goal of my research focuses on unraveling the origin and evolution of lavas erupted at hotspot volcanoes (e.g. Hawaii),” Adams said. “This is done by using integrative techniques, such as studying the geochemistry of lavas erupted at hotspot volcanoes combined with computational tools (i.e. thermodynamic and mineral equilibria modeling), to better understand the dynamics of magma behavior beneath a volcano, prior to eruption.”

These tools help illuminate the magmatic processes that occur beneath volcanoes and drive the compositional diversity of lavas that erupt at volcano hotspots around the globe. Adams believes that understanding how to effectively integrate analytical geochemistry and computational modeling into this research will help enhance predictions of volcanic eruptions. 

 

Adams began this project last summer with the help of her advisor, Frank Spera, and with funding provided by an ERI fellowship. “The project I conducted under the ERI fellowship was really a test of concept,” she explained. “I formulated two theoretical models (constrained under specific parameters, like temperature and pressure) illustrating two different magmatic processes.”

One model that Adams formulated involved the mixing of two compositionally distinct solids. Under extreme pressure in the Earth’s mantle, solids behave as very viscous fluids—over time, they can flow and mix in a solid state. After this mixing, the solids are partially melted to specific proportions. The second model involved the partial separate melting of two distinct solids, which were then mixed.

Through a series of tests and observations that closely matched the geochemistry of the Samoan hotspot volcano in the South Pacific, Adams’s research suggested that the Samoan lava geochemistry closely matches the first model (described above), revealing that her results were consistently lower in titanium concentration compared to the average geochemical compositions of lavas at other hotspot volcanoes.

To address the low titanium concentration in her model results, Adams is continuing her research with the future hope of applying thermodynamic modeling techniques to evaluate how magmatic processes affect this titanium concentrations. She also hopes to discover how these results change at high and low pressures within the Earth.

“The most rewarding part [of my research] was encountering an aspect of the results that was wholly unexpected and has now lead me down a research path that is new to me and has resulted in new collaborations with researchers outside of my expertise,” she said.

Her project was in part made possible by an ERI fellowship, which she said provided her with financial stability and allowed her to dedicate her summer to her research.

 

“It gave me the opportunity to take a short time off from being a Teaching Assistant,” Adams said. “Teaching is very fun and hugely rewarding but also time consuming, thus, it was great to have more time to focus my energy solely on my research, which increased my productivity immensely.”