Collaborative Research: Joint Electrical and Vibrational Spectroscopic Investigation of Volatile-carrying Minerals, and Implications for Fluid Transport in Subduction Zones

About This Grant

The distribution and circulation of fluids in the Earth’s interior are connected to volcanic activity, earthquakes, and plate tectonics in general. In this project, the chemical elements (termed “volatiles”) hydrogen (H) and carbon (C) at depths of several hundreds of kilometers below the Earth’s surface (i.e., in the upper mantle) are of particular interest. These light elements provide key information to understand the temperature and chemical composition of the Earth’s mantle, as well as the processes that have shaped the interior of our planet. This team will focus on H,C-bearing mantle rocks using a combination of techniques that are carefully selected to reveal the rock chemistry and the electrical response at high pressures and temperatures. This project is at the frontier of high-pressure research because of the high degree of synergy between two primary techniques (Raman spectroscopy and impedance spectroscopy), and the plan to make these measurements simultaneously at high pressures and temperatures. Electrical measurements (in situ) and vibrational spectroscopy (in & ex situ) are a powerful combination that is anticipated to significantly advance our understanding of transport, dehydration, and decarbonation in volatile-bearing minerals. This work will help develop an advanced model of the transport of volatiles in subduction zones, and presents an opportunity to foster multi-disciplinary collaborations between mineral physics, chemistry, and geophysics. These PIs will train and mentor a postdoctoral researcher, graduate student and several undergraduate students. This project features simultaneous, in situ electrical and Raman spectroscopic measurements on minerals that transport volatiles in subduction zones. Specifically, seven hydrous silicates and carbonates will be probed at pressures up to 8 GPa and temperatures up to 1300 C in presses at Carnegie Institution for Science-EPL. Ex situ vibrational spectroscopy measurements performed at UC San Diego, and electron microprobe analyses conducted at EPL will complement the dataset to probe the sample composition and texture, with particular emphasis on the chemical speciation of volatiles (H, C) and other species (particularly Fe2+ and Fe3+) that are most relevant to charge transport. Advances in the quantification of H and C using Raman spectroscopy will contribute to calibration standards that will be useful to the community. Simultaneous in situ impedance and vibrational spectroscopy are a powerful combination that have the potential to significantly advance our understanding of transport, dehydration, and decarbonation in volatile-bearing minerals. The laboratory-derived measurements will form the foundation for the development of an advanced model for volatile transport in subduction zones. The lab-based model will in turn allow predictions of the electrical response of volatile-carrying materials at depth that are testable using field electromagnetic surveys. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.