In situ monitoring of reaction progress during serpentinization of oceanic lithosphere using synthetic fluid inclusions

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Few techniques exist where visual observations and compositional measurements can be made of mineral reactions inside natural host minerals in real-time. This research by two investigators at Virginia Tech, one of whom is early career, explores an exciting and potentially transformative new experimental method by which synthetic fluid inclusions, filled with fluids of seawater-like composition, are grown in the laboratory and then held at temperatures and pressures at which important geological mineral reactions occur. In these reactions, secondary minerals precipitate inside the inclusion due to the reaction between the fluid and host mineral. This research targets serpentinization of the ocean crust, which involves the formation of serpentine, a hydrous mineral, and other secondary phases from anhydrous magnesium-rich silicate minerals (olivine, pyroxene,and garnet) that are the primary constituents of seafloor lavas. Serpentinization of ocean crust releases H2O into the mantle which can trigger melting and arc volcanism. It is also linked to the generation of abiotic organic compounds due to the release of hydrogen during mineral reaction. These organic molecules can form the base of the food chain for microbes living in in the ocean crust. Broader impacts of the work include (1) developing new experimental methods and demonstrating their utility, (2) developing the Raman spectroscopic identification of hydrous minerals associated with serpentinization reactions, (3) support of an early career female scientist and a minority graduate student; and (4) creation of podcasts on science in Spanish to inform and excite Hispanic audiences about science and the proposed research. This experimental program will react fluids in minerals at ~280 degrees C for a number of weeks and monitor the dissolution and precipitation reactions that take place in the fluid inclusions as a function of time, temperature, fluid composition, and host mineral composition using a variety of state-ot-the-art analytical techniques that include: microthermometry, Raman spectroscopy, laser ablation inductively coupled plasma mass spectrometry, micro-FTIR (Fourier Transform Infrared) spectroscopy, and FIB-SEM (focused ion beam scanning electron microscopy). An additional research goal is to develop Raman spectroscopy as a tool for the identification of phases associated with serpentinization, including the identification of chrysotile, lizardite, antigorite, and magnetite, as well as the protolith phases undergoing reaction. Results of the experiments will be compared with predictions from thermodynamic models. Successful development of this experimental technique and demonstation of its applicabilty has the potential to impact other fields of science such as pharmachology and materials science where the ability to observe chemical reactions and their rates of reaction in host crystals in real-time may lead to breakthroughs in understanding.