Collaborative Research: A Quantitative Study of Reaction Pathways in Oceanic Serpentinites

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The alteration of seafloor mantle rocks by seawater (referred to as serpentinization) is a widespread process. It affects global chemical cycles, earthquake potential, and possibly the origin of life. However, the process of serpentinization remains poorly understood. This work will conduct laboratory experiments to enable a better understanding of the underlying processes of serpentinization. The results will improve models and allow scientists to better interpret altered mantle rocks and fluid compositions. This project provides student training in geological oceanography, petrology, and aqueous geochemistry. To broaden participation in science, the researchers will involve undergraduate students from underrepresented minorities in this project. The students will be offered training in project design, sample analysis, data interpretation and presentation of results. Results of this project will be broadly disseminated through open access manuscripts, at international conferences, and workshops, and as well as through seminars, and teaching.It is hypothesized that distinct dissolution rates of minerals that constitute mantle rocks are decisive in controlling the fluxes of elements from the mantle rock and, therefore, in controlling the timing of secondary (hydrothermal) mineral formation events which dictate the temporal evolution of physical rock properties and compositions of vent fluids. To test this hypothesis, this work aims at systematically exploring the succession of chemical reactions recorded in altered mantle rocks by integrating chemical, isotopic, and quantitative mineralogical analyses with theoretical modeling. Chemical compositions, as well as mineralogical maps of partially altered mantle rocks will be used to reconstruct the original proportions of mantle minerals. By comparing mineral abundances of fresh and reacted rocks, relative dissolution rates and chemical fluxes will be inferred. To reconstruct the sequences of chemical reactions, abundances of minerals will be co-registered with the overall extents of alteration. Results from previous studies will be applied to determine the effect of temperature on the succession of dissolution-precipitation reactions. The analytical outcomes of this study will inform theoretical models that will take rock compositions, alteration temperature, surface areas, and distinct dissolution rates of minerals into account. By systematically varying the individual input parameters, these models will be developed that match the rock record. These models will then provide detailed insight on the evolution of fluid compositions associated with specific combinations of rock compositions, alteration temperatures, and mineral assemblages.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.