Investigating water-rock interactions in crust beneath the seafloor using the triple oxygen-isotope approach

The entire ocean volume circulates through the oceanic crust beneath the seafloor about every one million years. This project will use a new technique to study the interactions between water and rocks during this process. The triple oxygen-isotope method simultaneously provides constraints on temperature, water volume, and fluid composition. The analyses will resolve, for the first time, the composition of fluids circulating at various depths beneath the seafloor. The results are important for understanding alteration and evolution of oceanic crust and seafloor ore deposit origins. The project will support an early career principal investigator, provide research opportunities for graduate and undergraduate students, and support a laboratory at a regional, student-centered university. This study will apply the triple oxygen-isotope approach to mineral separates from a comprehensive suite of oceanic lithologies. The scientific ocean drilling samples include pillow basalts, sheeted dikes, and hydrated upper mantle. The results will be used to estimate the seawater isotope composition at the time of alteration and how it could have varied through geologic time. The project will support a new laboratory that will be available for use in course-based research projects and for collaborations with scientists at nearby universities; it will also develop an open reference page for scientific ocean drilling hole 504B, one of the deepest drill holes in oceanic crust. 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.