THE SCOPE AND SIGNIFICANCE OF TUNGSTEN ISOTOPE VARIATIONS: IMPLICATIONS FOR MANTLE EVOLUTION

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Tungsten isotopic variations have been documented in modern and ancient rocks over the past decade, yet their role in constraining mantle evolution remains debated. This is because their origin and mode of preservation in the mantle are unclear. Tungsten isotopic compositions, however, could provide unparalleled constraints on mantle evolution as tungsten is one of the few isotopic tracers able to track the final stages of accretion, early planetary differentiation, and potentially ongoing core-mantle interaction. To effectively utilize this tracer, the scope of tungsten isotopic variations must be robustly identified and incorporated into physical mantle evolution models. Our starting point is a survey of the most ubiquitous rock type sampling the mantle: mid-ocean ridge basalts. We will test hypotheses of the origin and preservation modes of tungsten isotopic anomalies in the mantle by synthesizing new and existing tungsten isotopic data with numerical models of thermochemical mantle convection. The proposed integration of data, techniques, and interpretations is novel and has the potential to significantly advance the understanding of mantle evolution beyond the tungsten isotope community. Three additional broader impacts planned. (1) Development of interdisciplinary partnerships by coordinating early career scientists who are experts in different disciplines. This includes support for a postdoctoral associate to conduct state-of-the-art research. (2) Advancement of teaching and participation in science by providing a structured research program for an undergraduate student at Rutgers University facilitated by the Aresty Research Center for Undergraduates and diversity and inclusion centers affiliated with the university. (3) Further development of the planetary science research track at the Department of Earth and Planetary Sciences, Rutgers University.With the recent discoveries of tungsten isotopic heterogeneity in ocean island basalts, it is now necessary to understand if mid-ocean ridge basalts possess tungsten isotopic variation and investigate what causes these variations. Using proven analytical methods, we will measure high-precision tungsten isotopic compositions in samples from compositional diverse mid-ocean ridges. This task will address the issue that little research has been reported to define mantle reservoirs which are purportedly normal for tungsten isotopic composition. To advance broader scientific implications provided by tungsten isotopic studies to the community, we will test the plausibility of the leading hypotheses of the origin of tungsten isotopic anomalies in the mantle by integrating our new and existing tungsten isotopic data with numerical models of thermochemical mantle convection. These results are anticipated to have broad implications for our understanding the dynamic evolution of our planet.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.