Collaborative Research: Hf-Isotopes as Tracers of Highly Depleted Oceanic Mantle

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Volcanic activity on mid-ocean ridges constitutes one of the largest scale and most important chemical differentiation processes on earth. Magmas, created from the selective melting of Earth's mantle, bring some elements and elemental ratios to Earth's surface and leave others behind as residues in Earth's mantle. Of all the potential geochemical tracers examined to date, Hafnium (Hf) and Neodymium (Nd) appear to be the most powerful in helping us understand not only the chemical evolution of the mantle but also the ages and process of melt segregation and mid-ocean ridge volcanism. This research will use samples of abyssal peridotite from various mid-ocean ridges, emphasizing samples from the recently discovered ultra-slow spreading Gakkel Ridge in the Arctic, where mantle rocks outcrop on the seafloor. It will focus on determining the fraction of the mantle source that melts to form the vast majority of volcanic rocks erupted on the seafloor. To make this determination, trace elements and Hf and Nd isotopes will be measured, with the Hf isotopes illuminating the melting process and Nd providing age constraints. This work complements, but does not overlap with, a geochemical study of Gakkel abyssal peridotites. Broader impacts of the work include student training in state-of-the art geochemical analytical techniques and engaging high school students and their teachers in the research. It will also involve the high school participants in the laboratory and its activities.