NSFGEO-NERC: An Investigation into the Possible Co-evolution of Si and O Isotopes in Igneous Rocks and Minerals From the Hadean to Present

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The first Eon of Earth was named the "Hadean" because of the expectation that Earth would have remained hellish and inhospitable hundreds of millions of years after its formation about 4.56 billion years ago. These models may have persisted, if it were not for the discovery of very ancient crystals from this Eon. These crystals - or specifically the mineral zircon (ZrSiO4) - have ages that extend back to about 4.4 billion years in age, and thus represent a unique source of information about the earliest Earth. The major goal of this research is to 'translate' the chemical information preserved within these crystals into physical and potentially planetary-wide constraints that specifically bear on water-rock interactions occurring on Earth before 4 billion years ago. This was an intriguing time on Earth, because it is likely that the crust or its chemically weathered constituents played a role in the origin of life. The research proposed capitalizes on the knowledge that elements of O (oxygen) and Si (silicon) have multiple isotopes, and furthermore that the isotope ratios recorded in minerals, including zircon, may tell complementary stories of a larger puzzle about water-rock interactions that have occurred on our planet. The investigation will begin by conducting: (i) high precision Si- and O- isotope measurements on well constrained rock and mineral samples; and (ii) high pressure/temperature experiments in the precision-controlled environment of the University of Rochester experimental geochemistry laboratory. This information will be used to interpret the Si- and O- isotope geochemistry of ancient zircon crystals to explore crustal recycling in a new manner. The broader impacts of this project come from the training of undergraduate and graduate students in high temperature/pressure experimental techniques and crystal synthesis, and isotope analysis using state-of-the-art mass spectrometers. The Rochester laboratory plans to host high school science teachers from the surrounding area to introduce them to the technology and the science used in this study. These workshops expose science teachers to cutting edge science and technology and data that they can take back into their classrooms.