Geological Sciences Seminar: Annie Bauer, Yale University - "Formation of early terrestrial crust in the Acasta Gneiss Complex."

Sponsored by Department of Geological Science


Tuesday, May 21, 2019
12:00 pm – 1:00 pm
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GeoCorner 220 - 450 Serra Mall, Building 320

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This event is open to:
Faculty/Staff, Students, Alumni/Friends

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Event Details:

Please join us for coffee and cookies in the GeoCorner Undergraduate lounge (bldg. 320, rm 114) before the talk, at 11:30am! - Seminar will be in room 220~

The Acasta Gneiss Complex (AGC) is a unique exposure of 4.0 to 2.9 billion-year-old (Ga) meta-igneous rocks in the Northwest Territories, Canada. The AGC represents the oldest known silicic and zircon-bearing terrestrial crust and thus can provide critical insight on the tectonic processes operating on the early Earth. The primary objective of my work is to track crust-forming processes in the AGC for over a billion years of its history using radiogenic isotopes (U-Pb, 176Lu-176Hf, 147Sm-143Nd). I will share three major conclusions from my Hf isotope investigation: 1) precursor Hadean crust (>4.0 Ga) is an important source to the 4.0-3.6 Ga magmas; 2) there was rejuvenation of the magmatic source at ~3.6 Ga, for which I will offer possible tectonic models; and 3) there is an absence of highly depleted mantle in the generation of these rocks. I will discuss these results in light of previous work proposing evidence for contributions from extensively depleted mantle to the AGC and further address this disparity through a careful reevaluation of its highly-contested Nd isotopic record.

Annie Bauer’s research focuses on crustal evolution, atmospheric oxygenation and the development of radiogenic and stable isotope methods to study these processes. She is currently a Simons Foundation Postdoctoral Fellow at Yale University.