OCGC Seminar - Crust formation on the early earth: Petrologic evidence from the Acasta Gneiss Complex, NWT, Canada


Dr. Jesse Reimink
Department of Terrestrial Magnetism,
Carnegie Institution for Science,
Washington, DC

10 a.m.
Wednesday, November 9

 233 Advanced Research Complex (ARC) 
25 Templeton Street
University of Ottawa  



Our knowledge of processes operating on the early Earth are limited by a paucity of samples preserved from this time period.  Various models exist that describe the growth of continental crust through time, with significant implications for the long-term geochemical evolution of the planet.  Here I present data from the Acasta Gneiss Complex, a multiply-metamorphosed gneiss terrain that hosts the oldest known evolved crust on Earth.  A combination of zircon geochronology and geochemistry paired with whole rock elemental compositions allows us to interrogate the processes that formed evolved crust on the early Earth, which may have been distinct from those that form the bulk of evolved crust on Earth now.  We document that the earliest evolved crust was similar to rocks formed on modern Iceland, a place that has long been thought to be analogous to ancient crust formation.