Cao co-authors chapter in GSA Memoirs

Department of Geology and Environmental Sciences Assistant Professor Wentao Cao co-authored a book chapter in “Laurentia: Turning Points in the Evolution of a Continent,” that has been published in Geological Society of America Memoirs 220.

According to GSA book series website, “The memoir series presents thorough, well-illustrated treatments of topics – expected to be definitive works on a subject for a decade or more.”

In this newly published book chapter, “Local Rapid Exhumation during the Long-Lived Grenville Orogeny,” Dr. Cao and coauthors from University of Toronto and Chinese Academy of Sciences examined the specimens from the Algonquin terrane [geological term] in southern Ontario utilizing thermodynamic modeling and diffusion modeling, aiming to estimate the peak metamorphic conditions and duration of peak metamorphism.

The authors examined the retrogressed eclogite [aka Christmas rock] from Mattawa area and documented petrographic textures and mineral chemistry. Utilizing thermodynamic modeling and reintegrated mineral chemistry, the authors estimated the peak metamorphic conditions to be ~2 GPa and 850 C. Diffusion modeling of garnet from the sample yielded a duration of metamorphism from peak pressure to ~1.2 GPa to be <0.1 million years.

The study demonstrated a case of fast decompression of the high-pressure rock, interpreted to be due to local extrusion of orogenic lower crustal materials. Very few examples of Precambrian short-duration regional metamorphism exist, which renders this study as a new valuable addition for studying the modern plate tectonic regime.

The paper can be viewed online.