UCSB Associate Professor of Earth Science John Cottle and three graduate students have made their way to the icy Antarctic frontier in hopes of finding more information about the effects of subduction on the deepest portions of the Earth’s crust, and what causes the phenomenon to ultimately stop. Subduction results from tectonic movement along plate boundaries, where sideways and downward movement of the plates causes one to slip below the other; it is the primary cause of earthquakes around the world.
The six-week mission, which began last week, studies the age and composition of igneous rocks, or lava-formed rocks, at the end of their subduction cycle. What make Antarctica an ideal field for this research are the Transantarctic Mountains: home to an ancient subduction zone. The researchers will camp at various locations to gather samples of lamprophyres. Lamprophyres, or igneous rocks at the end of the subduction cycle, are characteristically rich in potassium and therefore provide the most exact insight into the processes behind continental crust sinking into the mantle.
“These enigmatic rocks are important because they represent near-primary mantle melt compositions and therefore their age, geochemistry, and petrologic evolution reveal key information about both the composition of the upper mantle and its thermal state,” Cottle said in an interview with the UCSB Current. “Of equal importance, they reveal how these key parameters vary through both space and time.” The team will bring the collected samples back to a lab to analyze their ages, temperatures at which they formed, and their compositions in hopes of understanding what factors impact changes along the subduction zone.