FINE TUNING OF HIGH PRESSURE IN TRANSMISSION ELECTRON MICROSCOPY FOR EARTH SCIENCES

In-situ, high-pressure and high-temperature studies of minerals at atomic resolution are now feasible using a high-pressure transmission electron microscopy (HPTEM) technique that we have recently developed. Use of carbon nanostructures, including carbon nano-onions (CNOs) and carbon nanotubes (CNTs), as both the containers and presses of encapsulated materials, can achieve sample pressures and temperatures up to 40 GPa and 1773 K, respectively, in an electron microscope. We have applied this technique to addressing carbon storage in mantle minerals that is applicable to deep carbon recycling. By investigating analogs to minerals occurring deep inside Earth, we show concentration and thus storage of carbon at crystallographic defects (stacking faults) under extreme conditions. Currently, we are exploring the effect of deviatoric stress to cation diffusion in iron-bearing ringwoodite, with the expectation that chemical segregation between iron and magnesium might occur at conditions similar to those in Earth’s transition zone. If true, this phenomenon may be linked to mechanisms of deep earthquakes. As we continue to develop and refine this emerging technique, HPTEM will find increasingly broad and innovative applications to high-pressure mineralogy, mineral physics, geochemistry, and geophysics as well as materials science.