Diversity of Shock Compression Responses in Single Crystal Forsterite

Understanding a variety of geophysical phenomena, such as giant impact events and mantle stratification, relies on accurate determinations of mineralogical equations of state. This includes mapping phase boundaries and exploring rate-dependent transformation pathways. Forsterite (Mg₂SiO₄), the magnesium-rich endmember of the olivine Mg-Fe solid solution, has been a mainstay of both static and dynamic high pressure experiments due to its geophysical significance. We have performed a series of dynamic compression experiments on single crystal forsterite samples utilizing two-stage light gas guns to achieve pressures ranging from 86 to 211 GPa. To determine in-situ shock temperatures, we utilized both discrete wavelength multi-channel optical pyrometry and streaked spectral pyrometry. Rather than assuming greybody-like behavior, wavelength-dependent emissivity was incorporated into the temperature determination. Shock temperature data for forsterite below the liquidus and in a region of superheated solid metastability solid show complex wavelength dependent behavior that resolves after melting. Additionally, will discuss improvements to target design, temperature diagnostic setup and calibration, methods for in-situ emissivity determination, and data reduction to improve temperature measurements and reduce uncertainties.