Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session O04: Shock Compression of Geophysical Materials IFocus Recordings Available
|
Hide Abstracts |
Chair: Paul Asimow, Caltech Room: Anaheim Marriott Platinum 2 |
Wednesday, July 13, 2022 9:15AM - 9:30AM |
O04.00001: Shock and shock-ramp compression of iron-rich (Mg,Fe)O at Earth's core conditions Hannah Bausch, Joshua P Townsend, Steven D Jacobsen, Alisha N Clark, Sakun Duwal, Chad A McCoy, Jean-Paul Davis Where Earth’s iron core and silicate mantle meet is a region of the Earth’s interior that is still poorly understood. Seismological results suggest the presence of ultra-low velocity zones (ULVZ’s) sitting directly atop the core. One possible explanation for these features is that they are regions of highly iron-enriched ferropericlase (Mg,Fe)O (Wicks et al. 2010), however the thermodynamic properties at near-core conditions are poorly constrained. Here we present the results of combined ab-initio calculations and shock measurements of (Mg,Fe)O containing 25 and 50 mol% Fe. The results are being used to design shock-ramp experiments on the Z machine at Sandia National Laboratories. |
Wednesday, July 13, 2022 9:30AM - 9:45AM |
O04.00002: X-ray diffuse scattering of Fe-C alloys shock compressed to 3 Mbar Chris McGuire, Travis Volz, Saransh Singh, Richard Briggs, Cara Vennari, Francesca Miozzi, Sally J Tracy, Trevor M Hutchinson, Samantha M Clarke, Andrew Krygier, Jon H Eggert The density of Earth’s outer core is 8-10% lower than that of liquid iron at the relevant pressure and temperature conditions (137 - 330 GPa, 4500 - 6500 K). Candidate light alloying elements – Si, O, S, C and H – are expected to be dissolved in liquid iron to account for the discrepancy, but the proportions present in the core remain unknown. High quality measurements of the density of liquid iron alloys at multi-megabar (1 Mbar = 100 GPa) pressures are virtually non-existent due to experimental challenges at these pressures in the diamond anvil cell. We have recently made XRD measurements along the Hugoniot of Fe3C (25 at% C) and Fe-10at%C alloy by laser shock compression at the C-Hutch at the Dynamic Compression Sector (DCS) at APS, Argonne National Lab. Fe-10at%C samples were synthesized by physical vapor deposition directly onto LiF windows. We determine the density of Fe-10at%C liquids directly from the liquid structure factor. These novel equation of state measurements will be discussed in the context of the carbon content of Earth’s liquid outer core. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. |
Wednesday, July 13, 2022 9:45AM - 10:15AM |
O04.00003: Experimental temperature measurements of Fe-bearing silicate minerals and glasses to 1.6 TPa Invited Speaker: Bethany Chidester The Earth and other terrestrial planets experienced one to several giant impacts during accretion and growth. Dynamic simulations of planetary impacts rely on equations of state that define the properties of materials under extreme pressure and temperature conditions. Recent experiments on forsterite, the Mg-endmember of the olivine mineral series, have shown that traditional analytical equation of state models have largely over-estimated the shock temperatures of this material, requiring a reformulation of the heat capacity to match the data. The correction to the equations of state should be material dependent, and is likely different in Fe-bearing compositions. Here, we present experimental shock temperature measurements from the Sandia Z Machine and OMEGA EP facilities on the most abundant minerals in Earth’s upper mantle, olivine ((Mg,Fe)2SiO4) and enstatite/bronzite ((Mg,Fe)SiO3) to over 1 TPa in pressure. We find that Fe-bearing compositions shock to slightly higher temperatures than the end-member species. We also present shock compression and temperature measurements on a bulk silicate Earth (pyrolite) glass composition, analogous to a magma ocean. At low pressures (200-600 GPa), pyrolite is more compressible and shocks to higher temperatures than olivine or enstatite, but not quartz. However, at higher pressures (>600 GPa), pyrolite behaves very similarly to the crystalline silicates. Our experimental data are then combined to create a general analytical equation of state for silicates for use in planetary impact models. |
Wednesday, July 13, 2022 10:15AM - 10:30AM |
O04.00004: Formation conditions of Impact-induced Natural Glasses Toshimori Sekine Tektites and impact glasses are known as products by hypervelocity impacts onto the Earth surfaces. Their formation conditions, however, have been long debated, although the field geological works, mineralogical and geochemical data, and numerical simulations for hypervelocity impact and cratering have been accumulated so far. The difficulty to recover the post-shock samples in such extreme shock experiments suffers from direct evidences to unravel. The silicate glass structures and properties as the quenched melts may have been subjected to post-shock annealing during the release process and entry to the atmosphere and may not help to reveal the formation conditions due to such residual effects. The redox states of Fe were compared in the previous reports to understand the formation conditions of natural impact-induced glasses. We pay attention that x-ray absorption spectroscopy results on Ti K edge feature and found the presence of Ti3+ in glasses as a characteristic feature clearly to suggest a difference in the redox state at the time of hypervelocity impact, depended on the impact scale. The feature is closely related to high temperatures and found to be useful to characterize the formation conditions. |
Wednesday, July 13, 2022 10:30AM - 10:45AM |
O04.00005: Recovery of forsterite high-pressure polymorphs in gas gun shock-wave experiments Wade Mans, Josh Townsend, Kyle R Cochrane, Marcus Knudson Hypervelocity impact experiments using a 30 mm, 2-stage light gas gun were performed to study the formation, rapid quench, and physical recovery of the olivine high-pressure(P) polymorphs wadsleyite and ringwoodite. A series of 3 tantalum impact experiments were performed over a range from 1.5 to 3 km/s to study the effects of increasing P and temperature(T) conditions on the formation and crystallization of these high-P phases. ALEGRA shock physics hydrocode was used to model shock wave propagation, P, T, and material conditions due to the impact. We utilize and expand upon both the steel recovery assembly and experimental processes detailed in Tschauner et al. (2009). These experiments are part of a larger campaign to expand the studied compositions from the pure Mg end member olivine forsterite to more Fe-enriched fayalitic compositions that are representative of what is observed and recovered in shocked meteorites. The main goal of this extended study is to constrain the incoherent olivine high-pressure phase formation mechanisms to better describe the shock history within meteorites. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700