Shock synthesis of quasicrystals with implications for their origin in asteroid collisions.
We designed a plate impact shock recovery experiment to simulate the starting materials and shock conditions associated with the only known natural quasicrystals, in the Khatyrka meteorite. At the boundaries among CuAl5, (Mg0.75Fe(2+) 0.25)2SiO4 olivine, and the stainless steel chamber walls, the recovered specimen contains numerous micron-scale grains of a quasicrystalline phase displaying face-centered icosahedral symmetry and low phason strain. The compositional range of the icosahedral phase is Al68-73Fe11-16Cu10-12Cr1-4Ni1-2 and extends toward higher Al/(Cu+Fe) and Fe/Cu ratios than those reported for natural icosahedrite or for any previously known synthetic quasicrystal in the Al-Cu-Fe system. The shock-induced synthesis demonstrated in this experiment reinforces the evidence that natural quasicrystals formed during a shock event but leaves open the question of whether this synthesis pathway is attributable to the expanded thermodynamic stability range of the quasicrystalline phase at high pressure, to a favorable kinetic pathway that exists under shock conditions, or to both thermodynamic and kinetic factors.
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125; asimow@gps.caltech.edu.
Paul D
0000-0001-6025-8925
PD
Asimow
Department of Physics, Princeton University, Princeton, NJ 08544;
Chaney
C
Lin
Dipartimento di Scienze della Terra, Università degli Studi di Firenze, I-50121 Firenze, Italy; Consiglio Nazionale delle Ricerche-Istituto di Geoscienze e Georisorse, Sezione di Firenze, I-50121 Firenze, Italy;
Luca
L
Bindi
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125;
Chi
C
Ma
Department of Geoscience, University of Nevada, Las Vegas, NV 89154; High Pressure Science and Engineering Center, University of Nevada, Las Vegas, NV 89154;
Oliver
O
Tschauner
Department of Geosciences, Princeton University, Princeton, NJ 08544;
Lincoln S
LS
Hollister
Department of Physics, Princeton University, Princeton, NJ 08544; Princeton Center for Theoretical Science, Princeton University, Princeton, NJ 08544.
Paul J
PJ
Steinhardt
alloys; icosahedrite; meteorites; quasicrystals; shock metamorphism