A high-pressure, clinopyroxene-structured polymorph of albite in highly shocked terrestrial and meteoritic rocks

1Chi Ma,2Oliver Tschauner,3Mihye Kong,1John R. Beckett,4Eran Greenberg,4Vitali B. Prakapenka,3Yongjae Lee
American Mineralogist 107, 625-630 Link to Article [http://www.minsocam.org/msa/ammin/toc/2022/Abstracts/AM107P0625.pdf]
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.
2Department of Geoscience, University of Nevada, Las Vegas, Nevada 89154, U.S.A.
3Department of Earth System Sciences, Yonsei University, Seoul 03722, Republic of Korea
4GSECARS, University of Chicago, Argonne National Laboratory, Chicago, Illinois 60637, U.S.A
Copyright: The mineralogical Society of America

Clinopyroxenes with excess Si have been described in run products from high-pressure experi –
ments and inferred to have existed in nature from retrograde transformation phases. Here, we present
the discovery of albitic jadeite, (Na,Ca,1/4)(Al,Si)Si2O6—the first natural, sodic clinopyroxene with
excess Si occupying the octahedral cation site, M1, and a corresponding ¼ vacancy on the M2-site
in the Ries impact structure and in a suite of L6 ordinary chondrites, EET 13014, EET 13052, NWA
1662, and TIL 08001. Garnet compositions in these samples indicate shock pressures of 18–22 GPa.
Based on our survey, albitic jadeite is likely to be rather common in terrestrial and meteoritic shock-
metamorphic environments. Shock-generated jadeite should be reexamined with respect to excess

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