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Title: Shock-transformation of whitlockite to merrillite and the implications for meteoritic phosphate

Abstract

Meteorites represent the only samples available for study on Earth of a number of planetary bodies. The minerals within meteorites therefore hold the key to addressing numerous questions about our solar system. Of particular interest is the Ca-phosphate mineral merrillite, the anhydrous end-member of the merrillite-whitlockite solid solution series. For example, the anhydrous nature of merrillite in Martian meteorites has been interpreted as evidence of water-limited late-stage Martian melts. However, recent research on apatite in the same meteorites suggests higher water content in melts. One complication of using meteorites rather than direct samples is the shock compression all meteorites have experienced, which can alter meteorite mineralogy. Here we show whitlockite transformation into merrillite by shock-compression levels relevant to meteorites, including Martian meteorites. The results open the possibility that at least part of meteoritic merrillite may have originally been H + -bearing whitlockite with implications for interpreting meteorites and the need for future sample return.

Authors:
 [1];  [2];  [1];  [1];  [3];  [4];  [1];  [5];  [5];  [6];  [7]
  1. Univ. of Nevada, Las Vegas, NV (United States). Dept. of Geoscience
  2. Univ. of Nevada, Las Vegas, NV (United States). Dept. of Geoscience, High Pressure Science and Engineering Center, Galilee Inst.; Southwest Jiaotong Univ., Chengdu (China). Key Lab. of Advanced Technologies of Materials
  3. Southwest Jiaotong Univ., Chengdu (China). Key Lab. of Advanced Technologies of Materials; The Peace Inst. of Multiscale Sciences, Chengdu (China)
  4. The Peace Inst. of Multiscale Sciences, Chengdu (China); Univ. of Science and Technology of China, Hefei (China). Dept. of Modern Mechanics
  5. Univ. of Chicago, IL (United States). GeoScienceEnviro Center for Advanced Radiation Sources
  6. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source
  7. Carnegie Inst. of Washington, Argonne, IL (United States). High Pressure Collaborative Access Team (HPCAT)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1379764
Grant/Contract Number:
AC02-05CH11231; NA0001982; FG02-94ER14466; FG02-99ER45775; AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 8; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; geochemistry; meteoritics; petrology

Citation Formats

Adcock, C. T., Tschauner, O., Hausrath, E. M., Udry, A., Luo, S. N., Cai, Y., Ren, M., Lanzirotti, A., Newville, M., Kunz, M., and Lin, C. Shock-transformation of whitlockite to merrillite and the implications for meteoritic phosphate. United States: N. p., 2017. Web. doi:10.1038/ncomms14667.
Adcock, C. T., Tschauner, O., Hausrath, E. M., Udry, A., Luo, S. N., Cai, Y., Ren, M., Lanzirotti, A., Newville, M., Kunz, M., & Lin, C. Shock-transformation of whitlockite to merrillite and the implications for meteoritic phosphate. United States. doi:10.1038/ncomms14667.
Adcock, C. T., Tschauner, O., Hausrath, E. M., Udry, A., Luo, S. N., Cai, Y., Ren, M., Lanzirotti, A., Newville, M., Kunz, M., and Lin, C. Mon . "Shock-transformation of whitlockite to merrillite and the implications for meteoritic phosphate". United States. doi:10.1038/ncomms14667. https://www.osti.gov/servlets/purl/1379764.
@article{osti_1379764,
title = {Shock-transformation of whitlockite to merrillite and the implications for meteoritic phosphate},
author = {Adcock, C. T. and Tschauner, O. and Hausrath, E. M. and Udry, A. and Luo, S. N. and Cai, Y. and Ren, M. and Lanzirotti, A. and Newville, M. and Kunz, M. and Lin, C.},
abstractNote = {Meteorites represent the only samples available for study on Earth of a number of planetary bodies. The minerals within meteorites therefore hold the key to addressing numerous questions about our solar system. Of particular interest is the Ca-phosphate mineral merrillite, the anhydrous end-member of the merrillite-whitlockite solid solution series. For example, the anhydrous nature of merrillite in Martian meteorites has been interpreted as evidence of water-limited late-stage Martian melts. However, recent research on apatite in the same meteorites suggests higher water content in melts. One complication of using meteorites rather than direct samples is the shock compression all meteorites have experienced, which can alter meteorite mineralogy. Here we show whitlockite transformation into merrillite by shock-compression levels relevant to meteorites, including Martian meteorites. The results open the possibility that at least part of meteoritic merrillite may have originally been H + -bearing whitlockite with implications for interpreting meteorites and the need for future sample return.},
doi = {10.1038/ncomms14667},
journal = {Nature Communications},
number = ,
volume = 8,
place = {United States},
year = {Mon Mar 06 00:00:00 EST 2017},
month = {Mon Mar 06 00:00:00 EST 2017}
}

Journal Article:
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  • Eu{sup 3+}-doped triple phosphate Ca{sub 8}MgR(PO{sub 4}){sub 7} (R = La, Gd, Y) was synthesized by the general high temperature solid-state reaction. This phosphor was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and emission spectra. XRD and FT-IR analysis indicated that Ca{sub 8}MgR(PO{sub 4}){sub 7} (R = La, Gd, Y) crystallized in single-phase component with whitlockite-like structure (space group R3c) of {beta}-Ca{sub 3}(PO{sub 4}){sub 2}. Under the excitation of UV light, the phosphors show bright red emission assigned to the transition ({sup 5}D{sub 0} {yields} {sup 7}F{sub 2}) at 612 nm. The crystallographic sites of Eu{sup 3+}more » ions in Ca{sub 8}MgR(PO{sub 4}){sub 7} (R = La, Gd, Y) host were discussed on the base of site-selective excitation and emission spectra, luminescence decay and its host crystal structure.« less
  • The crystal structure of a new calcium thorium phosphate has been refined by the full-profile Rietveld method using X-ray powder diffraction data. The sample has been synthesized by the sol-gel technique. The phosphate has been identified by X-ray powder diffraction and IR spectroscopy. The refined composition is represented by the formula Ca{sub 10.26}Th{sub 0.12}(PO{sub 4}){sub 7}. The CaO{sub n} and PO{sub 4} polyhedra are distorted compared to the corresponding polyhedra in the basic compound {beta}-Ca{sub 3}(PO{sub 4}){sub 2}.
  • The relative proportion of divalent and trivalent Eu has proven to be a useful tool for estimating f{sub O{sub 2}} in various magmatic systems. However, in most cases, direct determination of the Eu valence state has not been made. In this study, direct determination of Eu valence by XANES and REE abundance in merrillite provide insights into the crystal chemistry of these phosphates and their ability to record conditions of magmatism. Merrillite strongly prefers Eu{sup 3+} to Eu{sup 2+}, with the average valence state of Eu ranging between 2.9 and 3 over approximately six orders of magnitude in f{sub O{submore » 2}}. The dramatic shift in the REE patterns of merrillite in martian basaltic magmas, from highly LREE-depleted to LREE-enriched, parallels many other trace element and isotopic variations and reflects the sources for these magmas. The behavior of REE in the merrillite directly reflects the relationship between the eightfold-coordinated Ca1 site and adjacent sixfold Na and tetrahedral P sites that enables charge balancing through coupled substitutions.« less