¹Heng-Ci Tian,¹Wei Yang,¹Di Zhang,^1,3Huijuan Zhang,²Lihui Jia,²Shitou Wu,¹Yangting Lin,²Xianhua Li,²Fuyuan Wu
American Mineralogist 108, 1669-1677 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1669.pdf]
¹Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
³School of Earth Sciences, East China University of Technology, Nanchang 330013, Jiangxi, China
Copyright: The Mineralogical Society of America

This study focuses on using the chemical compositions of plagioclase to further investigate the
petrogenesis of Chang’E-5 young mare basalts and constrain its parental melt composition. Together
with previously published data, our results show that the plagioclase in mare basalts overall displays
large variations in major and trace element concentrations. Inversion of the plagioclase data indicates
that the melt compositions parental to Chang’E-5 basalts have high rare earth elements (REE) concentrations similar to the high-K KREEP rocks (potassium, rare earth elements, and phosphorus). Such a signature is unlikely to result from the assimilation of KREEP components, because the estimated
melt Sr shows positive correlations with other trace elements (e.g., Ba, La), which are far from the
KREEP end-member. Instead, the nearly parallel REE distributions and a high degree of trace element
enrichment in plagioclase indicate an extensive fractional crystallization process. Furthermore, the
estimated melt REE concentrations from plagioclase are slightly higher than those from clinopyroxene,
consistent with its relatively later crystallization. Using the Ti partition coefficient between plagioclase
and melt, we estimated the parental melt TiO2 content from the earliest crystallized plagioclase to be
~3.3 ± 0.4 wt%, thus providing robust evidence for a low-Ti and non-KREEP origin for the Chang’E-5
young basalts in the Procellarum KREEP terrane.

^1,2Xiaojing Lai,³Feng Zhu,²Dongzhou Zhang,⁴Sergey Tkachev,⁴Vitali B. Prakapenka,²Keng-Hsien Chao,²Bin Chen
American Mineralogist 108, 1530-1537 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1530.pdf]
¹Gemmological Institute, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, Hubei, 430074, China 
²Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawaii 96822, U.S.A. 
³School of Earth Sciences, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, Hubei, 430074, China 
⁴Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, U.S.A.
Copyright: The Mineralogical Society of America

Ice-VII is a high-pressure polymorph of H2O ice and an important mineral widely present in many
planetary environments, such as in the interiors of large icy planetary bodies, within some cold subducted
slabs, and in diamonds of deep origin as mineral inclusions. However, its stability at high pressures
and high temperatures and thermoelastic properties are still under debate. In this study, we synthesized
ice-VII single crystals in externally heated diamond-anvil cells and conducted single-crystal X-ray
diffraction experiments up to 78 GPa and 1000 K to revisit the high-pressure and high-temperature
phase stability and thermoelastic properties of ice-VII. No obvious unit-cell volume discontinuity or
strain anomaly of the high-pressure ice was observed up to the highest achieved pressures and temperatures. The volume-pressure-temperature data were fitted to a high-temperature Birch-Murnaghan
equation of state formalism, yielding bulk modulus KT0 = 21.0(4) GPa, its first pressure derivative KT′0
= 4.45(6), dK/dT = –0.009(4) GPa/K, and thermal expansion relation αT = 15(5) × 10–5 + 15(8) × 10–8
× (T – 300) K–1. The determined phase stability and thermoelastic properties of ice-VII can be used to
model the inner structure of icy cosmic bodies. Combined with the thermoelastic properties of diamonds,
we can reconstruct the isomeke P-T paths of ice-VII inclusions in diamond from depth, offering clues
on the water-rich regions in Earth’s deep mantle and the formation environments of those diamonds.