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An example of high-T, high-symmetry crystallization: Spherical (Mg, Fe)-oxides formed by particle attachment in the shocked martian meteorite Northwest Africa 7755 TEXT SIZE: A A A
Crystallization is one of the most fundamental processes for both solid inorganic and organic materials in nature. The classical crystallization model mainly involves the monomer-by-monomer addition of simple chemical species. Recently, nanoparticle attachment has been realized as an important mechanism of crystallization in comparatively low-temperature aqueous natural and synthetic systems. However, no evidence of crystallization by particle attachment has been reported in petrologically important melts. In this study, we described spherical (Mg, Fe)-oxides with a protrusion surface in a shock-induced melt pocket from the martian meteorite Northwest Africa 7755. Transmission electron microscopic observations demonstrate that the (Mg, Fe)-oxides are structure-coherent intergrowth of ferropericlase and magnesioferrite. The magnesioferrite is mainly present adjacent to the interface between (Mg, Fe)-oxides spherules and surrounding silicate glass, but not in direct contact with the silicate glass. Thermodynamic and kinetic considerations suggest that development of the spherical (Mg, Fe)-oxides can be best interpreted with crystallization by particle attachment and subsequent Ostwald ripening. This indicates that crystallization by particle attachment can also take place in high-temperature melts and has potential implications for understanding the nucleation and growth of early-stage crystals in high-temperature melts, such as chondrules in the solar nebula, erupted volcanic melts, and probably even intrusive magmas.
 

Publication name

 AMERICAN MINERALOGIST, 104 (1):150-157; 10.2138/am-2019-6597 JAN 2019

Author(s)

 Zhang, Ai-Cheng; Wang, Shu-Zhou; Tomioka, Naotaka; Lu, Xian-Cai; Ding, Zhi-Yuan; Ma, Chi; Wang, Peng; Chen, Jia-Ni; Xu, Sheng; Gu, Li-Xin; Bai, Yuan-Qiang; Li, Yang; Sakamoto, Naoyaya; Wang, Ru-Cheng

Corresponding author(s) 

 ZHANG Aicheng 
 aczhang@nju.edu.cn  
 Nanjing Univ, State Key Lab Mineral Deposits Res, Nanjing 210046, Jiangsu, Peoples R China
 Nanjing Univ, Sch Earth Sci & Engn, Nanjing 210046, Jiangsu, Peoples R China

Author(s) from IGCAS   LI Yang

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