1Hyun Na Kim,2Changkun Park,2Sun Young Park,2Hwayoung Kim,1Min Sik Kim
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE005998]
1Department of Earth and Environmental SciencesKongju National University, Gongju, Republic of Korea
2Division of Polar Earth‐System Sciences, Korea Polar Research Institute, Incheon, Republic of Korea
Published by arrangement with John Wiley & Sons
Determining the formation mechanism of maskelynite is essential to understanding the shocked environments of meteorites on their parent bodies. Maskelynite has been accepted as a diaplectic glass for several decades, but there have been suggestions that it is a normal glass quenched from a dense melt. Morphological characteristics have been generally investigated to identify the formation mechanism of amorphous plagioclase in meteorites, but the chemical difference between crystalline and amorphous plagioclase has not been fully understood. In this study, we investigated the morphological, atomic‐scale structural, and chemical characteristics of amorphous plagioclase in the lunar meteorite DEW 12007 to constrain its formation mechanism via chemical analysis. The morphological characteristics showed that plagioclase was partially converted into amorphous phase through partial melting. Two‐dimensional Raman mapping confirmed the structural difference between amorphous and crystalline regions. Quantitative chemical analyses revealed that the amorphous regions were more albite‐rich than the crystalline regions, likely due to the partial melting of plagioclase. Under shocked conditions, the partial melting of plagioclase induced a chemical variation between amorphous and crystalline regions. The morphological and structural changes correspond well with the chemical variations, indicating that amorphization induced such variations. The chemical differences between amorphous and crystalline plagioclase in other meteorites also could be understood to be the results of partial melting. Thus, the chemical differences between amorphous and crystalline plagioclase in partially amorphized grains could elucidate the formation mechanism of amorphous plagioclase in many meteorites.