Plagioclase feldspars (Ca_1-<i>x</i>Na_<i>x</i>)(Al_2-<i>x</i>Si_2+<i>x</i>)O₈: synthesis and characterizations of mechanical weathering relevant to Martian regolith

Abstract Plagioclase feldspars draw intensive research attention in planetary sciences because of their abundance in the Martian regolith. Crystal chemical studies on plagioclase feldspars would be of crucial importance for possible in situ resource utilization for future human settlement on Mars. This study focuses on the synthesis of representative plagioclase feldspars followed by simulation of mechanical weathering using ball milling. A series of (Ca 1- x Na x )(Al 2- x Si 2+ x )O 8 plagioclase feldspars is synthesized perfoming the solid-state method, where the endmembers are the anorthite (CaAl 2 Si 2 O 8 ) and albite (NaAlSi 3 O 8 ). The bulk chemical composition, particularly the Al/Si ratio, of each member is determined from energy-dispersive X-ray spectroscopy, which is supported by X-ray powder diffraction data Rietveld refinements. Selective plagioclase members ( x = 0.0, 0.4 and 1.0) are mechanically weathered using high-energy ball milling, leading to significant changes of microstructural features such as average crystallite size and micro-strain. Total scattering data are collected using in-house X-ray facilities and analyzed by pair distribution function refinements. The vibrational modes of the samples are evaluated by Raman spectroscopy, complementing the local structural description.