Poirierite, a dense metastable polymorph of magnesium iron silicate in shocked meteorites

Abstract A dense magnesium iron silicate polymorph with a structure intermediate between olivine, ringwoodite, and wadsleyite was theoretically predicted about four decades ago. As this group of minerals constitute the major component shocked meteorites, constraining their transitional forms behaviour is potential importance for understanding impact events on parent bodies. Here we use high-resolution transmission electron microscopy techniques single-crystal X-ray diffraction analyses to identify naturally occurring examples mineral – recently named poirierite in chondritic meteorites. We observe nanoscale lamellar topotactically intergrown within wadsleyite, additionally ringwoodite as reported. Our results confirm suggest it might be relay point shear transformations its polymorphs. propose that formed during rapid decompression at relatively low temperature retrograde shock metamorphism