Enigma of ferruginous inclusions in Permian evaporites

Abstract

© 2020, Saudi Society for Geosciences. We studied Fe-rich microspherules and microparticles found as inclusions within a gypsum host rock, sourced from the Kamsko-Ustyinskoe gypsum field (Republic of Tatarstan, Russia). Using both in situ and destructive microanalysis techniques (micro CT, XRF, SEM, EDS, and Raman spectroscopy), we examined a range of different possibilities of their origin and concluded that studied Upper Roadian microinclusions have an extraterrestrial genesis. This conclusion is based upon the similarity of microspherules both to the diagenetically altered I-type cosmic spherules and meteorite ablation spherules previously reported from modern and ancient sediments: spherical morphologies and sizes 10–150 μm, dendritic textures exhibiting cruciform or cellular arrangements, large sub-circular cavities representing the former position of weathered metal beads, irregular cavity networks, representing vesicles and vesicle networks of residual trapped volatile gases, and Fe-rich magnetite mineralogy. All microparticles and microspherules have experienced diagenetic alteration, connected with a total loss of Ni in the corrosion process and often recrystallization with Mn enrichment. Based on extraordinary concentration of extraterrestrial microspherules and quite similar to them in composition microparticles both mixed in the thin interlayer of studied sample, we hypothesized their meteor ablation origin.