Magnetic Properties of Tektite-like Impact Glasses from Zhamanshin Astrobleme, Kazakhstan

Vyacheslav A. Starunov, Andrei Kosterov, Elena S. Sergienko, Svetlana Yu. Yanson, Gennady P. Markov, Petr V. Kharitonskii, Aleksandr S. Sakhatskii, Irina E. Lezova, Evgenii V. Shevchenko

Research outputpeer-review

Abstract

We measured the low-field magnetic susceptibility and natural remanent magnetization (NRM) for an extensive collection of irghizites, tektite-like impact glasses from the Zhamanshin meteorite crater, Kazakhstan. For a small subset of samples, more detailed magnetic measurements, scanning electron microscopy and microprobe analysis have been carried out. In agreement with a previous study (Rochette et al. 2015), ~95% of samples showed relatively low magnetic susceptibility ranging from 45 to 300 × 10−9 m3/kg. Combining susceptibility and NRM data, we are able to classify irghizites into “normal” (susceptibility <300 × 10−9 m3/kg, NRM < 4 × 10−6 A m2/kg) and “anomalous” groups. Detailed rock magnetic experiments and microscopic observation confirm this dichotomy. Normal irghizites contain very little ferrimagnetic material which, in addition, is predominantly in superparamagnetic state, implying an extremely small, on the order of a few nm, grain size. In contrast, anomalous samples exhibit magnetic properties consistent with much larger, µm to 10s of µm, ferrimagnetic grains, which were observed microscopically as well. We propose that this difference between two groups of samples is related to the initial temperature of the impact melts from which they were formed. Normal irghizites likely originate from the spray of a strongly overheated melt with initial temperatures up to 2500–3000 °C, cooling extremely fast, while anomalous ones could have been formed from less hot and slower cooling melt.
Original languageEnglish
Title of host publicationRecent Advances in Rock Magnetism, Environmental Magnetism and Paleomagnetism
Subtitle of host publicationInternational Conference on Geomagnetism, Paleomagnetism and Rock Magnetism (Kazan, Russia). Conference proceedings
EditorsD. K. Nurgaliev, V. P. Shcherbakov, A. Kosterov, S. Spassov
Place of PublicationCham
PublisherSpringer Nature
Chapter30
Pages445-465
ISBN (Electronic)9783319904375
ISBN (Print)9783319904368
DOIs
Publication statusPublished - 2019

Publication series

NameSpringer Geophysics

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