We present a comprehensive overview of the magnetic properties of the four known tektite fields and related fully melted impact glasses (Aouelloul, Belize, Darwin, Libyan desert and Wabar glasses, irghizites, and atacamaites), namely magnetic susceptibility and hysteresis properties as well as properties dependent on magnetic grain-size. Tektites appear to be characterized by pure Fe2+ paramagnetism, with ferromagnetic traces below 1 ppm. The different tektite fields yield mostly non-overlapping narrow susceptibility ranges. Belize and Darwin glasses share similar characteristics. On the other hand the other studied glasses have wider susceptibility ranges, with median close to paramagnetism (Fe2+ and Fe3+) but with a high-susceptibility population bearing variable amounts of magnetite. This signs a fundamental difference between tektites (plus Belize and Darwin glasses) and other studied glasses in terms of oxygen fugacity and heterogeneity during formation, thus bringing new light to the formation processes of these materials. It also appears that selecting the most magnetic glass samples allows to find impactor-rich material, opening new perspectives to identify the type of impactor responsible for the glass generation.
Bibliographical noteFunding Information:
We deeply acknowledge the curators of London and Paris Natural History Museums, C. Smith and B. Zanda, for allowing us to measure on site their tektite and glass collections, as well as D.D. Badyukov (Vernadsky Institute, Moscow, Russia) and the private collectors, A. Carion, J. Cornec, L. Labenne, N. Lehrman and M. Warner, who helped in completing our database through gifts and loans. N. Lehrman deserves a special acknowledgment for coining the term “tektoid”. Editor and reviewers, B. Marty, G. Giuli and T. Kohout, are thanked for timely and constructive assessment of the submitted manuscript. This work was partially performed according to the Russian Government Program of Competitive Growth of Kazan Federal University. We acknowledge the support of INSU/CNES Planetology Program on the atacamaite study.
© 2015 Elsevier B.V.
Copyright 2015 Elsevier B.V., All rights reserved.
- Impact glass
- Magnetic properties