Discussion of ‘Rare metals on shatter cone surfaces from the Steinheim Basin (SW Germany) – remnants of the impacting body?’

• Published in: Geological magazine 2019-09, Vol.156 (9), p.1639-1640
• Main Authors: El Goresy, Ahmed, Schmidt, Gerhard
• Format: Article
• Language: English
• Subjects: Affinity; Copper; Crystal structure; Crystallinity; Discussion; Heavy metals; Hydrothermal activity; Iron meteorites; Isotopes; Jurassic; Manganese; Metals; Meteors & meteorites; Microparticles; Nickel; Ratios; Sedimentary rocks; Shatter cones; Silt; Stone; Surface water
• ISSN: 0016-7568; 1469-5081
• DOI: 10.1017/S001675681800064X

In Section 1 the authors stated, ‘Similarly, microparticles of meteoritic affinity were recently detected on shatter cones from the structural crater floors of the Ries crater in Germany (Buchner & Schmieder, 2016) …’ Since this reference is only an abstract without any supporting evidence for the claims, it is difficult to understand why the authors concluded that the nature of such particles could relate a meteoritic affinity. Nickel and Co contents of ultramafic and mafic rocks from the crystalline basement are high, up to 1300 µg/g and 113 µg/g, respectively, and Ni/Co ratios vary between 2.2 and 11.6 (Matthes, Richter & Stettner, 1977), in the range of the ratio for the oxide flake. [...]it does not seem appropriate to discuss an iron meteorite as the possible source for the Ni/Co ratios without discussing the Ni/Co ratios of the crystalline basement. See PDF] In our opinion, two processes are likely responsible for the generation of these coatings on shatter cones that are characterized by elevated concentrations of Fe, Ni, Co, Mn and Cu: (1) weathering from interaction with surface water, and (2) mobilization of elements by water–rock interaction (post-impact hydrothermal activity) involving Middle Jurassic sedimentary rocks (silt- and claystone) and/or the Variscan crystalline basement.