A Prominent Iron Silicides Strewn Field and Its Relation to the Bronze Age/Iron Age Chiemgau Meteorite Impact Event (Germany)

Abstract

About 20 years ago, amateur archeologists and local history researchers discovered the iron silicide (FESI) strewn field measuring about 60 km x 30 km in the districts of the Chiemgau and the Inn-Salzach region in southeast Germany. They evidenced the connection between the FESi distribution and the pervasive rim wall craters and suggested a meteorite impact event, now widely recognized under the name of the Chiemgau impact. Widespread in the strewn field and in individual finds far beyond it they recovered and documented thousands of FESI particles of millimeter to centimeter size with a total mass of more than 2 kg, whereby a large lump of 8 kg stands out as a single find. The find layer is largely uniformly located at a depth of 30 - 40 cm in a glacial loose sediment soil. Microprobe, SEM-EDS, TEM and EBSD analyses determined as main minerals gupeiite and xifengite, subordinately hapkeite, naquite and linzhite. Besides the main elements Fe and Si of the matrix, more than 30 other chemical elements have been addressed so far, including uranium and various REE. Incorporated into the FESI matrix are the carbide minerals moissanite and titanium carbide as superpure crystals, and khamrabaevite, zirconium carbide, and uranium carbide, furthermore CAIs. SEM images indicate shock metamorphism. The present article describes the discovery history of this worldwide unique FESI occurrence with the exact find situations, as well as the very varied morphologies of the find particles with the macroscopically recognizable components and SEM EDS examples.