Some metallic spherules in calcareous-marly sediments of the Romanoro Flysch, Sestola-Vidiciatico tectonic unit (Modena district, Northern Apennines, Italy)

Abstract

Some metallic microspherules were found in a calcareous-marly sample from the Romanoro Flysch (Modena district, Northern Apennines, Italy). The outcrop is a tectonic scale, part of the Sestola-Vidiciatico Unit, without stratigraphic contacts with other formations. The age of the setting stratum was attributed at the middle Miocene, but this datum contradicts the previous authors, who dated the outcrop at the Eocene (Zanotti, 1988), or Cretaceous (Reutter, 1969; Rentz, 1971; Daniele et al. 1996). Morphological, mineralogical and chemical studies were carried out on the microspherules and on some grains. The crust of microspherules is essentially made of iron (from 66% to 48%, like FeO), with other minor elements (Al, Ti, Mn, Ni). The core is made of an FeNi alloy. There are other grains of: quartz, calcite, pyrite, mica and black minerals, with edges. The black ones are polymetallic aggregates of: Fe, Mn, Ti, Al, Cu. About the origin of these microspherules four hypotheses: cosmic origin (exceptional extraterrestrial event), volcanic origin, diagenetic origin, wartime origin (Extrema Ratio). The first one has been confirmed.