Metallic microspherules in carbonatites of the Southern Urals

The first data on findings of small magnetic microspherules in calcite and dolomite carbonatites of the Southern Urals (Ilmeny Mountains) are given. The composition of the microspherules is predominantly ferrous with a small admixture of manganese. Their diameter does not exceed 1 mm. Their form is spherical or slightly elongated, sometimes hollow inside. The surface of the microspherules is smooth shiny, rarely matte, sometimes trickle in the crust. The inner structure of the microspherules is shell-zonal, with voids in the center. They are characterized by the presence of dendritic and columnar crystals, their dense packing. These microstructures are similar to those of iron ingots. There are joints of microspherules of different diameter. The presence of an unusual association of elements for carbonatites in the iron matrix (Pt, Ni, Cu, Zn, Cl, Ca) was revealed by energy-dispersion spectrums from the inner surfaces of some hollow microspheres. The absence of the actual Ni-phases in the composition of the balls distinguishes them from similar formations of cosmic origin. Along with crystals of fluorapatite and fluorophlogopite, forsterite, garnet, pargasite, sadanagaite, ilmenite, rutile, diopside, which are equally rare in carbonatites, ferrous microspheres are scattered in the carbonate matrix of the rock, without detecting adherence to cracks or interlayers. As the microspherules of native iron in igneous rocks are crystallized at temperatures of about 1500 °С, their availability in carbonate rocks of the Ilmeny Mountains is another evidence of their igneous nature.