Home – Home – Jornals – Russian Geology and Geophysics 2001 number 9

EPR spectrscopy was used to study specific features of distribution of paramagnetic admixtures in endogenous carbonates formed in the zones of contact of trap complex with deposits of the Siberian Platform cover. It was established that the main paramagnetic centers in the studied samples are: a) ions Mn²⁺, isomorphously replacing Ca²⁺ and Mg²⁺, b) ions Fe³⁺, forming oxide or hydroxide clusters 100-1000 and more in size, and c) radiation centers, originated from natural ionizing radiation. Using indicator features of spectra, it was established that carbonates from magnesian-skarn associations are a solid solution of calcite with dolomite and ankerite. Compared with carbonatites, calcites from the contacts with traps have a lower Fe content and low concentrations of Fe³⁺ clusters. Radiation centers were detected in Fe-free calcites accompanying apatite. The number of paramagnetic ions Mn²⁺ decreases in low-temperature generations of calcite. All genetic groups have a tendency to replacement of structurally inhomogeneous high-temperature solid solutions of carbonates by stoichiometric calcites, dolomites, ankerites, and siderites.