CONDITIONS OF FORMATION AND SOURCE OF CARBONATITES OF THE DUBRAVINSKOYE OCCURRENCE, AS INFERRED FROM DATA OF SULFUR, OXYGEN AND CARBON ISOTOPES

Abstract

To establish the origin of the Dubravinskoye carbonatites more accurately, we undertook to determine the isotopic characteristics of a number of widespread minerals, considering that the isotopic data on such rocks, now well worked up, are very informative in this respect. The information given by the sulfur-, carbon- and oxygen-isotope compositions of carbonatite minerals is not uniform. The data on sulfur, oxygen and carbon isotopes are consistent with the carbonatite classification of the rocks studied and indicate their mantle source. The same can be said of the temperature limits of carbonatite formation, according to which these rocks correspond to the early stages (temperature facies), and in our case, to the first to the third stages in the well-known scheme of formation of carbonatite bodies, and to geochemical data on trace elements of the Dubravinskoye occurrence. All this, in our view, allows these rocks to be confidently identified as carbonatites that apparently belong to the association of linear carbonatite bodies and are not associated with typical intrusive magmatic silicate derivatives