Calcioburbankite (Na, Ca)3(Ca, REE,Sr)3(CO3)5, recently approved as a new mineral speciesdiscovered in Saint-HIlaire alkaline complex (Quebec,Canada) is the widespread typomorphic mineral of thelate hydrothermal dolomite-calcite carbonatites inVuoriyarvi alkaline-ultramafic massif (NorthernKarelia). It associates there with burbankite,baritocalcite, norsethite, Ce-ewaldite, vaterite,strontianite, olekminskite, ancylite-(Ce), Ba-Sr-pyrochlo-re, franconite, chalcopyrite and pyrrhotite.Relatively to burbankite and other Ba-Sr-REE-carbonates, calcioburbankite is the earliest one and,by prevalence, the main primary mineral-concentratorof REE. But it is unstable and thus, substituted by anaggregate of secondary carbonates and barite.Calcioburbankite and burbankite are quite similar bymorphology of their segregations, macroscopic, opticaland roentgenometric propertjes. Only IR spectra ofthese minerals reveal their tiny structuraldistinctions. The paper displays a comparativecharacteristic of chemical composition for theburbankite group minerals from carbonatites andhydrothermal veins in alkaline rocks. Directivity ofthe composition evolution is sharply dissimilar inthese different types of rocks, i. e. minerals of thisgroup may be regarded as indicators of geochemicalconditions and a specificity of hydrothermal processwithin carbonatites and alkaline rocks.
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