GEOQUÍMICA DE ISÓTOPOS DE CARBONO E OXIGÊNIO DOS CARBONATITOS DO COMPLEXO ALCALINO DE MATO PRETO, PARANÁ, BRASIL

Abstract

CARBON AND OXYGEN STABLE ISOTOPE GEOCHEMISTRY OF THE CARBONATITES FROM THE MATO PRETO ALKALINE COMPLEX, PARANA, BRAZIL. It is presented and discussed the C and O stable isotopes analyses of the carbonatites of the Mato Preto Alkaline Complex, Paraná, Brazil. There are two carbonatites generation in the complex. The main one is dominantiy calcitic and presents C and O isotopic values ranging besteen-3%o-0.0%o and + 11.0%o-+ 16.0%o, respectively. The samples show a linear trend when plotted in a δ O 18 SMOW versus 8 C PDB diagram, which may represent a Rayleigh distillation process. The older carbonatitic generation is mainly dolomitic and shows lower C and 0 isotopes values than the calcitic one. Some samples that were analyzed along the borehole DB47 show inexpressive variations of the isotopic values. The spatial distribution of the isotope data over the complex suggests that the carbonatites were isotopicaly contaminated by the host rocks.