The carbon and oxygen isotope study of the youngest and oldest carbonatites of the world

Abstract

C and O isotopic composition of carbonatites ranges of d13C -5.89 to -6.94%o, -5.53 to -6.08%o and 9.51 to 10.9%o, 9.46 to 10.4%o for d18O respectively. The d13C data in this study for OL lavas and Siilinjarvi carbonates coincide with previous studies. The d18O data fall on the heavier side of the primary igneous carbonatites range in contrast to the data of OL 1988 eruption. This enrichment can be explained on the basis of liquid immiscibility between coexisting carbonatites and silicate melts. The carbonates are generally heavier in 18O than the typical mantle minerals therefore such enrichment in d18O is in agreement with the mantle geochemistry.