Carbon-containing fluid inclusions in olivine and garnet from the kimberlites of the Udachnaia pipe

The physical and chemical characteristics of garnet and of three types of olivine crystals isolated from a kimberlite concentrate obtained from the Udachnaia pipe were investigated, together with the chemical compositions of fluid inclusions in these crystals, using a specially designed vacuum apparatus for the dissection of inclusions. Olivine inclusions were found to contain significant amounts of nitrogen and hydrocarbon compounds with two or more carbons. Results of isotope-composition analyses indicated that some fractions from olivine inclusions were significantly enriched in C-13 (up to 22 percent), relative to the average C-13 content (6.5 percent). It is suggested that the source of olivine inclusions might be mantle fluids containing methane and other reduced carbon compounds.