Mineralogy of garnets from the Jubileinaya kimberlite pipe and Ottorzhenets kimberlite body

Abstract

The article presents results of a study of the chemical composition of garnet xenocrystals from a concentrate of the heavy fraction of kimberlites from the Yubileinaya pipe and Ottorzhenets kimberlite body. Samples from porphyry kimberlites and autolithic kimberlite breccias were taken for analysis from the Yubileinaya pipe. Significant differences are noted in the studied samples of peridotite garnets from the Yubileinaya kimberlite pipe and the Ottorzhenets body. Compared to the Yubileinaya pipe, the Ottorzhenets body exhibits a decreased amount of garnets of the harzburgite-dunite paragenesis in the composition range of Cr2O3 > 8.5 wt. % and CaO < 3 wt. %. On this basis, we assume that the Ottorzhenets body is not a displaced fragment of the Yubileinaya pipe, but belongs to a new unknown kimberlite body. We also assume that the diamond-bearing potential of the primary Ottorzhenets body is reduced compared to the Yubileinaya pipe, which is consistent with the information on the diamond content, according to the data of ALROSA (PJSC).

Keywords

• kimberlite pipe
• diamond-associated indicator minerals
• garnet