NA-RICH CARBONATE INCLUSIONS IN PEROVSKITE AND CALZIRTITE FROM THE GULI INTRUSIVE CA-CARBONATITE, POLAR SIBERIA

Abstract

Carbonate phases, some rich in Na2O and comparatively rich in SrO and BaO, occur as inclusions in perovskite and calzirtite (Ca2Zr5Ti2O16) in the carbonatite of the Guli complex, Siberia. This is the first record of alkali carbonates, akin to nyerereite [Na2Ca(CO3)2], in plutonic igneous rocks. The inclusion populations suggest that the parental magma of the complex was Ca-rich but developed Na-rich differentiates during the latest stages. This points to the dominant calcic carbonatites of the complex not being derivatives of alkali-rich parental carbonatites. These alkali-rich carbonate inclusions (and rare inclusions of djerfisherite) have been preserved due to the resistance of perovskite and calzirtite to processes of leaching, hydrothermal alteration and weathering.