Hitherto unknown rare orbicular carbonatites and associated nodular structures occur in the southeastern parts of the Cretaceous Sung valley ultramafic-alkaline-carbonatite complex (SUACC), Shillong plateau, Meghalaya, northeast India. The orbicular structures are formed around fragmented pyroxenite xenoliths and uralitized sodium-richterite nodular patches during emplacement of a calcium-carbonatite plug. The orbicular structures surrounding the xenoliths were formed in at least three stages of chemical disequilibrium represented by three distinct sectors. They are: (i) an innermost shell of sodium-richterite developed around the core of xenoliths. These shells are associated with radial forsterite and/or fine to medium grained granular forsterites. The xenoliths are partially and at times completely metasomatized, due to the metasomatic interaction of the xenolith and the carbonatite melt (antiskarn); (ii) an intermediate zone resembling a “zebra” striped pattern comprising of alternating white calcite-rich and black forsterite-rich bands. These are formed through recrystallization of contaminated carbonatite melt after complex partial resorbtion and assimilation of the pyroxenite xenolith rims; and (iii) an outermost relatively thicker carbonate rich olivine layer formed by late phase intrusion of an ultramafic melt. This is followed by the development of sodium-richterite porphyroblastic grains representing post crystallization sodium metasomatism. Further, proto-orbicules in carbonatite with associated nodular minerals are present adjacent to the orbicular carbonatite suggesting local instability during intrusion at the contact of the pyroxenite xenolith with the calcium-carbonatite host. Apart from reporting the first occurrence of the orbicular carbonatites from the SUACC, petrogenetic implications involving antiskarn due to metasomatic processes induced by carbonatite magmatism is also presented.