Abstract:In this paper, geochemical characteristics of kimberlite, diabase and lamprophyre in three kimberlite belts in Mengyin area have been studied in terms of major, trace and rare earth elements. The lithology of kimberlite in Mengyin area is alkaline and rich in potassium. The contents of K2O, TiO2, P2O 5 are significantly higher than that of ordinary ultrabasic rocks. The contents of Ba, Th, Ta, Cr and Ni in trace elements are obviously high, and the contents of Sr, Y and Yb are relatively low compared with the original mantle. The total amount of rare earth elements is high, the light rare earth elements are enriched, and the heavy rare earth elements are depleted. There is no obvious negative Eu anomaly. It is indicated that the kimberlite magma of deep mantle origin has a low degree of differentiation and a relatively high degree of basicity. The magma mixes the deep eclogite with relatively shallow mantle peridotite, and there may be a mixture of lherzolite, eclogite, granitic and other xenolith xenoliths. Under the environment of high temperature and high pressure in the deep mantle, the kimberlite magma carries the deep diamond mineral xenoliths, invading and upwelling in the channel. When approaching the surface, the temperature and pressure drop suddenly, and the magmatic rock body implosively explodes in place. Finally, three kimberlite belts, such as Changma, Xiyu, and Poli are formed.
