Abstract:Based on chemical compositions of various types of kimberlites and their related mantlederived traps in Mengyin county in Shandong province, the relationship between the mixing degree of kimberlites and rock types has been studied. It is found that the degree of shellsource mixing increased gradually from peridotite, cataclastic peridotite, coarseporphyry kimberlite to finegrained kimberlite. The degree of shellderived mixing about coarse porphyry kimberlite is close to cataclysmic peridotite, which is the product of further cataclysmic peridotite fragmentation. The kimberlite underwent partial melting of mantle peridotite to form cataclastic peridotite and porphyritic kimberlite. According to the ReOs isotopic study about the marble and pyrite xenoliths in the kimberlite, the emplacement time of Mengyin kimberlite is 227.97Ma and 245.80Ma respectively, which belong to the Triassic and are consistent with the formation time of SuluDabei orogenic belt. Therefore, it is regarded that the emplacement of Mengyin kimberlite is related to the collision between the Yangtze Plate and the North China Plate. It also seems to hint at the initial stages of the destruction of the North China Craton. There are great differences between the transport mode, transport path and water transport of diamond in North China ice sheet glaciers. It is necessary to reunderstand the source and dispersion of diamond. The large amount of synthetic diamond distributed on the surface has misled the diamond prospecting work and should be paid more attention.
