Characteristics and tectonic significance of the formation source area of diamondiferouskimberlites in Mengyin area of Shandong Province

Kimberlite is the magma product with the deepest known source. It rises very fast and is less affected by the contamination of continental crust. It is an important window to study whether the deep mantle source region is disturbed.The whole rock geochemical characteristics show high Fe/Mn, high CaO/Al₂O₃, high (Dy/Yb) _N, and low Nb/Ta and low Nb/U,and neither the Nb/Ta value nor the Nb/U value showed a negative correlation with the SiO₂ content,indicating that the source area is enriched carbonated pyroxene mantle source area or eclogite source area;The discovery of coesite inclusions in diamond proves that the source region has contributions from continental or oceanic crustal materials;Combining the previous dating data, the formation time of the rock mass should be between 450Ma~484Ma, which just corresponds to the subduction time of the original Tethys Ocean (460Ma~520Ma).Based on these, the dynamic mechanism of kimberlite formation in Mengyin area is established.