Study On Characteristics And Diamondiferous Significance Of The Mengyin Kimberlite In Shandong Province,China

Mengyin is the most important diamond metallogenic area in China,accumulated proven diamond resources 15.608 million carats,accounted for half of the country,s total diamond resources.This area is an important prospect for future diamond resources and potential minerals.At present,the domestic diamond production capacity is far from meeting the rapid development of the economy and society,study on the characteristics of kimberlite in Mengyin area and its relationship with mineralization,to guide the Mengyin area to find large,graded diamond primary mines,it is of great significance to alleviate the diamond resource crisis in China.The article analyzes the geology of the Changmazhuang,Xiyu and Poli rocks and analyzes the data of 612 samples,describe the geological characteristics of the Mengyin kimberlite belt,through the study on the type,mineral composition,chemical composition and indicator mineral characteristics of kimberlite in Mengyin area,analysis of the mineralization of kimberlite,propose the characteristics of rich kimberlite.Main results achieved:1.Summarizing the mineralization characteristics of the Mengyin kimberlite belt:The ore-bearing between the rock belts is gradually becoming poor due to Changma-Xiyu-Poli.The interior of Changmazhuang rock belt combines the rich of southern section and the poverty of north part,and also include the rich of middle section and the poverty of both ends;The eastern branch of the Xiyu rock belt in the north-north-eastward belt is slightly richer than the grade of the vein,the overall performance of the veins is characterized by the poverty of north part and the rich of southern section;the Xizhi and NW-trending belts of the north-north-eastward belt of the Xiyu rock belt are characterized by the rich of middle section and the poverty of both ends;Poli rock belt contains little diamond,no obvious change law.The diamond grade of each rock mass in Changmazhuang rock belt is becoming poor in the deep,the dimond of Xiyu rock belt becomes richer in the deep.The pulse width in the same vein is rich in diamond grade,and the narrow is poor in grade.2.Relationship between rock type and ore-bearing of kimberlite:The ore-bearing of different lithologies of Mengyin kimberlite varies greatly,The general rule is the ore-bearing properties of plaque kimberlite>the ore-bearing properties of fine-grained kimberlite>the ore-bearing properties of the Kimberley breccia;Structural structure also affects the ore-bearing properties of plaque kimberlite,the kimberlite of the same lithologic coarse-spot structure in the same rock mass is richer than the kimberlite in the fine-spot structure,the multi-porphyry kimberlite is richer than the phenocryst feldspar,less plaques than fine granules,Block-like structure richer than breccia.3.Relationship between mineral characteristics and ore-bearing properties of kimberlite:?1?Relationship between rock-forming minerals and ore-bearing properties:The more olivine content,the larger the grain size,the higher the ratio of magnesium to iron and the less the content of phlogopite in kimberlite is rich in ore,on the contrary,the ore is poorer.?2?Relationship between standard mineral and ore-bearing properties:In the kimberlite,the magnesia garnet has a deep color,high refractive index,large specific gravity and large unit cell parameters,so the kimberlite has good ore-bearing properties,on the contrary,it has poor ore-bearing properties;for the kimberlite in the same area,the content of magnesium aluminum garnet is positively correlated with the ore-bearing property.The purple series in the magnesium-aluminum garnet has a higher proportion than the orange series.The specific gravity,reflectivity,refractive index and unit cell parameters of chromite are positively correlated with ore-bearing.The greater the value of each physical parameter,the richer the mineralization of diamond;the content of Cr₂O₃,FeO and TiO₂ in chromite is positively correlated with ore-bearing property,and the content of Fe₂O₃ and Al₂O₃ is negatively correlated with ore-bearing property;the content of chromium diopside with Cr₂O₃>1.65%is positively correlated with the ore content of kimberlite.The more chromium diopside containing Cr2O3>1.65%,the richer the diamond grade;in Kimberlite have high chromium high magnesium ilmenite,diamond rich in ore.4.Relationship between chemical composition and ore-bearing properties of kimberlite:The ore-bearing of kimberlite is related to the each group minerals,with the increase of Mg,Cr,Ni and Co content,kimberlite is rich in ore,with the increase of Ti,P,K,Na and Al content,the ore content of kimberlite is becoming poor.The total rare earth content of each kimberlite zone increases with the decrease of ore-bearing property,and the light-weight rare earth ratio decreases with the decrease of ore-bearing property,the La/Sm value decreases with the decrease of ore-bearing property,and the rare earth component curve shows obvious right-tilt type.