Metallogenic features of diamondiferous kimberlites in Botswana and China:Enlightenment for exploration of the same type deposits

Important implications for the interior workings, constituent, circulation between crust and mantle, convection between core and mantle of the Earth can be drawn by studying diamonds and their hosted rocks. Based on the geological comparison of metallogenic kimberlites from super-giant deposits in Botswana and Mengyin and Wafangdian deposits in China, the authors put forward some exploration suggestions and prospecting clues as follows:(1) Kimberlite is an unique diamondiferous rock in Botswana, whereas lamproite is a main hosted -rock in South China craton including two important lamproite zones along the Jiangnan orogenic belt and northern margin of South China craton. Kimberlite is dominantly distributed in the North China craton, which is composed of three kimberlitic zones along Tanlu fault, Trans-North China orogen and northern margin of North China. Two industrial value diamondiferous kimberlite deposits are distributed in the Tanlu zone. (2) In-situ U-Pb age and Sr, Nd isotopic data of perovskites show that 86-97 Ma Orapa kimberlites and 456-470 Ma Mengyin and Wafangdian kimberlites have low ⁸⁷Sr/⁸⁶Sr ratios of 0.703-0.705, medium εNd(t) values ranging from -0.09 to 5, indicating that primary kimberlitic magmas were likely derived from primitive mantle or convective lower mantle. (3) Primary kimberlites in Botswana dominantly occur as pipes, while in China they mainly occur as irregular fissures, expressed as dykes and lesser extent sills. Crater facies are pervasively observed in Orapa and Jwaneng kimberlite pipes in comparison with hypabyssal (or root zone) facies in Mengyin and Wafangdian pipe clusters. (4) Orapa A/K1 and Jwaneng mines are a few diamondiferous kimberlitic pipes yielding predominantly eclogitic xenoliths and E type diamond. In contrast, Letlhakane, Damtshaa and Karowe mines also occur in Orapa cluster, Mengyin and Wafangdian mines from the Tanlu kimberlite belt have mainly peridotite xenoliths as well as P type and E type diamonds. (5) Some exploration suggestions and prospecting clues of diamondiferous kimberlites are presented as follows:(A) Deep faults cutting through on-craton and off-craton subcontinental lithospheric mantle play a role in the emplacement of kimberlites; (B) Soil sampling for kimberlite indicator minerals such as picroilmenite and garnet, Cr-rich rutile, Cr-spinel and Cr-diopside is a primary exploration tool; (C) Geophysical surveys such as aeromagnetic mothed should be combined with soil sampling for better prospecting results. (6) Work in diamondiferous prospecting target areas in the Tanlu kimberlite zone, Jiangnan lamproite zone and Tarim block should be further strengthened. Illuvial type diamond deposits in China have great potential for mineralization.