Geological characteristics and prospecting significance of kimberlite pipe in Xicun area of Xuzhou, Jiangsu Province

The Xicun kimberlite pipe was discovered for the first time which has ended the kimberlite-nonexistent history in northern Jiangsu Province. The geological characteristics of Xicun pipe were analyzed by petrology, geochemistry and associated minerals, and the prospecting significance was discussed. According to the regional background and the conditions of the diamond formation, it is considered that there existed basic geological conditions for kimberlite emplacement and diamond ore formation in Xicun area. The Xicun kimberlite pipe provided mother rock conditions for diamond ore. The Xicun kimberlites have similar geochemical characteristics to Shandong and Liaoning kimberlites. They were all formed by low degree partial liquation of the mantle-derived magma. Besides, they suffered hybridism of the earth crust in the process of magma rising and widespread carbonatization in the late period. The values of compatible elements are similar to those of Shandong kimberite breccia, which constitute the typical patterns of kimberlite. The heavy and light rare earth elements are characterized by strong fractionation. Associated indicator minerals include eclogite-type pyrope, chrome-rich diopside, and magnesium-rich chrome spinels, which show the characteristics of ore-bearing kimberlite.