徐州白露山含金刚石橄榄玄武岩地球化学特征及其岩浆演化特征

江苏徐州地区位于华北克拉通的东南部，其区内及周边广泛发育碱性超基性岩-基性岩，其中不乏含金刚石母岩，但是主要为金伯利岩。笔者在苏北寻找金刚石原生矿的过程中，在徐州白露山地区发现了含金刚石的橄榄玄武岩。本区橄榄玄武岩SiO₂含量为42.64%~51.13%，K₂O+Na₂O为2.57%~5.93%，Al₂O₃为10.48%~13.53%，MgO含量变化范围较大，为3.11%~19.34%。以主量元素做TAS图解可以看出本区基性岩的投影点基本都落于玄武岩范围，属于高钾钙碱性。微量元素特征显示白露山的样品靠近OIB和火山弧区域。富集端元明显偏高的Ba/Th比值暗示玄武岩中含有大陆下地壳物质。而白露山橄榄玄武岩元素地球化学特征及组成变化范围大并不是主要由地壳混染引起的，而是因为源区含有残留的再循环大陆下地壳。这些地球化学特征说明徐州白露山橄榄玄武岩与辽宁、山东地区金伯利岩具有一定的成因联系，为该区金刚石找矿提供了有利线索。

Geochemistry of the diamondiferous olivine basalt and magmatic evolution in the Bailushan area,Xuzhou

Xuzhou is located in the southeast of the north China craton. Alkaline ultrabasic rocks-basic rocks are widely developed in and around it, where there are some diamondiferous rocks, but mainly kimberlite. During the prospecting of primary diamond deposit, the diamondiferous rocks were discovered in Bailushan, north of Xuzhou. The SiO₂ content of olive basalt ranges from 42.64% to 51.13%, K₂O+Na₂O from 2.57% to 5.93%,Al₂O₃ from 10.48% to 13.53%,and MgO content from 3.11% to 19.34%. On the TAS diagram, the points of basic rocks in this area all fall into the range of basalt, indicating high potassium calcium alkalinity. Trace element signatures indicate that samples from Bailushan are close to the OIB and volcanic arc regions. The higher Ba/Th ratio of enriched endmember suggests that the basalts contain lower continental crust materials. Therefore, the wide range of elements geochemistry and isotopic composition of olivine basalts is not mainly caused by crustal contamination, but because the source area contains residual recirculation subcontinental crust. These geochemical characteristics suggest that the Bailushan olivine basalt in Xuzhou is related to the kimberlite in Liaoning and Shandong, which provides a favorable clue for diamond prospecting in this area.