东天山红包山-碱泉-带镁铁超镁铁质岩体的地球化学特征与岩石成因

红包山-碱泉一带镁铁-超镁铁质岩体位于东天山卡瓦布拉克地区,岩体呈脉状或透镜状产出,出露面积约8km2。岩石类型主要为纯橄榄岩、橄榄岩、单辉橄榄岩等。地球化学数据表明,该区岩体具高Mg#的特征,属镁质超基性岩。岩石稀土元素为平缓右倾型配分模式,稀土元素总量(0.96×10-6~10.02×10-6)较低,轻重稀土元素组间分馏较强((La/Yb)N=2.14~4.08),δEu变化于0.63~1.08,可能与斜长石的结晶有关。微量元素蛛网图表明,岩石具富集大离子亲石元素Rb、Sr和高场强元素U、Pb及LREE,而亏损高场强元素Nb(Ta)、Hf、Ti的特征。主微量元素等地球化学相关图解说明,红包山-碱泉一带岩体原生岩浆为幔源的钙碱性玄武质岩浆,成岩作用以岩浆结晶分异为主导,并受到壳源物质的同化混染作用。

Geochemical Characteristics and Petrogenesis of Hongbaoshan-Jianquan Mafic-Ultramafic Intrusions in East Tianshan,Xinjiang

Located in the Kawabulake area of east Tianshan, the Hongbaoshan-Jianquan manfic-ultramafic intrusions exhibit as vein and lenticular, with outcropped area of ~8km2. It mainly consists of dunite, peridotite and wehrlite. The geochemical data shows that these intrusions belong to magnesian ultramafic rocks, which are characterized by high Mg# and gently LREE-rich pattern with low ∑REE values (0.96×10-6~10.02×10-6) and enrichment of LREE ((La/Yb)N=2.14~4.08). Additionally, they are enriched LILE (Rb and Sr) and HFSE (U and Pb), and depleted HFSE (Nb(Ta), Hf and Ti). The δEu values vary from 0.63 to 1.08, which may be related with the crystallization of plagioclase.The geochemical diagrams of major and trace elements correlation indicate that the primary magma of Hongbaoshan-Jianquan intrusions is cal-alkaline basaltic magma that formed in mantle, their diagenesis are mainly controlled by the magmatic crystallization, and contaminated by the crust during upward of magma.