内蒙古科尔沁右翼中旗地区孟恩陶勒盖岩体成因研究

内蒙古东部科尔沁右翼中旗地区孟恩陶勒盖岩体由二长花岗岩、 花岗闪长岩、 英云闪长岩组成，属于高钾钙碱性岩系。岩石具有SiO₂较高（平均为72.03%），富碱并相对富K₂O（K₂O/Na₂O平均为1.08），Mg^#较低（平均为0.30），铝饱和指数（A/CNK）较高（平均为1.08）的特点。在ACF图解中，岩石投影在S型花岗岩中，标准矿物中普遍出现刚玉分子，岩石中可见白云母，个别可见石榴石，应属S型花岗岩范畴。岩石稀土总量较低（∑ REE平均为120.76×10^-6），轻、 重稀土分馏明显（（La/Yb）_N=3.2～32.5），有变化较大的负铕异常（0.2～0.8）；在微量元素蜘蛛网图上，强烈富集大离子亲石元素（如Rb、 Ba），高场强元素（如Ti）强烈亏损，在微量元素与上陆壳标准化及（La/Yb）_N-δEu图解中，物源属于壳源。岩体Sr的含量平均为176.57×10^-6，小于300×10^-6，Yb含量平均为1.3×10^-6，小于2×10^-6，属于喜马拉雅型花岗岩，源岩可能为含石榴石和斜长石的高压麻粒岩相，形成于加厚地壳部分熔融的结果，其形成的压力可能为0.8～1.5 GPa。在R₁-R₂图解、 Yb-Ta图解中，岩石均投影在同碰撞环境。因此，该岩体是中三叠世挤压背景下同碰撞壳源S型花岗岩，为华北板块与西伯利亚板块碰撞上限的约束提供了资料。

Study on the genesis of Mengentaolegai pluton on Horqin Right Wing Middle Banner in Inner Mongolia

The Mengentaolegai pluton of Horqin Right Wing Middle Banner in eastern Inner Mongolia consists of monzonitic granite, granodiorite and tonalite, belonging to high-K calc-alkaline shoshonite series. It has higher SiO₂(72.03% in average), alkali-rich and relatively rich in K₂O(K₂O/Na₂O=1.08 in average), lower Mg^#(0.30 in average), and higher aluminum saturation index(A/CNK=1.08 in average). In ACF diagram, the rock is projected in S-type granite, with standard mineral of corundite, as well as muscovite and garnet in the rock, belonging to S-type granite category. It has lower amount of rare earth elements(ΣREE=120.76×10^-6 in average), stronger enrichment in LILE and depletion in HFSE((La/Yb)_N=3.2～32.5), and negative Eu anomaly of variety(0.2～0.8). The trace elements in spiders web diagram and(La/Yb)_N-δEu diagram show the enrichment of large ion lithophile elements(Rb, Ba), strongly depletion of high field strength elements(Ti), indicating the provenance of shell source. The pluton(Sr content in an average of 176.57×10^-6, less than 300×10^-6; Yb content in an average of 1.3×10^-6, less than 2×10^-6)belongs to the Himalayan-type granite, the source rocks may contain garnet and plagioclase granulite facies of the high pressure, which formed in the result of partial melting of thickened crust, the pressure of its formation may be between 0.8～1.5 GPa. In R₁-R₂ and Yb-Ta diagrams, the rock belongs to syncollisional granite. The comprehensive analysis indicates that the Mengentaolegai pluton is a syncollisional shell source S-type granite, to provide the new evidence for the collisional time of the Siberian plate and North China plate.