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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SiO_2较高(平均为72.03%),富碱并相对富K_2O(K_2O/Na_2O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R_1-R_2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。
The Meng’en Tolgoi body in the Horqin right wing area of eastern Inner Mongolia consists of monzogranite, granodiorite and diorite, belonging to the high-K calc-alkaline rock series. The rocks have higher SiO 2 content (72.03% on average), alkali-rich and relatively K 2 O-rich (K 2 O / Na 2 O average 1.08), lower Mg ~ (average 0.30) and higher A / CNK 1.08) features. In the ACF plot, the rock is projected into S-type granites. Corundum molecules are commonly found in standard minerals. Muscovite is visible in the rocks, and garnet is visible individually. It belongs to the S-type granite category. The total rare earth REEs (ΣREE average 120.76 × 10 -6), light and heavy rare earth fractionation obvious ((La / Yb) _N = 3.2 ~ 32.5) ~ 0.8). In the trace element spider web, strong ion lithophile elements (such as Rb and Ba) were strongly enriched, high field elements such as Ti were strongly depleted, and trace elements and the continental crust normalized and (La / Yb) _N-δEu In the diagram, the source belongs to the shell source. The content of Sr in rock mass is 176.57 × 10 -6, less than 300 × 10 -6, the average Yb content is 1.3 × 10 -6 and less than 2 × 10 -6, The Himalayan-type granites may have high-pressure granulite facies with garnet and plagioclase formed as a result of partial melting of the thickening crust, and the formation pressure may be 0.8-1.5 GPa. In the R_1-R_2 scheme, the Yb-Ta scheme, the rock is projected in the same collision environment. Therefore, the rock mass is the same crustal crust S-type granite under the extrusion background of Middle Triassic, which provides the information for the constraint of collision upper limit between North China Plate and Siberian Plate.