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夹持于甘孜—理塘结合带与金沙江结合带之间的义敦弧岩浆岩带上发育了3条纵贯南北的造山花岗岩带,其中:中带形成了由20余个岩体组成的雀而山—格聂花岗岩带和相关的银、锌、铅-锌多金属矿床。本文对格聂(南)花岗岩体进行研究,发现其岩石类型为花岗闪长岩、二长花岗岩和钾长花岗岩三类,以二长花岗岩为主体。锆石LA-ICP-MS U-Pb定年结果表明格聂花岗岩的成岩年龄为89.9±3.6Ma。地球化学研究表明,岩石中主量元素化学成分具有富硅、富铝、低钠高钾的特征,为典型的S型花岗岩。铝饱和指数ASI>1,指示岩浆源自地壳;(CaO)%/(Na2O)%值等于0.1左右,表明源岩为大陆地壳沉积岩区的泥质岩。稀土总量均值228.83×10-6,稀土配分曲线呈略右倾近直线海鸥型,与地壳熔融型花岗岩形态一致。轻重稀土分馏不明显;铕出现明显负异常(δEu=0.13),显示岩浆分异结晶作用强烈。微量元素蛛网图上明显亏损大离子亲石元素Sr;富集高场强元素U。Rb/Sr平均比值14.97,表明格聂花岗岩的源岩为上部陆壳。结合Rb-(Y+Nb)图解、(Rb/30)-Hf-(Ta×3)图解、R1-R2变异图解,格聂南岩体形成于后碰撞造山环境,应是甘孜-理塘洋盆和金沙江洋盆闭合后,造山后伸展作用活动的产物。
There are three orogenic granitic belts running north and south along the Yidun arc magmatic belt between the Ganzi-Litang belt and the Jinsha belt. Among them, there are more than 20 rock masses in the middle belt Titsuoshan - Granitic granite belt and related silver, zinc, lead - zinc polymetallic deposits. In this paper, we study the Ge Nie (South) granite body and find that the rock types are composed of granodiorite, monzogranite and potash-bearing granite, with the monzonitic granite as the main body. U-Pb dating of zircons by LA-ICP-MS shows that the diagenetic age of granitic granite is 89.9 ± 3.6Ma. Geochemical studies have shown that the chemical composition of major elements in rocks is characterized by rich silicon, aluminum-rich, low-sodium and high-potassium, and is a typical S-type granite. The ASI> 1 indicates that the magma is derived from the crust. The value of (CaO)% / (Na2O)% is equal to about 0.1, indicating that the source rocks are argillaceous in continental crustal sedimentary rock areas. The average total amount of rare earth is 228.83 × 10-6, and the distribution curve of rare earth is slightly right near linear rectilinear seagull, which is consistent with the morphology of crustal melting granite. Light and heavy rare earth fractional distillation is not obvious; europium showed a significant negative anomaly (δEu = 0.13), showing strong differentiation of the magma. Significant depletion of large ion-lithophile element Sr on the trace element cobweb; enrichment of high field strength elements U. The average ratio of Rb / Sr is 14.97, indicating that the source rocks of the granitic granite are the upper continental crust. According to the diagram of Rb- (Y + Nb), the diagram of (Rb / 30) -Hf- (Ta × 3) and the diagram of R1-R2 variation show that the Genernan pluton was formed in the post-collision orogenic environment and should be Ganzi-Litang oceanic basin and Jinsha River basin closed, after the orogenic extension activity of the product.