中国阿尔泰早古生代后碰撞花岗岩的发现及其地质意义  

Discovery of the Early Paleozoic post-collisional granite in Altay,China and its geological significance

作　　者：李会军[1,2] 何国琦[1] 吴泰然[1] 吴波[1] 

机构地区：[1]造山带与地壳演化教育部重点实验室北京大学地球与空间科学学院,北京100871 [2]中国地质科学院地质力学研究所,北京100081

出　　处：《岩石学报》2010年第8期2445-2451,共7页Acta Petrologica Sinica

基　　金：中央级公益性科研院所基本科研业务费(DZLXJK200802);国家重要基础研究发展规划项目(2001CB409810)联合资助

摘　　要：新疆哈巴河县白哈巴岩体主要岩石类型为黑云母斜长花岗岩,另有少量花岗闪长岩。SiO2含量介于65.58%～65.79%之间,A/CNK≤1.05,为弱过铝质岩石,属高钾钙碱性系列。稀土元素总量为174.1×10-6～210.6×10-6,具明显的Eu负异常(0.54～0.63),稀土元素分馏中等((La/Yb)N值为4.46～5.56),稀土配分曲线为轻稀土富集型,富集Rb,Th,U,K,La,Ce,Nd,Hf,Zr和Sm等元素,而强烈亏损Ba,Nb,Ta,Sr,P和Ti等元素。主量元素、稀土元素和微量元素特征表明,白哈巴岩体形成于挤压体制向拉张体制转换的构造环境,属后碰撞花岗岩类。SHRIMP锆石U-Pb年龄为413.8±6.4Ma。白哈巴岩体后碰撞花岗岩的发现,支持阿尔泰-蒙古微大陆的存在,丰富了对新疆北部构造演化的认识。Baihaba intrusion,located in Habahe County,Xinjiang Province,is mainly composed of biotite plagiogranite,and minor granodiorite. Baihaba rocks with higher SiO2 and K2O contents can be classified as high-K calc-alkaline series rock and considered as weakly per-aluminous rocks ( SiO2: 65. 58% ～ 65. 79% ,Na2O/CaO: 1. 73 ～ 3. 43,Shand index ≤ 1. 05 ) . The intrusion is characterized by high REE abundance( ∑REE = 174. 1 × 10 -6 ～ 210. 6 × 10 -6) ,strong negative Eu anomalies( δEu = 0. 54 ～ 0. 63) , medium REE fractionation [( La/Yb) N = 4. 46 ～ 5. 56],enrichments in Rb,Th,U,K,La,Ce,Nd,Hf,Zr and Sm,but strong depletions of Ba,Nb,Ta,Sr,P and Ti. These characteristics of major,REE and trace elements indicate that the intrusion was formed in a transitional tectonic setting from compression to extensional regime,which can be classified as post-collisional granitoids. SHRIMP U-Pb zircon analyses yield ages of 413. 8 ± 6. 4Ma. The discovery of Early Paleozoic post-collisional granites in Altay supports the presence of Altay-Mongolia microcontinent.

关 键 词：后碰撞花岗岩 SHRIMPU-Pb年龄 地球化学 阿尔泰 新疆 

分 类 号：P588.121[天文地球—岩石学]