东昆仑土鲁音花岗岩的地球化学、锆石U-Pb年龄及地质意义  

Geochemical and zircon U-Pb dating characteristics and significance of the Tuluyin granites in the east of East Kunlun orogenic belt

作　　者：董亮琼 董国臣[1] 黄慧[1] 白洋[1] DONG Liang-qiong DONG Guo-chen HUANG Hui BAI Yang(School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《中国地质》2016年第5期1737-1749,共13页Geology in China

基　　金：中国地质调查局地质调查项目(1212011121260;1212011220928)资助~~

摘　　要：岩浆活动在板块构造机制中可以看作是大洋板块俯冲或者大陆板块碰撞等过程所伴随的深部作用响应,也是探索深部作用过程的“岩石探针”.土鲁音岩体位于东昆仑东部,紧邻昆中断裂南部区域.在详细野外调研基础上,主要对土鲁音花岗岩体进行岩石学、地球化学以及年代学的研究.结果显示,土鲁音岩体主要岩性为花岗闪长岩,其SiO2为68.49%-70.87%,全碱含量为5.94%-7.16%,K2O/Na2O比值为0.34-0.57,Mg^#值中等（35.92-41.86）,A/CNK值（1-1.07）均小于1.1,属弱过铝质钙碱性I型花岗岩.岩体稀土总量较低（118.91×10^-6 -143.97×10^-6）,（La/Yb）N为4.17-9.14,具有轻稀土元素富集、重稀土元素平坦分布的特征,弱负Eu异常,且显著亏损Nb、Ta、P、Ti等高场强元素,富集Rb、Ba、Th等大离子亲石元素.锆石LA-ICP-MSU-Pb测年结果显示土鲁音花岗岩体侵位时代（245.1±3.3）Ma,和区域内下得波利、埃坑德勒斯特花岗岩体具有-致的成岩年龄,同属印支早期产物.地球化学特征反映壳源部分熔融成因,并有幔源物质及热流参与,结合区域已有的年代学、地球化学以及地质资料,笔者认为土鲁音岩体形成于阿尼玛卿-古特提斯洋北向俯冲的地球动力学背景.Magmatism is regarded as the deep response to the subduction and collision and also a petroprobe to explore the deepprocess. The Tuluyin area lies in the east of East Kunlun orogenic belt （EKOB）, close to the south of the middle fault of EKOB.Based on detailed field investigation, the authors studied the petrology, geochemistry and geochronology of Tuluyin granitoids.Geochemical composition shows that Tuluyin granitoids are lithologically dominated by granodiorite. The SiO2 varies from 68.49% to 70.87 %. The total alkali content is in the range of 5.94%-7.16%, and the K2O/Na2O ratios vary from 0.34 to 0.57. Mg# values aremedium in granitoids （35.92- 41.86）. The A/CNK values （1- 1.07） are lower than 1.1, showing that they belong to slightlyperaluminouscalc-alkaline I-type granites. The rocks are enriched in light RRE （LRRE） with a flat heavy RRE （HRRE） pattern.There are no or weak negative Eu anomalies. The ratios of （La/Yb） N are in the range of 4.17- 9.14, with the total REE contentvarying from 118.91×10^-6 to 143.97×10^-6. The rocks are enriched in large ion lithophile elements （Rb, Th, Ba） and depleted in highfield strength elements （Nb, Ta, P, Ti）. LA-ICP-MS zircon U-Pb dating shows a crystallization age of 245 Ma, identical with theage of Xiadeboli and Aikengdelesite granitoids, suggesting that they all belong to the Early Indosinian period. Geochemicalcharacteristics indicate that these rocks were derived from partial melting of the crust, with the addition of mass and heat flow fromthe mantle. Based on the existing geochronologic, geochemical and geological data, the authors hold that Tuluyin granitoids wereformed under a background of the Anyemaqen-Paleo-Tethys Oceanic crust subducted into EKOB.

关 键 词：土鲁音岩体 东昆仑造山带 印支早期 地球化学 锆石U-PB定年 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]