西藏改则地区阿布山岩体岩石地球化学、年代学及地质构造意义  

Geochemistry,Geochronology and Tectonic Significance of the Abushan Intrusive Body in the Gerze Area,Tibet,China

作　　者：黄强太[1,2,3] 张霄[1,2,3] 夏中宇[1,2,3] 石晓龙[1,2,3] 王志龙 胡西冲[1,2,3] 郑浩[1,2,3] 夏斌[1,2,3] 

机构地区：[1]中山大学海洋学院,广州510006 [2]海洋石油勘探开发广东省普通高校重点实验室,广州510006 [3]广东省海洋资源与近岸工程重点实验室,广州510006 [4]广东清远市建设工程质量监测站,广东清远511515

出　　处：《矿物岩石地球化学通报》2016年第3期515-526,共12页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局项目(1212011221087;1212011221088);矿床地球化学国家重点实验室开放基金项目(201304)

摘　　要：青藏高原西部改则地区的阿布山岩体位于班公湖—怒江缝合带北侧,岩性以闪长玢岩为主。岩石化学上表现为高K2O（1.11%～3.95%）,高Na2O（平均4.01%）,高Al2O3（〉15%,平均16.78%）,低Mg O（〈3%,平均2.69%）,显示为中钾钙碱性-高钾钙碱性过渡的特征。微量元素显示富集大离子亲石元素（Rb、Ba、Th等）、亏损高场强元素（Nb、Ta、Ti等）。稀土元素配分图显示为右倾模式,说明是轻稀土富集型,δEu平均为0.89,δCe平均为0.91,具有弱铕、铈异常,具有典型岛弧火山岩的特征。锆石LA-ICP-MS U-Pb加权平均年龄为113.3±1.1Ma、113.6±1.3Ma,表明在早白垩世晚期班公湖—怒江洋盆北向俯冲消减过程中,导致地幔楔部分熔融,形成岛弧岩浆,由于持续俯冲消减作用使得下地壳发生部分熔融,形成花岗岩熔体,并且向地壳浅部侵位、冷凝结晶形成。The Abushan intrusive body is located tectonically in the northern part of the Bangonghu-Nujiang Suture Zone（ BNSZ）,geographically in the western Tibetan Plateau. It consists mainly of diorite porphyry,with high contents of K2O（ 1. 11%- 3. 95%）,Na2O（ average 4. 01%）,and Al2O3（ average 16. 78%,totally 15%）,low contents of Mg O（ average 2. 69%,mostly less than 3%）,and the transitional characteristics of medium-K to high-K calc-alkaline series. In addition,the the intrusive rocks are rich in LREE,such as Rb,Ba,Th,but depleted in high field strength elements（ HFSE） including Nb,Ta and Ti,with right-declined REE distribution patterns,and weak Eu and Ce anomalies（ averageδEu value of 0. 89 and average δCe of 0. 91）. These are characteristics of the typical island arc volcanic rock. The zircon LA-ICP-MS U-Pb weighted ages of two diorite porphyry samples are 113. 3 ± 1. 1Ma and 113. 6 ± 1. 3Ma. Therefore,it is believed that the northward subduction of the Bangonghu-Nujiang oceanic basin at the Early Cretaceous resulted in the formation of island arc magma which was derived from the partial melting of mantle wedge. The continuing oceanic plate subduction and the uplift of original island arc magma resulted in the partial melting of the lower crust to form the andesiticmelt which was then intruded into the shallow level of the crust and then crystallized to form the diorite porphyry.

关 键 词：阿布山岩体 地球化学 锆石U-PB定年 改则 西藏 

分 类 号：P597.3[天文地球—地球化学] P588.1[天文地球—地质学]