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引用本文:尹滔,李威,尹显科,张伟,袁华云,裴亚伦. 西藏阿翁错地区早白垩世花岗闪长岩——班公湖-怒江洋壳南向俯冲消减证据[J]. 中国地质, 2019, 46(5): 1105-1115.
YIN Tao,LI Wei,YIN Xianke,ZHANG Wei,YUAN Huayun,PEI Yalun. The Early Cretaceous granodiorites in the Aweng Co area, Tibet: Evidence for the subduction of the Bangong Co-Nujiang River oceanic crust to the south[J]. Geology in China, 2019, 46(5): 1105-1115(in Chinese with English abstract).
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西藏阿翁错地区早白垩世花岗闪长岩——班公湖-怒江洋壳南向俯冲消减证据
尹滔, 李威, 尹显科, 张伟, 袁华云, 裴亚伦
四川省地质调查院 稀有稀土战略资源评价与利用四川省重点实验室, 四川 成都 610081
摘要:
对拉萨地块北部阿翁错地区花岗闪长岩进行了年龄分析、岩石地球化学研究。锆石LA-ICP-MS定年测得花岗闪长岩U-Pb年龄为(114.4±1.9)Ma,属于早白垩世晚期岩浆活动的产物。花岗闪长岩地球化学特征表明,其具有典型镁安山岩/闪长岩(MA)的地球化学特征,所有样品均具有较高Mg#值(45.42~54.29),低的TFeO*/MgO值(1.58~2.26);所有样品都显示轻稀土元素富集,富集大离子亲石元素,亏损高场强元素的特征。研究表明,阿翁错花岗闪长岩是班公湖-怒江洋壳在俯冲消减背景下,由俯冲洋壳脱水熔融产生的溶体与地幔橄榄岩发生交代作用的产物,为晚中生代班公湖-怒江洋盆的南向俯冲消减提供了直接的岩石学、地球化学、年代学证据。
关键词:  班公湖-怒江  镁安山岩/闪长岩  俯冲消减  锆石U-Pb测年  地质调查工程  拉萨地块  西藏
DOI:10.12029/gc20190511
分类号:P588.12+1
基金项目:中国地质调查局项目(DD20160026,DD20191029)资助。
The Early Cretaceous granodiorites in the Aweng Co area, Tibet: Evidence for the subduction of the Bangong Co-Nujiang River oceanic crust to the south
YIN Tao, LI Wei, YIN Xianke, ZHANG Wei, YUAN Huayun, PEI Yalun
Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Province, Sichuan Geological Survey, Chengdu 610081, Sichuan, China
Abstract:
This paper reports zircon U-Pb data of major and trace elements for the granodiorites from the Aweng Co area in northern Lhasa block. Zircon LA-ICP-MS U-Pb dating of granodiorite yielded an age of 163.3 ±1.7 Ma, suggesting that the intruded rocks were formed in late Early Cretaceous period. Geochemical studies show that Aweng Co granodiorites have typical geochemical characteristics similar to the magnesian andesite/diorite (MA). They are characterized by high Mg# values (45.42~54.29) and low TFeO*/MgO ratios (1.58~2.26). They are enriched in LREE in the chondrite-normalized REE patterns, and are enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs). Geochemical features of the Aweng Co magnesian granodiorites are considered to have been generated by the southward subduction of Bangong Co-Nujiang River oceanic lithosphere, and can be genetically regarded as resulting from partial melting of dewatered and subducted oceanic crust melts, which had been metasomatized by mantle peridotite under the condition of oceanic crust subduction. These results provide direct petrologic evidence of the intruded rocks for the southward subduction of the Bangong Co-Nujiang River Ocean.
Key words:  Bangong Co-Nujiang River  magnesian andesite/diorite  subduction  zircon U-Pb chronology  geological survey engineering  Lhasa Block  Tbbet