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| 西藏北部拉萨地块那曲地区约113Ma安山岩岩石成因与意义 | |
| 引用本文： | 黄玉,朱弟成,赵志丹,张亮亮,Don DEPAOLO,胡兆初,袁洪林,莫宣学.西藏北部拉萨地块那曲地区约113Ma安山岩岩石成因与意义[J].岩石学报,2012,28(5):1603-1614. |
| 作者姓名： | 黄玉 朱弟成 赵志丹 张亮亮 Don DEPAOLO 胡兆初 袁洪林 莫宣学 |
| 作者单位： | 1. 中国地质大学地质过程与矿产资源国家重点实验室,中国地质大学地球科学与资源学院,北京100083 2. 中国科学院地质与地球物理研究所,北京,100029 3. 加利福尼亚大学,伯克利CA 94720 4. 地质过程与矿产资源国家重点实验室,中国地质大学地球科学学院,武汉430074 5. 西北大学地质系,大陆动力学国家重点实验室,西安710069 |
| 基金项目： | 本文受国家973项目(2009CB421002、2011CB403102)、国家自然科学基金重点基金项目(40830317)、教育部新世纪优秀人才项目(NCET-10-0711)、长江学者和创新团队发展计划(IRT1083)、中国地质调查局工作项目(1212011121260,1212011121066)、美国自然科学基金(EAR1111959)和深部探测技术与实验研究专项课题(Sinoprobe-04-02)联合资助. |
| 摘 要： | 西藏北部拉萨地块广泛分布着早白垩世岩浆岩,由于缺少高质量的年代学和地球化学数据,其岩浆源区和岩石成因迄今未能很好约束。本文报道了北部拉萨地块那曲地区安山岩的锆石U-Pb定年、地球化学和Sr-Nd-Hf同位素数据。那曲安山岩锆石U-Pb年龄为112.7±0.7Ma。岩石为高钾钙碱性系列,富集大离子亲石元素、Th、U和轻稀土元素(La/Yb)N=6.62～11.68],亏损Nb、Ta、P和Ti等高场强元素。样品具有较高的(87Sr/86Sr)i值(0.7100～0.7126)、负的全岩εNd(t)值(-10.5～-7.8)和负的锆石εHf(t)值(-9.9～-4.7),对应于古老的Nd同位素二阶段模式年龄(1.5～1.8Ga)和锆石Hf同位素地幔模式年龄(1.0～1.6Ga)。综合岩石学、地球化学和区域构造背景研究认为,那曲地区安山岩形成于南向俯冲的班公湖-怒江洋壳岩石圈板片断离的背景,很可能是受早期流体/沉积物熔体交代富集的安多微陆块古老岩石圈地幔物质部分熔融的产物,并经历了不同程度的分离结晶。 |
| 关 键 词： | 古老岩石圈地幔 早白垩世安山岩 那曲 安多微陆块 北部拉萨地块 |
| 收稿时间： | 1/8/2012 12:00:00 AM |
| 修稿时间： | 2012/4/10 0:00:00 |
Petrogenesis and implication of the andesites at ～ 113Ma in the Nagqu region in the northern Lhasa subterrane |
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| HUANG Yu,ZHU DiCheng,ZHAO ZhiDan,ZHANG LiangLiang,Don DEPAOLO,HU ZhaoChu,YUAN HongLin and MO XuanXue.Petrogenesis and implication of the andesites at ～ 113Ma in the Nagqu region in the northern Lhasa subterrane[J].Acta Petrologica Sinica,2012,28(5):1603-1614. | |
| Authors: | HUANG Yu ZHU DiCheng ZHAO ZhiDan ZHANG LiangLiang Don DEPAOLO HU ZhaoChu YUAN HongLin and MO XuanXue |
| Institution: | State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;University of California, Berkeley, CA 94720, USA;State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China |
| Abstract: | The nature of magma source region and petrogenesis of the Early Cretaceous igneous rocks,which are widely distributed in the northern Lhasa subterrane,are not well constrained so far largely due to the limitation of high quality geochronological and geochemical data.This paper reports the petrological,zircon U-Pb dating,whole-rock geochemical and zircon Hf isotopic data of the andesites from Nagqu area,northern Lhasa subterrane.The andesites have been dated to be 112.7 ± 0.7Ma by zircon U-Pb dating method.These rocks are high-K calc-alkaline,enriched in large-ion lithophile elements(LILEs),Th,U,and light rare earth elements(LREEs),and depleted in high field strength elements(e.g.,Nb,Ta,P,and Ti;HFSEs).The andesites show high(87Sr/86Sr) i values(0.7100 ～0.7126),negative εNd(t) values(-10.5 ～-7.8),and negative zircon εHf(t) values(-9.9 ～-4.7),yielding ancient two-stage Nd model ages of 1.5 ～ 1.8Ga and zircon Hf isotope mantle model ages of 1.0 ～ 1.6Ga.The data reported here,combined with regional geological background of the northern Lhasa subterrane,we propose that the Nagqu andesites can be considered as the products of partial melting of ancient lithospheric mantle of the Amdo microcontinent that was modified by fluids or/and melts of the sediments,and subsequently experienced varying degrees of fractional crystallization.This magma event is most likely resulted from the slab break-off of the southward subduction of the Bangong-Nujiang Ocean seafloor. |
| Keywords: | Ancient lithosphere mantle Early Cretaceous andesites Nagqu Amdo microcontinent Northern Lhasa subterrane |
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