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| 滇西保山地块早古生代花岗岩类的年代学、地球化学及意义 | |
| 引用本文： | 董美玲,董国臣,莫宣学,朱弟成,聂飞,谢许峰,王霞,胡兆初.滇西保山地块早古生代花岗岩类的年代学、地球化学及意义[J].岩石学报,2012,28(5):1453-1464. |
| 作者姓名： | 董美玲 董国臣 莫宣学 朱弟成 聂飞 谢许峰 王霞 胡兆初 |
| 作者单位： | 1. 中国地质大学,北京,100083 2. 中国地质大学,北京100083国地质大学地质过程与矿产资源国家重点实验室,北京100083 3. 中国地质大学地质过程与矿产资源国家重点实验室,武汉,430074 |
| 基金项目： | 本文受国家重点基础研究发展规划项目(2009CB421002、2011CB403102)、111计划项目(B07011)、长江学者和创新团队发展计划(IRT1083)、深部探测技术与实验研究专项课题(Sinoprobe-04-02)、国土资源部公益性行业科研专项(201011054)和中国地质调查局研究项目(1212011220920)联合资助. |
| 摘 要： | 位于滇西特提斯构造带保山地块的平河岩体,岩石类型主要为花岗岩、二长花岗岩,其次有少量的花岗闪长岩。4件样品的锆石U-Pb年龄变化于480～486Ma,表明这些花岗岩类侵位于早奥陶世。平河花岗岩类的K2O/Na2O值大于1,铝饱和指数(A/CNK)为1.07～1.1,属高钾钙碱性过铝质花岗岩。岩石总体上富集大离子亲石元素和Pb,亏损高场强元素。明显富集轻稀土元素(La/Yb)N=4.33～7.05],显示明显的负Eu异常(δEu=0.25～0.48)。4件样品58个测点的锆石εHf(t)值变化范围较大(主要集中于-12.4～-3.0之间),对应的Hf同位素地壳模式年龄集中于2.2～1.7Ga。这些地球化学特征指示平河花岗岩类为S型花岗岩,主要来源于古老地壳物质(如砂屑岩)的重熔,并不同程度地混入了幔源物质。平河花岗岩类与出露于中部拉萨地体的变质酸性火山岩存在可比性,可能代表了早古生代冈瓦纳大陆原特提斯边缘岩浆弧的一部分。 |
| 关 键 词： | 早古生代花岗岩类 地球化学 锆石Hf同位素 保山地块 滇西 |
| 收稿时间： | 2/1/2012 12:00:00 AM |
| 修稿时间： | 2012/4/10 0:00:00 |
Geochronology and geochemistry of the Early Palaeozoic granitoids in Baoshan block, western Yunnan and their implications |
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| DONG MeiLing,DONG GuoChen,MO XuanXue,ZHU DiCheng,NIE Fei,XIE XuFeng,WANG Xia and HU ZhaoChu.Geochronology and geochemistry of the Early Palaeozoic granitoids in Baoshan block, western Yunnan and their implications[J].Acta Petrologica Sinica,2012,28(5):1453-1464. | |
| Authors: | DONG MeiLing DONG GuoChen MO XuanXue ZHU DiCheng NIE Fei XIE XuFeng WANG Xia and HU ZhaoChu |
| Institution: | China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China |
| Abstract: | The Pinghe granitoid pluton,located in the Baoshan block of the Tethyan belt,western Yunnan,consists mainly of granite and monzogranite with subordinate granodiorite.Zircon U-Pb ages of 480 ～ 486Ma for four samples from this pluton indicate that this pluton was emplaced during the Early Ordovician.The Pinghe granitoids are high-K calc-alkaline and peraluminous,with K2O/Na2O > 1 and A/CNK = 1.07 ～ 1.13.These rocks are enriched in large-ion lithophile elements(LILEs),light rare-earth elements(LREEs) (La/Yb) N =4.33 ～7.05]and Pb,and depleted in high field-strength elements(HFSEs).They show similar chondritenormalized REE patterns,with negative Eu anomalies(δEu = 0.25 ～ 0.48).58 analyses from four samples have a wide range zircon εHf(t) values(-12.4 ～-3.0) and varying Hf-isotope crustal model ages(2.2 ～ 1.7Ga).Such geochemical signatures indicate that the Pinghe granitoids are S-type granite in character and were derived mainly from anatexis of ancient crustal materials(such as greywacke) with varying contributions from mantle-derived components.The Pinghe granitoids are geochemically comparable to the coeval silicic metavolcanic rocks reported in the central Lhasa Terrane.It is suggested that the Baoshan block may represent a part of an Early Paleozoic magmatic arc in the Gondwana continental margin facing the proto-Tethyan Ocean. |
| Keywords: | Early Palaeozoic granitoids Geochemistry Zircon Hf isotope Baoshan block Western Yunnan |
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