| 广东南山花岗岩形成时代、地球化学特征与成因 |
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| 引用本文： | 姚正红,肖惠良,范飞鹏,陈乐柱,鲍晓明,周延,武玲,吴涵宇.广东南山花岗岩形成时代、地球化学特征与成因[J].火山地质与矿产,2011(1):66-78. |
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| 作者姓名： | 姚正红 肖惠良 范飞鹏 陈乐柱 鲍晓明 周延 武玲 吴涵宇 |
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| 作者单位： | [1]中国地质科学院,北京100037 [2]中国地质调查局南京地质调查中心,南京210016 |
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| 基金项目： | 中国地质调查局国土资源大调查项目（编号：12120140430335和1212010533003）资助 |
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| 摘 要： | 广东南山花岗岩体位于陂头复式岩体西端,锆石的SHRIMP U-Pb年龄为158.1±1.8Ma,是燕山早期岩浆活动的产物。岩石化学特征显示岩体以高硅、富碱、贫Ca和Mg以及高TFeO/MgO、低CaO/Na2O为特征。其K2O/Na2O〉1,A/NK=7.8~11.92,A/CNK=1.33~1.68,属过铝质碱性岩石。在稀土和微量元素组成上,岩石富含稀土元素（除明显的负Eu异常,δEu=0.09~0.16）以及Zr、Y、Th、U、Nb等高场强元素,贫Ba、Sr、Ti等,高10000x Ga/Al（比值大于2.6）。在Zr、Nb、Ce、Y对10000×Ga/Al以及TFeO/MgO-SiO2等A型花岗岩多种判别图上,投影点主要落在A型花岗岩区,而与高分异的I、S型花岗岩明显不同。这些特征均指示,南山岩体具有铝质A型花岗岩的特点。通过Y-Nb-3Ga和Y-Nb-Ce构造环境判别图解将其进一步划分为A2型花岗岩,代表其形成于拉张的构造背景之下。本文在此研究基础上,认为南山花岗质岩浆可能形成于相对挤压的中侏罗世。而在晚侏罗世早期相对拉张的作用下,岩石圈减薄,软流圈地幔上涌,地壳的泥质岩和少量砂质岩受到幔源流体富集后发生部分熔融后上侵形成铝质A型花岗岩,且有较强的结晶分异作用。
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| 关 键 词： | 燕山期 铝质A型花岗岩 锆石SHRIMPU-Pb年龄 地球化学 南山花岗岩 广东 |
Formation age,geochemistry and petrogenesis of Nanshan granite body,Guangdong Province |
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| YAO Zheng-hong,XIAO Hui-liang,FAN Fei-peng,CHEN Le-zhu,BAO Xiao-ming,ZHOU Yan,WU Ling,WU Han-yu.Formation age,geochemistry and petrogenesis of Nanshan granite body,Guangdong Province[J].Volcanology & Mineral Resources,2011(1):66-78. |
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| Authors: | YAO Zheng-hong XIAO Hui-liang FAN Fei-peng CHEN Le-zhu BAO Xiao-ming ZHOU Yan WU Ling WU Han-yu |
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| Institution: | 1 Chinese Academy of Geological Science,Beijing 100037,China)(2 Nanjing Institute of Geology and Mineral Resource,Nanjing 210016,China) |
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| Abstract: | The Nanshan granite body,which is tectonically located at the western part of Beitou composite body,yields a SHRIMP zircon U-Pb age of 158.1±1.8Ma which suggests that the granite body is the product of magmatism during the early Yanshanian period.The geochemical characteristics indicate that the granite body consists of peraluminous alkaline rocks characterized by high contents of silica and alkali,low contents of CaO and MgO,high values of TFeO/MgO and low values of CaO/Na2O,K2O/Na2O1,A/NK=7.8～11.92,A/CNK=1.33～1.68.The composition features of rare earth elements and trace elements are as follows： enrichment with rare earth elements（REE）（except distinct negative Eu anomalies,δEu=0.09～0.16）and high field-strength elements of Zr,Y,Th,U and Nb,relatively depleted Ba,Sr,Ti and high ratios of 10000×Ga/Al（2.6）.On diagrams for discriminating A-type granite（such as Zr,Nb,Ce,Y vs.10000×Ga/Al and TFeO/MgO vs.SiO2 diagrams）,most of samples are plotted on the field of A-type granite,which is distinctively different from the strongly differentiated I-type and S-type granites.All these characteristics mentioned above show that the Nanshan granite body exhibits characteristics of aluminous A-type granites.By using Y-Nb-3Ga and Y-Nb-Ce tectonic setting discrimination diagrams,the Nanshan aluminous A-type granites may further divided into A2-type granite which is usually believed to be formed in extensional tectonic settings.Based on the above-mentioned researches,it is suggested that the Nanshan granitic magma probably formed in a relative compression tectonic setting during middle Jurassic period.While in the relative extention tectonic setting during early stage of late-Jurassic epoch,there occured thinning of lithosphere and upwelling of asthenospheric mantle,aluminious A-type granites with strong crystallization differentiation were formed by partial melting of mudstone and small-volume sandstone enriched by mantle-derived fluid. |
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| Keywords: | Yanshanian period alumininous A-type granite SHRIMP zircon U-Pb dating geochemistry Nanshan granite Guangdong province |
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