| 安徽牯牛降A型花岗岩的年代学、地球化学和构造意义 |
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| 引用本文： | 谢建成,陈思,荣伟,李全忠,杨晓勇,孙卫东.安徽牯牛降A型花岗岩的年代学、地球化学和构造意义[J].岩石学报,2012,28(12):4007-4020. |
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| 作者姓名： | 谢建成 陈思 荣伟 李全忠 杨晓勇 孙卫东 |
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| 作者单位： | 中国科学院广州地球化学研究所, 广州 510640;合肥工业大学资源与环境工程学院, 合肥 230009;合肥工业大学资源与环境工程学院, 合肥 230009;中国科学技术大学地球和空间科学学院, 合肥 230026;合肥工业大学资源与环境工程学院, 合肥 230009;中国科学技术大学地球和空间科学学院, 合肥 230026;中国科学院广州地球化学研究所, 广州 510640 |
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| 基金项目： | 本文受国家科技部973项目(2012CB416703);安徽省公益性地质工作项目(2011-K-08);国家自然科学基金项目(41090370)和高等学校博士学科点专项科研新教师类基金(20100111120012)联合资助. |
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| 摘 要： | 皖南地区牯牛降岩体位于扬子板块东南缘,江南隆起带内。本文报道了牯牛降花岗岩体新的锆石U-Pb年龄和地球化学数据,并对岩体成因及其构造意义进行了探讨。锆石原位LA-ICP-MS U-Pb定年表明牯牛降岩体的形成年龄为130.1±1.3Ma (95% confidence, MSWD=0.55)。结合己发表的其他高质量锆石U-Pb同位素年龄数据表明皖南地区花岗岩的形成年龄主要集中在125~130Ma。牯牛降花岗岩为高钾钙碱性、准铝质岩石,SiO2 含量为72.21%~74.85%,具有高K2O含量(>5.11%)、高铁值(FeOT/(FeOT+MgO)>0.91)和K2O/Na2O比值(>1.61),低MgO和CaO含量的特征。微量元素地球化学性质上表现为强烈亏损Ba、Sr、Eu(Eu*/Eu=0.29~0.30),富集REE(>419×10-6)、Rb、Th 和U,较高的高场强元素Zr、Nb、Y和Ga含量。主量和微量元素均表现为A型花岗岩的特征。非常低的Mg#值(0.14~0.16)和较低Cr含量(Cr=10×10-6),高Yb(7.08×10-6~9.02×10-6)、Y(78.7×10-6~90.8×10-6)含量和较高的Th/U比值(5.17~7.79)说明古老地壳物质的部分熔融可能是牯牛降岩体主要形成机制。牯牛降A2型花岗岩特征代表了拉张的碰撞后构造环境。
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| 关 键 词： | A型花岗岩 古老地壳部分熔融 构造环境 牯牛降花岗岩体 皖南地区 |
| 收稿时间： | 2012/9/11 0:00:00 |
| 修稿时间： | 2012/11/5 0:00:00 |
Geochronology, geochemistry and tectonic significance of Guniujiang A-type granite in Anhui Province |
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| XIE JianCheng,CHEN Si,RONG Wei,LI QuanZhong,YANG XiaoYong and SUN WeiDong.Geochronology, geochemistry and tectonic significance of Guniujiang A-type granite in Anhui Province[J].Acta Petrologica Sinica,2012,28(12):4007-4020. |
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| Authors: | XIE JianCheng CHEN Si RONG Wei LI QuanZhong YANG XiaoYong and SUN WeiDong |
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| Institution: | Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;Department of Resource and Environmental Sciences, Hefei University of Technology, Hefei 230009, China;Department of Resource and Environmental Sciences, Hefei University of Technology, Hefei 230009, China;School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;Department of Resource and Environmental Sciences, Hefei University of Technology, Hefei 230009, China;School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China |
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| Abstract: | The Guniujiang intrusion in southern Anhui Province is located at the southeastern boundary of Yangtze plate, and situated in Jiangnan uplift. Here we report new zircon U-Pb age and geochemical data, and discuss the petrogenesis and tectonic significance of the Guniujiang granite. Laser ablation ICP-MS zircon U-Pb dating suggests that the age of the Guniujiang granite is 130.1±1.3Ma (95% confidence, MSWD=0.55). Combined with other available high-precision zircon U-Pb data, the ages of these granites from southern Anhui are mainly concentrated in 125~130Ma. The Guniujiang granite is a high calc-alkaline and metaluminous granite with SiO2 contents of 72.21%~74.85%, and high K2O (>5.11%), Fe values (FeOT/(FeOT+MgO)>0.91), and K2O/Na2O ratios (>1.61). The rock also shows relatively high Zr, Nb, Y and Ga concentrations, enriched in REE (>419×10-6) and strong incompatible elements such as Rb, Th and U, low CaO and MgO, extremely depleted in Ba, Sr, and Eu (Eu*/Eu=0.29~0.30). The geochemical characteristics indicate that this granite belongs to A-type. The very low Mg# values (0.14~0.16) and relatively low Cr concentration (Cr=10×10-6), high Yb (7.08×10-6~9.02×10-6), Y (78.7×10-6~90.8×10-6) concentrations and Th/U ratios (5.17~7.79) show that the partial melting of old continental crust materials might have been the main mechanism for petrogenesis of the Guniujiang granite. The Guniujiang granite can be classified into A2 subtype, which is usually believe to be formed under a post-collision extensional tectonic setting. |
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| Keywords: | A-type granite Partial melting of old continental crust Tectonic setting Guniujiang granite intrusion Southern Anhui Province |
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