| 江西赣州隆木花岗岩体年龄、成分特征及其构造意义 |
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| 引用本文： | 胡刚,钟达洪,邓新,杨坤光.江西赣州隆木花岗岩体年龄、成分特征及其构造意义[J].地球科学与环境学报,2012(3):44-56. |
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| 作者姓名： | 胡刚 钟达洪 邓新 杨坤光 |
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| 作者单位： | 1. 中国地质大学武汉地球科学学院,湖北 武汉 430074
2. 江西省地质调查研究院,江西 南昌 330030 |
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| 基金项目： | 中国地质调查局项目(基(2010)矿评01-14-06);国家自然科学基金项目(40972137) |
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| 摘 要： | 为了查明江西赣州隆木花岗岩形成时代及演化过程,对隆木岩体中的黑云母花岗岩与似斑状黑云母二长花岗岩进行LA-ICP-MS锆石U-Pb定年和同位素地球化学研究。结果表明:黑云母花岗岩与似斑状黑云母二长花岗岩的锆石U-Pb定年结果分别为(457±6)、(450±9)Ma,表明岩体形成于晚奥陶世;岩体铝饱和指数为1.11～1.29,K2O与Na2O含量(质量分数)之比为0.97～1.51,属强过铝质及高钾钙碱性岩石;根据ACF图解,岩体投影于S型花岗岩区域内;岩体Rb、Th+U、La+Ce、P、Nd、Zr+Hf+Sm相对富集,而Ba、Nb、Sr、Ti相对亏损,总体上属于低Ba、低Sr的花岗岩;岩体Rb与Sr含量之比为0.60～2.82,平均值为1.68,明显高于大陆地壳与上地壳的平均值,具壳源花岗岩特征;根据A/MF-C/MF图解,岩体物源区为砂质岩;岩体稀土元素含量总量偏低,为(113～176)×10-6,轻稀土元素富集明显,配分模式明显呈右倾型,Eu异常为0.38～0.67,Eu亏损程度中等偏高;化学成分显示,岩体属于强过铝质高钾钙碱性S型花岗岩,是一种壳源花岗岩,岩浆源区为成熟上地壳的砂质岩源区;构造判别图解、年龄信息及野外特征表明,岩体形成于后碰撞伸展构造环境。总之,隆木岩体形成于早古生代晚期的加里东构造运动,是华夏古陆块与扬子古陆块在新元古代碰撞拼贴之后裂解、在中奥陶世再次发生陆内碰撞使得地壳加厚部分重融、造山后期地壳伸展减薄、熔融物质上升侵位形成的岩体。
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| 关 键 词： | 地球化学 锆石U-Pb定年 S型花岗岩 隆木岩体 加里东运动 华南陆内造山 赣州 江西 |
Formation Age and Geochemical Characteristics of Longmu Granite Body in Ganzhou,Jiangxi Province and Its Tectonic Significance |
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| HU Gang,ZHONG Da-hong,DENG Xin,YANG Kun-guang.Formation Age and Geochemical Characteristics of Longmu Granite Body in Ganzhou,Jiangxi Province and Its Tectonic Significance[J].Journal of Earth Sciences and Environment,2012(3):44-56. |
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| Authors: | HU Gang ZHONG Da-hong DENG Xin YANG Kun-guang |
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| Institution: | 1(1.School of Earth Sciences,China University of Geosciences,Wuhan 430074,Hubei,China; 2.Jiangxi Provincial Institute of Geological Survey,Nanchang 330030,Jiangxi,China) |
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| Abstract: | In order to find out the formation age and evolution process of Longmu Granite in Ganzhou of Jiangxi Province,LA-ICP-MS zircon U-Pb dating and isotope geochemistry of biotite granite and like-porphyritic biotite monzogranite in Longmu Pluton were studied.The results showed that the ages of zircon U-Pb dating of biotite granite and like-porphyritic biotite monzogranite were(457±6)Ma and(450±9)Ma respectively,which indicated that the pluton emplaced in Late Ordovician;aluminum saturation index was 1.11-1.29,the ratio of contents(mass fractions) of K2O and Na2O was 0.97-1.51,so the plutons were categorized as strong peraluminous and high potassium calc-alkaline;according to the ACF diagram,the pluton was plotted in the field of S-type granite;Longmu Pluton was enriched in Rb,Th+U,La+Ce,P,Nd,Zr+Hf+Sm and depleted in Ba,Nb,Sr,Ti,so the pluton belonged to the granite with low Ba and Sr on the whole;the ratio of contents of Rb and Sr was 0.60-2.82 with an average of 1.68,which was higher than the average of continental crust and supracrust,so the pluton was categorized as crustal derived granite;according to the A/MF-C/MF diagram,the provenance of pluton was psammite;the content of rare earth element of pluton was lower((113-176)×10-6),the enrichment of light rare earth element was significant,the distribution pattern was significantly right-wing type,and Eu anomaly was 0.38-0.67 and the depletion was more than middle;chemical composition showed that the pluton was S-type strong peraluminous high potassium calc-alkaline granite which was a kind of crustal derived granite,and magma protolith was the psammite source of mature supracrust;the tectonic discrimination diagram,zircon U-Pb dating and field characteristics indicated the pluton emplaced in a post-orogenic extension environment.In general,the emplacement time of Longmu Pluton was the late of Early Paleozoic under the control of Caledonian Movement;Cathaysia Plate and Yangtze Plate collided in Neoproterozoic and then cracked,and in the middle of Ordovician,the two plates happened intracontinental collision again which thickened the crust,and in post-orogenic stage,the crust began to strongly extension and partial melting and formed the mantle crust granite. |
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| Keywords: | geochemistry zircon U-Pb dating S-type granite Longmu Pluton Caledonian Movement intracontinental orogeny of South China Ganzhou Jiangxi |
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