豫南新县岩体地球化学、年代学和Hf同位素特征及地质意义

发布时间：2018-03-13 00:22

本文选题：大别山　切入点：新县　出处：《地球科学》2016年08期 　论文类型：期刊论文

【摘要】：新县岩体位于秦岭-大别造山带上,对其进行系统的岩石地球化学探讨有助于加深对秦岭-大别造山带中生代构造-岩浆演化及地球动力学背景的认识.岩石地球化学分析结果显示,SiO_2含量为74.94%~78.16%,K_2O含量为3.87%~5.86%,Na_2O含量为3.82%~4.24%,Al_2O_3含量为12.38%~13.57%,具有高钾钙碱性和过铝质(A/CNK=1.05~1.11)特征.岩石稀土总量较低(42.67×10~(-6)~110.45×10~(-6)),轻稀土元素相对富集,重稀土元素相对亏损,具有Eu的负异常,岩体富集Rb、U、Hf和Y,亏损Ba、Nb、Ta和Ti,显示出I型高分异花岗岩的特点.3个期次岩石的U-Pb年龄分别为153.4±1.1Ma、146.4±1.6Ma和131.6±1.8Ma.锆石Hf同位素分析结果表明,新县岩体的ε_(Hf)(t)值为-24.5~-20.3,位于地幔演化线之下,t_(DM2)值为2.68~2.93Ga,指示其源于扬子板块北缘的古老地壳,其组成类似于扬子板块北缘TTG型岩浆岩.结合区域地质背景,新县岩体形成于扬子陆块与华北陆块碰撞造山后的陆内伸展环境,对应的地球动力学背景为晚侏罗世-早白垩世地壳从挤压收缩向区域性伸展的构造体制大转换过程和大规模的地壳伸展和岩石圈减薄时期.
[Abstract]:The Xinxian rock body is located on the Qinling-Dabie orogenic belt. The systematic petrogeochemical study is helpful to the understanding of the Mesozoic tectonic-magmatic evolution and geodynamic background of the Qinling Dabie orogenic belt. The results of petrogeochemical analysis show that the content of SiO-2 is 74.94g / 78.16K _ 2O in Qinling Dabie orogenic belt. The content of Na _ 2O is 3.82%, and the content of Al _ 2O _ 2O _ 3 is 12.38 ~ 13.57, which is characterized by high potassium calc-alkalinity and peraluminous content A / CNK ~ (1.11). The total amount of rare earth elements in rock is relatively low (42.67 脳 10110.-6110.45 脳 10 ~ (-6)), and the content of light rare earth elements is relatively rich. The heavy rare earth elements are relatively depleted and have negative EU anomalies. The rock bodies are enriched in RbPU Hf and Y, and depleted in Baqian NbPU Ta and Ti. the U-Pb ages of the three stages are 153.4 卤1.1 Ma 146.4 卤1.6 Ma and 131.6 卤1.8 MaA, respectively. The results of zircon HF isotopic analysis show that: 1) the U-Pb age of the rocks is 153.4 卤1.1 Ma, 146.4 卤1.6 Ma and 131.6 卤1.8 MaA, respectively. The 蔚 ~ (-1) value of the Xinxian rock mass is -24.5 ~ (-20.3), and the value is 2.68 ~ 2.93Gabeneath the mantle evolution line, indicating that it originated from the ancient crust of the northern margin of the Yangtze plate, and its composition is similar to that of the TTG type magmatic rock in the northern margin of the Yangtze plate, which is combined with the regional geological background, and its composition is similar to that of the TTG type magmatic rock in the northern margin of the Yangtze plate. The Xinxian rock mass was formed in the intracontinental extensional environment after collision orogeny between the Yangtze and North China landmasses. The corresponding geodynamic background is the large transition process of tectonic system from compressional contraction to regional extension in the crust of late Jurassic-early Cretaceous and the period of large-scale crustal extension and lithospheric thinning.
【作者单位】：中南大学有色金属成矿预测与地质环境监测教育部重点实验室;中南大学地球科学与信息物理学院;河南省有色金属地质勘查总院;河南省有色金属地质矿产局第七地质大队;
【基金】：中国地质调查局地质矿产调查评价专项(No.12120113091200) 中南大学创新驱动计划项目(No.2015CX008)
【分类号】：P59;P584

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