| 吉林敦化松江河地区中生代似斑状花岗岩成因和形成环境:元素、Hf同位素和锆石U-Pb年代学证据 |
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| 引用本文： | 鲁倩,孙景贵,安久海,韩吉龙,褚小磊.吉林敦化松江河地区中生代似斑状花岗岩成因和形成环境:元素、Hf同位素和锆石U-Pb年代学证据[J].吉林大学学报(地球科学版),2019,49(3):673-689. |
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| 作者姓名： | 鲁倩 孙景贵 安久海 韩吉龙 褚小磊 |
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| 作者单位： | 1. 吉林大学地球科学学院, 长春 130061;2. 吉林省有色金属地质勘查局, 长春 130012 |
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| 基金项目： | 国家科技部项目（2017YFC0601306）；中国地质调查局项目（DD2016005202） |
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| 摘 要： | 花岗岩是陆壳的重要组成部分,它是揭示地壳演化地球动力学过程的主要对象之一。为了揭示夹皮沟—海沟构造带的中生代地质演化,本文系统地开展了该带中段松江河地区花岗岩体内部产出的似斑状花岗岩的野外地质调查、岩相学、单颗粒锆石U-Pb同位素年代学、全岩元素、Hf同位素地球化学的研究。研究结果揭示:岩石呈粉红色、普遍发生较强的糜棱岩化作用,发育糜棱叶理构造;获得岩浆锆石的U-Pb同位素谐和年龄为217～169Ma;加权平均年龄为(169.6±1.8)Ma(n=9,MSWD=1.3);主量元素呈现高硅(71.18%～71.99%)、富碱(8.54%～8.93%)、贫镁(0.42%～0.52%)、贫钙(0.93%～1.38%)特征,并且A/NK>1.0,A/CNK<1.1;微量元素呈现低Rb、Zr和高Sr、Ba等质量分数,高Sr/Y和(La/Yb)_N特征;稀土元素表现轻稀土元素富集、重稀土元素亏损和较弱Eu的正异常特征;获得锆石原位^(176 )Yb/^(177 )Hf值为0.010 517～0.050 159,^(176 )Lu/^(177 )Hf值为0.000 476～0.001 784,^(176 )Hf/^(177 )Hf为0.282 310～0.282 457,对应的锆石εHf(t)值为-12.7～-7.5,二阶段模式年龄为2 792～2 325Ma。上述特征揭示,松江河地区中生代似斑状花岗岩属准中等分异、同碰撞向伸展转换的Ⅰ型花岗岩,原始岩浆起源于新太古代陆壳重熔作用,岩浆就位发生在中侏罗世早阶段;它记录了燕山期早侏罗世古太平洋板块向欧亚大陆之下俯冲的挤压陆壳活化产生岩浆,并于中侏罗世地壳伸展岩浆上升过程中经岩浆结晶分离作用而产生的中等分异岩浆结晶形成,成岩后于晚侏罗世遭受了韧脆性构造作用改造。
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| 关 键 词： | 元素地球化学 HF同位素 锆石U-PB年代学 岩石成因 形成环境 似斑状花岗岩 |
| 收稿时间： | 2018-10-22 |
Petrogenesis and Forming Environment of Mesozoic Porphyritic Granite in Songjianghe Region of Dunhua,Jilin Province: Evidences from Element Geochemistry,Hf Isotope and U-Pb |
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| Lu Qian,Sun Jinggui,An Jiuhai,Han Jilong,Chu Xiaolei.Petrogenesis and Forming Environment of Mesozoic Porphyritic Granite in Songjianghe Region of Dunhua,Jilin Province: Evidences from Element Geochemistry,Hf Isotope and U-Pb[J].Journal of Jilin Unviersity:Earth Science Edition,2019,49(3):673-689. |
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| Authors: | Lu Qian Sun Jinggui An Jiuhai Han Jilong Chu Xiaolei |
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| Institution: | 1. College of Earth Sciences, Jilin University, Changchun 130061, China;2. Jilin Nonferrous Metals Geological Exploration Bureau, Changchun 130012, China |
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| Abstract: | As an important part of continental crust, granite is one of the main objects to reveal the dynamic process of crustal evolution. The research of geology,geochronology and geochemistry was carried out on the porphyritic granite in Songjianghe granite to reveal the Mesozoic geological evolution of Jiapigou-Haigou structural belt. The Songjianghe porphyritic granite is pink,and mylonitization and mylonite foliation structure are widely developed. Zircon U-Pb apparent ages range from 217 Ma to 169 Ma with a weighted mean age of (169.6±1.8)Ma (n=9,MSWD=1.3). The major element data show that the porphyritic granite is characterized by high SiO2(71.18%-71.99%),alkali (8.54%-8.93%),low MgO (0.42%-0.52%), CaO (0.93%-1.38%),A/NK greater than 1.0,and A/CNK less than 1.1. The trace element data reveal that the porphyritic granite is characterized by depletion of Rb and Zr,enrichment of Sr and Ba,and high Sr/Y and (La/Yb)N. The REEs are characterized by enrichment of LREE, loss of HREE, and weak negative Eu anomalies. Hf isotope data show that 176Yb/177Hf ranges from 0.010 517 to 0.050 159,176Lu/177Hf ranges from 0.000 476 to 0.001 784,176Hf/177Hf ranges from 0.282 310 to 0.282 457,and the εHf(t) value of zircon ranges from -12.7 to -7.5,and the two-stage Hf model ages range from 2 792 to 2 325 Ma. The above features indicate that the Songjianghe porphyritic granites belong to the medium differentiated Ⅰ-type granite,and its geodynamic background is related to the transition from syn-collision to extension. The primary magma was derived from a re-melting and emplacement of late Neoarchean crust in the early Middle Jurassic. The magmatism was associated with the continental crust activation caused by the subduction of the Paleo Pacific plate to the Eurasian plate in the Early Jurassic. The porphyritic granite was generated by medium differentiated magmatic crystallization during the magma rising in the Middle Jurassic crustal extension, and followed by the transformation of the Late Jurassic ductile-brittle tectonic action. |
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| Keywords: | element geochemistry Hf isotope Zircon U-Pb geochronology petrogenesis forming environment porphyritic granite |
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