| 吉林通化赤柏松地区早白垩世花岗质岩脉（株）的成因:锆石U-Pb年代学、Hf同位素和地球化学证据 |
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| 引用本文： | 周皓,裴福萍,焦骥,王枫,许文良.吉林通化赤柏松地区早白垩世花岗质岩脉（株）的成因:锆石U-Pb年代学、Hf同位素和地球化学证据[J].地球科学,2020,45(2):519-533. |
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| 作者姓名： | 周皓 裴福萍 焦骥 王枫 许文良 |
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| 作者单位： | 吉林大学地球科学学院, 吉林长春 130061 |
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| 基金项目： | 国家重点研发计划项目2016YFC0600108-02吉林大学研究生创新研究计划101832018C037 |
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| 摘 要： | 中国吉林省通化县赤柏松地区早白垩世花岗质岩脉（株）的锆石U-Pb年代学、Hf同位素和全岩地球化学特征，为探讨华北克拉通东北部中生代时期大陆下地壳的属性和构造演化历史提供了重要依据.研究区花岗质岩脉（株）中的锆石普遍发育振荡生长环带，并具有较高的Th/U比值（0.53~1.94），表明其为岩浆成因.对采自花岗质岩脉（株）中4个样品的锆石U-Pb测年结果表明，它们的206Pb/238U加权平均年龄分别为116 Ma、124 Ma、127 Ma和130 Ma，即早白垩世早期和早白垩世晚期.这些花岗质岩石具有变化的SiO2（60.61%~76.07%）和MgO（0.01%~2.48%）含量、富碱（K2O+Na2O=6.26%~9.14%）及富Al2O3（11.99%~16.13%）的特征，总体属于高钾钙碱性系列岩石.微量元素上富集轻稀土和大离子亲石元素，亏损重稀土和Ba、Sr、P、Ti和Eu等元素（Eu/Eu*=0.05~0.30），暗示其主要来自地壳岩石的部分熔融，并在演化过程中经历了斜长石、碱性长石、磷灰石和钛铁矿等矿物的分离结晶作用和围岩的同化混染作用.与早白垩世早期花岗质岩石相比，早白垩世晚期岩石的碱性程度提高.样品中锆石εHf（t）值介于-21.84~-10.74之间，两阶段亏损地幔模式年龄为1.86~2.56 Ga.上述地球化学特征暗示，赤柏松地区下地壳以古元古代地壳物质为主，存在少量新太古代地壳物质.早白垩世时期研究区以双峰式岩石组合为特征，进一步结合区域上已有的火成岩和区域构造演化的研究成果，认为早白垩世时期研究区处于俯冲背景下的伸展环境.与早白垩世早期相比，早白垩世晚期伸展作用增强.
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| 关 键 词： | 早白垩世 通化赤柏松 花岗质岩脉（株） 地球化学 锆石Hf同位素 |
| 收稿时间： | 2018-12-30 |
Petrogenesis of Early Cretaceous Chibaisong Granitoid Dyke (Stock) from Tonghua Area,Jilin Province: Evidences from Zircon U-Pb Geochronology,Hf Isotope and Whole-Rock Geochemistry |
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| Abstract: | LA-ICP-MS zircon U-Pb geochronology, whole-rock geochemistry and Hf isotope of zircons of Early Cretaceous Chibaisong granitoids in Tonghua area, southern Jilin Province, northeast (NE) China provide the insights into the nature of the lower crust and tectonic evolution of the eastern North China Craton (NCC). Zircons from the Chibaisong granitoid dyke (stock) show fine-scale oscillatory zoning, and relatively high Th/U ratios (0.53~1.94), indicative a magmatic origin. The weighted mean of 206Pb/238U ages for four samples from four granitoids are 116 Ma, 124 Ma, 127 Ma and 130 Ma, respectively. The Chibaisong granitoids have variable content of SiO2 (60.61%-76.07%) and MgO (0.01%-2.48%), high content of total-alkali (K2O+Na2O=6.26%-9.14%) and Al2O3 (11.99%-16.13%), characterized by the nature of high-K calc-alkaline series.Additionally, they show enrichment of LREEs and LILEs, depletion of HREEs and HFSEs, Ba, Sr, P, Ti and Eu (Eu/Eu*=0.05-0.30), suggesting that they were derived from the partial melting of the lower crust, and suffered from the fractional crystallization of plagioclase, alkali feldspar, apatite and ilmenite. Furthermore, they were assimilated by the country rock according to their variable major element contents and zircon εHf(t)values. Granitoids were more alkaline in the early stage of the Early Cretaceous and Mg# was increased, which may be attributed to mantle material. The zircon εHf(t) values in the samples ranged from -21.84 to -10.74, and the two-stage model ages of zircon Hf isotope of granite porphyry yield 1.86-2.56 Ga, which imply that the accretion of the lower crust within the Tonghua area mainly happened in the Paleoproterozoic, with small amounts during Neoproterozoic. The bimodal rock associationin the Early Cretaceous, together with the results from the contemporaneous volcanic rocks and regional evolution history in this area, indicate that the granitoid dykes may formed in an extensional setting, and more strongly extension happened during the late stage of Early Cretaceous associated with the subduction of the Paleo-Pacific Plate beneath the Eurasian continent. |
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